Can basic concepts explain EIT, LWI, and STIRAP?

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The key idea is to manipulate the energy levels of an atom to allow for transitions that are not typically allowed by selection rules. This is achieved by using two lasers, a "coupling" laser and a "probe" laser, to create a "dark state" where the amplitudes of the wave function for two possible paths are out of phase and cancel each other out. This prevents the electron from occupying a certain state, leading to the desired outcome. While this may be a simplified explanation, it provides an intuitive </div> <script src="https://www.physicsforums.com/check-for-tex.js" defer></script> <div class="block block--messages" data-xf-init="" data-type="post" data-href="/inline-mod/" data-search-target="*"> <span class="u-anchorTarget" id="posts"></span> <div class="block-outer"></div> <div class="block-outer js-threadStatusField"></div> <div class="block-container lbContainer" data-xf-init="lightbox select-to-quote old-new-message-indicator" data-sv-live-content-time-element-selector=".message-attribution-main time.u-dt" data-message-selector=".js-post" data-lb-id="thread-863515" data-lb-universal="0"> <div class="block-body js-replyNewMessageContainer">  <article class="message message--post js-post js-inlineModContainer " data-author="secur" data-content="post-5419525" id="js-post-5419525" > <span class="u-anchorTarget" id="post-5419525"></span> <div class="message-header"> <header class="message-attribution message-attribution--split"> <ul class="message-attribution-main listInline "> <li class="u-concealed"> <time class="u-dt" dir="auto" datetime="2016-03-23T23:20:49-0500" data-time="1458793249" data-date-string="Mar 23, 2016" data-time-string="11:20 PM" title="Mar 23, 2016 at 11:20 PM">Mar 23, 2016</time> </li> </ul> <ul class="message-attribution-opposite message-attribution-opposite--list "> <li> <span style="cursor:pointer;" data-xf-init="share-tooltip" data-href="/posts/5419525/share" aria-label="Share" role="button" rel="nofollow"> <i class="fa--xf fal fa-share-alt" aria-hidden="true"></i> </span> </li> <li> #1 </li> </ul> </header> </div> <div class="message-inner"> <div class="message-cell message-cell--user"> <section class="message-user" > <div class="message-userDetails"> <span class="message-name"><span class="username " dir="auto" data-user-id="588176">secur</span></span>   <span class="threadstarter" data-xf-init="tooltip" title="Thread Starter"><i class="fal fa-user-edit"></i></span>   </div> <div class="message-userExtras"> <dl class="pairs pairs--justified"> <dt><i class="fa--xf fal fa-comments fa-fw" aria-hidden="true" data-xf-init="tooltip" title="Messages"></i></dt> <dd>381</dd> </dl> <dl class="pairs pairs--justified"> <dt><i class="fa--xf fal fa-thumbs-up fa-fw" aria-hidden="true" data-xf-init="tooltip" title="Reaction score"></i></dt> <dd>118</dd> </dl> </div> <span class="message-userArrow"></span> </section> </div> <div class="message-cell message-cell--main"> <div class="message-main js-quickEditTarget"> <div class="message-content js-messageContent"> <div class="message-userContent lbContainer js-lbContainer " data-lb-id="post-5419525" data-lb-caption-desc="secur · Mar 23, 2016 at 11:20 PM"> <article class="message-body js-selectToQuote"> <div class="googleads_fixed"> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-6580726045122001" crossorigin="anonymous"></script>  <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-6580726045122001" data-ad-slot="3049969336" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div> <div > <div class="bbWrapper">I'm interested in Electromagnetically Induced Transparency (EIT), Lasing Without Interference (LWI) and/or Stimulated Raman adiabatic passage (STIRAP) and have some basic questions.<br /> <br /> First, I think the concepts involved, at this basic level, are similar for these three. Yes?<br /> <br /> I don't understand some of the explanations given in sources. Here are two quotes to illustrate:<br /> <br /> "One approach is to extend the density matrix treatment used to derive Rabi oscillation of a two-state, single field system. In this picture the probability amplitude for the system to transfer between states can interfere destructively, preventing absorption."<br /> "Another approach is the 'dressed state' picture, wherein the system + coupling field Hamiltonian is diagonalized and the effect on the probe is calculated in the new basis. In this picture EIT resembles a combination of Autler-Townes splitting and Fano interference between the dressed states."<br /> <br /> - For the time being, I'm giving up on Rabi oscillation and Autler-Townes splitting, etc, and want to get an intuitive picture using basic ideas.<br /> <br /> Key question: is this simple approach (that I'm about to show) close enough to be, at least, intuitively useful? Or is it hopeless, and the new (to me) concepts are necessary for any understanding at all?