Proposal and Proof-of-Principle Demonstration of Fast-Switching Broadband Frequency-Shifting for a Frequency-Multiplexed Quantum Repeater

TL;DR

This paper proposes a fast, broadband frequency-shifting method using nonlinear crystals for quantum repeaters, demonstrating proof-of-principle results and analyzing system performance for quantum communication applications.

Contribution

It introduces a novel frequency-shifting technique utilizing a bank of pump modes and demonstrates its potential for quantum repeater architectures.

Findings

Achieved expected frequency-shifting in proof-of-principle experiments.

Estimated system performance with up to 25 dB SNR in optimized conditions.

Proposed solution supports 16 channels within a 100 GHz spectral region.

Abstract

A proposal for fast-switching broadband frequency-shifting technology making use of frequency conversion in a nonlinear crystal is set forth, whereby the shifting is imparted to the converted photons by creating a bank of frequency-displaced pump modes that can be selected by a photonic switch and directed to the nonlinear crystal. Proof-of-principle results show that the expected frequency-shifting operation can be achieved. Even though the dimensions of the currently employed crystal and significant excess loss in the experimental setup prevented conversion of single-photon-level inputs, thorough experimental and theoretical analysis of the noise contribution allowed for the estimation of the system performance in an optimized scenario, where the expected signal-to-noise ratio for single-photon conversion and frequency-shifting can reach up to 25 dB with proper narrow-band filtering and state-of-the-art devices. The proposed frequency-shifting solution figures as a promising candidate for applications in frequency-multiplexed quantum repeater architectures with 25 dB output SNR (with 20\% conversion efficiency) and capacity for 16 channels spread around a 100 GHz spectral region.