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Quantum Computing, Communication, and Simulation

Coexistence of 100 wave-multiplexed quantum channels with classical synchronization

Ivan A. Burenkov, Alexandra Semionova, Thomas Gerrits, Anouar Rahmouni, Dhananjay Aanand, Ya-Shian Li-Baboud, Oliver Slattery, Abdella Battou, Sergey Vladimirovich Polyakov

Published Mar 8, 2023• 0 citations
Publisher

Abstract

We investigate the coexistence of clock synchronization protocols with quantum signals propagating in a common optical single-mode fiber channel. By measuring optical forward and backward scattering noise in a range from 1510 nm to 1620 nm we demonstrate a potential for up to 100 quantum channels each with 100 GHz bandwidth coexisting with the classical synchronization signals using off-the-shelf optical components. Both “White Rabbit'' and a pulsed laser-based synchronization were characterized and compared.

DOI
10.1117/12.2648488

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We investigate the coexistence of clock synchronization protocols with quantum signals propagating in a common optical single-mode fiber channel. By measuring optical forward and backward scattering noise in a range from 1510 nm to 1620 nm we demonstrate a potential for up to 100 quantum channels each with 100 GHz bandwidth coexisting with the classical synchronization signals using off-the-shelf optical components. Both “White Rabbit'' and a pulsed laser-based synchronization were characterized and compared.
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 rising interest in quantum-level communication has resulted in proposals for coexistence schemes with classical signals within the same fiber optic channel, where the most recent proposals leverage novel fibers designed for space-division multiplexing (SDM) transmission. In all cases the large power difference between classical and quantum channels presents challenges for such schemes, as the classical signals generate interfering noise that corrupts the quantum signal. In this work, we discuss the main interference mechanisms in coexistence scenarios and provide a model to quantify their impact on the quantum signal quality. Analytical approximations in the model allow accurate and fast numerical solutions in the millisecond time-scale. The model accounts for out-of-band non-linear interference effects, namely spontaneous Raman scattering (SpRS) and four-wave-mixing (FWM) in both cases of single-mode and SDM fibers with weakly-coupled degenerate mode groups. Rayleigh and SpRS backscattering are considered in counter-propagating scenarios. Since broadband classical transmission is targeted, the model also accounts for the effect of stimulated Raman scattering (SRS)-induced power tilt. Use of the model in sample scenarios indicates that the interference noise power is minimized at the high end of the transmission band in both cases were the quantum is co- and counter-propagating with respect to the classical signals, with a preference of one or the other scheme depending on the link length and quantum signal center frequency. Our model reveals that FWM has negligible impact in counter-propagating schemes, but can be relevant in co-propagating schemes under certain scenarios. Nevertheless, the FWM interference can be mitigated by deallocating the classical signals adjacent to the quantum channel.