{"id":12756,"date":"2017-07-30T06:33:41","date_gmt":"2017-07-30T06:33:41","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=12756"},"modified":"2017-07-30T06:33:41","modified_gmt":"2017-07-30T06:33:41","slug":"ultracold-molecules-hold-promise-quantum-computing","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/ultracold-molecules-hold-promise-quantum-computing\/","title":{"rendered":"Ultracold molecules hold promise for quantum computing"},"content":{"rendered":"

New approach yields long-lasting configurations that could provide long-sought \u201cqubit\u201d material.<\/strong><\/span><\/p>\n

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This vacuum chamber with apertures for several laser beams was used to cool molecules of sodium-potassium down to temperatures of a few hundred nanoKelvins, or billionths of a degree above absolute zero. Such molecules could be used as a new kind of qubit, a building block for eventual quantum computers.
Courtesy of the researchers<\/figcaption><\/figure>\n

CAMBRIDGE, Mass. — Researchers have taken an important step toward the long-sought goal of a quantum computer, which in theory should be capable of vastly faster computations than conventional computers, for certain kinds of problems. The new work shows that collections of ultracold molecules can retain the information stored in them, for hundreds of times longer than researchers have previously achieved in these materials.<\/span><\/p>\n

These two-atom molecules are made of sodium and potassium and were cooled to temperatures just a few ten-millionths of a degree above absolute zero (measured in hundreds of nanokelvins, or nK). The results are described in a report this week in\u00a0Science<\/em>, by Martin Zwierlein, an MIT professor of physics; Jee Woo Park, a former MIT graduate student; Sebastian Will, a former research scientist at MIT and now an assistant professor at Columbia University, and two others, all at the MIT-Harvard Center for Ultracold Atoms.<\/span><\/p>\n

Many different approaches are being studied as possible ways of creating qubits, the basic building blocks of long-theorized but not yet fully realized quantum computers. Researchers have tried using superconducting materials, ions held in ion traps, or individual neutral atoms, as well as molecules of varying complexity. The new approach uses a cluster of very simple molecules made of just two atoms.<\/span><\/p>\n

\u201cMolecules have more \u2018handles\u2019 than atoms,\u201d Zwierlein says, meaning more ways to interact with each other and with outside influences. \u201cThey can vibrate, they can rotate, and in fact they can strongly interact with each other, which atoms have a hard time doing. Typically, atoms have to really meet each other, be on top of each other almost, before they see that there’s another atom there to interact with, whereas molecules can see each other\u201d over relatively long ranges. \u201cIn order to make these qubits talk to each other and perform calculations, using molecules is a much better idea than using atoms,\u201d he says.<\/span><\/p>\n

Using this kind of two-atom molecules for quantum information processing \u201chad been suggested some time ago,\u201d says Park, \u201cand this work demonstrates the first experimental step toward realizing this new platform, which is that quantum information can be stored in dipolar molecules for extended times.\u201d<\/span><\/p>\n

\u201cThe most amazing thing is that [these] molecules are a system which may allow realizing both storage and processing of quantum information, using the very same physical system,\u201d Will says. \u201cThat is actually a pretty rare feature that is not typical at all among the qubit systems that are mostly considered today.\u201d<\/span><\/p>\n

In the team\u2019s initial proof-of-principle lab tests, a few thousand of the simple molecules were contained in a microscopic puff of gas, trapped at the intersection of two laser beams and cooled to ultracold temperatures of about 300 nanokelvins. \u201cThe more atoms you have in a molecule the harder it gets to cool them,\u201d Zwierlein says, so they chose this simple two-atom structure. \u00a0<\/span><\/p>\n

The molecules have three key characteristics: rotation, vibration, and the spin direction of the nuclei of the two individual atoms. For these experiments, the researchers got the molecules under perfect control in terms of all three characteristics \u2014 that is, into the lowest state of vibration, rotation, and nuclear spin alignment.<\/span><\/p>\n

\u201cWe have been able to trap molecules for a long time, and also demonstrate that they can carry quantum information and hold onto it for a long time,\u201d Zwierlein says. And that, he says, is \u201cone of the key breakthroughs or milestones one has to have before hoping to build a quantum computer, which is a much more complicated endeavor.\u201d<\/span><\/p>\n

The use of sodium-potassium molecules provides a number of advantages, Zwierlein says. For one thing, \u201cthe molecule is chemically stable, so if one of these molecules meets another one they don’t break apart.\u201d<\/span><\/p>\n

In the context of quantum computing, the \u201clong time\u201d Zwierlein refers to is one second \u2014 which is \u201cin fact on the order of a thousand times longer than a comparable experiment that has been done\u201d using rotation to encode the qubit, he says. \u201cWithout additional measures, that experiment gave a millisecond, but this was great already.\u201d With this team\u2019s method, the system\u2019s inherent stability means \u201cyou get a full second for free.\u201d<\/span><\/p>\n

That suggests, though it remains to be proven, that such a system would be able to carry out thousands of quantum computations, known as gates, in sequence within that second of coherence. The final results could then be \u201cread\u201d optically through a microscope, revealing the final state of the molecules.<\/span><\/p>\n

\u201cWe have strong hopes that we can do one so-called gate \u2014 that’s an operation between two of these qubits, like addition, subtraction, or that sort of equivalent \u2014 in a fraction of a millisecond,\u201d Zwierlein says. \u201cIf you look at the ratio, you could hope to do 10,000 to 100,000 gate operations in the time that we have the coherence in the sample. That has been stated as one of the requirements for a quantum computer, to have that sort of ratio of gate operations to coherence times.\u201d<\/span><\/p>\n

\u201cThe next great goal will be to \u2018talk\u2019 to individual molecules. Then we are really talking quantum information,\u201d Will says. \u201cIf we can trap one molecule, we can trap two. And then we can think about implementing a \u2018quantum gate operation\u2019 \u2014 an elementary calculation \u2014 between two molecular qubits that sit next to each other,\u201d he says.<\/span><\/p>\n

Using an array of perhaps 1,000 such molecules, Zwierlein says, would make it possible to carry out calculations so complex that no existing computer could even begin to check the possibilities. Though he stresses that this is still an early step and that such computers could be a decade or more away, in principle such a device could quickly solve currently intractable problems such as factoring very large numbers \u2014 a process whose difficulty forms the basis of today\u2019s best encryption systems for financial transactions.<\/span><\/p>\n

Besides quantum computing, the new system also offers the potential for a new way of carrying out precision measurements and quantum chemistry, Zwierlein says.<\/span><\/p>\n

The team also included MIT graduate student Zoe Yan and postdoc Huanqian Loh. The work was supported by the National Science Foundation, the U.S. Air Force Office of Scientific Research, the U.S. Army Research Office, and the David and Lucile Packard Foundation.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

New approach yields long-lasting configurations that could provide long-sought \u201cqubit\u201d material. CAMBRIDGE, Mass. — Researchers have taken an important step toward the long-sought goal of a quantum computer, which in theory should be capable of vastly faster computations than conventional computers, for certain kinds of problems. The new work shows that collections of ultracold molecules […]<\/p>\n","protected":false},"author":6,"featured_media":12757,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-12756","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",575,383,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/07\/MIT-UltraColdQ_0.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/12756","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=12756"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/12756\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/12757"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=12756"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=12756"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=12756"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}