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<button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2501.12925">arXiv:2501.12925</a> <span> [<a href="https://arxiv.org/pdf/2501.12925">pdf</a>, <a href="https://arxiv.org/format/2501.12925">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> </div> <p class="title is-5 mathjax"> A Denser Hydrogen Inferred from First-Principles Simulations Challenges Jupiter's Interior Models </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Cozza%2C+C">Cesare Cozza</a>, <a href="/search/cond-mat?searchtype=author&query=Nakano%2C+K">Kousuke Nakano</a>, <a href="/search/cond-mat?searchtype=author&query=Howard%2C+S">Saburo Howard</a>, <a href="/search/cond-mat?searchtype=author&query=Xie%2C+H">Hao Xie</a>, <a href="/search/cond-mat?searchtype=author&query=Helled%2C+R">Ravit Helled</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2501.12925v1-abstract-short" style="display: inline;"> First-principle modeling of dense hydrogen is crucial in materials and planetary sciences. Despite its apparent simplicity, predicting the ionic and electronic structure of hydrogen is a formidable challenge, and it is connected with the insulator-to-metal transition, a century-old problem in condensed matter. Accurate simulations of liquid hydrogen are also essential for modeling gas giant planet… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2501.12925v1-abstract-full').style.display = 'inline'; document.getElementById('2501.12925v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2501.12925v1-abstract-full" style="display: none;"> First-principle modeling of dense hydrogen is crucial in materials and planetary sciences. Despite its apparent simplicity, predicting the ionic and electronic structure of hydrogen is a formidable challenge, and it is connected with the insulator-to-metal transition, a century-old problem in condensed matter. Accurate simulations of liquid hydrogen are also essential for modeling gas giant planets. Here we perform an exhaustive study of the equation of state of hydrogen using Density Functional Theory and quantum Monte Carlo simulations. We find that the pressure predicted by Density Functional Theory may vary qualitatively when using different functionals. The predictive power of first-principle simulations is restored by validating each functional against higher-level wavefunction theories, represented by computationally intensive variational and diffusion Monte Carlo calculations. Our simulations provide evidence that hydrogen is denser at planetary conditions, compared to currently used equations of state. For Jupiter, this implies a lower bulk metallicity (i.e., a smaller mass of heavy elements). Our results further amplify the inconsistency between Jupiter's atmospheric metallicity measured by the Galileo probe and the envelope metallicity inferred from interior models. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2501.12925v1-abstract-full').style.display = 'none'; document.getElementById('2501.12925v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 January, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2501.10594">arXiv:2501.10594</a> <span> [<a href="https://arxiv.org/pdf/2501.10594">pdf</a>, <a href="https://arxiv.org/format/2501.10594">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Machine Learning">cs.LG</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> </div> <p class="title is-5 mathjax"> Accurate and thermodynamically consistent hydrogen equation of state for planetary modeling with flow matching </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Xie%2C+H">Hao Xie</a>, <a href="/search/cond-mat?searchtype=author&query=Howard%2C+S">Saburo Howard</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2501.10594v1-abstract-short" style="display: inline;"> Accurate determination of the equation of state of dense hydrogen is essential for understanding gas giants. Currently, there is still no consensus on methods for calculating its entropy, which play a fundamental role and can result in qualitatively different predictions for Jupiter's interior. Here, we investigate various aspects of entropy calculation for dense hydrogen based on ab initio molecu… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2501.10594v1-abstract-full').style.display = 'inline'; document.getElementById('2501.10594v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2501.10594v1-abstract-full" style="display: none;"> Accurate determination of the equation of state of dense hydrogen is essential for understanding gas giants. Currently, there is still no consensus on methods for calculating its entropy, which play a fundamental role and can result in qualitatively different predictions for Jupiter's interior. Here, we investigate various aspects of entropy calculation for dense hydrogen based on ab initio molecular dynamics simulations. Specifically, we employ the recently developed flow matching method to validate the accuracy of the traditional thermodynamic integration approach. We then clearly identify pitfalls in previous attempts and propose a reliable framework for constructing the hydrogen equation of state, which is accurate and thermodynamically consistent across a wide range of temperature and pressure conditions. This allows us to conclusively address the long-standing discrepancies in Jupiter's adiabat among earlier studies, demonstrating the potential of our approach for providing reliable equations of state of diverse materials. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2501.10594v1-abstract-full').style.display = 'none'; document.getElementById('2501.10594v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 January, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2025. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7+7 pages, 4+9 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.17821">arXiv:2411.17821</a> <span> [<a href="https://arxiv.org/pdf/2411.17821">pdf</a>, <a href="https://arxiv.org/format/2411.17821">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> </div> <p class="title is-5 mathjax"> From quantum enhanced to quantum inspired Monte Carlo </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Christmann%2C+J">Johannes Christmann</a>, <a href="/search/cond-mat?searchtype=author&query=Ivashkov%2C+P">Petr Ivashkov</a>, <a href="/search/cond-mat?searchtype=author&query=Chiurco%2C+M">Mattia Chiurco</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.17821v1-abstract-short" style="display: inline;"> We perform a comprehensive analysis of the quantum-enhanced Monte Carlo method [Nature, 619, 282-287 (2023)], aimed at identifying the optimal working point of the algorithm. We observe an optimal mixing Hamiltonian strength and analyze the scaling of the total evolution time with the size of the system. We also explore extensions of the circuit, including the use of time-dependent Hamiltonians an… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.17821v1-abstract-full').style.display = 'inline'; document.getElementById('2411.17821v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.17821v1-abstract-full" style="display: none;"> We perform a comprehensive analysis of the quantum-enhanced Monte Carlo method [Nature, 619, 282-287 (2023)], aimed at identifying the optimal working point of the algorithm. We observe an optimal mixing Hamiltonian strength and analyze the scaling of the total evolution time with the size of the system. We also explore extensions of the circuit, including the use of time-dependent Hamiltonians and reverse digitized annealing. Additionally, we propose that classical, approximate quantum simulators can be used for the proposal step instead of the original real-hardware implementation. We observe that tensor-network simulators, even with unconverged settings, can maintain a scaling advantage over standard classical samplers. This may extend the utility of quantum enhanced Monte Carlo as a quantum-inspired algorithm, even before the deployment of large-scale quantum hardware. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.17821v1-abstract-full').style.display = 'none'; document.getElementById('2411.17821v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">JC and PI contributed equally</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.01988">arXiv:2410.01988</a> <span> [<a href="https://arxiv.org/pdf/2410.01988">pdf</a>, <a href="https://arxiv.org/format/2410.01988">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-ph</span> </div> </div> <p class="title is-5 mathjax"> Exploring diffusion bonding of niobium and its alloys with tungsten and a molybdenum alloy for high-energy particle target applications </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Griesemer%2C+T">Tina Griesemer</a>, <a href="/search/cond-mat?searchtype=author&query=Ximenes%2C+R+F">Rui Franqueira Ximenes</a>, <a href="/search/cond-mat?searchtype=author&query=Ahdida%2C+C">Claudia Ahdida</a>, <a href="/search/cond-mat?searchtype=author&query=Izquierdo%2C+G+A">Gonzalo Arnau Izquierdo</a>, <a href="/search/cond-mat?searchtype=author&query=Santillana%2C+I+A">Ignacio Aviles Santillana</a>, <a href="/search/cond-mat?searchtype=author&query=Callaghan%2C+J">Jack Callaghan</a>, <a href="/search/cond-mat?searchtype=author&query=Dumont%2C+G">Gerald Dumont</a>, <a href="/search/cond-mat?searchtype=author&query=Dutilleul%2C+T">Thomas Dutilleul</a>, <a href="/search/cond-mat?searchtype=author&query=Terricabras%2C+A+G">Adria Gallifa Terricabras</a>, <a href="/search/cond-mat?searchtype=author&query=H%C3%B6ll%2C+S">Stefan H枚ll</a>, <a href="/search/cond-mat?searchtype=author&query=Jacobsson%2C+R">Richard Jacobsson</a>, <a href="/search/cond-mat?searchtype=author&query=Kyffin%2C+W">William Kyffin</a>, <a href="/search/cond-mat?searchtype=author&query=Mamun%2C+A+A">Abdullah Al Mamun</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Giuseppe Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Fontenla%2C+A+T+P">Ana Teresa P茅rez Fontenla</a>, <a href="/search/cond-mat?searchtype=author&query=De+Frutos%2C+O+S">Oscar Sacristan De Frutos</a>, <a href="/search/cond-mat?searchtype=author&query=Esposito%2C+L+S">Luigi Salvatore Esposito</a>, <a href="/search/cond-mat?searchtype=author&query=Sgobba%2C+S">Stefano Sgobba</a>, <a href="/search/cond-mat?searchtype=author&query=Calviani%2C+M">Marco Calviani</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.01988v1-abstract-short" style="display: inline;"> Particle-producing targets in high-energy research facilities are often made from refractory metals, and they typically require dedicated cooling systems due to the challenging thermomechanical conditions they experience. However, direct contact of water with target blocks can induce erosion, corrosion, and embrittlement, especially of tungsten (W). One approach to overcoming this problem is cladd… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.01988v1-abstract-full').style.display = 'inline'; document.getElementById('2410.01988v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.01988v1-abstract-full" style="display: none;"> Particle-producing targets in high-energy research facilities are often made from refractory metals, and they typically require dedicated cooling systems due to the challenging thermomechanical conditions they experience. However, direct contact of water with target blocks can induce erosion, corrosion, and embrittlement, especially of tungsten (W). One approach to overcoming this problem is cladding the blocks with tantalum (Ta). Unfortunately, Ta generates high decay heat when irradiated, raising safety concerns in the event of a loss-of-cooling accident. This study explored the capacity of niobium (Nb) and its alloys to form diffusion bonds with W and TZM (a molybdenum alloy with titanium and zirconium). This is because the Beam Dump Facility (BDF), a planned new fixed-target installation in CERN's North Area, uses these target materials. The bonding quality of pure Nb, Nb1Zr, and C103 (a Nb alloy with 10% hafnium and 1% titanium) with TZM and W obtained using hot isostatic pressing (HIP) was evaluated. The effects of different HIP temperatures and the introduction of a Ta interlayer were examined. Optical microscopy indicated promising bonding interfaces, which were further characterized using tensile tests and thermal-diffusivity measurements. Their performance under high-energy beam impact was validated using thermomechanical simulations. C103 exhibited higher interface strengths and safety factors than Ta2.5W, positioning it as a potential alternative cladding material for the BDF production target. The findings highlight the viability of Nb-based materials, particularly C103, for improving operational safety and efficiency in fixed-target physics experiments; however, considerations regarding the long half-life of 94Nb require further attention. