Entanglement is not a critical resource for quantum metrology

TL;DR

This paper challenges the notion that entanglement is essential for quantum metrology, showing that in some cases it can hinder reaching fundamental measurement limits.

Contribution

The study demonstrates that entanglement is not always a beneficial resource for quantum high-precision measurements and can sometimes prevent achieving the fundamental limit.

Findings

Entanglement does not always improve measurement precision.

In some regimes, entanglement prevents reaching the fundamental limit.

The advantage of entanglement depends on the measurement scenario.

Abstract

We have investigated high-precision measurements, beyond the standard quantum limit, utilizing non-classical states. Although entanglement has been considered a resource for achieving the Heisenberg limit in measurements, we show that any advantage expected from using entanglement is dependent on the measurement in question. We investigate several measurement scenarios and illustrate the role of entanglement as a resource for quantum high-precision measurement. In particular, we demonstrate that there is a regime wherein entanglement not only does not help, but prevents the achievement of the fundamental limit.