Urban Fiber Infrastructure Analysis for Entangled Photon Distribution

Urban fiber-based quantum networks are highly sensitive to environmental factors like temperature swings and polarization drift due to their interconnected, multi-segment structure. We present a framework for characterizing quantum networks, focusing on achieving high-fidelity remote entanglement between distributed trapped-ion QPUs. We report on three critical noise sources [1, 2] inherent to this real-world infrastructure: (1) time jitter measurements quantifying the timing uncertainty of photon arrival and its impact on coincidence windows; (2) polarization stability analysis, characterizing birefringence fluctuations driven by mechanical vibrations; and (3) the temperature dependence of optical path length, which correlates diurnal thermal cycles with phase instability in the link. In addition, we will present active stabilization protocols, enabling robust photonically mediated remote entanglement between distributed quantum computers.

[1] Krutyanskiy, V., Meraner, M., Schupp, J. et al. Light-matter entanglement over 50 km of optical fibre. npj Quantum Inf 5, 72 (2019).

[2] Kucera, S., Haen, C., Arenskötter, E. et al. Demonstration of quantum network protocols over a 14-km urban fiber link. npj Quantum Inf 10, 88 (2024).