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</div> <div class="control"> <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/2502.01040">arXiv:2502.01040</a> <span> [<a href="https://arxiv.org/pdf/2502.01040">pdf</a>, <a href="https://arxiv.org/format/2502.01040">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> </div> <p class="title is-5 mathjax"> Enhancement of Electric Drive in Silicon Quantum Dots with Electric Quadrupole Spin Resonance </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mai%2C+P+Y">Philip Y. Mai</a>, <a href="/search/cond-mat?searchtype=author&query=Pereira%2C+P+H">Pedro H. Pereira</a>, <a href="/search/cond-mat?searchtype=author&query=Alonso%2C+L+A">Lucas Andrade Alonso</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">Chih Hwan Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Hwang%2C+J+C+C">Jason C. C. Hwang</a>, <a href="/search/cond-mat?searchtype=author&query=Dunmore%2C+D">Daniel Dunmore</a>, <a href="/search/cond-mat?searchtype=author&query=Lemyre%2C+J+C">Julien Camirand Lemyre</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">Tuomo Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+W">Wister Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Chan%2C+K+W">Kok Wai Chan</a>, <a href="/search/cond-mat?searchtype=author&query=Tan%2C+K+Y">Kuan Yen Tan</a>, <a href="/search/cond-mat?searchtype=author&query=Cifuentes%2C+J+D">Jes煤s D. Cifuentes</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">Fay E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">Kohei M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">Arne Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Pioro-Ladri%C3%A8re%2C+M">Michel Pioro-Ladri猫re</a>, <a href="/search/cond-mat?searchtype=author&query=Escott%2C+C+C">Christopher C. Escott</a>, <a href="/search/cond-mat?searchtype=author&query=Feng%2C+M">MengKe Feng</a>, <a href="/search/cond-mat?searchtype=author&query=Souza%2C+R+d+M+e">Reinaldo de Melo e Souza</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A">Andrew Dzurak</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">Andre Saraiva</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="2502.01040v2-abstract-short" style="display: inline;"> Quantum computation with electron spin qubits requires coherent and efficient manipulation of these spins, typically accomplished through the application of alternating magnetic or electric fields for electron spin resonance (ESR). In particular, electrical driving allows us to apply localized fields on the electrons, which benefits scale-up architectures. However, we have found that Electric Dipo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.01040v2-abstract-full').style.display = 'inline'; document.getElementById('2502.01040v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2502.01040v2-abstract-full" style="display: none;"> Quantum computation with electron spin qubits requires coherent and efficient manipulation of these spins, typically accomplished through the application of alternating magnetic or electric fields for electron spin resonance (ESR). In particular, electrical driving allows us to apply localized fields on the electrons, which benefits scale-up architectures. However, we have found that Electric Dipole Spin Resonance (EDSR) is insufficient for modeling the Rabi behavior in recent experimental studies. Therefore, we propose that the electron spin is being driven by a new method of electric spin qubit control which generalizes the spin dynamics by taking into account a quadrupolar contribution of the quantum dot: electric quadrupole spin resonance (EQSR). In this work, we explore the electric quadrupole driving of a quantum dot in silicon, specifically examining the cases of 5 and 13 electron occupancies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.01040v2-abstract-full').style.display = 'none'; document.getElementById('2502.01040v2-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> 3 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">Main: 5 pages, 4 figures Supp: 4 pages</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.01241">arXiv:2408.01241</a> <span> [<a href="https://arxiv.org/pdf/2408.01241">pdf</a>, <a href="https://arxiv.org/format/2408.01241">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Exchange control in a MOS double quantum dot made using a 300 mm wafer process </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Chittock-Wood%2C+J+F">Jacob F. Chittock-Wood</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Fogarty%2C+M+A">Michael A. Fogarty</a>, <a href="/search/cond-mat?searchtype=author&query=Murphy%2C+T">Tara Murphy</a>, <a href="/search/cond-mat?searchtype=author&query=Patom%C3%A4ki%2C+S+M">Sofia M. Patom盲ki</a>, <a href="/search/cond-mat?searchtype=author&query=Oakes%2C+G+A">Giovanni A. Oakes</a>, <a href="/search/cond-mat?searchtype=author&query=von+Horstig%2C+F">Felix-Ekkehard von Horstig</a>, <a href="/search/cond-mat?searchtype=author&query=Johnson%2C+N">Nathan Johnson</a>, <a href="/search/cond-mat?searchtype=author&query=Jussot%2C+J">Julien Jussot</a>, <a href="/search/cond-mat?searchtype=author&query=Kubicek%2C+S">Stefan Kubicek</a>, <a href="/search/cond-mat?searchtype=author&query=Govoreanu%2C+B">Bogdan Govoreanu</a>, <a href="/search/cond-mat?searchtype=author&query=Wise%2C+D+F">David F. Wise</a>, <a href="/search/cond-mat?searchtype=author&query=Gonzalez-Zalba%2C+M+F">M. Fernando Gonzalez-Zalba</a>, <a href="/search/cond-mat?searchtype=author&query=Morton%2C+J+J+L">John J. L. Morton</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="2408.01241v2-abstract-short" style="display: inline;"> Leveraging the advanced manufacturing capabilities of the semiconductor industry promises to help scale up silicon-based quantum processors by increasing yield, uniformity and integration. Recent studies of quantum dots fabricated on 300 mm wafer metal-oxide-semiconductor (MOS) processes have shown control and readout of individual spin qubits, yet quantum processors require two-qubit interactions… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.01241v2-abstract-full').style.display = 'inline'; document.getElementById('2408.01241v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.01241v2-abstract-full" style="display: none;"> Leveraging the advanced manufacturing capabilities of the semiconductor industry promises to help scale up silicon-based quantum processors by increasing yield, uniformity and integration. Recent studies of quantum dots fabricated on 300 mm wafer metal-oxide-semiconductor (MOS) processes have shown control and readout of individual spin qubits, yet quantum processors require two-qubit interactions to operate. Here, we use a 300 mm wafer MOS process customized for spin qubits and demonstrate coherent control of two electron spins using the spin-spin exchange interaction, forming the basis of an entangling gate such as $\sqrt{\text{SWAP}}$. We observe gate dephasing times of up to $T_2^{*}\approx500$ ns and a gate quality factor of 10. We further extend the coherence by up to an order of magnitude using an echo sequence. For readout, we introduce a dispersive readout technique, the radiofrequency electron cascade, that amplifies the signal while retaining the spin-projective nature of dispersive measurements. Our results demonstrate an industrial grade platform for two-qubit operations, alongside integration with dispersive sensing techniques. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.01241v2-abstract-full').style.display = 'none'; document.getElementById('2408.01241v2-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 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.01849">arXiv:2309.01849</a> <span> [<a href="https://arxiv.org/pdf/2309.01849">pdf</a>, <a href="https://arxiv.org/format/2309.01849">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/10.1103/PhysRevB.110.125414">10.1103/PhysRevB.110.125414 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Impact of electrostatic crosstalk on spin qubits in dense CMOS quantum dot arrays </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Cifuentes%2C+J+D">Jesus D. Cifuentes</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">Tuomo Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Steinacker%2C+P">Paul Steinacker</a>, <a href="/search/cond-mat?searchtype=author&query=Serrano%2C+S">Santiago Serrano</a>, <a href="/search/cond-mat?searchtype=author&query=Hansen%2C+I">Ingvild Hansen</a>, <a href="/search/cond-mat?searchtype=author&query=Slack-Smith%2C+J+P">James P. Slack-Smith</a>, <a href="/search/cond-mat?searchtype=author&query=Gilbert%2C+W">Will Gilbert</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+J+Y">Jonathan Y. