Optimal Quantum Phase Estimation

TL;DR

This paper identifies optimal quantum states for phase estimation in optical interferometry, accounting for photon losses, and demonstrates they outperform classical limits while approaching the theoretical quantum limit.

Contribution

It introduces a systematic optimization method to find quantum states that maximize phase estimation precision under realistic loss conditions.

Findings

Optimized quantum states surpass the standard quantum limit.

The precision achieved is close to the quantum Heisenberg limit.

Alternative, easier-to-generate states offer nearly comparable performance.

Abstract

By using a systematic optimization approach we determine quantum states of light with definite photon number leading to the best possible precision in optical two mode interferometry. Our treatment takes into account the experimentally relevant situation of photon losses. Our results thus reveal the benchmark for precision in optical interferometry. Although this boundary is generally worse than the Heisenberg limit, we show that the obtained precision beats the standard quantum limit thus leading to a significant improvement compared to classical interferometers. We furthermore discuss alternative states and strategies to the optimized states which are easier to generate at the cost of only slightly lower precision.