The capacity of coherent-state adaptive decoders with interferometry and single-mode detectors

Abstract

A class of Adaptive Decoders (AD's) for coherent-state sequences is studied, including in particular the most common technology for optical-signal processing, e.g., interferometers, coherent displacements and photon-counting detectors. More generally we consider AD's comprising adaptive procedures based on passive multi-mode Gaussian unitaries and arbitrary single-mode destructive measurements. For classical communication on quantum phase-insensitive Gaussian channels with a coherent-state encoding, we show that the AD's optimal information transmission rate is not greater than that of a single-mode decoder. Our result also implies that the ultimate classical capacity of quantum phase-insensitive Gaussian channels is unlikely to be achieved with the considered class of AD's.

v3: final version; 6 pages; 2 figures

References in corpus (5)

• Coding Theorem and Strong Converse for Quantum Channels
• Error Exponent in Asymmetric Quantum Hypothesis Testing and Its Application to Classical-Quantum Channel coding
• Quantum channels and their entropic characteristics
• Sequential projective measurements for channel decoding
• Multi-Phase Hadamard receivers for classical communication on lossy bosonic channels

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• Generalized bipartite quantum state discrimination problems with sequential measurements
• A learning theory for quantum photonic processors and beyond
• Mutual information of optical communication in phase conjugating Gaussian channels
• Decoding Protocols for Classical Communication on Quantum Channels