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Vahapoglu%2C+E">Ensar Vahapoglu</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Stuyck%2C+N+D">Nard Dumoulin Stuyck</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K">Kohei Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Abrosimov%2C+N">Nikolay Abrosimov</a>, <a href="/search/cond-mat?searchtype=author&query=Pohl%2C+H">Hans-Joachim Pohl</a>, <a href="/search/cond-mat?searchtype=author&query=Thewalt%2C+M">Michael Thewalt</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">Arne Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">Chih Hwan Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Escott%2C+C+C">Christopher C. Escott</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">Fay E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Lim%2C+W+H">Wee Han Lim</a>, <a href="/search/cond-mat?searchtype=author&query=Rahman%2C+R">Rajib Rahman</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">Andrew S. Dzurak</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">Andre Saraiva</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="2309.01849v1-abstract-short" style="display: inline;"> Quantum processors based on integrated nanoscale silicon spin qubits are a promising platform for highly scalable quantum computation. Current CMOS spin qubit processors consist of dense gate arrays to define the quantum dots, making them susceptible to crosstalk from capacitive coupling between a dot and its neighbouring gates. Small but sizeable spin-orbit interactions can transfer this electros… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.01849v1-abstract-full').style.display = 'inline'; document.getElementById('2309.01849v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.01849v1-abstract-full" style="display: none;"> Quantum processors based on integrated nanoscale silicon spin qubits are a promising platform for highly scalable quantum computation. Current CMOS spin qubit processors consist of dense gate arrays to define the quantum dots, making them susceptible to crosstalk from capacitive coupling between a dot and its neighbouring gates. Small but sizeable spin-orbit interactions can transfer this electrostatic crosstalk to the spin g-factors, creating a dependence of the Larmor frequency on the electric field created by gate electrodes positioned even tens of nanometers apart. By studying the Stark shift from tens of spin qubits measured in nine different CMOS devices, we developed a theoretical frawework that explains how electric fields couple to the spin of the electrons in increasingly complex arrays, including those electric fluctuations that limit qubit dephasing times $T_2^*$. The results will aid in the design of robust strategies to scale CMOS quantum technology. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.01849v1-abstract-full').style.display = 'none'; document.getElementById('2309.01849v1-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 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">9 pages, 4 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/2303.14864">arXiv:2303.14864</a> <span> [<a href="https://arxiv.org/pdf/2303.14864">pdf</a>, <a href="https://arxiv.org/format/2303.14864">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="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/s41467-024-48557-x">10.1038/s41467-024-48557-x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Bounds to electron spin qubit variability for scalable CMOS architectures </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Cifuentes%2C+J+D">Jes煤s D. Cifuentes</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">Tuomo Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Gilbert%2C+W">Will Gilbert</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+J+Y">Jonathan Y. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Vahapoglu%2C+E">Ensar Vahapoglu</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Serrano%2C+S">Santiago Serrano</a>, <a href="/search/cond-mat?searchtype=author&query=Otter%2C+D">Dennis Otter</a>, <a href="/search/cond-mat?searchtype=author&query=Dunmore%2C+D">Daniel Dunmore</a>, <a href="/search/cond-mat?searchtype=author&query=Mai%2C+P+Y">Philip Y. Mai</a>, <a href="/search/cond-mat?searchtype=author&query=Schlattner%2C+F">Fr茅d茅ric Schlattner</a>, <a href="/search/cond-mat?searchtype=author&query=Feng%2C+M">MengKe Feng</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K">Kohei Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Abrosimov%2C+N">Nikolay Abrosimov</a>, <a href="/search/cond-mat?searchtype=author&query=Pohl%2C+H">Hans-Joachim Pohl</a>, <a href="/search/cond-mat?searchtype=author&query=Thewalt%2C+M">Michael Thewalt</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">Arne Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">Chih Hwan Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Escott%2C+C+C">Christopher C. Escott</a>, <a href="/search/cond-mat?searchtype=author&query=Lim%2C+W+H">Wee Han Lim</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">Fay E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Rahman%2C+R">Rajib Rahman</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">Andrew S. Dzurak</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">Andre Saraiva</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="2303.14864v3-abstract-short" style="display: inline;"> Spins of electrons in CMOS quantum dots combine exquisite quantum properties and scalable fabrication. In the age of quantum technology, however, the metrics that crowned Si/SiO2 as the microelectronics standard need to be reassessed with respect to their impact upon qubit performance. We chart the spin qubit variability due to the unavoidable atomic-scale roughness of the Si/SiO$_2$ interface, co… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.14864v3-abstract-full').style.display = 'inline'; document.getElementById('2303.14864v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2303.14864v3-abstract-full" style="display: none;"> Spins of electrons in CMOS quantum dots combine exquisite quantum properties and scalable fabrication. In the age of quantum technology, however, the metrics that crowned Si/SiO2 as the microelectronics standard need to be reassessed with respect to their impact upon qubit performance. We chart the spin qubit variability due to the unavoidable atomic-scale roughness of the Si/SiO$_2$ interface, compiling experiments in 12 devices, and developing theoretical tools to analyse these results. Atomistic tight binding and path integral Monte Carlo methods are adapted for describing fluctuations in devices with millions of atoms by directly analysing their wavefunctions and electron paths instead of their energy spectra. We correlate the effect of roughness with the variability in qubit position, deformation, valley splitting, valley phase, spin-orbit coupling and exchange coupling. These variabilities are found to be bounded and lie within the tolerances for scalable architectures for quantum computing as long as robust control methods are incorporated. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.14864v3-abstract-full').style.display = 'none'; document.getElementById('2303.14864v3-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> 5 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">20 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nat Commun 15, 4299 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2303.04090">arXiv:2303.04090</a> <span> [<a href="https://arxiv.org/pdf/2303.04090">pdf</a>, <a href="https://arxiv.org/format/2303.04090">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="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/s41567-024-02614-w">10.1038/s41567-024-02614-w <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Assessment of error variation in high-fidelity two-qubit gates in silicon </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">Tuomo Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Lim%2C+W+H">Wee Han Lim</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+J+Y">Jonathan Y. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Stuyck%2C+N+D">Nard Dumoulin Stuyck</a>, <a href="/search/cond-mat?searchtype=author&query=Gilbert%2C+W">Will Gilbert</a>, <a href="/search/cond-mat?searchtype=author&query=Su%2C+R+Y">Rocky Y. Su</a>, <a href="/search/cond-mat?searchtype=author&query=Feng%2C+M">MengKe Feng</a>, <a href="/search/cond-mat?searchtype=author&query=Cifuentes%2C+J+D">Jesus D. Cifuentes</a>, <a href="/search/cond-mat?searchtype=author&query=Seedhouse%2C+A+E">Amanda E. Seedhouse</a>, <a href="/search/cond-mat?searchtype=author&query=Seritan%2C+S+K">Stefan K. Seritan</a>, <a href="/search/cond-mat?searchtype=author&query=Ostrove%2C+C+I">Corey I. Ostrove</a>, <a href="/search/cond-mat?searchtype=author&query=Rudinger%2C+K+M">Kenneth M. Rudinger</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+W">Wister Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Escott%2C+C+C">Christopher C. Escott</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">Kohei M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Abrosimov%2C+N+V">Nikolay V. Abrosimov</a>, <a href="/search/cond-mat?searchtype=author&query=Pohl%2C+H">Hans-Joachim Pohl</a>, <a href="/search/cond-mat?searchtype=author&query=Thewalt%2C+M+L+W">Michael L. W. Thewalt</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">Fay E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Blume-Kohout%2C+R">Robin Blume-Kohout</a>, <a href="/search/cond-mat?searchtype=author&query=Bartlett%2C+S+D">Stephen D. Bartlett</a>, <a href="/search/cond-mat?searchtype=author&query=Morello%2C+A">Andrea Morello</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">Arne Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">Chih Hwan Yang</a> , et al. (2 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="2303.04090v3-abstract-short" style="display: inline;"> Achieving high-fidelity entangling operations between qubits consistently is essential for the performance of multi-qubit systems and is a crucial factor in achieving fault-tolerant quantum