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.01988v1-abstract-full').style.display = 'none'; document.getElementById('2410.01988v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2404.08053">arXiv:2404.08053</a> <span> [<a href="https://arxiv.org/pdf/2404.08053">pdf</a>, <a href="https://arxiv.org/format/2404.08053">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PRXQuantum.5.040320">10.1103/PRXQuantum.5.040320 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Benchmarking digital quantum simulations above hundreds of qubits using quantum critical dynamics </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Miessen%2C+A">Alexander Miessen</a>, <a href="/search/cond-mat?searchtype=author&query=Egger%2C+D+J">Daniel J. Egger</a>, <a href="/search/cond-mat?searchtype=author&query=Tavernelli%2C+I">Ivano Tavernelli</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2404.08053v2-abstract-short" style="display: inline;"> The real-time simulation of large many-body quantum systems is a formidable task, that may only be achievable with a genuine quantum computational platform. Currently, quantum hardware with a number of qubits sufficient to make classical emulation challenging is available. This condition is necessary for the pursuit of a so-called quantum advantage, but it also makes verifying the results very dif… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.08053v2-abstract-full').style.display = 'inline'; document.getElementById('2404.08053v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2404.08053v2-abstract-full" style="display: none;"> The real-time simulation of large many-body quantum systems is a formidable task, that may only be achievable with a genuine quantum computational platform. Currently, quantum hardware with a number of qubits sufficient to make classical emulation challenging is available. This condition is necessary for the pursuit of a so-called quantum advantage, but it also makes verifying the results very difficult. In this manuscript, we flip the perspective and utilize known theoretical results about many-body quantum critical dynamics to benchmark quantum hardware and various error mitigation techniques on up to 133 qubits. In particular, we benchmark against known universal scaling laws in the Hamiltonian simulation of a time-dependent transverse field Ising Hamiltonian. Incorporating only basic error mitigation and suppression methods, our study shows reliable control up to a two-qubit gate depth of 28, featuring a maximum of 1396 two-qubit gates, before noise becomes prevalent. These results are transferable to applications such as Hamiltonian simulation, variational algorithms, optimization, or quantum machine learning. We demonstrate this on the example of digitized quantum annealing for optimization and identify an optimal working point in terms of both circuit depth and time step on a 133-site optimization problem. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.08053v2-abstract-full').style.display = 'none'; document.getElementById('2404.08053v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 4 pages appendix, 10 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> PRX Quantum 5 (4), 040320 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.07964">arXiv:2308.07964</a> <span> [<a href="https://arxiv.org/pdf/2308.07964">pdf</a>, <a href="https://arxiv.org/format/2308.07964">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/5.0173591">10.1063/5.0173591 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum computing for chemistry and physics applications from a Monte Carlo perspective </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.07964v3-abstract-short" style="display: inline;"> This Perspective focuses on the several overlaps between quantum algorithms and Monte Carlo methods in the domains of physics and chemistry. We will analyze the challenges and possibilities of integrating established quantum Monte Carlo solutions in quantum algorithms. These include refined energy estimators, parameter optimization, real and imaginary-time dynamics, and variational circuits. Conve… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.07964v3-abstract-full').style.display = 'inline'; document.getElementById('2308.07964v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.07964v3-abstract-full" style="display: none;"> This Perspective focuses on the several overlaps between quantum algorithms and Monte Carlo methods in the domains of physics and chemistry. We will analyze the challenges and possibilities of integrating established quantum Monte Carlo solutions in quantum algorithms. These include refined energy estimators, parameter optimization, real and imaginary-time dynamics, and variational circuits. Conversely, we will review new ideas in utilizing quantum hardware to accelerate the sampling in statistical classical models, with applications in physics, chemistry, optimization, and machine learning. This review aims to be accessible to both communities and intends to foster further algorithmic developments at the intersection of quantum computing and Monte Carlo methods. Most of the works discussed in this Perspective have emerged within the last two years, indicating a rapidly growing interest in this promising area of research. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.07964v3-abstract-full').style.display = 'none'; document.getElementById('2308.07964v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">18 pages, 3 figures. Added new references, fixed some typos</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> J. Chem. Phys. 160, 010901 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.00044">arXiv:2308.00044</a> <span> [<a href="https://arxiv.org/pdf/2308.00044">pdf</a>, <a href="https://arxiv.org/format/2308.00044">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Other Condensed Matter">cond-mat.other</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.109.032408">10.1103/PhysRevA.109.032408 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Challenges of variational quantum optimization with measurement shot noise </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Scriva%2C+G">Giuseppe Scriva</a>, <a href="/search/cond-mat?searchtype=author&query=Astrakhantsev%2C+N">Nikita Astrakhantsev</a>, <a href="/search/cond-mat?searchtype=author&query=Pilati%2C+S">Sebastiano Pilati</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.00044v2-abstract-short" style="display: inline;"> Quantum enhanced optimization of classical cost functions is a central theme of quantum computing due to its high potential value in science and technology. The variational quantum eigensolver (VQE) and the quantum approximate optimization algorithm (QAOA) are popular variational approaches that are considered the most viable solutions in the noisy-intermediate scale quantum (NISQ) era. Here, we s… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.00044v2-abstract-full').style.display = 'inline'; document.getElementById('2308.00044v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.00044v2-abstract-full" style="display: none;"> Quantum enhanced optimization of classical cost functions is a central theme of quantum computing due to its high potential value in science and technology. The variational quantum eigensolver (VQE) and the quantum approximate optimization algorithm (QAOA) are popular variational approaches that are considered the most viable solutions in the noisy-intermediate scale quantum (NISQ) era. Here, we study the scaling of the quantum resources, defined as the required number of circuit repetitions, to reach a fixed success probability as the problem size increases, focusing on the role played by measurement shot noise, which is unavoidable in realistic implementations. Simple and reproducible problem instances are addressed, namely, the ferromagnetic and disordered Ising chains. Our results show that: (i) VQE with the standard heuristic ansatz scales comparably to direct brute-force search when energy-based optimizers are employed. The performance improves at most quadratically using a gradient-based optimizer. (ii) When the parameters are optimized from random guesses, also the scaling of QAOA implies problematically long absolute runtimes for large problem sizes. (iii) QAOA becomes practical when supplemented with a physically-inspired initialization of the parameters. Our results suggest that hybrid quantum-classical algorithms should possibly avoid a brute force classical outer loop, but focus on smart parameters initialization. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.00044v2-abstract-full').style.display = 'none'; document.getElementById('2308.00044v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 31 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 11 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 109, 032408 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2305.14162">arXiv:2305.14162</a> <span> [<a href="https://arxiv.org/pdf/2305.14162">pdf</a>, <a href="https://arxiv.org/format/2305.14162">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevB.108.104417">10.1103/PhysRevB.108.104417 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Jastrow wave function for the spin-1 Heisenberg chain: the string order revealed by the mapping to the classical Coulomb gas </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Piccioni%2C+D">Davide Piccioni</a>, <a href="/search/cond-mat?searchtype=author&query=Apostoli%2C+C">Christian Apostoli</a>, <a href="/search/cond-mat?searchtype=author&query=Becca%2C+F">Federico Becca</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Parola%2C+A">Alberto Parola</a>, <a href="/search/cond-mat?searchtype=author&query=Sorella%2C+S">Sandro Sorella</a>, <a href="/search/cond-mat?searchtype=author&query=Santoro%2C+G+E">Giuseppe E. Santoro</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2305.14162v1-abstract-short" style="display: inline;"> We show that a two-body Jastrow wave function is able to capture the ground-state properties of the $S=1$ antiferromagnetic Heisenberg chain with the single-ion anisotropy term, in both the topological and trivial phases. Here, the optimized Jastrow pseudo potential assumes a very simple form in Fourier space, i.e., $v_{q} \approx 1/q^2$, which is able to give rise to a finite string-order paramet… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.14162v1-abstract-full').style.display = 'inline'; document.getElementById('2305.14162v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2305.14162v1-abstract-full" style="display: none;"> We show that a two-body Jastrow wave function is able to capture the ground-state properties of the $S=1$ antiferromagnetic Heisenberg chain with the single-ion anisotropy term, in both the topological and trivial phases. Here, the optimized Jastrow pseudo potential assumes a very simple form in Fourier space, i.e., $v_{q} \approx 1/q^2$, which is able to give rise to a finite string-order parameter in the topological regime. The results are analysed by using an exact mapping from the quantum expectation values over the variational state to the classical partition function of the one-dimensional Coulomb gas of particles with charge $q=\pm 1$. Here, two phases are present at low temperatures: the first one is a diluted gas of dipoles (bound states of particles with opposite charges), which are randomly oriented (describing the trivial phase); the other one is a dense liquid of dipoles, which are aligned thanks to the residual dipole-dipole interactions (describing the topological phase, with the finite string order being related to the dipole alignment). Our results provide an insightful interpretation of the ground-state nature of the spin-1 antiferromagnetic Heisenberg model. