Precision bounds for quantum phase estimation using two-mode squeezed Gaussian states

TL;DR

This paper investigates the ultimate precision limits of quantum phase estimation using two-mode squeezed Gaussian states, demonstrating their potential to surpass classical limits even with photon loss.

Contribution

It derives the quantum Fisher information for two-mode squeezed states, identifies optimal input states, and analyzes robustness against photon loss, advancing practical quantum metrology.

Findings

Two single-mode squeezed vacuum states are optimal inputs.

The precision bound exceeds the Heisenberg limit by a factor of 2.

Performance remains superior to shot-noise limit with photon loss below 0.4.

Abstract

Quantum phase estimation based on Gaussian states plays a crucial role in many application fields. In this paper, we study the precision bound for the scheme using two-mode squeezed Gaussian states. The quantum Fisher information is calculated and its maximization is used to determine the optimal parameters. We find that two single-mode squeezed vacuum states are the optimal inputs and the corresponding precision bound is superior to the Heisenberg limit by a factor of 2. For practical purposes, we consider the effects originating from photon loss. The precision bound can still outperform the shot-noise limit when the lossy rate is below 0.4. Our work may demonstrate a significant and promising step towards practical quantum metrology.