Frequency drift corrected ultra-stable laser through phase-coherent fiber producing a quantum channel

Phase coherent fibers (PCF) are essential to distribute nearly monochromatic photons, ultra-stable in their frequency and phases, which have demanding requirements for state-of-the-art networked experiments, quantum as well as very high-speed communications. We report the development of a system that produces PCF links, also actively corrects the unavoidable slow frequency drift of the source laser. The PCF follows white phase noise limited σo × τ−1 stability behavior having σo values 1.9(2) × 10−16 and 2.6(1) × 10−16 for a 3.3 km field-deployed and 71 km spool fibers, respectively, with up to 47.5 dB suppression of the phase noise compared to a normal fiber. Additionally, the system is featured to correct the source laser’s 33.8 mHz/s frequency drift to as low as ≃ 0.05 mHz/s. Therefore, this all-in-one solution producing a quantum link can potentially enhance the effectiveness of the twin field quantum key distribution (TF-QKD) by nearly a 73-fold reduction of the QBER that arises from using unstabilized fiber links, as well as relaxes the laser frequency drift correction constraints by severalfold. The authors develop a technique to generate Phase Coherent optical Fibers (PCF) with additional capability of active correction of the source laser’s frequency drift. PCF is capable in distributing nearly monochromatic and low phase noise photons, which has demanding requirements in quantum communication, distributed sensing, time & frequency metrology.