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.14162v1-abstract-full').style.display = 'none'; document.getElementById('2305.14162v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. B 108, 104417 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2302.04919">arXiv:2302.04919</a> <span> [<a href="https://arxiv.org/pdf/2302.04919">pdf</a>, <a href="https://arxiv.org/format/2302.04919">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1126/science.adg9774">10.1126/science.adg9774 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Variational Benchmarks for Quantum Many-Body Problems </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Wu%2C+D">Dian Wu</a>, <a href="/search/cond-mat?searchtype=author&query=Rossi%2C+R">Riccardo Rossi</a>, <a href="/search/cond-mat?searchtype=author&query=Vicentini%2C+F">Filippo Vicentini</a>, <a href="/search/cond-mat?searchtype=author&query=Astrakhantsev%2C+N">Nikita Astrakhantsev</a>, <a href="/search/cond-mat?searchtype=author&query=Becca%2C+F">Federico Becca</a>, <a href="/search/cond-mat?searchtype=author&query=Cao%2C+X">Xiaodong Cao</a>, <a href="/search/cond-mat?searchtype=author&query=Carrasquilla%2C+J">Juan Carrasquilla</a>, <a href="/search/cond-mat?searchtype=author&query=Ferrari%2C+F">Francesco Ferrari</a>, <a href="/search/cond-mat?searchtype=author&query=Georges%2C+A">Antoine Georges</a>, <a href="/search/cond-mat?searchtype=author&query=Hibat-Allah%2C+M">Mohamed Hibat-Allah</a>, <a href="/search/cond-mat?searchtype=author&query=Imada%2C+M">Masatoshi Imada</a>, <a href="/search/cond-mat?searchtype=author&query=L%C3%A4uchli%2C+A+M">Andreas M. L盲uchli</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Mezzacapo%2C+A">Antonio Mezzacapo</a>, <a href="/search/cond-mat?searchtype=author&query=Millis%2C+A">Andrew Millis</a>, <a href="/search/cond-mat?searchtype=author&query=Moreno%2C+J+R">Javier Robledo Moreno</a>, <a href="/search/cond-mat?searchtype=author&query=Neupert%2C+T">Titus Neupert</a>, <a href="/search/cond-mat?searchtype=author&query=Nomura%2C+Y">Yusuke Nomura</a>, <a href="/search/cond-mat?searchtype=author&query=Nys%2C+J">Jannes Nys</a>, <a href="/search/cond-mat?searchtype=author&query=Parcollet%2C+O">Olivier Parcollet</a>, <a href="/search/cond-mat?searchtype=author&query=Pohle%2C+R">Rico Pohle</a>, <a href="/search/cond-mat?searchtype=author&query=Romero%2C+I">Imelda Romero</a>, <a href="/search/cond-mat?searchtype=author&query=Schmid%2C+M">Michael Schmid</a>, <a href="/search/cond-mat?searchtype=author&query=Silvester%2C+J+M">J. Maxwell Silvester</a>, <a href="/search/cond-mat?searchtype=author&query=Sorella%2C+S">Sandro Sorella</a> , et al. (8 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2302.04919v2-abstract-short" style="display: inline;"> The continued development of computational approaches to many-body ground-state problems in physics and chemistry calls for a consistent way to assess its overall progress. In this work, we introduce a metric of variational accuracy, the V-score, obtained from the variational energy and its variance. We provide an extensive curated dataset of variational calculations of many-body quantum systems,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.04919v2-abstract-full').style.display = 'inline'; document.getElementById('2302.04919v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.04919v2-abstract-full" style="display: none;"> The continued development of computational approaches to many-body ground-state problems in physics and chemistry calls for a consistent way to assess its overall progress. In this work, we introduce a metric of variational accuracy, the V-score, obtained from the variational energy and its variance. We provide an extensive curated dataset of variational calculations of many-body quantum systems, identifying cases where state-of-the-art numerical approaches show limited accuracy, and future algorithms or computational platforms, such as quantum computing, could provide improved accuracy. The V-score can be used as a metric to assess the progress of quantum variational methods toward a quantum advantage for ground-state problems, especially in regimes where classical verifiability is impossible. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.04919v2-abstract-full').style.display = 'none'; document.getElementById('2302.04919v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">27 pages, 6 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Science 386, 296-301 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.09203">arXiv:2205.09203</a> <span> [<a href="https://arxiv.org/pdf/2205.09203">pdf</a>, <a href="https://arxiv.org/format/2205.09203">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> </div> </div> <p class="title is-5 mathjax"> Exponential challenges in unbiasing quantum Monte Carlo algorithms with quantum computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Carleo%2C+G">Giuseppe Carleo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2205.09203v1-abstract-short" style="display: inline;"> Recently, Huggins et. al. [Nature, 603, 416-420 (2022)] devised a general projective Quantum Monte Carlo method suitable for implementation on quantum computers. This hybrid approach, however, relies on a subroutine -the computation of the local energy estimator on the quantum computer -that is intrinsically affected by an exponential scaling of the computational time with the number of qubits. By… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.09203v1-abstract-full').style.display = 'inline'; document.getElementById('2205.09203v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.09203v1-abstract-full" style="display: none;"> Recently, Huggins et. al. [Nature, 603, 416-420 (2022)] devised a general projective Quantum Monte Carlo method suitable for implementation on quantum computers. This hybrid approach, however, relies on a subroutine -the computation of the local energy estimator on the quantum computer -that is intrinsically affected by an exponential scaling of the computational time with the number of qubits. By means of numerical experiments, we show that this exponential scaling manifests prominently already on systems below the point of "quantum advantage". For the prototypical transverse-field Ising model, we show that the required time resources to compete with classical simulations on around 40 qubits are already of the order of $10^{13}$ projective measurements, with an estimated running time of a few thousand years on superconducting hardware. These observations strongly suggest that the proposed hybrid method, in its present form, is unlikely to offer a sizeable advantage over conventional quantum Monte Carlo approaches. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.09203v1-abstract-full').style.display = 'none'; document.getElementById('2205.09203v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.06278">arXiv:2205.06278</a> <span> [<a href="https://arxiv.org/pdf/2205.06278">pdf</a>, <a href="https://arxiv.org/format/2205.06278">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> </div> </div> <p class="title is-5 mathjax"> Phenomenological Theory of Variational Quantum Ground-State Preparation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Astrakhantsev%2C+N">Nikita Astrakhantsev</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Tavernelli%2C+I">Ivano Tavernelli</a>, <a href="/search/cond-mat?searchtype=author&query=Carleo%2C+G">Giuseppe Carleo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2205.06278v4-abstract-short" style="display: inline;"> The variational approach is a cornerstone of computational physics, considering both conventional and quantum computing computational platforms. The variational quantum eigensolver (VQE) algorithm aims to prepare the ground state of a Hamiltonian exploiting parametrized quantum circuits that may offer an advantage compared to classical trial states used, for instance, in quantum Monte Carlo or ten… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.06278v4-abstract-full').style.display = 'inline'; document.getElementById('2205.06278v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.06278v4-abstract-full" style="display: none;"> The variational approach is a cornerstone of computational physics, considering both conventional and quantum computing computational platforms. The variational quantum eigensolver (VQE) algorithm aims to prepare the ground state of a Hamiltonian exploiting parametrized quantum circuits that may offer an advantage compared to classical trial states used, for instance, in quantum Monte Carlo or tensor network calculations. While traditionally, the main focus has been on developing better trial circuits, we show that the algorithm's success crucially depends on other parameters such as the learning rate, the number $N_s$ of measurements to estimate the gradient components, and the Hamiltonian gap $螖$. We first observe the existence of a finite $N_s$ value below which the optimization is impossible, and the energy variance resembles the behavior of the specific heat in second-order phase transitions. Secondly, when $N_s$ is above such threshold level, and learning is possible, we develop a phenomenological model that relates the fidelity of the state preparation with the optimization hyperparameters as well as $螖$. More specifically, we observe that the computational resources scale as $1/螖^2$, and we propose a symmetry-enhanced simulation protocol that should be used if the gap closes. We test our understanding on several instances of two-dimensional frustrated quantum magnets, which are believed to be the most promising candidates for near-term quantum advantage through variational quantum simulations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.06278v4-abstract-full').style.display = 'none'; document.getElementById('2205.06278v4-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 December, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 13 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2203.12497">arXiv:2203.12497</a> <span> [<a href="https://arxiv.org/pdf/2203.12497">pdf</a>, <a href="https://arxiv.org/format/2203.12497">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Disordered Systems and Neural Networks">cond-mat.dis-nn</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Machine Learning">cs.LG</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41586-023-06095-4">10.1038/s41586-023-06095-4 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum-enhanced Markov chain Monte Carlo </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Layden%2C+D">David Layden</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Mishmash%2C+R+V">Ryan V. Mishmash</a>, <a href="/search/cond-mat?searchtype=author&query=Motta%2C+M">Mario Motta</a>, <a href="/search/cond-mat?searchtype=author&query=Wocjan%2C+P">Pawel Wocjan</a>, <a href="/search/cond-mat?searchtype=author&query=Kim%2C+J">Jin-Sung Kim</a>, <a href="/search/cond-mat?searchtype=author&query=Sheldon%2C+S">Sarah Sheldon</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2203.12497v1-abstract-short" style="display: inline;"> Sampling from complicated probability distributions is a hard computational problem arising in many fields, including statistical physics, optimization, and machine learning. Quantum computers have recently been used to sample from complicated distributions that are hard to sample from classically, but which seldom arise in applications. Here we introduce a quantum algorithm to sample from distrib… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.12497v1-abstract-full').style.display = 'inline'; document.getElementById('2203.12497v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2203.12497v1-abstract-full" style="display: none;"> Sampling from complicated probability distributions is a hard computational problem arising in many fields, including statistical physics, optimization, and machine learning. Quantum computers have recently been used to sample from complicated distributions that are hard to sample from classically, but which seldom arise in applications. Here we introduce a quantum algorithm to sample from distributions that pose a bottleneck in several applications, which we implement on a superconducting quantum processor. The algorithm performs Markov chain Monte Carlo (MCMC), a popular iterative sampling technique, to sample from the Boltzmann distribution of classical Ising models. In each step, the quantum processor explores the model in superposition to propose a random move, which is then accepted or rejected by a classical computer and returned to the quantum processor, ensuring convergence to the desired Boltzmann distribution. We find that this quantum algorithm converges in fewer iterations than common classical MCMC alternatives on relevant problem instances, both in simulations and experiments. It therefore opens a new path for quantum computers to solve useful--not merely difficult--problems in the near term. