Quantum-enhanced quickest change detection of transmission loss

• URL: http://arxiv.org/abs/2503.12276v1
• Date: Sat, 15 Mar 2025 22:18:43 GMT
• Title: Quantum-enhanced quickest change detection of transmission loss
• Authors: Saikat Guha, Tiju Cherian John, Prithwish Basu,
• Abstract summary: A sudden increase of loss in an optical communications channel can be caused by a malicious wiretapper, or for a benign reason such as inclement weather in a free-space channel or an unintentional bend in an optical fiber.<n>We show that adding a small amount of squeezing to bright phase-modulated coherent-state pulses can dramatically increase the homodyne detection receiver's sensitivity to change detection in channel loss, without affecting the communications rate.
• Score: 0.9633494094538018
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: A sudden increase of loss in an optical communications channel can be caused by a malicious wiretapper, or for a benign reason such as inclement weather in a free-space channel or an unintentional bend in an optical fiber. We show that adding a small amount of squeezing to bright phase-modulated coherent-state pulses can dramatically increase the homodyne detection receiver's sensitivity to change detection in channel loss, without affecting the communications rate. We further show that augmenting blocks of $n$ pulses of a coherent-state codeword with weak continuous-variable entanglement generated by splitting squeezed vacuum pulses in a temporal $n$-mode equal splitter progressively enhances this change-detection sensitivity as $n$ increases; the aforesaid squeezed-light augmentation being the $n=1$ special case. For $n$ high enough, an arbitrarily small amount of quantum-augmented photons per pulse diminishes the change-detection latency by the inverse of the pre-detection channel loss. This superadditivity-like phenomenon in the entanglement-augmented relative entropy rate, which quantifies the latency of change-point detection, may find other uses. We discuss the quantum limit of quickest change detection and a receiver that achieves it, tradeoffs between continuous and discrete-variable quantum augmentation, and the broad problem of joint classical-and-quantum communications and channel-change-detection that our study opens up.

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