Tunnelling across a nanowire

Abstract

The observation of a phenomenon known as coherent quantum phase slip, across a nanowire in a superconducting system, paves the way for applications in quantum computing and metrology. See Letter p.355 Coherent quantum phase slip (CQPS) has not, until now, been observed experimentally. It is a phenomenon exactly dual to the Josephson effect, but whereas the latter is a coherent transfer of charges between superconducting contacts, CQPS is a coherent transfer of vortices or fluxes across a superconducting wire. This paper reports direct observation of CQPS in a strongly disordered indium oxide superconducting wire inserted in a loop; the effect manifests through the superposition of quantum states with different fluxes. The CQPS may — like the Josephson effect before it — lead to innovative applications in superconducting electronics and quantum metrology.