Using non-Gaussian quantum states for detection of a given phase shift

TL;DR

This paper proposes a method using non-Gaussian quantum states in interferometry to detect phase shifts unambiguously, achieving higher fidelity than Gaussian states despite optical losses.

Contribution

It introduces a novel approach employing non-Gaussian states like Fock or Schrödinger cat states for phase shift detection in interferometers, surpassing Gaussian state performance.

Findings

Non-Gaussian states enable unambiguous phase shift detection.

Detection fidelity exceeds that of Gaussian states with current photodetectors.

Optical losses impact sensitivity but do not negate the advantage.

Abstract

Injecting a non-Gaussian (Fock or Shr\"odinger cat) quantum state into the dark port of a two-arm interferometer and a strong classical light into the bright one, it is possible, in principle, to detect a given phase shift unambiguously using the orthogonality between the original and displaced in the interferometer non-Gaussian states. The optical losses degrade the sensitivity, introducing the finite "false positive" and "false negative" detection errors. However, using the state-of-art photodetectors, it is still possible to obtain better detection fidelity than in the case of Gaussian quantum states.