Andreev Spectroscopy for Superconductive Phase Qubit

TL;DR

This paper proposes a novel method using Andreev spectroscopy to investigate quantum phase dynamics in superconductive qubits, enabling differentiation of internal phase behaviors through conductance measurements.

Contribution

It introduces a new experimental approach to probe the quantum dynamics of superconductive phase qubits via Andreev subgap conductance measurements.

Findings

Differentiates phase tunneling behaviors through conductance signatures

Predicts distinct conductance patterns for different internal phase dynamics

Provides a tool for analyzing quantum behavior in superconducting qubits

Abstract

New method to probe quantum dynamics of the order parameter phase of a small superconductive island is proposed. The idea is to measure Andreev subgap conductance between the island and a dirty normal-metal wire connected with the island by very high-resistance tunnel barrier. The phase on the island is supposed to stay primarly in one of the two nearly degenerate classical minima i.e. the island is an active element of the Superconductive Phase Qubit. Voltage-dependence of the differential subgap conductance measured at low temperatures are predicted to demonstrate crucially different behavior depending on the type of the internal dynamics of phase (coherent tunnelling of phase, non-coherent tunnelling, or no tunneling). Thus the measurements of nonliner Andreev conductance is a tool to probe the type of quantum behavior of the artificial two-level system.