Anneal-path correction in flux qubits

Abstract Quantum annealers require accurate control and optimized operation schemes to reduce noise levels, in order to eventually demonstrate a computational advantage over classical algorithms. We study a high coherence four-junction capacitively shunted flux qubit (CSFQ), using dispersive measure...

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Main Authors:	Mostafa Khezri, Jeffrey A. Grover, James I. Basham, Steven M. Disseler, Huo Chen, Sergey Novikov, Kenneth M. Zick, Daniel A. Lidar
Format:	article
Language:	EN
Published:	Nature Portfolio 2021
Subjects:	Physics QC1-999 Electronic computers. Computer science QA75.5-76.95
Online Access:	https://doaj.org/article/65b8ffe8f23b46ba828fa8400d4b4c05
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spelling	oai:doaj.org-article:65b8ffe8f23b46ba828fa8400d4b4c052021-12-02T14:04:43ZAnneal-path correction in flux qubits10.1038/s41534-021-00371-92056-6387https://doaj.org/article/65b8ffe8f23b46ba828fa8400d4b4c052021-02-01T00:00:00Zhttps://doi.org/10.1038/s41534-021-00371-9https://doaj.org/toc/2056-6387Abstract Quantum annealers require accurate control and optimized operation schemes to reduce noise levels, in order to eventually demonstrate a computational advantage over classical algorithms. We study a high coherence four-junction capacitively shunted flux qubit (CSFQ), using dispersive measurements to extract system parameters and model the device. Josephson junction asymmetry inherent to the device causes a deleterious nonlinear cross-talk when annealing the qubit. We implement a nonlinear annealing path to correct the asymmetry in situ, resulting in a substantial increase in the probability of the qubit being in the correct state given an applied flux bias. We also confirm the multi-level structure of our CSFQ circuit model by annealing it through small spectral gaps and observing quantum signatures of energy level crossings. Our results demonstrate an anneal-path correction scheme designed and implemented to improve control accuracy for high-coherence and high-control quantum annealers, which leads to an enhancement of success probability in annealing protocols.Mostafa KhezriJeffrey A. GroverJames I. BashamSteven M. DisselerHuo ChenSergey NovikovKenneth M. ZickDaniel A. LidarNature PortfolioarticlePhysicsQC1-999Electronic computers. Computer scienceQA75.5-76.95ENnpj Quantum Information, Vol 7, Iss 1, Pp 1-8 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Physics QC1-999 Electronic computers. Computer science QA75.5-76.95
spellingShingle	Physics QC1-999 Electronic computers. Computer science QA75.5-76.95 Mostafa Khezri Jeffrey A. Grover James I. Basham Steven M. Disseler Huo Chen Sergey Novikov Kenneth M. Zick Daniel A. Lidar Anneal-path correction in flux qubits
description	Abstract Quantum annealers require accurate control and optimized operation schemes to reduce noise levels, in order to eventually demonstrate a computational advantage over classical algorithms. We study a high coherence four-junction capacitively shunted flux qubit (CSFQ), using dispersive measurements to extract system parameters and model the device. Josephson junction asymmetry inherent to the device causes a deleterious nonlinear cross-talk when annealing the qubit. We implement a nonlinear annealing path to correct the asymmetry in situ, resulting in a substantial increase in the probability of the qubit being in the correct state given an applied flux bias. We also confirm the multi-level structure of our CSFQ circuit model by annealing it through small spectral gaps and observing quantum signatures of energy level crossings. Our results demonstrate an anneal-path correction scheme designed and implemented to improve control accuracy for high-coherence and high-control quantum annealers, which leads to an enhancement of success probability in annealing protocols.
format	article
author	Mostafa Khezri Jeffrey A. Grover James I. Basham Steven M. Disseler Huo Chen Sergey Novikov Kenneth M. Zick Daniel A. Lidar
author_facet	Mostafa Khezri Jeffrey A. Grover James I. Basham Steven M. Disseler Huo Chen Sergey Novikov Kenneth M. Zick Daniel A. Lidar
author_sort	Mostafa Khezri
title	Anneal-path correction in flux qubits
title_short	Anneal-path correction in flux qubits
title_full	Anneal-path correction in flux qubits
title_fullStr	Anneal-path correction in flux qubits
title_full_unstemmed	Anneal-path correction in flux qubits
title_sort	anneal-path correction in flux qubits
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/65b8ffe8f23b46ba828fa8400d4b4c05
work_keys_str_mv	AT mostafakhezri annealpathcorrectioninfluxqubits AT jeffreyagrover annealpathcorrectioninfluxqubits AT jamesibasham annealpathcorrectioninfluxqubits AT stevenmdisseler annealpathcorrectioninfluxqubits AT huochen annealpathcorrectioninfluxqubits AT sergeynovikov annealpathcorrectioninfluxqubits AT kennethmzick annealpathcorrectioninfluxqubits AT danielalidar annealpathcorrectioninfluxqubits
_version_	1718392024616402944

Anneal-path correction in flux qubits

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