Abstract

We demonstrate an optical receiver that achieves the quantum Chernoff bound for discriminating coherent states from thermal states in the multicopy scenario. In contrast, we find that repeated use of the receiver approaching the Helstrom bound for single-copy measurement is suboptimal in this multicopy case. Furthermore, for a large class of multicopy discrimination tasks between a pure and a mixed state, we prove that any Helstrom-bound achieving single-copy receiver is suboptimal by a factor of at least 2 in error-probability exponent compared to the multicopy quantum Chernoff bound. This behavior has a classical analog in the performance gap between soft-decision and hard-decision receivers for detecting a multicopy signal embedded in white Gaussian noise.

Date

January 1, 1970

Authors

Arunkumar Jagannathan, Michael Grace, Olivia Brasher, Jeffrey H Shapiro, Saikat Guha, Jonathan L Habif

Journal

Physical Review A

Volume

105

Issue

3

Pages

032446

Publisher

American Physical Society