A search algorithm for quantum state engineering and metrology

TL;DR

This paper introduces a search algorithm that identifies practical quantum states for enhanced metrology, achieving high-precision phase measurements surpassing classical limits with robustness to losses.

Contribution

The paper presents a novel search algorithm that discovers experimentally feasible quantum states for metrology, outperforming existing states in precision and robustness.

Findings

States that beat shot noise limit by over 4 times

Robust quantum states resilient to photon losses

Simple measurement scheme saturating Cramér-Rao bound

Abstract

In this paper we present a search algorithm that finds useful optical quantum states which can be created with current technology. We apply the algorithm to the field of quantum metrology with the goal of finding states that can measure a phase shift to a high precision. Our algorithm efficiently produces a number of novel solutions: we find experimentally-ready schemes to produce states that show significant improvements over the state-of-the-art, and can measure with a precision that beats the shot noise limit by over a factor of 4. Furthermore, these states demonstrate a robustness to moderate/high photon losses, and we present a conceptually simple measurement scheme that saturates the Cram\'er-Rao bound.