Entanglement Distribution in Quantum Optical Networks Using Multimode Photonic Circuits

Future quantum networks depend on reliable distribution of entanglement between distant nodes to power device-independent cryptography, blind quantum computing, and distributed sensing. Integrated photonics offers a scalable, phase-stable route to interconnects, yet long-distance rates are limited by fiber loss and the probabilistic nature of Bell-state measurements (BSMs). We present a system model and performance analysis for multimode photonic circuits that exploit time-, frequency-, and path-multiplexing to raise the success probability over lossy links. Closedform expressions are derived for single-shot success, end-to-end rate with Μ parallel modes, and fidelity under multi-pair noise, dark counts, and imperfect indistinguishability. We outline a practical architecture combining SPDC sources, integrated ( de)multiplexers, MMIs, thermo-optic phase shifters, and SNSPD arrays. Using representative device parameters and standard fiber attenuation, we simulate rate-distance trade-offs and quantify multiplexing gains. Moderate multiplexing (e.g., Μ = 16) delivers >10× higher rate at 50km without sacrificing fidelity, offering design guidance and a reproducible LaTeX/ PGFPlots workflow.

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