Quantum Fisher Information with Coherence

TL;DR

This paper critically examines the role of coherence in optical super-resolution, revealing that normalized Quantum Fisher Information shows no advantage of coherent sources over incoherent ones, challenging previous claims.

Contribution

It demonstrates that claims of resolution enhancement due to coherence are invalid when properly normalized QFI is used, clarifying the true limits of optical precision.

Findings

Normalized QFI shows no advantage of coherence over incoherence

Claims of super-resolution enhancement from coherence are questionable

Proper normalization is essential for accurate precision assessment

Abstract

In recent proposals for achieving optical super-resolution, variants of the Quantum Fisher Information (QFI) quantify the attainable precision. We find that claims about a strong enhancement of the resolution resulting from coherence effects are questionable because they refer to very small subsets of the data without proper normalization. When the QFI is normalized, accounting for the strength of the signal, there is no advantage of coherent sources over incoherent ones. Our findings have a bearing on further studies of the achievable precision of optical instruments.