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.12497v1-abstract-full').style.display = 'none'; document.getElementById('2203.12497v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature 619, 282-287 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2203.07219">arXiv:2203.07219</a> <span> [<a href="https://arxiv.org/pdf/2203.07219">pdf</a>, <a href="https://arxiv.org/format/2203.07219">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/5.0099469">10.1063/5.0099469 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Extending the reach of quantum computing for materials science with machine learning potentials </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Schuhmacher%2C+J">Julian Schuhmacher</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Tacchino%2C+F">Francesco Tacchino</a>, <a href="/search/cond-mat?searchtype=author&query=Dmitriyeva%2C+O">Olga Dmitriyeva</a>, <a href="/search/cond-mat?searchtype=author&query=Bui%2C+T">Tai Bui</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+S">Shanshan Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Tavernelli%2C+I">Ivano Tavernelli</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2203.07219v1-abstract-short" style="display: inline;"> Solving electronic structure problems represents a promising field of application for quantum computers. Currently, much effort has been spent in devising and optimizing quantum algorithms for quantum chemistry problems featuring up to hundreds of electrons. While quantum algorithms can in principle outperform their classical equivalents, the polynomially scaling runtime, with the number of consti… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.07219v1-abstract-full').style.display = 'inline'; document.getElementById('2203.07219v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2203.07219v1-abstract-full" style="display: none;"> Solving electronic structure problems represents a promising field of application for quantum computers. Currently, much effort has been spent in devising and optimizing quantum algorithms for quantum chemistry problems featuring up to hundreds of electrons. While quantum algorithms can in principle outperform their classical equivalents, the polynomially scaling runtime, with the number of constituents, can still prevent quantum simulations of large scale systems. We propose a strategy to extend the scope of quantum computational methods to large scale simulations using a machine learning potential, trained on quantum simulation data. The challenge of applying machine learning potentials in today's quantum setting arises from the several sources of noise affecting the quantum computations of electronic energies and forces. We investigate the trainability of a machine learning potential selecting various sources of noise: statistical, optimization and hardware noise.Finally, we construct the first machine learning potential from data computed on actual IBM Quantum processors for a hydrogen molecule. This already would allow us to perform arbitrarily long and stable molecular dynamics simulations, outperforming all current quantum approaches to molecular dynamics and structure optimization. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.07219v1-abstract-full').style.display = 'none'; document.getElementById('2203.07219v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> AIP Advances 12, 115321 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2108.11410">arXiv:2108.11410</a> <span> [<a href="https://arxiv.org/pdf/2108.11410">pdf</a>, <a href="https://arxiv.org/format/2108.11410">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.104.022431">10.1103/PhysRevA.104.022431 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Sampling, rates, and reaction currents through reverse stochastic quantization on quantum computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2108.11410v1-abstract-short" style="display: inline;"> The quest for improved sampling methods to solve statistical mechanics problems of physical and chemical interest proceeds with renewed efforts since the invention of the Metropolis algorithm, in 1953. In particular, the understanding of thermally activated rare-event processes between long-lived metastable states, such as protein folding, is still elusive. In this case, one needs both the finite-… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.11410v1-abstract-full').style.display = 'inline'; document.getElementById('2108.11410v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2108.11410v1-abstract-full" style="display: none;"> The quest for improved sampling methods to solve statistical mechanics problems of physical and chemical interest proceeds with renewed efforts since the invention of the Metropolis algorithm, in 1953. In particular, the understanding of thermally activated rare-event processes between long-lived metastable states, such as protein folding, is still elusive. In this case, one needs both the finite-temperature canonical distribution function and the reaction current between the reactant and product states, to completely characterize the dynamic. Here we show how to tackle this problem using a quantum computer. We use the connection between a classical stochastic dynamics and the Schroedinger equation, also known as stochastic quantization, to variationally prepare quantum states allowing us to unbiasedly sample from a Boltzmann distribution. Similarly, reaction rate constants can be computed as ground state energies of suitably transformed operators, following the supersymmetric extension of the formalism. Finally, we propose a hybrid quantum-classical sampling scheme to escape local minima, and explore the configuration space in both real-space and spin hamiltonians. We indicate how to realize the quantum algorithms constructively, without assuming the existence of oracles, or quantum walk operators. The quantum advantage concerning the above applications is discussed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.11410v1-abstract-full').style.display = 'none'; document.getElementById('2108.11410v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 August, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Original submission date to the journal 12 April 2021</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> PRA, 104, 022431 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2005.10271">arXiv:2005.10271</a> <span> [<a href="https://arxiv.org/pdf/2005.10271">pdf</a>, <a href="https://arxiv.org/format/2005.10271">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Lattice">hep-lat</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.102.094501">10.1103/PhysRevD.102.094501 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Toward scalable simulations of Lattice Gauge Theories on quantum computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mathis%2C+S+V">Simon V. Mathis</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Tavernelli%2C+I">Ivano Tavernelli</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2005.10271v1-abstract-short" style="display: inline;"> The simulation of real-time dynamics in lattice gauge theories is particularly hard for classical computing due to the exponential scaling of the required resources. On the other hand, quantum algorithms can potentially perform the same calculation with a polynomial dependence on the number of degrees of freedom. A precise estimation is however particularly challenging for the simulation of lattic… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.10271v1-abstract-full').style.display = 'inline'; document.getElementById('2005.10271v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2005.10271v1-abstract-full" style="display: none;"> The simulation of real-time dynamics in lattice gauge theories is particularly hard for classical computing due to the exponential scaling of the required resources. On the other hand, quantum algorithms can potentially perform the same calculation with a polynomial dependence on the number of degrees of freedom. A precise estimation is however particularly challenging for the simulation of lattice gauge theories in arbitrary dimensions, where, gauge fields are dynamical variables, in addition to the particle fields. Moreover, there exist several choices for discretizing particles and gauge fields on a lattice, each of them coming at different prices in terms of qubit register size and circuit depth. Here we provide a resource counting for real-time evolution of $U(1)$ gauge theories, such as Quantum Electrodynamics, on arbitrary dimension using the Wilson fermion representation for the particles, and the Quantum Link Model approach for the gauge fields. We study the phenomena of flux-string breaking up to a genuine bi-dimensional model using classical simulations of the quantum circuits, and discuss the advantages of our discretization choice in simulation of more challenging $SU(N)$ gauge theories such as Quantum Chromodynamics. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.10271v1-abstract-full').style.display = 'none'; document.getElementById('2005.10271v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 May, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages, 14 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 102, 094501 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2002.07401">arXiv:2002.07401</a> <span> [<a href="https://arxiv.org/pdf/2002.07401">pdf</a>, <a href="https://arxiv.org/ps/2002.07401">ps</a>, <a href="https://arxiv.org/format/2002.07401">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/5.0005037">10.1063/5.0005037 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> TurboRVB: a many-body toolkit for {\it ab initio} electronic simulations by quantum Monte Carlo </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Nakano%2C+K">Kousuke Nakano</a>, <a href="/search/cond-mat?searchtype=author&query=Attaccalite%2C+C">Claudio Attaccalite</a>, <a href="/search/cond-mat?searchtype=author&query=Barborini%2C+M">Matteo Barborini</a>, <a href="/search/cond-mat?searchtype=author&query=Capriotti%2C+L">Luca Capriotti</a>, <a href="/search/cond-mat?searchtype=author&query=Casula%2C+M">Michele Casula</a>, <a href="/search/cond-mat?searchtype=author&query=Coccia%2C+E">Emanuele Coccia</a>, <a href="/search/cond-mat?searchtype=author&query=Dagrada%2C+M">Mario Dagrada</a>, <a href="/search/cond-mat?searchtype=author&query=Genovese%2C+C">Claudio Genovese</a>, <a href="/search/cond-mat?searchtype=author&query=Luo%2C+Y">Ye Luo</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Zen%2C+A">Andrea Zen</a>, <a href="/search/cond-mat?searchtype=author&query=Sorella%2C+S">Sandro Sorella</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2002.07401v2-abstract-short" style="display: inline;"> TurboRVB is a computational package for {\it ab initio} Quantum Monte Carlo (QMC) simulations