Dissipative Quantum Metrology with Spin Cat States

TL;DR

This paper proposes a robust quantum metrology scheme using spin cat states that maintains high precision beyond the standard quantum limit even with particle losses, outperforming traditional methods.

Contribution

It introduces a new measurement scheme employing spin cat states that are resilient to dissipation, enabling high-precision quantum measurements beyond the SQL.

Findings

Spin cat states are robust against particle losses.

Parity measurement yields higher precision than population measurement.

The scheme achieves high-precision measurements beyond the SQL in dissipative systems.

Abstract

The maximally entangled states are excellent candidates for achieving Heisenberg-limited measurements in ideal quantum metrology, however, they are fragile against dissipation such as particle losses and their achievable precisions may become even worse than the standard quantum limit (SQL). Here we present a robust high-precision measurement scheme via spin cat states (a kind of non-Gaussian entangled states in superposition of two spin coherent states) in the presence of particle losses. The input spin cat states are of excellent robustness against particle losses and their achievable precisions may still beat the SQL. For realistic measurements based upon our scheme, comparing with the population measurement, the parity measurement is more suitable for yielding higher precisions. In phase measurement with realistic dissipative systems of bosons, our scheme provides a robust and realizable way to achieve high-precision measurements beyond the SQL.