processors. Solid-state platforms are particularly exposed to errors due to materials-induced variability between qubits, which leads to performance inconsistencies. Here we study the errors in a spin qubit pro… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.04090v3-abstract-full').style.display = 'inline'; document.getElementById('2303.04090v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2303.04090v3-abstract-full" style="display: none;"> Achieving high-fidelity entangling operations between qubits consistently is essential for the performance of multi-qubit systems and is a crucial factor in achieving fault-tolerant quantum processors. Solid-state platforms are particularly exposed to errors due to materials-induced variability between qubits, which leads to performance inconsistencies. Here we study the errors in a spin qubit processor, tying them to their physical origins. We leverage this knowledge to demonstrate consistent and repeatable operation with above 99% fidelity of two-qubit gates in the technologically important silicon metal-oxide-semiconductor (SiMOS) quantum dot platform. We undertake a detailed study of these operations by analysing the physical errors and fidelities in multiple devices through numerous trials and extended periods to ensure that we capture the variation and the most common error types. Physical error sources include the slow nuclear and electrical noise on single qubits and contextual noise. The identification of the noise sources can be used to maintain performance within tolerance as well as inform future device fabrication. Furthermore, we investigate the impact of qubit design, feedback systems, and robust gates on implementing scalable, high-fidelity control strategies. These results are achieved by using three different characterization methods, we measure entangling gate fidelities ranging from 96.8% to 99.8%. Our analysis tools identify the causes of qubit degradation and offer ways understand their physical mechanisms. These results highlight both the capabilities and challenges for the scaling up of silicon spin-based qubits into full-scale quantum processors. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.04090v3-abstract-full').style.display = 'none'; document.getElementById('2303.04090v3-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 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nat. Phys. 6 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.01650">arXiv:2301.01650</a> <span> [<a href="https://arxiv.org/pdf/2301.01650">pdf</a>, <a href="https://arxiv.org/format/2301.01650">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-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/10.1103/PhysRevApplied.21.054042">10.1103/PhysRevApplied.21.054042 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> An elongated quantum dot as a distributed charge sensor </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Patom%C3%A4ki%2C+S+M">S. M. Patom盲ki</a>, <a href="/search/cond-mat?searchtype=author&query=Williams%2C+J">J. Williams</a>, <a href="/search/cond-mat?searchtype=author&query=Berritta%2C+F">F. Berritta</a>, <a href="/search/cond-mat?searchtype=author&query=Laine%2C+C">C. Laine</a>, <a href="/search/cond-mat?searchtype=author&query=Fogarty%2C+M+A">M. A. Fogarty</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">R. C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Jussot%2C+J">J. Jussot</a>, <a href="/search/cond-mat?searchtype=author&query=Kubicek%2C+S">S. Kubicek</a>, <a href="/search/cond-mat?searchtype=author&query=Chatterjee%2C+A">A. Chatterjee</a>, <a href="/search/cond-mat?searchtype=author&query=Govoreanu%2C+B">B. Govoreanu</a>, <a href="/search/cond-mat?searchtype=author&query=Kuemmeth%2C+F">F. Kuemmeth</a>, <a href="/search/cond-mat?searchtype=author&query=Morton%2C+J+J+L">J. J. L. Morton</a>, <a href="/search/cond-mat?searchtype=author&query=Gonzalez-Zalba%2C+M+F">M. F. Gonzalez-Zalba</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="2301.01650v1-abstract-short" style="display: inline;"> Increasing the separation between semiconductor quantum dots offers scaling advantages by fa- cilitating gate routing and the integration of sensors and charge reservoirs. Elongated quantum dots have been utilized for this purpose in GaAs heterostructures to extend the range of spin-spin interactions. Here, we study a metal-oxide-semiconductor (MOS) device where two quantum dot arrays are separate… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.01650v1-abstract-full').style.display = 'inline'; document.getElementById('2301.01650v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.01650v1-abstract-full" style="display: none;"> Increasing the separation between semiconductor quantum dots offers scaling advantages by fa- cilitating gate routing and the integration of sensors and charge reservoirs. Elongated quantum dots have been utilized for this purpose in GaAs heterostructures to extend the range of spin-spin interactions. Here, we study a metal-oxide-semiconductor (MOS) device where two quantum dot arrays are separated by an elongated quantum dot (340 nm long, 50 nm wide). We monitor charge transitions of the elongated quantum dot by measuring radiofrequency single-electron currents to a reservoir to which we connect a lumped-element resonator. We operate the dot as a single electron box to achieve charge sensing of remote quantum dots in each array, separated by a distance of 510 nm. Simultaneous charge detection on both ends of the elongated dot demonstrates that the charge is well distributed across its nominal length, supported by the simulated quantum-mechanical electron density. Our results illustrate how single-electron boxes can be realised with versatile foot- prints that may enable novel and compact quantum processor layouts, offering distributed charge sensing in addition to the possibility of mediated coupling. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.01650v1-abstract-full').style.display = 'none'; document.getElementById('2301.01650v1-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 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">14 pages, 9 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NBI QDEV 2024 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Applied 21, 054042 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2208.04724">arXiv:2208.04724</a> <span> [<a href="https://arxiv.org/pdf/2208.04724">pdf</a>, <a href="https://arxiv.org/format/2208.04724">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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="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/10.1002/adma.202208557">10.1002/adma.202208557 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Jellybean quantum dots in silicon for qubit coupling and on-chip quantum chemistry </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Wang%2C+Z">Zeheng Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Feng%2C+M">MengKe Feng</a>, <a href="/search/cond-mat?searchtype=author&query=Serrano%2C+S">Santiago Serrano</a>, <a href="/search/cond-mat?searchtype=author&query=Gilbert%2C+W">William Gilbert</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">Tuomo Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Mai%2C+P">Philip Mai</a>, <a href="/search/cond-mat?searchtype=author&query=Liang%2C+D">Dylan Liang</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+J+Y">Jonathan Y. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Su%2C+Y">Yue Su</a>, <a href="/search/cond-mat?searchtype=author&query=Lim%2C+W+H">Wee Han Lim</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">Fay E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Escott%2C+C+C">Christopher C. Escott</a>, <a href="/search/cond-mat?searchtype=author&query=Morello%2C+A">Andrea Morello</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">Chih Hwan Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">Andrew S. Dzurak</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">Andre Saraiva</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">Arne Laucht</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="2208.04724v1-abstract-short" style="display: inline;"> The small size and excellent integrability of silicon metal-oxide-semiconductor (SiMOS) quantum dot spin qubits make them an attractive system for mass-manufacturable, scaled-up quantum processors. Furthermore, classical control electronics can be integrated on-chip, in-between the qubits, if an architecture with sparse arrays of qubits is chosen. In such an architecture qubits are either transpor… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.04724v1-abstract-full').style.display = 'inline'; document.getElementById('2208.04724v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2208.04724v1-abstract-full" style="display: none;"> The small size and excellent integrability of silicon metal-oxide-semiconductor (SiMOS) quantum dot spin qubits make them an attractive system for mass-manufacturable, scaled-up quantum processors. Furthermore, classical control electronics can be integrated on-chip, in-between the qubits, if an architecture with sparse arrays of qubits is chosen. In such an architecture qubits are either transported across the chip via shuttling, or coupled via mediating quantum systems over short-to-intermediate distances. This paper investigates the charge and spin characteristics of an elongated quantum dot -- a so-called jellybean quantum dot -- for the prospects of acting as a qubit-qubit coupler. Charge transport, charge sensing and magneto-spectroscopy measurements are performed on a SiMOS quantum dot device at mK temperature, and compared to Hartree-Fock multi-electron simulations. At low electron occupancies where disorder effects and strong electron-electron interaction dominate over the electrostatic confinement potential, the data reveals the formation of three coupled dots, akin to a tunable, artificial molecule. One dot is formed centrally under the gate and two are formed at the edges. At high electron occupancies, these dots merge into one large dot with well-defined spin states, verifying that jellybean dots have the potential to be used as qubit couplers in future quantum computing architectures. