Multiplexing of Continuous-Variable and Discrete-Variable Quantum Key Distribution Systems over Fibered and Free-Space Channels

• URL: http://arxiv.org/abs/2608.19745v1
• Date: Thu, 20 Aug 2026 07:43:56 GMT
• Title: Multiplexing of Continuous-Variable and Discrete-Variable Quantum Key Distribution Systems over Fibered and Free-Space Channels
• Abstract summary: We report the first simultaneous operation of two independent CV- and DV-QKD systems on a common optical channel.<n>On fiber, the two systems exhibit the expected complementarity, crossing over at 7.56 dB of channel loss.<n>Across all configurations we observe no measurable multiplexing-induced penalty in QBER or excess noise.
• Score: 0.10486135378491268
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Future quantum communication infrastructures will need to serve heterogeneous users on shared physical channels: short-range, high-throughput links favor Continuous-Variable Quantum Key Distribution (CV-QKD), while long-reach, high-loss links remain the domain of Discrete-Variable QKD (DV-QKD). Wavelength-division multiplexing (WDM) of the two protocols on a common channel would address both regimes simultaneously, but their markedly different noise sensitivities make coexistence non-trivial and, to date, experimentally untested. Here we report the first simultaneous operation of two independent CV- and DV-QKD systems on a common optical channel, using standard C-band DWDM filters at 1550.12 nm (CV) and 1545.32 nm (DV). We demonstrate joint operation on both optical fiber and a 620 m urban daylight free-space link. On fiber, the two systems exhibit the expected complementarity, crossing over at 7.56 dB of channel loss where both deliver $\sim$1.43 Mbit/s; in daylight free-space, both sustain Mbit/s key rates under time-varying atmospheric attenuation. Across all configurations we observe no measurable multiplexing-induced penalty in QBER or excess noise. These results establish hybrid CV-DV WDM as a practical building block for heterogeneous quantum communication networks, where metropolitan high-throughput users and long-reach backbone links can be served on a single physical infrastructure.

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