Superresolution picks entanglement over coherence

TL;DR

This paper demonstrates that entanglement enhances superresolution measurement precision, unlike coherence which hampers it, showing entanglement's fundamental role in improving optical measurement techniques.

Contribution

It provides a quantitative comparison between entanglement and coherence, revealing that entanglement always improves superresolution Fisher Information, a novel insight in optical measurement.

Findings

Entanglement increases superresolution Fisher Information.

Non-zero entanglement guarantees non-vanishing Fisher Information.

Coherence is detrimental to superresolution measurement precision.

Abstract

Fundamental wave features of light play an important role in the realization of superresolution for two spatially separated point sources. It has been shown that (partial) coherence, which is an inevitable feature in practical light propagation, is harmful to measurement precision thus preventing superresolution. Here we study the quantitative effect of another fundamental feature, entanglement, on the quality of superresolution and compare it with that of coherence. Both single- and two-parameter estimations are analyzed in detail. Surprisingly, contrary to coherence, it is found that superresolution measurement precision (in terms of Fisher Information) can be enhanced as the amount of entanglement increases. More importantly, our analysis shows that non-zero entanglement always guarantees the non-vanishing of Fisher Information. Thus, while coherence is unwanted, entanglement is a favorable feature for superresolution.