Fock state interferometry for quantum enhanced phase discrimination

TL;DR

This paper demonstrates that Fock state interferometry in a Mach-Zehnder setup enables quantum-enhanced phase discrimination with lower error probabilities than classical methods, especially for small phase shifts, and has applications in quantum reading.

Contribution

It introduces a novel Fock state interferometry technique that surpasses classical limits in phase discrimination and is practically advantageous over complex quantum probes.

Findings

Lower error probability in phase discrimination than classical methods.

Ability to discriminate null from small phases with zero error.

Application demonstrated in quantum reading of binary memory pixels.

Abstract

We study Fock state interferometry, consisting of a Mach-Zehnder Interferometer with two Fock state inputs and photon-number-resolved detection at the two outputs. We show that it allows discrimination of a discrete number of apriori-known optical phase shifts with an error probability lower than what is feasible with classical techniques under a mean photon number constraint. We compare its performance with the optimal quantum probe for M-ary phase discrimination, which unlike our probe, is difficult to prepare. Our technique further allows discriminating a null phase shift from an increasingly small one at zero probability of error under ideal conditions, a feature impossible to attain using classical probe light. Finally, we describe one application to quantum reading with binary phase-encoded memory pixels.