<br /> <br /> Now consider the "ladder" configuration, with 3 states at ascending energy levels. For example 3 adjacent orbitals for an electron in an atom.<br /> <br /> Let's call the 3 states a, b, and c instead of (what seems to be usual) |1>, |2> and |3>, to simplify notation. Should be good enough for this discussion. a is the ground state.<br /> <br /> Transitions a=>b and b=>c must be allowed by selection rules. But a=>c is not; normally you must go through b to get from a to c. The key idea here is to make that a=>c transition possible without stopping at b. Or, for EIT (not so much STIRAP), the key idea is to disallow a=>b. Is there much of a difference between these two "key ideas"?<br /> <br /> We have two lasers tuned to the two allowed transitions: "probe" for a=>b, "coupling" for b=>c. I.e., the photons have the energy needed to transition between those states. For instance if W is the energy gap between a and b, then the probe photons' frequency is W/h.<br /> <br /> First we shine the coupling laser on the atom(s). That "couples" b and c. Thus, if the electron were in b state, it would absorb a photon and "jump" to c.<br /> <br /> Note that it's required for state c to be robust and metastable.<br /> <br /> Question: Since c is metastable the electron won't readily fall to b (which is not very stable). But in the presence of the coupling laser, it would fall easily, due to stimulated emission - right?<br /> <br /> Second, we now shine the probe laser, at a lower intensity. Normally that would cause the electron in a (the ground state) to absorb a probe photon and jump (i.e. transition) to b. Then the coupling photon would be absorbed, the electron would jump to c; it would then transit back to b, by stimulated emission (or, just drop naturally), then maybe it would drop to a. In general it would hop around in the presence of these 2 lasers.<br /> <br /> This is where the "trick", sometimes called "dark state", comes in. There are two paths the electron can take from a to b:<br /> <br /> a=>b<br /> a=>b=>c=>b<br /> <br /> So we cleverly "tune" or "adjust" the whole set-up so that the amplitudes of the wave function for these two paths are out of phase. So, they interfere and cancel, making it impossible for the electron to occupy state b.<br /> <br /> Obviously this adjusting is difficult. Probably that's the "hard part" of the whole technique. But at the moment I'm not interested in those details, just want to get the picture.<br /> <br /> Given it can't live in state b, but it's being stimulated to leave state a, there's only one place it can go, state c. Mission accomplished.<br /> <br /> Question: why doesn't it just stay in, or return to, state a? Or, it can stay in a, and that's alright - the point is just to keep it out of b?<br /> <br /> For EIT the point is not so much to keep it out of b, rather to stop it from absorbing the probe photon, by using it to transit from a=>b. That absorption would destroy the transparency. But then, is it important for it to actually go to c?<br /> <br /> That's as far as I've gotten; getting confused at the end. It may be that my picture is more appropriate for STIRAP, which is what I was first looking at. What I'm hoping to hear is that I've got the right idea, BUT ... followed by an intuitive answer, phrased in my language. (Perhaps I shouldn't try to put together these 3 different techniques?) But if instead, I have to learn Fano interference, etc, to get anywhere, then a link for same would be appreciated. If you wish to give your take on it using those more correct concepts, fine, but don't waste too much of your time. If that's the way it is I'll study any links you might provide and come back later.<br /> <br /> Thanks for reading, if in fact you did!</div> </div> <div class="js-selectToQuoteEnd"> </div> </article> </div> </div> <footer class="message-footer"> <div class="reactionsBar js-reactionsList "> </div> <div class="js-historyTarget message-historyTarget toggleTarget" data-href="trigger-href"></div> </footer> </div> </div> </div> </article>  <article class="message message--post js-post js-inlineModContainer " data-author="secur" data-content="post-5426027" id="js-post-5426027" itemscope itemtype="https://schema.org/Comment" itemid="https://www.physicsforums.com/posts/5426027/"> <meta itemprop="parentItem" itemscope itemid="https://www.physicsforums.com/threads/can-basic-concepts-explain-eit-lwi-and-stirap.863515/" /> <span class="u-anchorTarget" id="post-5426027"></span> <div class="message-header"> <header class="message-attribution message-attribution--split"> <ul class="message-attribution-main listInline "> <li class="u-concealed"> <time class="u-dt" dir="auto" datetime="2016-03-29T21:17:18-0500" data-time="1459304238" data-date-string="Mar 