Energy-constrained two-way capacities of the pure-loss channel

Abstract:We determine the two-way quantum and secret-key capacities of the pure-loss channel under an average input photon-number constraint. For transmissivity $\eta$ and photon budget $N$, both capacities equal $g(N)-g((1-\eta)N)$, where $g$ is the entropy of a thermal state. This coincides with the rate achieved by the known reverse coherent information of a two-mode squeezed vacuum. Our result provides the last missing capacity formula for the celebrated pure-loss channel, completing the picture of bosonic quantum communication under pure loss.

arXiv:2610.12365 [quant-ph]

(or arXiv:2610.12365v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2610.12365 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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