Approaching maximal precision of Hong-Ou-Mandel interferometry with non-perfect visibility

TL;DR

This paper models the precision limits of Hong-Ou-Mandel interferometry with non-perfect visibility, demonstrating near-optimal experimental performance and establishing a new benchmark close to the quantum limit.

Contribution

It provides a general model for precision limits under realistic visibility conditions and experimentally validates the optimal scaling of precision in two-photon interference.

Findings

Precision scales with visibility depending on the state’s phase space area.

Experimental setup achieved up to 99.5% visibility.

Observed precision is 97% of the quantum limit.

Abstract

In quantum mechanics, the precision achieved in parameter estimation using a quantum state as a probe is determined by the measurement strategy employed. The ultimate quantum limit of precision is bounded by a value set by the state and its dynamics. Theoretical results have revealed that in interference measurements with two possible outcomes, this limit can be reached under ideal conditions of perfect visibility and zero losses. However, in practice, this cannot be achieved, so precision {\it never} reaches the quantum limit. But how do experimental setups approach precision limits under realistic circumstances? In this work we provide a general model for precision limits in two-photon Hong-Ou-Mandel interferometry for non-perfect visibility. We show that the scaling of precision with visibility depends on the effective area in time-frequency phase space occupied by the state used as a probe, and we find that an optimal scaling exists. We demonstrate our results experimentally for different states in a set-up where the visibility can be controlled and reaches up to $99.5\%$. In the optimal scenario, a ratio of $0.97$ is observed between the experimental precision and the quantum limit, establishing a new benchmark in the field.