29, 2016" data-time-string="9:17 PM" title="Mar 29, 2016 at 9:17 PM" itemprop="datePublished">Mar 29, 2016</time> </li> </ul> <ul class="message-attribution-opposite message-attribution-opposite--list "> <li> <span style="cursor:pointer;" data-xf-init="share-tooltip" data-href="/posts/5426027/share" aria-label="Share" role="button" rel="nofollow"> <i class="fa--xf fal fa-share-alt" aria-hidden="true"></i> </span> </li> <li> #3 </li> </ul> </header> </div> <div class="message-inner"> <div class="message-cell message-cell--user"> <section class="message-user" itemprop="author" itemscope itemtype="https://schema.org/Person" itemid="https://www.physicsforums.com/members/secur.588176/"> <meta itemprop="url" content="https://www.physicsforums.com/members/secur.588176/" /> <div class="message-userDetails"> <span class="message-name"><span class="username " dir="auto" data-user-id="588176"><span itemprop="name">secur</span></span></span>   <span class="threadstarter" data-xf-init="tooltip" title="Thread Starter"><i class="fal fa-user-edit"></i></span>   </div> <div class="message-userExtras"> <dl class="pairs pairs--justified"> <dt><i class="fa--xf fal fa-comments fa-fw" aria-hidden="true" data-xf-init="tooltip" title="Messages"></i></dt> <dd>381</dd> </dl> <dl class="pairs pairs--justified"> <dt><i class="fa--xf fal fa-thumbs-up fa-fw" aria-hidden="true" data-xf-init="tooltip" title="Reaction score"></i></dt> <dd>118</dd> </dl> </div> <span class="message-userArrow"></span> </section> </div> <div class="message-cell message-cell--main"> <div class="message-main js-quickEditTarget"> <div class="message-content js-messageContent"> <div class="message-userContent lbContainer js-lbContainer " data-lb-id="post-5426027" data-lb-caption-desc="secur · Mar 29, 2016 at 9:17 PM"> <article class="message-body js-selectToQuote"> <div class="googleads_fixed"> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-6580726045122001" crossorigin="anonymous"></script>  <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-6580726045122001" data-ad-slot="5961342082" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div> <div itemprop="text"> <div class="bbWrapper">It's basically a case of "too long; didn't read." Anyway I've figured out a lot of it myself. But any comments or links welcome of course</div> </div> <div class="js-selectToQuoteEnd"> </div> </article> </div> </div> <footer class="message-footer"> <div class="message-microdata" itemprop="interactionStatistic" itemtype="https://schema.org/InteractionCounter" itemscope> <meta itemprop="userInteractionCount" content="0" /> <meta itemprop="interactionType" content="https://schema.org/LikeAction" /> </div> <div class="reactionsBar js-reactionsList "> </div> <div class="js-historyTarget message-historyTarget toggleTarget" data-href="trigger-href"></div> </footer> <script> if (typeof parseNewPost == 'function') { $(document).ajaxStop(parseNewPost(5426027)); } </script> </div> </div> </div> </article> </div> </div> </div> <h2 style="font-weight:bold;"> FAQ: Can basic concepts explain EIT, LWI, and STIRAP? </h2> <h2> What is EIT and how does it work?</h2><p>EIT stands for Electromagnetically Induced Transparency and it is a phenomenon in which the absorption of light by a medium can be greatly reduced due to the presence of a control laser. This is achieved by manipulating the energy levels of the atoms in the medium, creating a "window" of transparency for a specific frequency of light. This effect is used in various applications such as quantum computing and atomic clocks.</p><h2> What is LWI and how is it related to EIT?</h2><p>LWI stands for Light-Induced Waveguiding and it is a technique that uses EIT to control the propagation of light in a medium. By creating a waveguide, or a channel for light to travel through, using EIT, LWI allows for the manipulation of light at the quantum level. This technology has potential applications in quantum computing and communication.</p><h2> What is STIRAP and how is it used in quantum systems?</h2><p>STIRAP stands for Stimulated Raman Adiabatic Passage and it is a technique used to transfer population between two quantum states. It involves using a series of laser pulses to drive the system from one state to another, without causing any non-adiabatic transitions. This technique is used in quantum systems for applications such as quantum information processing and precision measurements.</p><h2> What are the advantages of using EIT, LWI, and STIRAP in quantum systems?</h2><p>One of the main advantages of using EIT, LWI, and STIRAP in quantum systems is the ability to control and manipulate light and matter at the quantum level. This allows for the creation of new quantum technologies such as quantum computers, communication systems, and sensors. Additionally, these techniques offer high precision and low noise, making them ideal for applications that require high accuracy.