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Chin. Phys. B, 2012, Vol. 21(4): 040307    DOI: 10.1088/1674-1056/21/4/040307
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Flux qubit with a large loop size and tunable Josephson junctions

Deng Hui(邓辉), Yu Hai-Feng(于海峰), Xue Guang-Ming(薛光明), Tian Ye(田野), Ren Jian-Kun(任建坤), Wu Yu-Lin(吴玉林), Huang Ke-Qiang(黄克强), Zhao Shi-Ping(赵士平), and Zheng Dong-Ning(郑东宁)
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Abstract  We present the design of a superconducting flux qubit with a large loop inductance. The large loop inductance is desirable for coupling between qubits. The loop is configured into a gradiometer form that could reduce the interference from environmental magnetic noise. A combined Josephson junction, i.e., a DC-SQUID is used to replace the small Josephson junction in the usual 3-JJ (Josephaon junction) flux qubit, leading to a tunable energy gap by using an independent external flux line. We perform numerical calculations to investigate the dependence of the energy gap on qubit parameters such as junction capacitance, critical current, loop inductance, and the ratio of junction energy between small and large junctions in the flux qubit. We suggest a range of values for the parameters.
Keywords:  flux qubit      four Josephson junctions      tunable energy gap  
Received:  16 December 2011      Revised:  29 December 2011      Accepted manuscript online: 
PACS:  03.67.Lx (Quantum computation architectures and implementations)  
  85.25.Cp (Josephson devices)  
  85.25.Dq (Superconducting quantum interference devices (SQUIDs))  
Fund: Project supported by the National Basic Research Program of China(Grant Nos.2011CBA00106 and 2009CB929102)and the National Natural Science Foundation of China(Grant Nos.11104340,11161130519,and 10974243)
Corresponding Authors:  Zheng Dong-Ning, E-mail:dzheng@aphy.iphy.ac.cn     E-mail:  dzheng@aphy.iphy.ac.cn

Cite this article: 

Deng Hui(邓辉), Yu Hai-Feng(于海峰), Xue Guang-Ming(薛光明), Tian Ye(田野), Ren Jian-Kun(任建坤), Wu Yu-Lin(吴玉林), Huang Ke-Qiang(黄克强), Zhao Shi-Ping(赵士平), and Zheng Dong-Ning(郑东宁) Flux qubit with a large loop size and tunable Josephson junctions 2012 Chin. Phys. B 21 040307

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