of both molecular and bulk electronic systems. The code implements two types of well established QMC algorithms: Variational Monte Carlo (VMC), and Diffusion Monte Carlo in its robust and efficient lattice regularized variant. A key feature of the code is the possibility of using strongly correlated many-… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.07401v2-abstract-full').style.display = 'inline'; document.getElementById('2002.07401v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2002.07401v2-abstract-full" style="display: none;"> TurboRVB is a computational package for {\it ab initio} Quantum Monte Carlo (QMC) simulations of both molecular and bulk electronic systems. The code implements two types of well established QMC algorithms: Variational Monte Carlo (VMC), and Diffusion Monte Carlo in its robust and efficient lattice regularized variant. A key feature of the code is the possibility of using strongly correlated many-body wave functions. The electronic wave function (WF) is obtained by applying a Jastrow factor, which takes into account dynamical correlations, to the most general mean-field ground state, written either as an antisymmetrized geminal product with spin-singlet pairing, or as a Pfaffian, including both singlet and triplet correlations. This wave function can be viewed as an efficient implementation of the so-called resonating valence bond (RVB) ansatz, first proposed by L. Pauling and P. W. Anderson in quantum chemistry and condensed matter physics, respectively. The RVB ansatz implemented in TurboRVB has a large variational freedom, including the Jastrow correlated Slater determinant as its simplest, but nontrivial case. Moreover, it has the remarkable advantage of remaining with an affordable computational cost, proportional to the one spent for the evaluation of a single Slater determinant. The code implements the adjoint algorithmic differentiation that enables a very efficient evaluation of energy derivatives, comprising the ionic forces. Thus, one can perform structural optimizations and molecular dynamics in the canonical NVT ensemble at the VMC level. For the electronic part, a full WF optimization is made possible thanks to state-of-the-art stochastic algorithms for energy minimization. The code has been efficiently parallelized by using a hybrid MPI-OpenMP protocol, that is also an ideal environment for exploiting the computational power of modern GPU accelerators. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.07401v2-abstract-full').style.display = 'none'; document.getElementById('2002.07401v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 June, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 February, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">41 pages, 21 figures, 3 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> J. Chem. Phys. 152, 204121 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1910.07596">arXiv:1910.07596</a> <span> [<a href="https://arxiv.org/pdf/1910.07596">pdf</a>, <a href="https://arxiv.org/format/1910.07596">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Disordered Systems and Neural Networks">cond-mat.dis-nn</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.2.022060">10.1103/PhysRevResearch.2.022060 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Precise measurement of quantum observables with neural-network estimators </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Torlai%2C+G">Giacomo Torlai</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Carleo%2C+G">Giuseppe Carleo</a>, <a href="/search/cond-mat?searchtype=author&query=Mezzacapo%2C+A">Antonio Mezzacapo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1910.07596v1-abstract-short" style="display: inline;"> The measurement precision of modern quantum simulators is intrinsically constrained by the limited set of measurements that can be efficiently implemented on hardware. This fundamental limitation is particularly severe for quantum algorithms where complex quantum observables are to be precisely evaluated. To achieve precise estimates with current methods, prohibitively large amounts of sample stat… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1910.07596v1-abstract-full').style.display = 'inline'; document.getElementById('1910.07596v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1910.07596v1-abstract-full" style="display: none;"> The measurement precision of modern quantum simulators is intrinsically constrained by the limited set of measurements that can be efficiently implemented on hardware. This fundamental limitation is particularly severe for quantum algorithms where complex quantum observables are to be precisely evaluated. To achieve precise estimates with current methods, prohibitively large amounts of sample statistics are required in experiments. Here, we propose to reduce the measurement overhead by integrating artificial neural networks with quantum simulation platforms. We show that unsupervised learning of single-qubit data allows the trained networks to accommodate measurements of complex observables, otherwise costly using traditional post-processing techniques. The effectiveness of this hybrid measurement protocol is demonstrated for quantum chemistry Hamiltonians using both synthetic and experimental data. Neural-network estimators attain high-precision measurements with a drastic reduction in the amount of sample statistics, without requiring additional quantum resources. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1910.07596v1-abstract-full').style.display = 'none'; document.getElementById('1910.07596v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 October, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 5 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Research 2, 022060 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1910.01830">arXiv:1910.01830</a> <span> [<a href="https://arxiv.org/pdf/1910.01830">pdf</a>, <a href="https://arxiv.org/format/1910.01830">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevLett.123.130501">10.1103/PhysRevLett.123.130501 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Non-unitary operations for ground-state calculations in near term quantum computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Ollitrault%2C+P">Pauline Ollitrault</a>, <a href="/search/cond-mat?searchtype=author&query=Barkoutsos%2C+P">Panagiotis Barkoutsos</a>, <a href="/search/cond-mat?searchtype=author&query=Tavernelli%2C+I">Ivano Tavernelli</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1910.01830v1-abstract-short" style="display: inline;"> We introduce a quantum Monte Carlo inspired reweighting scheme to accurately compute energies from optimally short quantum circuits. This effectively hybrid quantum-classical approach features both entanglement provided by a short quantum circuit, and the presence of an effective non-unitary operator at the same time. The functional form of this projector is borrowed from classical computation and… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1910.01830v1-abstract-full').style.display = 'inline'; document.getElementById('1910.01830v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1910.01830v1-abstract-full" style="display: none;"> We introduce a quantum Monte Carlo inspired reweighting scheme to accurately compute energies from optimally short quantum circuits. This effectively hybrid quantum-classical approach features both entanglement provided by a short quantum circuit, and the presence of an effective non-unitary operator at the same time. The functional form of this projector is borrowed from classical computation and is able to filter-out high-energy components generated by a sub-optimal variational quantum heuristic ansatz. The accuracy of this approach is demonstrated numerically in finding energies of entangled ground-states of many-body lattice models. We demonstrate a practical implementation on IBM quantum hardwares up to an 8 qubits circuit. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1910.01830v1-abstract-full').style.display = 'none'; document.getElementById('1910.01830v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 October, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages + supplementary materials</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Lett. 123, 130501 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1906.03341">arXiv:1906.03341</a> <span> [<a href="https://arxiv.org/pdf/1906.03341">pdf</a>, <a href="https://arxiv.org/format/1906.03341">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41586-020-2677-y">10.1038/s41586-020-2677-y <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Evidence for supercritical behavior of high-pressure liquid hydrogen </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Cheng%2C+B">Bingqing Cheng</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Ceriotti%2C+M">Michele Ceriotti</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1906.03341v1-abstract-short" style="display: inline;"> Hydrogen exhibits unusual behaviors at megabar pressures, with consequences for planetary science, condensed matter physics and materials science. Experiments at such extreme conditions are challenging, often resulting in hard-to-interpret and controversial observations. We present a theoretical study of the phase diagram of dense hydrogen, using machine learning to overcome time and length scale… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.03341v1-abstract-full').style.display = 'inline'; document.getElementById('1906.03341v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1906.03341v1-abstract-full" style="display: none;"> Hydrogen exhibits unusual behaviors at megabar pressures, with consequences for planetary science, condensed matter physics and materials science. Experiments at such extreme conditions are challenging, often resulting in hard-to-interpret and controversial observations. We present a theoretical study of the phase diagram of dense hydrogen, using machine learning to overcome time and length scale limitations while describing accurately interatomic forces. We reproduce the re-entrant melting behavior and the polymorphism of the solid phase. In simulations based on the machine learning potential we find evidence for continuous metallization in the liquid, as a first-order liquid-liquid transition is pre-empted by freezing. This suggests a smooth transition between insulating and metallic layers in giant gas planets, and reconciles existing discrepancies between experiments as a manifestation of supercritical behavior. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.03341v1-abstract-full').style.display = 'none'; document.getElementById('1906.03341v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 7 June, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2019. