Phase estimation in lossy optical interferometry without a reference beam

TL;DR

This paper analyzes phase estimation in lossy optical interferometry without a reference beam, revealing how loss affects the equivalence of different configurations and comparing the performance of entangled coherent states to NOON states.

Contribution

It demonstrates the breakdown of ideal lossless equivalence under photon loss and shows the performance differences between entangled coherent and NOON states without a reference beam.

Findings

Loss breaks the equivalence between scenarios with and without a reference beam.

Entangled coherent states perform worse than NOON states in the presence of a reference beam, but this difference vanishes without it.

Photon loss significantly impacts phase estimation strategies in optical interferometry.

Abstract

We investigate phase estimation in a lossy interferometer using entangled coherent states, with particular focus on a scenario where no reference beam is employed. By calculating the quantum Fisher information, we reveal two key results: (1) the metrological equivalence between scenarios with and without a reference beam, established under ideal lossless conditions for the two-phase-shifting configuration,breaks down in the presence of photon loss, and (2) the pronounced inferior performance of entangled coherent states relative to NOON states, observed in the presence of a reference beam, disappears in its absence.