Evidence for coherent quantum phase slips across a Josephson junction array

Vladimir E. Manucharyan*, Nicholas A. Masluk, Archana Kamal, Jens Koch, Leonid I. Glazman, Michel H. Devoret

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

79 Scopus citations


Superconducting order in a sufficiently narrow and infinitely long wire is destroyed at zero temperature by quantum fluctuations, which induce 2π slips of the phase of the order parameter. However, in a finite-length wire, coherent quantum phase slips would manifest themselves simply as shifts of energy levels in the excitation spectrum of an electrical circuit incorporating this wire. The higher the phase slips' probability amplitude, the larger are the shifts. Phase slips occurring at different locations along the wire interfere with each other. Due to the Aharonov-Casher effect, the resulting full amplitude of a phase slip depends on the offset charges surrounding the wire. Slow temporal fluctuations of the offset charges make the phase-slip amplitudes random functions of time, and therefore turn energy level shifts into linewidths. We experimentally observed this effect on a long Josephson junction array acting as a "slippery" wire. The slip-induced linewidths, despite being only of order 100kHz, were resolved from the flux-dependent dephasing of the fluxonium qubit.

Original languageEnglish (US)
Article number024521
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number2
StatePublished - Jan 11 2012

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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