Letter | Published:

Coherent quantum phase slip

Nature volume 484, pages 355358 (19 April 2012) | Download Citation

Abstract

A hundred years after the discovery of superconductivity, one fundamental prediction of the theory, coherent quantum phase slip (CQPS), has not been observed. CQPS is a phenomenon exactly dual1 to the Josephson effect; whereas the latter is a coherent transfer of charges between superconducting leads2,3, the former is a coherent transfer of vortices or fluxes across a superconducting wire. In contrast to previously reported observations4,5,6,7,8 of incoherent phase slip, CQPS has been only a subject of theoretical study9,10,11,12. Its experimental demonstration is made difficult by quasiparticle dissipation due to gapless excitations in nanowires or in vortex cores. This difficulty might be overcome by using certain strongly disordered superconductors near the superconductor–insulator transition. Here we report direct observation of CQPS in a narrow segment of a superconducting loop made of strongly disordered indium oxide; the effect is made manifest through the superposition of quantum states with different numbers of flux quanta13. As with the Josephson effect, our observation should lead to new applications in superconducting electronics and quantum metrology1,10,11.

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Acknowledgements

We are grateful to M. Feigel’man, J. Mooij and Y. Nazarov for discussions. This work was supported by Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST), MEXT KAKENHI “Quantum Cybernetics”, Ministry of Science and Education of Russian Federation grant 2010-1.5-508-005-037. L.B.I. was supported by ARO W911NF-09-1-0395, DARPA HR0011-09-1- 0009 and NIRT ECS-0608842. D.S. and O.C. were supported by Minerva Fund.

Author information

Affiliations

  1. NEC Green Innovation Research Laboratories, 34 Miyukigaoka, Tsukuba, Ibaraki, 305-8501, Japan

    • O. V. Astafiev
    • , S. Kafanov
    • , Yu. A. Pashkin
    •  & J. S. Tsai
  2. The Institute of Physical and Chemical Research (RIKEN), 34 Miyukigaoka, Tsukuba, Ibaraki, 305-8501, Japan

    • O. V. Astafiev
    • , S. Kafanov
    • , Yu. A. Pashkin
    •  & J. S. Tsai
  3. Center for Materials Theory, Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA

    • L. B. Ioffe
  4. Department of Physics, Lancaster University, Lancaster LA1 4YB, UK

    • Yu. A. Pashkin
  5. University of Jyväskylä, Department of Physics, PB 35, 40014 Jyväskylä, Finland

    • K. Yu. Arutyunov
  6. Moscow State University, Institute of Nuclear Physics, Leninskie gory, GSP-1, Moscow 119899, Russia

    • K. Yu. Arutyunov
  7. Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel

    • D. Shahar
    •  & O. Cohen

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Contributions

O.V.A. planned the experiment, designed and fabricated the samples, performed measurements and data analysis. L.B.I. came up with the idea of using materials close to the SIT and provided theoretical support. S.K. fabricated the sample and contributed to understanding the data . Yu.A.P. participated in discussions of the experiment. K.Yu.A. triggered the research direction and suggested the realization of the phase-slip qubit. D.S. and O.C. fabricated the InOx films. J.S.T. discussed the data and provided support for the work within the FIRST and KAKENHI projects. O.V.A. wrote the manuscript with feedback from all authors, including significant contributions from L.B.I. and K.Yu.A.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to O. V. Astafiev.

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DOI

https://doi.org/10.1038/nature10930

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