</p><h2> What are some potential future developments in EIT, LWI, and STIRAP research?</h2><p>Some potential future developments in EIT, LWI, and STIRAP research include the use of these techniques in more advanced quantum technologies, such as quantum teleportation and quantum cryptography. There is also ongoing research in using EIT, LWI, and STIRAP in combination with other quantum technologies to create more complex systems for information processing and communication. 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Are you sure you want to submit this form?", attach: "Attach files", rich_text_box: "Rich text box", close: "Close", link_copied_to_clipboard: "Link copied to clipboard.", text_copied_to_clipboard: "Text copied to clipboard.", loading: "Loading…", you_have_exceeded_maximum_number_of_selectable_items: "You have exceeded the maximum number of selectable items.", processing: "Processing", 'processing...': "Processing…", showing_x_of_y_items: "Showing {count} of {total} items", showing_all_items: "Showing all items", no_items_to_display: "No items to display", number_button_up: "Increase", number_button_down: "Decrease", push_enable_notification_title: "Push notifications enabled successfully at Physics Forums: Science Discussion, Homework Help, Articles", push_enable_notification_body: "Thank you for enabling push notifications!", pull_down_to_refresh: "Pull down to refresh", release_to_refresh: "Release to refresh", refreshing: "Refreshing…" , "svStandardLib_time.day": "{count} day", "svStandardLib_time.days": "{count} days", "svStandardLib_time.hour": "{count} hour", "svStandardLib_time.hours": "{count} hours", "svStandardLib_time.minute": "{count} minutes", "svStandardLib_time.minutes": "{count} minutes", "svStandardLib_time.month": "{count} month", "svStandardLib_time.months": "{count} months", "svStandardLib_time.second": "{count} second", "svStandardLib_time.seconds": "{count} seconds", "svStandardLib_time.week": "time.week", "svStandardLib_time.weeks": "{count} weeks", "svStandardLib_time.year": "{count} year", "svStandardLib_time.years": "{count} years" }); </script> <form style="display:none" hidden="hidden"> <input type="text" name="_xfClientLoadTime" value="" id="_xfClientLoadTime" title="_xfClientLoadTime" tabindex="-1" /> </form>  <script type="application/ld+json"> { "@context": "https://schema.org", "@type": "WebPage", "url": "https://www.physicsforums.com/threads/can-basic-concepts-explain-eit-lwi-and-stirap.863515/", "mainEntity": { "@type": "DiscussionForumPosting", "@id": "https://www.physicsforums.com/threads/can-basic-concepts-explain-eit-lwi-and-stirap.863515/", "headline": "Can basic concepts explain EIT, LWI, and STIRAP?", "datePublished": "2016-03-24T04:20:49+00:00", "keywords": "eit", "url": "https://www.physicsforums.com/threads/can-basic-concepts-explain-eit-lwi-and-stirap.863515/", "articleSection": "Quantum Physics", "author": { "@type": "Person", "@id": "https://www.physicsforums.com/members/secur.588176/", "name": "secur", "url": "https://www.physicsforums.com/members/secur.588176/" }, "interactionStatistic": [ { "@type": "InteractionCounter", "interactionType": "https://schema.org/ViewAction", "userInteractionCount": 1245 }, { "@type": "InteractionCounter", "interactionType": "https://schema.org/CommentAction", "userInteractionCount": 1 }, { "@type": "InteractionCounter", "interactionType": "https://schema.org/LikeAction", "userInteractionCount": 0 } ], "articleBody": "I'm interested in Electromagnetically Induced Transparency (EIT), Lasing Without Interference (LWI) and/or Stimulated Raman adiabatic passage (STIRAP) and have some basic questions.\n\nFirst, I think the concepts involved, at this basic level, are similar for these three. Yes?\n\nI don't understand some of the explanations given in sources. Here are two quotes to illustrate:\n\n\"One approach is to extend the density matrix treatment used to derive Rabi oscillation of a two-state, single field system. In this picture the probability amplitude for the system to transfer between states can interfere destructively, preventing absorption.\"\n\"Another approach is the 'dressed state' picture, wherein the system + coupling field Hamiltonian is diagonalized and the effect on the probe is calculated in the new basis. In this picture EIT resembles a combination of Autler-Townes splitting and Fano interference between the dressed states.\"\n\n- For the time being, I'm giving up on Rabi oscillation and Autler-Townes splitting, etc, and want to get an intuitive picture using basic ideas.\n\nKey question: is this simple approach (that I'm about to show) close enough to be, at least, intuitively useful? Or is it hopeless, and the new (to me) concepts are necessary for any understanding at all?