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.04724v1-abstract-full').style.display = 'none'; document.getElementById('2208.04724v1-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> 8 August, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2207.11865">arXiv:2207.11865</a> <span> [<a href="https://arxiv.org/pdf/2207.11865">pdf</a>, <a href="https://arxiv.org/format/2207.11865">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/10.1103/PhysRevB.107.085427">10.1103/PhysRevB.107.085427 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Control of dephasing in spin qubits during coherent transport in silicon </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Feng%2C+M">MengKe Feng</a>, <a href="/search/cond-mat?searchtype=author&query=Yoneda%2C+J">Jun Yoneda</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+W">Wister Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Su%2C+Y">Yue Su</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">Tuomo Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">Chih Hwan Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Cifuentes%2C+J+D">Jesus D. Cifuentes</a>, <a href="/search/cond-mat?searchtype=author&query=Chan%2C+K+W">Kok Wai Chan</a>, <a href="/search/cond-mat?searchtype=author&query=Gilbert%2C+W">William Gilbert</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">Fay E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">Kohei M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">Arne Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">Andrew S. Dzurak</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">Andre Saraiva</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="2207.11865v2-abstract-short" style="display: inline;"> One of the key pathways towards scalability of spin-based quantum computing systems lies in achieving long-range interactions between electrons and increasing their inter-connectivity. Coherent spin transport is one of the most promising strategies to achieve this architectural advantage. Experimental results have previously demonstrated high fidelity transportation of spin qubits between two quan… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.11865v2-abstract-full').style.display = 'inline'; document.getElementById('2207.11865v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2207.11865v2-abstract-full" style="display: none;"> One of the key pathways towards scalability of spin-based quantum computing systems lies in achieving long-range interactions between electrons and increasing their inter-connectivity. Coherent spin transport is one of the most promising strategies to achieve this architectural advantage. Experimental results have previously demonstrated high fidelity transportation of spin qubits between two quantum dots in silicon and identified possible sources of error. In this theoretical study, we investigate these errors and analyze the impact of tunnel coupling, magnetic field and spin-orbit effects on the spin transfer process. The interplay between these effects gives rise to double dot configurations that include regimes of enhanced decoherence that should be avoided for quantum information processing. These conclusions permit us to extrapolate previous experimental conclusions and rationalize the future design of large scale quantum processors. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.11865v2-abstract-full').style.display = 'none'; document.getElementById('2207.11865v2-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 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">18 pages, 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/2201.06679">arXiv:2201.06679</a> <span> [<a href="https://arxiv.org/pdf/2201.06679">pdf</a>, <a href="https://arxiv.org/format/2201.06679">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/s41565-022-01280-4">10.1038/s41565-022-01280-4 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> On-demand electrical control of spin qubits </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Gilbert%2C+W">Will Gilbert</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">Tuomo Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Lim%2C+W+H">Wee Han Lim</a>, <a href="/search/cond-mat?searchtype=author&query=Feng%2C+M">MengKe Feng</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+J+Y">Jonathan Y. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Cifuentes%2C+J+D">Jesus D. Cifuentes</a>, <a href="/search/cond-mat?searchtype=author&query=Serrano%2C+S">Santiago Serrano</a>, <a href="/search/cond-mat?searchtype=author&query=Mai%2C+P+Y">Philip Y. Mai</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Escott%2C+C+C">Christopher C. Escott</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">Kohei M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Abrosimov%2C+N+V">Nikolay V. Abrosimov</a>, <a href="/search/cond-mat?searchtype=author&query=Pohl%2C+H">Hans-Joachim Pohl</a>, <a href="/search/cond-mat?searchtype=author&query=Thewalt%2C+M+L+W">Michael L. W. Thewalt</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">Fay E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Morello%2C+A">Andrea Morello</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">Arne Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">Chih Hwan Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">Andre Saraiva</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">Andrew S. Dzurak</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="2201.06679v2-abstract-short" style="display: inline;"> Once called a "classically non-describable two-valuedness" by Pauli , the electron spin is a natural resource for long-lived quantum information since it is mostly impervious to electric fluctuations and can be replicated in large arrays using silicon quantum dots, which offer high-fidelity control. Paradoxically, one of the most convenient control strategies is the integration of nanoscale magnet… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.06679v2-abstract-full').style.display = 'inline'; document.getElementById('2201.06679v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2201.06679v2-abstract-full" style="display: none;"> Once called a "classically non-describable two-valuedness" by Pauli , the electron spin is a natural resource for long-lived quantum information since it is mostly impervious to electric fluctuations and can be replicated in large arrays using silicon quantum dots, which offer high-fidelity control. Paradoxically, one of the most convenient control strategies is the integration of nanoscale magnets to artificially enhance the coupling between spins and electric field, which in turn hampers the spin's noise immunity and adds architectural complexity. Here we demonstrate a technique that enables a \emph{switchable} interaction between spins and orbital motion of electrons in silicon quantum dots, without the presence of a micromagnet. The naturally weak effects of the relativistic spin-orbit interaction in silicon are enhanced by more than three orders of magnitude by controlling the energy quantisation of electrons in the nanostructure, enhancing the orbital motion. Fast electrical control is demonstrated in multiple devices and electronic configurations, highlighting the utility of the technique. Using the electrical drive we achieve coherence time $T_{2,{\rm Hahn}}\approx50 渭$s, fast single-qubit gates with ${T_{蟺/2}=3}$ ns and gate fidelities of 99.93 % probed by randomised benchmarking. The higher gate speeds and better compatibility with CMOS manufacturing enabled by on-demand electric control improve the prospects for realising scalable silicon quantum processors. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.06679v2-abstract-full').style.display = 'none'; document.getElementById('2201.06679v2-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 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Nanotechnology (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2107.14622">arXiv:2107.14622</a> <span> [<a href="https://arxiv.org/pdf/2107.14622">pdf</a>, <a href="https://arxiv.org/format/2107.14622">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/s41534-022-00645-w">10.1038/s41534-022-00645-w <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Coherent control of electron spin qubits in silicon using a global field </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Vahapoglu%2C+E">E. Vahapoglu</a>, <a href="/search/cond-mat?searchtype=author&query=Slack-Smith%2C+J+P">J. P. Slack-Smith</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">R. C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Lim%2C+W+H">W. H. Lim</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">F. E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Day%2C+T">T. Day</a>, <a href="/search/cond-mat?searchtype=author&query=Cifuentes%2C+J+D">J. D. Cifuentes</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">T. Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">C. H. Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">A. Saraiva</a>, <a href="/search/cond-mat?searchtype=author&query=Abrosimov%2C+N+V">N. V. Abrosimov</a>, <a href="/search/cond-mat?searchtype=author&query=Pohl%2C+H+-">H. -J. Pohl</a>, <a href="/search/cond-mat?searchtype=author&query=Thewalt%2C+M+L+W">M. L. W. Thewalt</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">A. Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">A. S. Dzurak</a>, <a href="/search/cond-mat?searchtype=author&query=Pla%2C+J+J">J. J. Pla</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="2107.14622v2-abstract-short" style="display: inline;"> Silicon spin qubits promise to leverage the extraordinary progress in silicon nanoelectronic device fabrication over the past half century to deliver large-scale quantum processors. Despite the scalability advantage of using silicon technology, realising a quantum computer with the millions of qubits required to run some of the most demanding quantum algorithms poses several outstanding challenges… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.14622v2-abstract-full').style.display = 'inline'; document.getElementById('2107.14622v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2107.14622v2-abstract-full" style="display: none;"> Silicon spin qubits promise to leverage the extraordinary progress in silicon nanoelectronic device fabrication over the past half century to deliver large-scale quantum processors. Despite the scalability advantage of using silicon technology, realising a quantum computer with the millions of qubits required to run some of the most demanding quantum algorithms poses several outstanding challenges, including how to control so many qubits simultaneously. Recently, compact 3D microwave dielectric resonators were proposed as a way to deliver the magnetic fields for spin qubit control across an entire quantum chip using only a single microwave source. Although spin resonance of individual electrons in the globally applied microwave field was demonstrated, the spins were controlled incoherently. Here we report coherent Rabi oscillations of single electron spin qubits in a planar SiMOS quantum dot device using a global magnetic field generated off-chip. The observation of coherent qubit control driven by a dielectric resonator establishes a credible pathway to achieving large-scale control in a spin-based quantum computer. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.14622v2-abstract-full').style.display = 'none'; document.getElementById('2107.14622v2-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> 6 October, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 30 July, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> npj Quantum Information 8, 126 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.06433">arXiv:2103.06433</a> <span> [<a href="https://arxiv.org/pdf/2103.06433">pdf</a>, <a href="https://arxiv.org/format/2103.06433">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/10.1021/acs.nanolett.1c01003">10.1021/acs.nanolett.1c01003 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A high-sensitivity charge sensor for silicon qubits above one kelvin </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Huang%2C+J+Y">Jonathan Y. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Lim%2C+W+H">Wee Han Lim</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">Chih Hwan Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">Fay E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Escott%2C+C+C">Christopher C. Escott</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">Andre Saraiva</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">Andrew S. Dzurak</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">Arne Laucht</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="2103.06433v2-abstract-short" style="display: inline;"> Recent studies of silicon spin qubits at temperatures above 1 K are encouraging demonstrations that the cooling requirements for solid-state quantum computing can be considerably relaxed. However, qubit readout mechanisms that rely on charge sensing with a single-island single-electron transistor (SISET) quickly lose sensitivity due to thermal broadening of the electron distribution in the reservo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.06433v2-abstract-full').style.display = 'inline'; document.getElementById('2103.06433v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.06433v2-abstract-full" style="display: none;"> Recent studies of silicon spin qubits at temperatures above 1 K are encouraging demonstrations that the cooling requirements for solid-state quantum computing can be considerably relaxed. However, qubit readout mechanisms that rely on charge sensing with a single-island single-electron transistor (SISET) quickly lose sensitivity due to thermal broadening of the electron distribution in the reservoirs. Here we exploit the tunneling between two quantised states in a double-island SET (DISET) to demonstrate a charge sensor with an improvement in signal-to-noise by an order of magnitude compared to a standard SISET, and a single-shot charge readout fidelity above 99 % up to 8 K at a bandwidth > 100 kHz. These improvements are consistent with our theoretical modelling of the temperature-dependent current transport for both types of SETs. With minor additional hardware overheads, these sensors can be integrated into existing qubit architectures for high fidelity charge readout at few-kelvin temperatures. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.06433v2-abstract-full').style.display = 'none'; document.getElementById('2103.06433v2-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> 8 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 March, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nano Letters v12, 6328 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2012.10225">arXiv:2012.10225</a> <span> [<a href="https://arxiv.org/pdf/2012.10225">pdf</a>, <a href="https://arxiv.org/format/2012.10225">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/sciadv.abg9158">10.1126/sciadv.abg9158 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Single-electron spin resonance in a nanoelectronic device using a global field </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Vahapoglu%2C+E">E. Vahapoglu</a>, <a href="/search/cond-mat?searchtype=author&query=Slack-Smith%2C+J+P">J. P. Slack-Smith</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">R. C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Lim%2C+W+H">W. H. Lim</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">F. E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Day%2C+T">T. Day</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">T. Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">C. H. Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">A. Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">A. S. Dzurak</a>, <a href="/search/cond-mat?searchtype=author&query=Pla%2C+J+J">J. J. Pla</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="2012.10225v3-abstract-short" style="display: inline;"> Spin-based silicon quantum electronic circuits offer a scalable platform for quantum computation, combining the manufacturability of semiconductor devices with the long coherence times afforded by spins in silicon. Advancing from current few-qubit devices to silicon quantum processors with upwards of a million qubits, as required for fault-tolerant operation, presents several unique challenges, on… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.10225v3-abstract-full').style.display = 'inline'; document.getElementById('2012.10225v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2012.10225v3-abstract-full" style="display: none;"> Spin-based silicon quantum electronic circuits offer a scalable platform for quantum computation, combining the manufacturability of semiconductor devices with the long coherence times afforded by spins in silicon. Advancing from current few-qubit devices to silicon quantum processors with upwards of a million qubits, as required for fault-tolerant operation, presents several unique challenges, one of the most demanding being the ability to deliver microwave signals for large-scale qubit control. Here we demonstrate a potential solution to this problem by using a three-dimensional dielectric resonator to broadcast a global microwave signal across a quantum nanoelectronic circuit. Critically, this technique utilizes only a single microwave source and is capable of delivering control signals to millions of qubits simultaneously. We show that the global field can be used to perform spin resonance of single electrons confined in a silicon double quantum dot device, establishing the feasibility of this approach for scalable spin qubit control. