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arXiv · 1012.1928

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
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Abstract

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 excitations 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-slips amplitudes random functions of time, and therefore turn energy levels 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 100 kHz, were resolved from the flux-dependent dephasing of the fluxonium qubit.

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Vladimir E. Manucharyan, Nicholas A. Masluk, Archana Kamal, Jens Koch, Leonid I. Glazman, Michel H. Devoret. 2012-01-11. Evidence for coherent quantum phase-slips across a Josephson junction array. https://doi.org/10.1103/physrevb.85.024521

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