中国物理B ›› 2017, Vol. 26 ›› Issue (6): 60308-060308.doi: 10.1088/1674-1056/26/6/060308

• GENERAL • 上一篇    下一篇

Superconducting phase qubits with shadow-evaporated Josephson junctions

Fei-Fan Su(宿非凡), Wei-Yang Liu(刘伟洋), Hui-Kai Xu(徐晖凯), Hui Deng(邓辉), Zhi-Yuan Li(李志远), Ye Tian(田野), Xiao-Bo Zhu(朱晓波), Dong-Ning Zheng(郑东宁), Li Lv(吕力), Shi-Ping Zhao(赵士平)   

  1. 1 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;
    2 School of Physical Sciences, University of Chinese Academy of Sciences(CAS), Beijing 100049, China;
    3 National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China;
    4 CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China;
    5 Collaborative Innovation Center of Quantum Matter, Beijing, China
  • 收稿日期:2017-01-13 修回日期:2017-02-28 出版日期:2017-06-05 发布日期:2017-06-05
  • 通讯作者: Shi-Ping Zhao E-mail:spzhao@iphy.ac.cn
  • 基金资助:
    Project supported by the National Basic Research Program of China (Grant Nos. 2014CB921202, 2015CB921104, and 2016YFA0300601) and the National Natural Science Foundation of China (Grant Nos. 91321208 and 11674380).

Superconducting phase qubits with shadow-evaporated Josephson junctions

Fei-Fan Su(宿非凡)1,2, Wei-Yang Liu(刘伟洋)1,2, Hui-Kai Xu(徐晖凯)1,2, Hui Deng(邓辉)1, Zhi-Yuan Li(李志远)1,3, Ye Tian(田野)1, Xiao-Bo Zhu(朱晓波)4, Dong-Ning Zheng(郑东宁)1, Li Lv(吕力)1, Shi-Ping Zhao(赵士平)1,2,5   

  1. 1 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;
    2 School of Physical Sciences, University of Chinese Academy of Sciences(CAS), Beijing 100049, China;
    3 National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China;
    4 CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China;
    5 Collaborative Innovation Center of Quantum Matter, Beijing, China
  • Received:2017-01-13 Revised:2017-02-28 Online:2017-06-05 Published:2017-06-05
  • Contact: Shi-Ping Zhao E-mail:spzhao@iphy.ac.cn
  • Supported by:
    Project supported by the National Basic Research Program of China (Grant Nos. 2014CB921202, 2015CB921104, and 2016YFA0300601) and the National Natural Science Foundation of China (Grant Nos. 91321208 and 11674380).

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摘要： We develop a fabrication process for the superconducting phase qubits in which Josephson junctions for both the qubit and superconducting quantum interference device (SQUID) detector are prepared by shadow evaporation with a suspended bridge. Al junctions with areas as small as 0.05 μ2 are fabricated for the qubit, in which the number of the decoherence-causing two-level systems (TLS) residing in the tunnel barrier and proportional to the junction area are greatly reduced. The measured energy spectrum shows no avoided crossing arising from coherent TLS in the experimentally reachable flux bias range of the phase qubit, which demonstrates the energy relaxation time T1 and dephasing time Tφ on the order of 100 ns and 50 ns, respectively. We discuss several possible origins of decoherence from incoherent or weakly-coupled coherent TLS and further improvements of the qubit performance.

关键词: superconducting phase qubit, two-level system, decoherence, shadow evaporated junction

Abstract: We develop a fabrication process for the superconducting phase qubits in which Josephson junctions for both the qubit and superconducting quantum interference device (SQUID) detector are prepared by shadow evaporation with a suspended bridge. Al junctions with areas as small as 0.05 μ2 are fabricated for the qubit, in which the number of the decoherence-causing two-level systems (TLS) residing in the tunnel barrier and proportional to the junction area are greatly reduced. The measured energy spectrum shows no avoided crossing arising from coherent TLS in the experimentally reachable flux bias range of the phase qubit, which demonstrates the energy relaxation time T1 and dephasing time Tφ on the order of 100 ns and 50 ns, respectively. We discuss several possible origins of decoherence from incoherent or weakly-coupled coherent TLS and further improvements of the qubit performance.

Key words: superconducting phase qubit, two-level system, decoherence, shadow evaporated junction

中图分类号:  (Quantum computation architectures and implementations)

  • 03.67.Lx
03.65.Yz (Decoherence; open systems; quantum statistical methods) 85.25.Cp (Josephson devices) 74.50.+r (Tunneling phenomena; Josephson effects)