\n\nNow consider the \"ladder\" configuration, with 3 states at ascending energy levels. For example 3 adjacent orbitals for an electron in an atom.\n\nLet's call the 3 states a, b, and c instead of (what seems to be usual) |1>, |2> and |3>, to simplify notation. Should be good enough for this discussion. a is the ground state.\n\nTransitions a=>b and b=>c must be allowed by selection rules. But a=>c is not; normally you must go through b to get from a to c. The key idea here is to make that a=>c transition possible without stopping at b. Or, for EIT (not so much STIRAP), the key idea is to disallow a=>b. Is there much of a difference between these two \"key ideas\"?\n\nWe have two lasers tuned to the two allowed transitions: \"probe\" for a=>b, \"coupling\" for b=>c. I.e., the photons have the energy needed to transition between those states. For instance if W is the energy gap between a and b, then the probe photons' frequency is W/h.\n\nFirst we shine the coupling laser on the atom(s). That \"couples\" b and c. Thus, if the electron were in b state, it would absorb a photon and \"jump\" to c.\n\nNote that it's required for state c to be robust and metastable.\n\nQuestion: Since c is metastable the electron won't readily fall to b (which is not very stable). But in the presence of the coupling laser, it would fall easily, due to stimulated emission - right?\n\nSecond, we now shine the probe laser, at a lower intensity. Normally that would cause the electron in a (the ground state) to absorb a probe photon and jump (i.e. transition) to b. Then the coupling photon would be absorbed, the electron would jump to c; it would then transit back to b, by stimulated emission (or, just drop naturally), then maybe it would drop to a. In general it would hop around in the presence of these 2 lasers.\n\nThis is where the \"trick\", sometimes called \"dark state\", comes in. There are two paths the electron can take from a to b:\n\na=>b\na=>b=>c=>b\n\nSo we cleverly \"tune\" or \"adjust\" the whole set-up so that the amplitudes of the wave function for these two paths are out of phase. So, they interfere and cancel, making it impossible for the electron to occupy state b.\n\nObviously this adjusting is difficult. Probably that's the \"hard part\" of the whole technique. But at the moment I'm not interested in those details, just want to get the picture.\n\nGiven it can't live in state b, but it's being stimulated to leave state a, there's only one place it can go, state c. Mission accomplished.\n\nQuestion: why doesn't it just stay in, or return to, state a? Or, it can stay in a, and that's alright - the point is just to keep it out of b?\n\nFor EIT the point is not so much to keep it out of b, rather to stop it from absorbing the probe photon, by using it to transit from a=>b. That absorption would destroy the transparency. But then, is it important for it to actually go to c?\n\nThat's as far as I've gotten; getting confused at the end. It may be that my picture is more appropriate for STIRAP, which is what I was first looking at. What I'm hoping to hear is that I've got the right idea, BUT ... followed by an intuitive answer, phrased in my language. (Perhaps I shouldn't try to put together these 3 different techniques?) But if instead, I have to learn Fano interference, etc, to get anywhere, then a link for same would be appreciated. If you wish to give your take on it using those more correct concepts, fine, but don't waste too much of your time. If that's the way it is I'll study any links you might provide and come back later.\n\nThanks for reading, if in fact you did!" }, "publisher": { "@type": "Organization", "name": "Physics Forums: Science Discussion, Homework Help, Articles", "alternateName": "Physics Forums", "description": "Join Physics Forums, where students, scientists, and enthusiasts come together to explore and discuss the current understanding and practice of various scientific fields.", "url": "https://www.physicsforums.com", "logo": "https://www.physicsforums.com/styles/physicsforums/images/physics-forums-logo-og.png" } } </script> <script type="text/javascript" src="https://www.physicsforums.com/copyright.js" defer></script> <script> function parseNewPost(postid) { var newpost = document.getElementById("js-post-" + postid), npa = [newpost]; MathJax.typeset(npa); } function parsePreview() { var preview = document.getElementsByClassName("xfPreview"); MathJax.typeset(preview); } function parseNewConversationPost(postid) { var newpost = document.getElementsByClassName("convMessage-" + postid); MathJax.typeset(newpost); } function parseNewProfilePost(postid) { var newpost = document.getElementById("js-profilePost-" + postid), npa = [newpost]; MathJax.typeset(npa); } function parseTooltip() { MathJax.typeset(); } </script> </body> </html>

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Can basic concepts explain EIT, LWI, and STIRAP?