Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit

The heavy-fluxonium circuit is a promising building block for superconducting quantum processors due to its long relaxation and dephasing time at the flux-frustration point. However, the suppressed charge matrix elements and low transition frequency make it challenging to perform fast single-qubit g...

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Autores principales:	Helin Zhang, Srivatsan Chakram, Tanay Roy, Nathan Earnest, Yao Lu, Ziwen Huang, D. K. Weiss, Jens Koch, David I. Schuster
Formato:	article
Lenguaje:	EN
Publicado:	American Physical Society 2021
Materias:	Physics QC1-999
Acceso en línea:	https://doaj.org/article/76b2640a0f0c4316b0312514a26cd76a
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spelling	oai:doaj.org-article:76b2640a0f0c4316b0312514a26cd76a2021-12-02T14:26:23ZUniversal Fast-Flux Control of a Coherent, Low-Frequency Qubit10.1103/PhysRevX.11.0110102160-3308https://doaj.org/article/76b2640a0f0c4316b0312514a26cd76a2021-01-01T00:00:00Zhttp://doi.org/10.1103/PhysRevX.11.011010http://doi.org/10.1103/PhysRevX.11.011010https://doaj.org/toc/2160-3308The heavy-fluxonium circuit is a promising building block for superconducting quantum processors due to its long relaxation and dephasing time at the flux-frustration point. However, the suppressed charge matrix elements and low transition frequency make it challenging to perform fast single-qubit gates using standard protocols. We report on new protocols for reset, fast coherent control, and readout that allow high-quality operation of the qubit with a 14 MHz transition frequency, an order of magnitude lower in energy than the ambient thermal energy scale. We utilize higher levels of the fluxonium to read out the qubit state and to initialize the qubit with 97% fidelity corresponding to cooling it to 190 μK. Instead of using standard microwave pulses, we control the qubit only with fast-flux pulses, generating control fields much larger than the qubit frequency. We develop a universal set of gates based on nonadiabatic Landau-Zener transitions that act in 20–60 ns, less than the single-qubit Larmor period. We measure qubit coherence of T_{1},T_{2e}∼300 μs for a fluxonium in a 2D architecture and realize single-qubit gates with an average gate fidelity of 99.8% as characterized by randomized benchmarking.Helin ZhangSrivatsan ChakramTanay RoyNathan EarnestYao LuZiwen HuangD. K. WeissJens KochDavid I. SchusterAmerican Physical SocietyarticlePhysicsQC1-999ENPhysical Review X, Vol 11, Iss 1, p 011010 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Physics QC1-999
spellingShingle	Physics QC1-999 Helin Zhang Srivatsan Chakram Tanay Roy Nathan Earnest Yao Lu Ziwen Huang D. K. Weiss Jens Koch David I. Schuster Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit
description	The heavy-fluxonium circuit is a promising building block for superconducting quantum processors due to its long relaxation and dephasing time at the flux-frustration point. However, the suppressed charge matrix elements and low transition frequency make it challenging to perform fast single-qubit gates using standard protocols. We report on new protocols for reset, fast coherent control, and readout that allow high-quality operation of the qubit with a 14 MHz transition frequency, an order of magnitude lower in energy than the ambient thermal energy scale. We utilize higher levels of the fluxonium to read out the qubit state and to initialize the qubit with 97% fidelity corresponding to cooling it to 190 μK. Instead of using standard microwave pulses, we control the qubit only with fast-flux pulses, generating control fields much larger than the qubit frequency. We develop a universal set of gates based on nonadiabatic Landau-Zener transitions that act in 20–60 ns, less than the single-qubit Larmor period. We measure qubit coherence of T_{1},T_{2e}∼300 μs for a fluxonium in a 2D architecture and realize single-qubit gates with an average gate fidelity of 99.8% as characterized by randomized benchmarking.
format	article
author	Helin Zhang Srivatsan Chakram Tanay Roy Nathan Earnest Yao Lu Ziwen Huang D. K. Weiss Jens Koch David I. Schuster
author_facet	Helin Zhang Srivatsan Chakram Tanay Roy Nathan Earnest Yao Lu Ziwen Huang D. K. Weiss Jens Koch David I. Schuster
author_sort	Helin Zhang
title	Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit
title_short	Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit
title_full	Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit
title_fullStr	Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit
title_full_unstemmed	Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit
title_sort	universal fast-flux control of a coherent, low-frequency qubit
publisher	American Physical Society
publishDate	2021
url	https://doaj.org/article/76b2640a0f0c4316b0312514a26cd76a
work_keys_str_mv	AT helinzhang universalfastfluxcontrolofacoherentlowfrequencyqubit AT srivatsanchakram universalfastfluxcontrolofacoherentlowfrequencyqubit AT tanayroy universalfastfluxcontrolofacoherentlowfrequencyqubit AT nathanearnest universalfastfluxcontrolofacoherentlowfrequencyqubit AT yaolu universalfastfluxcontrolofacoherentlowfrequencyqubit AT ziwenhuang universalfastfluxcontrolofacoherentlowfrequencyqubit AT dkweiss universalfastfluxcontrolofacoherentlowfrequencyqubit AT jenskoch universalfastfluxcontrolofacoherentlowfrequencyqubit AT davidischuster universalfastfluxcontrolofacoherentlowfrequencyqubit
_version_	1718391318600744960

Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit

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