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arXiv · 2111.14890

Demonstration of quantum-limited discrimination of multi-copy pure versus mixed states

Arunkumar Jagannathan·Olivia Brasher·Michael Grace·Jeffrey H. Shapiro·Saikat Guha·Jonathan L. Habif
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Abstract

We demonstrate an optical receiver that achieves the quantum Chernoff bound for discriminating coherent states from thermal states in the multi-copy scenario. In contrast, we find that repeated use of the receiver approaching the Helstrom bound for single-copy measurement is sub-optimal in this multi-copy case. Furthermore, for a large class of multi-copy 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 two in error-probability exponent compared to the multi-copy quantum Chernoff bound. This behavior has a classical analog in the performance gap between soft-decision and hard-decision receivers for detecting a multi-copy signal embedded in white Gaussian noise.

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Arunkumar Jagannathan, Olivia Brasher, Michael Grace, Jeffrey H. Shapiro, Saikat Guha, Jonathan L. Habif. 2021-11-29. Demonstration of quantum-limited discrimination of multi-copy pure versus mixed states. https://doi.org/10.1103/physreva.105.032446

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