Passive synchronization of nonlocal Franson interferometry for fiber-based quantum networks using copropagating classical clock signals
Phys. Rev. Applied 26, 024073 – Published 26 August, 2026
DOI: https://doi.org/10.1103/2dl9-6t4n
Abstract
We demonstrate a robust, high-visibility nonlocal Franson interferometry for fiber-based quantum networks by copropagating a classical radio-over-fiber clock signal with energy-time entangled photon pairs in the same fiber. Utilizing cross-band allocation (O-band for classical, L-band for quantum signals), the spontaneous Raman scattering noise photons are effectively suppressed. At the same time, their environmental delay fluctuations remain highly correlated for common-mode noise cancellation, achieving a passive synchronization with picoseconds precision. Over 50 km of single-mode fiber, this copropagation enables nonlocal quantum interference with a visibility of , without relying on external dedicated timing infrastructure. This work provides a practical, scalable synchronization solution for metropolitan-scale entanglement-based quantum networks.