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1904.00031">arXiv:1904.00031</a> <span> [<a href="https://arxiv.org/pdf/1904.00031">pdf</a>, <a href="https://arxiv.org/format/1904.00031">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Disordered Systems and Neural Networks">cond-mat.dis-nn</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Data Analysis, Statistics and Probability">physics.data-an</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1016/j.softx.2019.100311">10.1016/j.softx.2019.100311 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> NetKet: A Machine Learning Toolkit for Many-Body Quantum Systems </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Carleo%2C+G">Giuseppe Carleo</a>, <a href="/search/cond-mat?searchtype=author&query=Choo%2C+K">Kenny Choo</a>, <a href="/search/cond-mat?searchtype=author&query=Hofmann%2C+D">Damian Hofmann</a>, <a href="/search/cond-mat?searchtype=author&query=Smith%2C+J+E+T">James E. T. Smith</a>, <a href="/search/cond-mat?searchtype=author&query=Westerhout%2C+T">Tom Westerhout</a>, <a href="/search/cond-mat?searchtype=author&query=Alet%2C+F">Fabien Alet</a>, <a href="/search/cond-mat?searchtype=author&query=Davis%2C+E+J">Emily J. Davis</a>, <a href="/search/cond-mat?searchtype=author&query=Efthymiou%2C+S">Stavros Efthymiou</a>, <a href="/search/cond-mat?searchtype=author&query=Glasser%2C+I">Ivan Glasser</a>, <a href="/search/cond-mat?searchtype=author&query=Lin%2C+S">Sheng-Hsuan Lin</a>, <a href="/search/cond-mat?searchtype=author&query=Mauri%2C+M">Marta Mauri</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Mendl%2C+C+B">Christian B. Mendl</a>, <a href="/search/cond-mat?searchtype=author&query=van+Nieuwenburg%2C+E">Evert van Nieuwenburg</a>, <a href="/search/cond-mat?searchtype=author&query=O%27Reilly%2C+O">Ossian O'Reilly</a>, <a href="/search/cond-mat?searchtype=author&query=Th%C3%A9veniaut%2C+H">Hugo Th茅veniaut</a>, <a href="/search/cond-mat?searchtype=author&query=Torlai%2C+G">Giacomo Torlai</a>, <a href="/search/cond-mat?searchtype=author&query=Wietek%2C+A">Alexander Wietek</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1904.00031v1-abstract-short" style="display: inline;"> We introduce NetKet, a comprehensive open source framework for the study of many-body quantum systems using machine learning techniques. The framework is built around a general and flexible implementation of neural-network quantum states, which are used as a variational ansatz for quantum wave functions. NetKet provides algorithms for several key tasks in quantum many-body physics and quantum tech… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1904.00031v1-abstract-full').style.display = 'inline'; document.getElementById('1904.00031v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1904.00031v1-abstract-full" style="display: none;"> We introduce NetKet, a comprehensive open source framework for the study of many-body quantum systems using machine learning techniques. The framework is built around a general and flexible implementation of neural-network quantum states, which are used as a variational ansatz for quantum wave functions. NetKet provides algorithms for several key tasks in quantum many-body physics and quantum technology, namely quantum state tomography, supervised learning from wave-function data, and ground state searches for a wide range of customizable lattice models. Our aim is to provide a common platform for open research and to stimulate the collaborative development of computational methods at the interface of machine learning and many-body physics. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1904.00031v1-abstract-full').style.display = 'none'; document.getElementById('1904.00031v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 March, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> SoftwareX 10, 100311 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1806.06081">arXiv:1806.06081</a> <span> [<a href="https://arxiv.org/pdf/1806.06081">pdf</a>, <a href="https://arxiv.org/format/1806.06081">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Disordered Systems and Neural Networks">cond-mat.dis-nn</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.100.030303">10.1103/PhysRevA.100.030303 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Uncertain fate of fair sampling in quantum annealing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=K%C3%B6nz%2C+M+S">Mario S. K枚nz</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Ochoa%2C+A+J">Andrew J. Ochoa</a>, <a href="/search/cond-mat?searchtype=author&query=Katzgraber%2C+H+G">Helmut G. Katzgraber</a>, <a href="/search/cond-mat?searchtype=author&query=Troyer%2C+M">Matthias Troyer</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1806.06081v3-abstract-short" style="display: inline;"> Recently, it was demonstrated both theoretically and experimentally on the D-Wave quantum annealer that transverse-field quantum annealing does not find all ground states with equal probability. In particular, it was proposed that more complex driver Hamiltonians beyond transverse fields might mitigate this shortcoming. Here, we investigate the mechanisms of (un)fair sampling in quantum annealing.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.06081v3-abstract-full').style.display = 'inline'; document.getElementById('1806.06081v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1806.06081v3-abstract-full" style="display: none;"> Recently, it was demonstrated both theoretically and experimentally on the D-Wave quantum annealer that transverse-field quantum annealing does not find all ground states with equal probability. In particular, it was proposed that more complex driver Hamiltonians beyond transverse fields might mitigate this shortcoming. Here, we investigate the mechanisms of (un)fair sampling in quantum annealing. While higher-order terms can improve the sampling for selected small problems, we present multiple counterexamples where driver Hamiltonians that go beyond transverse fields do not remove the sampling bias. Using perturbation theory we explain why this is the case. In addition, we present large-scale quantum Monte Carlo simulations for spin glasses with known degeneracy in two space dimensions and demonstrate that the fair-sampling performance of quadratic driver terms is comparable to standard transverse-field drivers. Our results suggest that quantum annealing machines are not well suited for sampling applications, unless post-processing techniques to improve the sampling are applied. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.06081v3-abstract-full').style.display = 'none'; document.getElementById('1806.06081v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 September, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 June, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 5 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 100, 030303 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1709.08648">arXiv:1709.08648</a> <span> [<a href="https://arxiv.org/pdf/1709.08648">pdf</a>, <a href="https://arxiv.org/format/1709.08648">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevLett.120.025701">10.1103/PhysRevLett.120.025701 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Phase diagram of hydrogen and a hydrogen-helium mixture at planetary conditions by Quantum Monte Carlo simulations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Helled%2C+R">Ravit Helled</a>, <a href="/search/cond-mat?searchtype=author&query=Sorella%2C+S">Sandro Sorella</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1709.08648v2-abstract-short" style="display: inline;"> Understanding planetary interiors is directly linked to our ability of simulating exotic quantum mechanical systems such as hydrogen (H) and hydrogen-helium (H-He) mixtures at high pressures and temperatures. Equations of State (EOSs) tables based on Density Functional Theory (DFT), are commonly used by planetary scientists, although this method allows only for a qualitative description of the pha… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1709.08648v2-abstract-full').style.display = 'inline'; document.getElementById('1709.08648v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1709.08648v2-abstract-full" style="display: none;"> Understanding planetary interiors is directly linked to our ability of simulating exotic quantum mechanical systems such as hydrogen (H) and hydrogen-helium (H-He) mixtures at high pressures and temperatures. Equations of State (EOSs) tables based on Density Functional Theory (DFT), are commonly used by planetary scientists, although this method allows only for a qualitative description of the phase diagram, due to an incomplete treatment of electronic interactions. Here we report Quantum Monte Carlo (QMC) molecular dynamics simulations of pure H and H-He mixture. We calculate the first QMC EOS at 6000 K for an H-He mixture of a proto-solar composition, and show the crucial influence of He on the H metallization pressure. Our results can be used to calibrate other EOS calculations and are very timely given the accurate determination of Jupiter's gravitational field from the NASA Juno mission and the effort to determine its structure. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1709.08648v2-abstract-full').style.display = 'none'; document.getElementById('1709.08648v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 October, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 September, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages + supplementary methods and figures. Updated references</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Lett. 120, 025701 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1703.08189">arXiv:1703.08189</a> <span> [<a href="https://arxiv.org/pdf/1703.08189">pdf</a>, <a href="https://arxiv.org/format/1703.08189">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevB.96.134305">10.1103/PhysRevB.96.134305 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum Monte Carlo tunneling from quantum chemistry to quantum annealing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Smelyanskiy%2C+V+N">Vadim N. Smelyanskiy</a>, <a href="/search/cond-mat?searchtype=author&query=Troyer%2C+M">Matthias Troyer</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1703.08189v1-abstract-short" style="display: inline;"> Quantum Tunneling is ubiquitous across different fields, from quantum chemical reactions, and magnetic materials to quantum simulators and quantum computers. While simulating the real-time quantum dynamics of tunneling is infeasible for high-dimensional systems, quantum tunneling also shows up in quantum Monte Carlo (QMC) simulations that scale polynomially with system size. Here we extend a recen… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1703.08189v1-abstract-full').style.display = 'inline'; document.getElementById('1703.08189v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1703.08189v1-abstract-full" style="display: none;"> Quantum Tunneling is ubiquitous across different fields, from quantum chemical reactions, and magnetic materials to quantum simulators and quantum computers. While simulating the real-time quantum dynamics of tunneling is infeasible for high-dimensional systems, quantum tunneling also shows up in quantum Monte Carlo (QMC) simulations that scale polynomially with system size. Here we extend a recent results obtained for quantum spin models {[{Phys. Rev. Lett.} {\bf 117}, 180402 (2016)]}, and study high-dimensional continuos variable models for proton transfer reactions. We demonstrate that QMC simulations efficiently recover ground state tunneling rates due to the existence of an instanton path, which always connects the reactant state with the product. We discuss the implications of our results in the context of quantum chemical reactions and quantum annealing, where quantum tunneling is expected to be a valuable resource for solving combinatorial optimization problems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1703.08189v1-abstract-full').style.display = 'none'; document.getElementById('1703.08189v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 March, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. B 96, 134305 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1703.05334">arXiv:1703.05334</a> <span> [<a href="https://arxiv.org/pdf/1703.05334">pdf</a>, <a href="https://arxiv.org/format/1703.05334">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Disordered Systems and Neural Networks">cond-mat.dis-nn</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Gases">cond-mat.quant-gas</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41567-018-0048-5">10.1038/s41567-018-0048-5 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Many-body quantum state tomography with neural networks </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Torlai%2C+G">Giacomo Torlai</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Carrasquilla%2C+J">Juan Carrasquilla</a>, <a href="/search/cond-mat?searchtype=author&query=Troyer%2C+M">Matthias Troyer</a>, <a href="/search/cond-mat?searchtype=author&query=Melko%2C+R">Roger Melko</a>, <a href="/search/cond-mat?searchtype=author&query=Carleo%2C+G">Giuseppe Carleo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1703.05334v2-abstract-short" style="display: inline;"> The experimental realization of increasingly complex synthetic quantum systems calls for the development of general theoretical methods, to validate and fully exploit quantum resources. Quantum-state tomography (QST) aims at reconstructing the full quantum state from simple measurements, and therefore provides a key tool to obtain reliable analytics. Brute-force approaches to QST, however, demand… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1703.05334v2-abstract-full').style.display = 'inline'; document.getElementById('1703.05334v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1703.05334v2-abstract-full" style="display: none;"> The experimental realization of increasingly complex synthetic quantum systems calls for the development of general theoretical methods, to validate and fully exploit quantum resources. Quantum-state tomography (QST) aims at reconstructing the full quantum state from simple measurements, and therefore provides a key tool to obtain reliable analytics. Brute-force approaches to QST, however, demand resources growing exponentially with the number of constituents, making it unfeasible except for small systems. Here we show that machine learning techniques can be efficiently used for QST of highly-entangled states, in both one and two dimensions. Remarkably, the resulting approach allows one to reconstruct traditionally challenging many-body quantities - such as the entanglement entropy - from simple, experimentally accessible measurements. This approach can benefit existing and future generations of devices ranging from quantum computers to ultra-cold atom quantum simulators. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1703.05334v2-abstract-full').style.display = 'none'; document.getElementById('1703.05334v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 October, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 March, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Update version and method, now discussing how to reconstruct the complex amplitudes of the wave function</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Physics 14, 447-450 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1701.08775">arXiv:1701.08775</a> <span> [<a href="https://arxiv.org/pdf/1701.08775">pdf</a>, <a href="https://arxiv.org/format/1701.08775">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1742-5468/aa6de1">10.1088/1742-5468/aa6de1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum Monte Carlo Annealing with Multi-Spin Dynamics </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Troyer%2C+M">Matthias Troyer</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1701.08775v1-abstract-short" style="display: inline;"> We introduce a novel Simulated Quantum Annealing (SQA) algorithm which employs a multispin quantum fluctuation operator. At variance with the usual transverse field, short-range two-spin flip interactions are included in the driver Hamiltonian. A Quantum Monte Carlo algorithm, capable of efficiently simulating large disordered systems, is described and tested. A first application to SQA, on a rand… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.08775v1-abstract-full').style.display = 'inline'; document.getElementById('1701.08775v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1701.08775v1-abstract-full" style="display: none;"> We introduce a novel Simulated Quantum Annealing (SQA) algorithm which employs a multispin quantum fluctuation operator. At variance with the usual transverse field, short-range two-spin flip interactions are included in the driver Hamiltonian. A Quantum Monte Carlo algorithm, capable of efficiently simulating large disordered systems, is described and tested. A first application to SQA, on a random square lattice Ising spin glass reveals that the multi-spin driver Hamiltonian improves upon the usual transverse field. This work paves the way for more systematic investigations using multi-spin quantum fluctuations on a broader range of problems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.08775v1-abstract-full').style.display = 'none'; document.getElementById('1701.08775v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 January, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2017. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1605.08423">arXiv:1605.08423</a> <span> [<a href="https://arxiv.org/pdf/1605.08423">pdf</a>, <a href="https://arxiv.org/ps/1605.08423">ps</a>, <a href="https://arxiv.org/format/1605.08423">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevLett.118.015703">10.1103/PhysRevLett.118.015703 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Accelerated ab-initio Molecular Dynamics: probing the weak dispersive forces in dense liquid hydrogen </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Sorella%2C+S">Sandro Sorella</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1605.08423v2-abstract-short" style="display: inline;"> We propose an ab-initio molecular dynamics method, capable to reduce dramatically the autocorrelation time required for the simulation of classical and quantum particles at finite temperature. The method is based on an efficient implementation of a first order Langevin dynamics modified by means of a suitable, position dependent acceleration matrix $S$. Here we apply this technique, within a Qua… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1605.08423v2-abstract-full').style.display = 'inline'; document.getElementById('1605.08423v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1605.08423v2-abstract-full" style="display: none;"> We propose an ab-initio molecular dynamics method, capable to reduce dramatically the autocorrelation time required for the simulation of classical and quantum particles at finite temperature. The method is based on an efficient implementation of a first order Langevin dynamics modified by means of a suitable, position dependent acceleration matrix $S$. Here we apply this technique, within a Quantum Monte Carlo (QMC) based wavefuntion approach and within the Born-Oppheneimer approximation, for determining the phase diagram of high-pressure Hydrogen with simulations much longer than the autocorrelation time. With the proposed method, we are able to equilibrate in few hundreds steps even close to the liquid-liquid phase transition (LLT). Within our approach we find that the LLT transition is consistent with recent density functionals predicting a much larger transition pressures when the long range dispersive forces are taken into account. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1605.08423v2-abstract-full').style.display = 'none'; document.getElementById('1605.08423v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 7 July, 2016; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 May, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages plus supplementary</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Lett. 118, 015703 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1602.00035">arXiv:1602.00035</a> <span> [<a href="https://arxiv.org/pdf/1602.00035">pdf</a>, <a href="https://arxiv.org/ps/1602.00035">ps</a>, <a href="https://arxiv.org/format/1602.00035">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.4938089">10.1063/1.4938089 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Geminal embedding scheme for optimal atomic basis set construction in correlated calculations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Sorella%2C+S">Sandro Sorella</a>, <a href="/search/cond-mat?searchtype=author&query=Devaux%2C+N">Nicolas Devaux</a>, <a href="/search/cond-mat?searchtype=author&query=Dagrada%2C+M">Mario Dagrada</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Casula%2C+M">Michele Casula</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1602.00035v1-abstract-short" style="display: inline;"> We introduce an efficient method to construct optimal and system adaptive basis sets for use in electronic structure and quantum Monte Carlo calculations. The method is based on an embedding scheme in which a reference atom is singled out from its environment, while the entire system (atom and environment) is described by a Slater determinant or its antisymmetrized geminal power (AGP) extension. T… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1602.00035v1-abstract-full').style.display = 'inline'; document.getElementById('1602.00035v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1602.00035v1-abstract-full" style="display: none;"> We introduce an efficient method to construct optimal and system adaptive basis sets for use in electronic structure and quantum Monte Carlo calculations. The method is based on an embedding scheme in which a reference atom is singled out from its environment, while the entire system (atom and environment) is described by a Slater determinant or its antisymmetrized geminal power (AGP) extension. The embedding procedure described here allows for the systematic and consistent contraction of the primitive basis set into geminal embedded orbitals (GEOs), with a dramatic reduction of the number of variational parameters necessary to represent the many-body wave function, for a chosen target accuracy. Within the variational Monte Carlo method, the Slater or AGP part is determined by a variational minimization of the energy of the whole system in presence of a flexible and accurate Jastrow factor, representing most of the dynamical electronic correlation. The resulting GEO basis set opens the way for a fully controlled optimization of many-body wave functions in electronic structure calculation of bulk materials, namely, containing a large number of electrons and atoms. We present applications on the water molecule, the volume collapse transition in cerium, and the high-pressure liquid hydrogen. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1602.00035v1-abstract-full').style.display = 'none'; document.getElementById('1602.00035v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 January, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Journal of Chemical Physics, 143, 244112 (2015) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1510.08057">arXiv:1510.08057</a> <span> [<a href="https://arxiv.org/pdf/1510.08057">pdf</a>, <a href="https://arxiv.org/format/1510.08057">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevLett.117.180402">10.1103/PhysRevLett.117.180402 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Understanding Quantum Tunneling through Quantum Monte Carlo Simulations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Isakov%2C+S+V">Sergei V. Isakov</a>, <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Smelyanskiy%2C+V+N">Vadim N. Smelyanskiy</a>, <a href="/search/cond-mat?searchtype=author&query=Jiang%2C+Z">Zhang Jiang</a>, <a href="/search/cond-mat?searchtype=author&query=Boixo%2C+S">Sergio Boixo</a>, <a href="/search/cond-mat?searchtype=author&query=Neven%2C+H">Hartmut Neven</a>, <a href="/search/cond-mat?searchtype=author&query=Troyer%2C+M">Matthias Troyer</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1510.08057v1-abstract-short" style="display: inline;"> The tunneling between the two ground states of an Ising ferromagnet is a typical example of many-body tunneling processes between two local minima, as they occur during quantum annealing. Performing quantum Monte Carlo (QMC) simulations we find that the QMC tunneling rate displays the same scaling with system size, as the rate of incoherent tunneling. The scaling in both cases is $O(螖^2)$, where… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1510.08057v1-abstract-full').style.display = 'inline'; document.getElementById('1510.08057v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1510.08057v1-abstract-full" style="display: none;"> The tunneling between the two ground states of an Ising ferromagnet is a typical example of many-body tunneling processes between two local minima, as they occur during quantum annealing. Performing quantum Monte Carlo (QMC) simulations we find that the QMC tunneling rate displays the same scaling with system size, as the rate of incoherent tunneling. The scaling in both cases is $O(螖^2)$, where $螖$ is the tunneling splitting. An important consequence is that QMC simulations can be used to predict the performance of a quantum annealer for tunneling through a barrier. Furthermore, by using open instead of periodic boundary conditions in imaginary time, equivalent to a projector QMC algorithm, we obtain a quadratic speedup for QMC, and achieve linear scaling in $螖$. We provide a physical understanding of these results and their range of applicability based on an instanton picture. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1510.08057v1-abstract-full').style.display = 'none'; document.getElementById('1510.08057v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 October, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2015. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, 4 figures, 10 pages of supplemental material</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Lett. 117, 180402 (2016) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1411.6433">arXiv:1411.6433</a> <span> [<a href="https://arxiv.org/pdf/1411.6433">pdf</a>, <a href="https://arxiv.org/format/1411.6433">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevLett.114.105701">10.1103/PhysRevLett.114.105701 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Distinct metallization and atomization transitions in dense liquid hydrogen </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Sorella%2C+S">Sandro Sorella</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1411.6433v1-abstract-short" style="display: inline;"> We perform molecular dynamics simulations driven by accurate Quantum Monte Carlo forces on dense liquid hydrogen. Recently it has been reported a complete atomization transition between a mixed-atomic liquid and a completely dissociated fluid in an almost unaccessible pressure range {[\emph{Nat. Commun.} {\bf 5}, 3487 (2014)]}. Here instead, in a much more interesting pressure range, we identify a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1411.6433v1-abstract-full').style.display = 'inline'; document.getElementById('1411.6433v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1411.6433v1-abstract-full" style="display: none;"> We perform molecular dynamics simulations driven by accurate Quantum Monte Carlo forces on dense liquid hydrogen. Recently it has been reported a complete atomization transition between a mixed-atomic liquid and a completely dissociated fluid in an almost unaccessible pressure range {[\emph{Nat. Commun.} {\bf 5}, 3487 (2014)]}. Here instead, in a much more interesting pressure range, we identify a different transition between the fully molecular liquid and the mixed-atomic fluid at $\sim$ 400 GPa, with numerical evidence supporting its metallic behavior. Therefore we predict that the metallization at finite temperature occurs in this partially dissociated molecular fluid, well before the complete atomization of the liquid. At high temperature this first-order transition becomes a crossover, in very good agreement with the experimental observation. Several systematic tests supporting the quality of our large scale calculations are also reported. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1411.6433v1-abstract-full').style.display = 'none'; document.getElementById('1411.6433v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 November, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2014. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1404.5471">arXiv:1404.5471</a> <span> [<a href="https://arxiv.org/pdf/1404.5471">pdf</a>, <a href="https://arxiv.org/format/1404.5471">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/ncomms4487">10.1038/ncomms4487 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Unexpectedly high pressure for molecular dissociation in liquid hydrogen by a reliable electronic simulation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Yunoki%2C+S">Seiji Yunoki</a>, <a href="/search/cond-mat?searchtype=author&query=Sorella%2C+S">Sandro Sorella</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1404.5471v1-abstract-short" style="display: inline;"> The study of the high pressure phase diagram of hydrogen has continued with renewed effort for about one century as it remains a fundamental challenge for experimental and theoretical techniques. Here we employ an efficient molecular dynamics based on the quantum Monte Carlo method, which can describe accurately the electronic correlation and treat a large number of hydrogen atoms, allowing a real… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1404.5471v1-abstract-full').style.display = 'inline'; document.getElementById('1404.5471v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1404.5471v1-abstract-full" style="display: none;"> The study of the high pressure phase diagram of hydrogen has continued with renewed effort for about one century as it remains a fundamental challenge for experimental and theoretical techniques. Here we employ an efficient molecular dynamics based on the quantum Monte Carlo method, which can describe accurately the electronic correlation and treat a large number of hydrogen atoms, allowing a realistic and reliable prediction of thermodynamic roperties. We find that the molecular liquid phase is unexpectedly stable and the transition towards a fully atomic liquid phase occurs at much higher pressure than previously believed. The old standing problem of low temperature atomization is, therefore, still far from experimental reach. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1404.5471v1-abstract-full').style.display = 'none'; document.getElementById('1404.5471v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 April, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2014. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages and supplementary informations</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nat. Commun. 5, 3487 (2014) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1205.4526">arXiv:1205.4526</a> <span> [<a href="https://arxiv.org/pdf/1205.4526">pdf</a>, <a href="https://arxiv.org/ps/1205.4526">ps</a>, <a href="https://arxiv.org/format/1205.4526">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.4755992">10.1063/1.4755992 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Finite temperature electronic simulations beyond the Born-Oppenheimer approximation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Zen%2C+A">Andrea Zen</a>, <a href="/search/cond-mat?searchtype=author&query=Sorella%2C+S">Sandro Sorella</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1205.4526v1-abstract-short" style="display: inline;"> We introduce a general technique to compute finite temperature electronic properties by a novel covariant formulation of the electronic partition function. By using a rigorous variational upper bound to the free energy we are led to the evaluation of a partition function that can be computed stochastically by sampling electronic wave functions and atomic positions (assumed classical). In order to… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1205.4526v1-abstract-full').style.display = 'inline'; document.getElementById('1205.4526v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1205.4526v1-abstract-full" style="display: none;"> We introduce a general technique to compute finite temperature electronic properties by a novel covariant formulation of the electronic partition function. By using a rigorous variational upper bound to the free energy we are led to the evaluation of a partition function that can be computed stochastically by sampling electronic wave functions and atomic positions (assumed classical). In order to achieve this target we show that it is extremely important to consider the non trivial geometry of the space defined by the wave function ansatz. The method can be extended to any technique capable to provide an energy value over a given wave function ansatz depending on several variational parameters and atomic positions. In particular we can take into account electronic correlation, by using the standard variational quantum Monte Carlo method, that has been so far limited to zero temperature ground state properties. We show that our approximation reduces correctly to the standard Born-Oppenheimer (BO) one at zero temperature and to the correct high temperature limit. At large enough temperatures this method allows to improve the BO, providing lower values of the electronic free energy, because within this method it is possible to take into account the electron entropy. We test this new method on the simple hydrogen molecule, where at low temperature we recover the correct BO low temperature limit. Moreover, we show that the dissociation of the molecule is possible at a temperature much smaller than the BO prediction. Several extension of the proposed technique are also discussed, as for instance the calculation of critical (magnetic, superconducting) temperatures, or transition rates in chemical reactions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1205.4526v1-abstract-full').style.display = 'none'; document.getElementById('1205.4526v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 May, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> J. Chem. Phys. 137, 134112 (2012) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1012.3424">arXiv:1012.3424</a> <span> [<a href="https://arxiv.org/pdf/1012.3424">pdf</a>, <a href="https://arxiv.org/format/1012.3424">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Soft Condensed Matter">cond-mat.soft</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Biological Physics">physics.bio-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.3581892">10.1063/1.3581892 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Fluctuations in the Ensemble of Reaction Pathways </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mazzola%2C+G">G. Mazzola</a>, <a href="/search/cond-mat?searchtype=author&query=Beccara%2C+S+a">S. a Beccara</a>, <a href="/search/cond-mat?searchtype=author&query=Faccioli%2C+P">P. Faccioli</a>, <a href="/search/cond-mat?searchtype=author&query=Orland%2C+H">H. Orland</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1012.3424v1-abstract-short" style="display: inline;"> The dominant reaction pathway (DRP) is a rigorous framework to microscopically compute the most probable trajectories, in non-equilibrium transitions. In the low-temperature regime, such dominant pathways encode the information about the reaction mechanism and can be used to estimate non-equilibrium averages of arbitrary observables. On the other hand, at sufficiently high temperatures, the stocha… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1012.3424v1-abstract-full').style.display = 'inline'; document.getElementById('1012.3424v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1012.3424v1-abstract-full" style="display: none;"> The dominant reaction pathway (DRP) is a rigorous framework to microscopically compute the most probable trajectories, in non-equilibrium transitions. In the low-temperature regime, such dominant pathways encode the information about the reaction mechanism and can be used to estimate non-equilibrium averages of arbitrary observables. On the other hand, at sufficiently high temperatures, the stochastic fluctuations around the dominant paths become important and have to be taken into account. In this work, we develop a technique to systematically include the effects of such stochastic fluctuations, to order k_B T. This method is used to compute the probability for a transition to take place through a specific reaction channel and to evaluate the reaction rate. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1012.3424v1-abstract-full').style.display = 'none'; document.getElementById('1012.3424v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 December, 2010; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2010. </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> </div> </main> <footer> <div class="columns is-desktop" role="navigation" aria-label="Secondary">  <div class="column"> <div class="columns"> <div class="column"> <ul 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