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.10225v3-abstract-full').style.display = 'none'; document.getElementById('2012.10225v3-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 February, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 December, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Science Advances 7, eabg9158 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2008.04020">arXiv:2008.04020</a> <span> [<a href="https://arxiv.org/pdf/2008.04020">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/s41467-021-24371-7">10.1038/s41467-021-24371-7 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Coherent spin qubit transport in silicon </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Yoneda%2C+J">J. Yoneda</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+W">W. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Feng%2C+M">M. Feng</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">C. H. Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Chan%2C+K+W">K. W. Chan</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">T. Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Gilbert%2C+W">W. Gilbert</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">R. C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">F. E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">K. M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Morello%2C+A">A. Morello</a>, <a href="/search/cond-mat?searchtype=author&query=Bartlett%2C+S+D">S. D. Bartlett</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">A. Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">A. Saraiva</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">A. S. Dzurak</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="2008.04020v2-abstract-short" style="display: inline;"> A fault-tolerant quantum processor may be configured using stationary qubits interacting only with their nearest neighbours, but at the cost of significant overheads in physical qubits per logical qubit. Such overheads could be reduced by coherently transporting qubits across the chip, allowing connectivity beyond immediate neighbours. Here we demonstrate high-fidelity coherent transport of an ele… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2008.04020v2-abstract-full').style.display = 'inline'; document.getElementById('2008.04020v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2008.04020v2-abstract-full" style="display: none;"> A fault-tolerant quantum processor may be configured using stationary qubits interacting only with their nearest neighbours, but at the cost of significant overheads in physical qubits per logical qubit. Such overheads could be reduced by coherently transporting qubits across the chip, allowing connectivity beyond immediate neighbours. Here we demonstrate high-fidelity coherent transport of an electron spin qubit between quantum dots in isotopically-enriched silicon. We observe qubit precession in the inter-site tunnelling regime and assess the impact of qubit transport using Ramsey interferometry and quantum state tomography techniques. We report a polarization transfer fidelity of 99.97% and an average coherent transfer fidelity of 99.4%. Our results provide key elements for high-fidelity, on-chip quantum information distribution, as long envisaged, reinforcing the scaling prospects of silicon-based spin qubits. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2008.04020v2-abstract-full').style.display = 'none'; document.getElementById('2008.04020v2-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> 3 September, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 August, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Communications 12, 4114 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2008.03968">arXiv:2008.03968</a> <span> [<a href="https://arxiv.org/pdf/2008.03968">pdf</a>, <a href="https://arxiv.org/format/2008.03968">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/s41467-021-23437-w">10.1038/s41467-021-23437-w <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Bell-state tomography in a silicon many-electron artificial molecule </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">Chih Hwan Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Hwang%2C+J+C+C">Jason C. C. Hwang</a>, <a href="/search/cond-mat?searchtype=author&query=Lemyre%2C+J+C">Julien Camirand Lemyre</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">Tuomo Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+W">Wei Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+J+Y">Jonathan Y. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">Fay E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">Kohei M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">Arne Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Pioro-Ladri%C3%A8re%2C+M">Michel Pioro-Ladri猫re</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">Andre Saraiva</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">Andrew S. Dzurak</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="2008.03968v1-abstract-short" style="display: inline;"> An error-corrected quantum processor will require millions of qubits, accentuating the advantage of nanoscale devices with small footprints, such as silicon quantum dots. However, as for every device with nanoscale dimensions, disorder at the atomic level is detrimental to qubit uniformity. Here we investigate two spin qubits confined in a silicon double-quantum-dot artificial molecule. Each quant… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2008.03968v1-abstract-full').style.display = 'inline'; document.getElementById('2008.03968v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2008.03968v1-abstract-full" style="display: none;"> An error-corrected quantum processor will require millions of qubits, accentuating the advantage of nanoscale devices with small footprints, such as silicon quantum dots. However, as for every device with nanoscale dimensions, disorder at the atomic level is detrimental to qubit uniformity. Here we investigate two spin qubits confined in a silicon double-quantum-dot artificial molecule. Each quantum dot has a robust shell structure and, when operated at an occupancy of 5 or 13 electrons, has single spin-$\frac{1}{2}$ valence electron in its $p$- or $d$-orbital, respectively. These higher electron occupancies screen atomic-level disorder. The larger multielectron wavefunctions also enable significant overlap between neighbouring qubit electrons, while making space for an interstitial exchange-gate electrode. We implement a universal gate set using the magnetic field gradient of a micromagnet for electrically-driven single qubit gates, and a gate-voltage-controlled inter-dot barrier to perform two-qubit gates by pulsed exchange coupling. We use this gate set to demonstrate a Bell state preparation between multielectron qubits with fidelity 90.3%, confirmed by two-qubit state tomography using spin parity measurements. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2008.03968v1-abstract-full').style.display = 'none'; document.getElementById('2008.03968v1-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 August, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Communications 12, 3228 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2004.07078">arXiv:2004.07078</a> <span> [<a href="https://arxiv.org/pdf/2004.07078">pdf</a>, <a href="https://arxiv.org/format/2004.07078">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="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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.2.010303">10.1103/PRXQuantum.2.010303 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Pauli Blockade in Silicon Quantum Dots with Spin-Orbit Control </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Seedhouse%2C+A">Amanda Seedhouse</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">Tuomo Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">Ross C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Zhao%2C+R">Ruichen Zhao</a>, <a href="/search/cond-mat?searchtype=author&query=Tan%2C+K+Y">Kuan Yen Tan</a>, <a href="/search/cond-mat?searchtype=author&query=Hensen%2C+B">Bas Hensen</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">Fay E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">Kohei M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Yoneda%2C+J">Jun Yoneda</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">Chih Hwan Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Morello%2C+A">Andrea Morello</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">Arne Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Coppersmith%2C+S+N">Susan N. Coppersmith</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">Andre Saraiva</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">Andrew S. Dzurak</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="2004.07078v3-abstract-short" style="display: inline;"> Quantum computation relies on accurate measurements of qubits not only for reading the output of the calculation, but also to perform error correction. Most proposed scalable silicon architectures utilize Pauli blockade of triplet states for spin-to-charge conversion. In recent experiments, there have been instances when instead of conventional triplet blockade readout, Pauli blockade is sustained… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2004.07078v3-abstract-full').style.display = 'inline'; document.getElementById('2004.07078v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2004.07078v3-abstract-full" style="display: none;"> Quantum computation relies on accurate measurements of qubits not only for reading