Dispersive Qubit Measurement by Interferometry with Parametric Amplifiers

TL;DR

This paper analyzes how an amplified interferometer can improve dispersive qubit measurement quality in circuit-QED, demonstrating reduced error probabilities with realistic modeling of current experimental conditions.

Contribution

It introduces a detailed, realistic model of interferometric qubit measurement with parametric amplifiers, showing potential improvements over traditional methods.

Findings

Significant reduction in measurement error probability.

Enhanced signal-to-noise ratio with SU(1,1) interferometers.

Feasible improvements within current experimental setups.

Abstract

We perform a detailed analysis of how an amplified interferometer can be used to enhance the quality of a dispersive qubit measurement, such as one performed on a superconducting transmon qubit, using homodyne detection on an amplified microwave signal. Our modeling makes a realistic assessment of what is possible in current circuit-QED experiments; in particular, we take into account the frequency-dependence of the qubit-induced phase shift for short microwaves pulses. We compare the possible signal-to-noise ratios obtainable with (single-mode) SU(1,1) interferometers with the current coherent measurement and find a considerable reduction in measurement error probability in an experimentally-accessible range of parameters.