One-shot quantum measurement using a hysteretic DC-SQUID

TL;DR

This paper introduces a novel single-shot quantum measurement method for Josephson charge qubits using a hysteretic DC-SQUID, leveraging macroscopic quantum tunneling for efficient read-out.

Contribution

It presents a new measurement scheme combining a Cooper pair box with a hysteretic DC-SQUID, enabling rapid and reliable qubit state detection.

Findings

Feasibility demonstrated with realistic circuit parameters

Analysis of phase fluctuations supports measurement robustness

Potential for high-fidelity qubit read-out

Abstract

We propose a single shot quantum measurement to determine the state of a Josephson charge quantum bit (qubit). The qubit is a Cooper pair box (CPB) and the measuring device is a two junction superconducting quantum interference device (dc-SQUID). This coupled system exhibits a close analogy with a Rydberg atom in a high Q cavity, except that in the present device we benefit from the additional feature of escape from the supercurrent state by macroscopic quantum tunneling, which provides the final read-out. We test the feasibility of our idea against realistic experimental circuit parameters and by analyzing the phase fluctuations of the qubit.