Mismatch in the Inverse-Squeezing Kennedy Receiver for Binary Displaced Squeezed-State Discrimination

TL;DR

This paper investigates how mismatch affects the inverse-squeezing Kennedy receiver in binary displaced squeezed-state discrimination, highlighting phase sensitivity and the impact on detection performance.

Contribution

It reveals that mismatch acts as residual squeezing, alters photon statistics, and emphasizes phase locking for effective implementation.

Findings

Mismatch causes non-single-threshold MAP rule.

Receiver is more sensitive to phase mismatch than amplitude mismatch.

Finite-resolution detection shows parity-step error scaling.

Abstract

We analyze mismatch in the inverse-squeezing Kennedy receiver for binary displaced squeezed vacuum state discrimination. Mismatch is shown to be equivalent to a residual squeezing after nulling, which modifies the output photon-number statistics and makes the optimal maximum-a-posteriori (MAP) rule generally non-single-threshold. We find that the receiver is much more sensitive to phase mismatch than to amplitude mismatch. Under amplitude-only mismatch, the saturation error with finite-resolution photon-number-resolving detection exhibits a parity-step scaling, decreasing only when the detector resolution crosses even-photon thresholds. These results clarify the physical origin of mismatch-induced degradation and identify phase locking as the key requirement for practical implementations.