{"id":1103,"date":"2005-10-17T15:39:37","date_gmt":"2005-10-17T22:39:37","guid":{"rendered":"http:\/\/dabacon.org\/pontiff\/?p=1103"},"modified":"2005-10-17T15:39:37","modified_gmt":"2005-10-17T22:39:37","slug":"1103","status":"publish","type":"post","link":"https:\/\/dabacon.org\/pontiff\/2005\/10\/17\/1103\/","title":{"rendered":"Your Symmetry Broke My Quantum Computer?"},"content":{"rendered":"

An article<\/a> in Scientific American (of all places….I stopped reading Scientific American when they started a section on science\/pseudoscience. Sure I agree with them, but I don’t want to read a science magazine to read about how science is different from pseudoscience, I already know that. Plus they stopped the amateur science section and mathematical recreations section: really the two best reasons to read Scientific American in the good old days) on a mechanism for decoherence due to symmetry breaking.<\/p>\n

\nJeroen van den Brink and his colleagues at Leiden University in the Netherlands, however, suggest that even perfect isolation would not keep decoherence at bay. A process called spontaneous symmetry breaking will ruin the delicate state required for quantum computing. In the case of one proposed device based on superconducting quantum bits (qubits), they predict that this new source of decoherence would degrade the qubits after just a few seconds.\n<\/p><\/blockquote>\n

The paper in question, published in Physical Review Letters (and available as quant-ph\/0408357<\/del>cond-mat\/0408357<\/a>) presents an interesting mechanism for decoherence. What is most interesting about this decoherence mechanism is the rate they obtain for decoherence: [tex]$t_D={N h over k_B T}$[\/tex], where N is the number of microscopic degress of freedom, and h, k_B, and T should be recognizable to every physicist \ud83d\ude09
\nWhat does this mean for quantum computers? Well the above might indicate that this is some fundamental limit for quantum computing (and in particular for superconducting implementations of quantum computers for which this result will hold). But I don’t think this is true. I’ll let the article explain why:<\/p>\n

\nNot everyone agrees that the constraint of a few seconds is a serious obstacle for superconducting qubits. John Martinis of the University of California at Santa Barbara says that one second “is fine for us experimentalists, since I think other physics will limit us well before this timescale.” According to theorist Steven M. Girvin of Yale University, “if we could get a coherence time of one second for a superconducting qubit, that would mean that decoherence would probably not be a limitation at all.” That is because quantum error correction can overcome decoherence once the coherence time is long enough, Girvin argues. By running on batches of qubits that each last for only a second, a quantum computer as a whole could continue working indefinitely.\n<\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"

An article in Scientific American (of all places….I stopped reading Scientific American when they started a section on science\/pseudoscience. Sure I agree with them, but I don’t want to read a science magazine to read about how science is different from pseudoscience, I already know that. Plus they stopped the amateur science section and mathematical … <\/p>\n

Continue reading “Your Symmetry Broke My Quantum Computer?”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[20,53,63],"tags":[],"class_list":["post-1103","post","type-post","status-publish","format-standard","hentry","category-computer-science","category-physics","category-quantum"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/dabacon.org\/pontiff\/wp-json\/wp\/v2\/posts\/1103","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dabacon.org\/pontiff\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dabacon.org\/pontiff\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dabacon.org\/pontiff\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dabacon.org\/pontiff\/wp-json\/wp\/v2\/comments?post=1103"}],"version-history":[{"count":0,"href":"https:\/\/dabacon.org\/pontiff\/wp-json\/wp\/v2\/posts\/1103\/revisions"}],"wp:attachment":[{"href":"https:\/\/dabacon.org\/pontiff\/wp-json\/wp\/v2\/media?parent=1103"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dabacon.org\/pontiff\/wp-json\/wp\/v2\/categories?post=1103"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dabacon.org\/pontiff\/wp-json\/wp\/v2\/tags?post=1103"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}