{"id":198425,"date":"2024-10-29T00:27:20","date_gmt":"2024-10-29T05:27:20","guid":{"rendered":"https:\/\/lifeboat.com\/blog\/2024\/10\/the-floquet-fluxonium-molecule-driving-down-dephasing-in-coupled-superconducting-qubits"},"modified":"2024-10-29T00:27:20","modified_gmt":"2024-10-29T05:27:20","slug":"the-floquet-fluxonium-molecule-driving-down-dephasing-in-coupled-superconducting-qubits","status":"publish","type":"post","link":"https:\/\/lifeboat.com\/blog\/2024\/10\/the-floquet-fluxonium-molecule-driving-down-dephasing-in-coupled-superconducting-qubits","title":{"rendered":"The Floquet Fluxonium Molecule: Driving Down Dephasing in Coupled Superconducting Qubits"},"content":{"rendered":"<p><a class=\"blog-photo\" href=\"https:\/\/lifeboat.com\/blog.images\/the-floquet-fluxonium-molecule-driving-down-dephasing-in-coupled-superconducting-qubits2.jpg\"><\/a><\/p>\n<p>Here we propose a novel protected erasure qubit, the Floquet fluxonium molecule (FFM). The FFM qubit exhibits (i) extremely long predicted logical coherence times and relatively long erasure lifetimes, (ii) a simple superconducting circuit structure, and (iii) high-fidelity single-qubit gates, which are much faster than the coherence timescale. Based on a Floquet-driven pair of inductively coupled fluxonium circuits [13\u201315], the FFM is a multi-DOF superconducting circuit with engineered, highly coherent quasieigenstates.<\/p>\n<p>Our key technical contribution is a novel form of Floquet protection in a multi-DOF qubit, which strongly suppresses phase-flip errors, removing them at first and second order in the flux noise. The combination of drive and multi-DOF allows the low-lying eigenstates to be disjoint and delocalized with a nonvanishing energy gap. The second-order sweet spot has no analogue in the single-DOF circuits that have been studied thus far [16\u201318]; in fact, in single-DOF circuits there is a generic trade-off between bit-and phase-flip errors arising from the inability to keep two eigenstates simultaneously disjoint and flux delocalized using accessible circuit QED Hamiltonians [19].<\/p>\n<p>The higher-order phase-flip in<i>sensitivity<\/i> allow the predicted coherence time of the FFM qubit to significantly outperform other multi-DOF circuits. These include the following: the dual-rail erasure transmon, with experimentally achieved logical lifetimes of approximately ms and erasure lifetimes of approximately [12]; the dual-rail cavity, with logical lifetimes predicted [10] (achieved [11]) at approximately ms (3 ms), limited by cavity and ancilla dephasing, and erasure lifetimes of approximately in both cases; and the cold echo qubit, with predicted logical lifetime of ms with erasure rates unreported [8]. Theoretically, we find the FFM exhibits long bit-flip coherence times of approximately 50 ms while suppressing phase flips even further, along with a 500-erasure lifetime.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Here we propose a novel protected erasure qubit, the Floquet fluxonium molecule (FFM). The FFM qubit exhibits (i) extremely long predicted logical coherence times and relatively long erasure lifetimes, (ii) a simple superconducting circuit structure, and (iii) high-fidelity single-qubit gates, which are much faster than the coherence timescale. Based on a Floquet-driven pair of inductively [\u2026]<\/p>\n","protected":false},"author":709,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1497,1617],"tags":[],"class_list":["post-198425","post","type-post","status-publish","format-standard","hentry","category-energy","category-quantum-physics"],"_links":{"self":[{"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/posts\/198425","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/users\/709"}],"replies":[{"embeddable":true,"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/comments?post=198425"}],"version-history":[{"count":0,"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/posts\/198425\/revisions"}],"wp:attachment":[{"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/media?parent=198425"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/categories?post=198425"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/tags?post=198425"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}