the output of the calculation, but also to perform error correction. Most proposed scalable silicon architectures utilize Pauli blockade of triplet states for spin-to-charge conversion. In recent experiments, there have been instances when instead of conventional triplet blockade readout, Pauli blockade is sustained only between parallel spin configurations, with $|T_0\rangle$ relaxing quickly to the singlet state and leaving $|T_+\rangle$ and $|T_-\rangle$ states blockaded -- which we call \textit{parity readout}. Both types of blockade can be used for readout in quantum computing, but it is crucial to maximize the fidelity and understand in which regime the system operates. We devise and perform an experiment in which the crossover between parity and singlet-triplet readout can be identified by investigating the underlying physics of the $|T_0\rangle$ relaxation rate. This rate is tunable over four orders of magnitude by controlling the Zeeman energy difference between the dots induced by spin-orbit coupling, which in turn depends on the direction of the applied magnetic field. We suggest a theoretical model incorporating charge noise and relaxation effects that explains quantitatively our results. Investigating the model both analytically and numerically, we identify strategies to obtain on-demand either singlet-triplet or parity readout consistently across large arrays of dots. We also discuss how parity readout can be used to perform full two-qubit state tomography and its impact on quantum error detection schemes in large-scale silicon quantum computers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2004.07078v3-abstract-full').style.display = 'none'; document.getElementById('2004.07078v3-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> 13 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 April, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">Updated title and text</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> PRX Quantum 2, 010303 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1902.09126">arXiv:1902.09126</a> <span> [<a href="https://arxiv.org/pdf/1902.09126">pdf</a>, <a href="https://arxiv.org/format/1902.09126">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/s41586-020-2171-6">10.1038/s41586-020-2171-6 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Silicon quantum processor unit cell operation above one Kelvin </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">C. H. Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">R. C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Hwang%2C+J+C+C">J. C. C. Hwang</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">A. Saraiva</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">T. Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+W">W. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Lemyre%2C+J+C">J. Camirand Lemyre</a>, <a href="/search/cond-mat?searchtype=author&query=Chan%2C+K+W">K. W. Chan</a>, <a href="/search/cond-mat?searchtype=author&query=Tan%2C+K+Y">K. Y. Tan</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">F. E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">K. M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Morello%2C+A">A. Morello</a>, <a href="/search/cond-mat?searchtype=author&query=Pioro-Ladri%C3%A8re%2C+M">M. Pioro-Ladri猫re</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">A. Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">A. S. Dzurak</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="1902.09126v2-abstract-short" style="display: inline;"> Quantum computers are expected to outperform conventional computers for a range of important problems, from molecular simulation to search algorithms, once they can be scaled up to large numbers of quantum bits (qubits), typically millions. For most solid-state qubit technologies, e.g. those using superconducting circuits or semiconductor spins, scaling poses a significant challenge as every addit… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1902.09126v2-abstract-full').style.display = 'inline'; document.getElementById('1902.09126v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1902.09126v2-abstract-full" style="display: none;"> Quantum computers are expected to outperform conventional computers for a range of important problems, from molecular simulation to search algorithms, once they can be scaled up to large numbers of quantum bits (qubits), typically millions. For most solid-state qubit technologies, e.g. those using superconducting circuits or semiconductor spins, scaling poses a significant challenge as every additional qubit increases the heat generated, while the cooling power of dilution refrigerators is severely limited at their operating temperature below 100 mK. Here we demonstrate operation of a scalable silicon quantum processor unit cell, comprising two qubits confined to quantum dots (QDs) at $\sim$1.5 Kelvin. We achieve this by isolating the QDs from the electron reservoir, initialising and reading the qubits solely via tunnelling of electrons between the two QDs. We coherently control the qubits using electrically-driven spin resonance (EDSR) in isotopically enriched silicon $^{28}$Si, attaining single-qubit gate fidelities of 98.6% and coherence time $T_2^*$ = 2$渭$s during `hot' operation, comparable to those of spin qubits in natural silicon at millikelvin temperatures. Furthermore, we show that the unit cell can be operated at magnetic fields as low as 0.1 T, corresponding to a qubit control frequency of 3.5 GHz, where the qubit energy is well below the thermal energy. The unit cell constitutes the core building block of a full-scale silicon quantum computer, and satisfies layout constraints required by error correction architectures. Our work indicates that a spin-based quantum computer could be operated at elevated temperatures in a simple pumped $^4$He system, offering orders of magnitude higher cooling power than dilution refrigerators, potentially enabling classical control electronics to be integrated with the qubit array. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1902.09126v2-abstract-full').style.display = 'none'; document.getElementById('1902.09126v2-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> 19 June, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 February, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature 580, 350-354 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1902.01550">arXiv:1902.01550</a> <span> [<a href="https://arxiv.org/pdf/1902.01550">pdf</a>, <a href="https://arxiv.org/format/1902.01550">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/s41467-019-14053-w">10.1038/s41467-019-14053-w <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Coherent spin control of s-, p-, d- and f-electrons in a silicon quantum dot </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">R. C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">C. H. Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Hwang%2C+J+C+C">J. C. C. Hwang</a>, <a href="/search/cond-mat?searchtype=author&query=Lemyre%2C+J+C">J. Camirand Lemyre</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">T. Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+W">W. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Chan%2C+K+W">K. W. Chan</a>, <a href="/search/cond-mat?searchtype=author&query=Tan%2C+K+Y">K. Y. Tan</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">F. E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">K. M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Morello%2C+A">A. Morello</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">A. Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Pioro-Ladriere%2C+M">M. Pioro-Ladriere</a>, <a href="/search/cond-mat?searchtype=author&query=Saraiva%2C+A">A. Saraiva</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">A. S. Dzurak</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="1902.01550v3-abstract-short" style="display: inline;"> Once the periodic properties of elements were unveiled, chemical bonds could be understood in terms of the valence of atoms. Ideally, this rationale would extend to quantum dots, often termed artificial atoms, and quantum computation could be performed by merely controlling the outer-shell electrons of dot-based qubits. Imperfections in the semiconductor material, including at the atomic scale, di… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1902.01550v3-abstract-full').style.display = 'inline'; document.getElementById('1902.01550v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1902.01550v3-abstract-full" style="display: none;"> Once the periodic properties of elements were unveiled, chemical bonds could be understood in terms of the valence of atoms. Ideally, this rationale would extend to quantum dots, often termed artificial atoms, and quantum computation could be performed by merely controlling the outer-shell electrons of dot-based qubits. Imperfections in the semiconductor material, including at the atomic scale, disrupt this analogy between atoms and quantum dots, so that real devices seldom display such a systematic many-electron arrangement. We demonstrate here an electrostatically-defined quantum dot that is robust to disorder, revealing a well defined shell structure. We observe four shells (31 electrons) with multiplicities given by spin and valley degrees of freedom. We explore various fillings consisting of a single valence electron -- namely 1, 5, 13 and 25 electrons -- as potential qubits, and we identify fillings that yield a total spin-1 on the dot. An integrated micromagnet allows us to perform electrically-driven spin resonance (EDSR). Higher shell states are shown to be more susceptible to the driving field, leading to faster Rabi rotations of the qubit. We investigate the impact of orbital excitations of the p- and d-shell electrons on single qubits as a function of the dot deformation. This allows us to tune the dot excitation spectrum and exploit it for faster qubit control. Furthermore, hotspots arising from this tunable energy level structure provide a pathway towards fast spin initialisation. The observation of spin-1 states may be exploited in the future to study symmetry-protected topological states in antiferromagnetic spin chains and their application to quantum computing. