Phase estimation without a priori knowledge in the presence of loss

TL;DR

This paper determines the best quantum phase estimation method without prior phase knowledge under loss, showing that quantum advantage is limited to a constant factor over classical methods.

Contribution

It provides an explicit lower bound on estimation uncertainty and identifies the optimal scheme for loss-affected quantum phase estimation without prior information.

Findings

Quantum precision enhancement is at most a constant factor over classical strategies.

An explicit lower bound on estimation uncertainty is derived.

The optimal estimation scheme under loss without prior knowledge is characterized.

Abstract

We find the optimal scheme for quantum phase estimation in the presence of loss when no a priori knowledge on the estimated phase is available. We prove analytically an explicit lower bound on estimation uncertainty, which shows that, as a function of number of probes, quantum precision enhancement amounts at most to a constant factor improvement over classical strategies