Ideal Quantum non-demolishing measurement of a flux qubit at variable bias

TL;DR

This paper proposes a scheme for high-fidelity quantum non-demolition measurement of a flux qubit using a Josephson bifurcation amplifier, effective across various magnetic biases, with suppressed back-action.

Contribution

It introduces a method enabling perfect QND measurement of a flux qubit at variable bias, reducing measurement back-action and enhancing fidelity.

Findings

High QND fidelity over a wide bias range

Suppressed qubit relaxation due to measurement back-action

Effective implementation with Josephson bifurcation amplifier

Abstract

We propose a scheme to realize a quantum non-demolition (QND) measurement of a superconducting flux qubit by a Josephson bifurcation amplifier. Our scheme can implement a perfect QND measurement for a qubit subject to a variable magnetic bias. Measurement back-action induced qubit relaxation can be suppressed and hence the QND fidelity is expected to be high over a wide range of bias conditions.