Heisenberg-limited qubit readout with two-mode squeezed light

TL;DR

This paper proposes a method using two-mode squeezed light to achieve Heisenberg-limited qubit readout, significantly improving measurement precision in cavity-based quantum systems.

Contribution

It introduces a novel scheme leveraging two-mode squeezed light and quantum-mechanics-free subsystems for exponentially enhanced, robust qubit measurement.

Findings

Achieves Heisenberg-limited measurement scaling

Demonstrates robustness against imperfections

Provides a feasible implementation in circuit QED

Abstract

We show how to use two-mode squeezed light to exponentially enhance cavity-based dispersive qubit measurement. Our scheme enables true Heisenberg-limited scaling of the measurement, and crucially, is not restricted to small dispersive couplings or unrealistically long measurement times. It involves coupling a qubit dispersively to two cavities, and making use of a symmetry in the dynamics of joint cavity quadratures (a so-called quantum-mechanics-free subsystem). We discuss the basic scaling of the scheme and its robustness against imperfections, as well as a realistic implementation in circuit quantum electrodynamics.