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Fundamental Coexistence Limit of Quantum States with White Rabbit Synchronization in Quantum Networks

Ivan A. Burenkov, Alexandra Semionova, Hala Hala, Thomas Gerrits, Anouar Rahmouni, DJ Anand, Ya-Shian Li-Baboud, Oliver Slattery, Abdella Battou, Sergey V. Polyakov

Published Jan 1, 2023• 0 citations
Publisher

Abstract

We theoretically establish a distance limit and experimentally demonstrate coexisting quantum and classical channels in common fiber. When coexistence criteria are met, a single-mode fiber can carry >100 quantum channels and classical synchronization channels.
DOI
10.1364/cleo_fs.2023.fm1a.4

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We investigate the coexistence of clock synchronization protocols with quantum signals in a common single-mode optical fiber. By measuring optical noise between 1500 nm to 1620 nm we demonstrate a potential for up to 100 quantum, 100 GHz wide channels coexisting with the classical synchronization signals. Both "White Rabbit" and pulsed laser-based synchronization protocols were characterized and compared. We establish a theoretical limit of the fiber link length for coexisting quantum and classical channels. The maximal fiber length is below approximately 100 km for off-the-shelf optical transceivers and can be significantly improved by taking advantage of quantum receivers.
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The development of prototype metropolitan-scale quantum networks is underway and entails transmitting quantum information via single photons through deployed optical fibers spanning several tens of kilometers. The major challenges in building metropolitan-scale quantum networks are compensation for polarization fluctuation, high-precision clock synchronization, and compensation for cumulative transmission time fluctuations. One approach addressing these challenges is to copropagate classical probe signals in the same fiber as the quantum signal. Thus, both signals experience the same conditions, and the changes of the fiber can therefore be monitored and compensated. Here, we demonstrate the distribution of polarization-entangled quantum signals copropagating with the White Rabbit precision time protocol classical signals in the same single-core fiber strand at metropolitan-scale distances. Our results demonstrate the feasibility of this quantum-classical coexistence by achieving high-fidelity entanglement distribution between nodes separated by 100 km of optical fiber. This advancement is a significant step towards the practical implementation of robust and efficient metropolitan-scale quantum networks.