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1902.01550v3-abstract-full').style.display = 'none'; document.getElementById('1902.01550v3-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> 6 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 February, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Communications 11, 797 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1812.08347">arXiv:1812.08347</a> <span> [<a href="https://arxiv.org/pdf/1812.08347">pdf</a>, <a href="https://arxiv.org/format/1812.08347">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/s41467-019-13416-7">10.1038/s41467-019-13416-7 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Single-spin qubits in isotopically enriched silicon at low magnetic field </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Zhao%2C+R">R. Zhao</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">T. Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Tan%2C+K+Y">K. Y. Tan</a>, <a href="/search/cond-mat?searchtype=author&query=Hensen%2C+B">B. Hensen</a>, <a href="/search/cond-mat?searchtype=author&query=Chan%2C+K+W">K. W. Chan</a>, <a href="/search/cond-mat?searchtype=author&query=Hwang%2C+J+C+C">J. C. C. Hwang</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">R. C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">C. H. Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Gilbert%2C+W">W. Gilbert</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">F. E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">K. M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Kiselev%2C+A+A">A. A. Kiselev</a>, <a href="/search/cond-mat?searchtype=author&query=Ladd%2C+T+D">T. D. Ladd</a>, <a href="/search/cond-mat?searchtype=author&query=Morello%2C+A">A. Morello</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">A. Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">A. S. Dzurak</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="1812.08347v5-abstract-short" style="display: inline;"> Single-electron spin qubits employ magnetic fields on the order of 1 Tesla or above to enable quantum state readout via spin-dependent-tunnelling. This requires demanding microwave engineering for coherent spin resonance control and significant on-chip real estate for electron reservoirs, both of which limit the prospects for large scale multi-qubit systems. Alternatively, singlet-triplet (ST) rea… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.08347v5-abstract-full').style.display = 'inline'; document.getElementById('1812.08347v5-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1812.08347v5-abstract-full" style="display: none;"> Single-electron spin qubits employ magnetic fields on the order of 1 Tesla or above to enable quantum state readout via spin-dependent-tunnelling. This requires demanding microwave engineering for coherent spin resonance control and significant on-chip real estate for electron reservoirs, both of which limit the prospects for large scale multi-qubit systems. Alternatively, singlet-triplet (ST) readout enables high-fidelity spin-state measurements in much lower magnetic fields, without the need for reservoirs. Here, we demonstrate low-field operation of metal-oxide-silicon (MOS) quantum dot qubits by combining coherent single-spin control with high-fidelity, single-shot, Pauli-spin-blockade-based ST readout. We discover that the qubits decohere faster at low magnetic fields with $T_{2}^{Rabi}=18.6$~$渭$s and $T_2^*=1.4$~$渭$s at 150~mT. Their coherence is limited by spin flips of residual $^{29}$Si nuclei in the isotopically enriched $^{28}$Si host material, which occur more frequently at lower fields. Our finding indicates that new trade-offs will be required to ensure the frequency stabilization of spin qubits and highlights the importance of isotopic enrichment of device substrates for the realization of a scalable silicon-based quantum processor. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.08347v5-abstract-full').style.display = 'none'; document.getElementById('1812.08347v5-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 August, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 December, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nat Commun 10, 5500 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1805.05027">arXiv:1805.05027</a> <span> [<a href="https://arxiv.org/pdf/1805.05027">pdf</a>, <a href="https://arxiv.org/format/1805.05027">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</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/s41586-019-1197-0">10.1038/s41586-019-1197-0 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Fidelity benchmarks for two-qubit gates in silicon </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Huang%2C+W">W. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+C+H">C. H. Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Chan%2C+K+W">K. W. Chan</a>, <a href="/search/cond-mat?searchtype=author&query=Tanttu%2C+T">T. Tanttu</a>, <a href="/search/cond-mat?searchtype=author&query=Hensen%2C+B">B. Hensen</a>, <a href="/search/cond-mat?searchtype=author&query=Leon%2C+R+C+C">R. C. C. Leon</a>, <a href="/search/cond-mat?searchtype=author&query=Fogarty%2C+M+A">M. A. Fogarty</a>, <a href="/search/cond-mat?searchtype=author&query=Hwang%2C+J+C+C">J. C. C. Hwang</a>, <a href="/search/cond-mat?searchtype=author&query=Hudson%2C+F+E">F. E. Hudson</a>, <a href="/search/cond-mat?searchtype=author&query=Itoh%2C+K+M">K. M. Itoh</a>, <a href="/search/cond-mat?searchtype=author&query=Morello%2C+A">A. Morello</a>, <a href="/search/cond-mat?searchtype=author&query=Laucht%2C+A">A. Laucht</a>, <a href="/search/cond-mat?searchtype=author&query=Dzurak%2C+A+S">A. S. Dzurak</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="1805.05027v3-abstract-short" style="display: inline;"> Universal quantum computation will require qubit technology based on a scalable platform, together with quantum error correction protocols that place strict limits on the maximum infidelities for one- and two-qubit gate operations. While a variety of qubit systems have shown high fidelities at the one-qubit level, superconductor technologies have been the only solid-state qubits manufactured via s… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1805.05027v3-abstract-full').style.display = 'inline'; document.getElementById('1805.05027v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1805.05027v3-abstract-full" style="display: none;"> Universal quantum computation will require qubit technology based on a scalable platform, together with quantum error correction protocols that place strict limits on the maximum infidelities for one- and two-qubit gate operations. While a variety of qubit systems have shown high fidelities at the one-qubit level, superconductor technologies have been the only solid-state qubits manufactured via standard lithographic techniques which have demonstrated two-qubit fidelities near the fault-tolerant threshold. Silicon-based quantum dot qubits are also amenable to large-scale manufacture and can achieve high single-qubit gate fidelities (exceeding 99.9%) using isotopically enriched silicon. However, while two-qubit gates have been demonstrated in silicon, it has not yet been possible to rigorously assess their fidelities using randomized benchmarking, since this requires sequences of significant numbers of qubit operations ($\gtrsim 20$) to be completed with non-vanishing fidelity. Here, for qubits encoded on the electron spin states of gate-defined quantum dots, we demonstrate Bell state tomography with fidelities ranging from 80% to 89%, and two-qubit randomized benchmarking with an average Clifford gate fidelity of 94.7% and average Controlled-ROT (CROT) fidelity of 98.0%. These fidelities are found to be limited by the relatively slow gate times employed here compared with the decoherence times $T_2^*$ of the qubits. Silicon qubit designs employing fast gate operations based on high Rabi frequencies, together with advanced pulsing techniques, should therefore enable significantly higher fidelities in the near future. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1805.05027v3-abstract-full').style.display = 'none'; document.getElementById('1805.05027v3-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 July, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 14 May, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature 569, 532-536 (2019) </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a 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