Advantages and limitations of channel multiplexing for discrete-variable quantum key distribution

TL;DR

This paper explores the use of wavelength-division multiplexing in discrete-variable quantum key distribution to enhance key generation rates, emphasizing the importance of source optimization for maximum benefit.

Contribution

It provides a theoretical analysis and optimization strategy for implementing WDM in QKD, demonstrating potential for significantly increased key rates.

Findings

WDM can accelerate quantum key distribution rates.

Proper source optimization is crucial for maximizing WDM benefits.

Theoretical models show significant potential improvements.

Abstract

Typically practical realizations of discrete-variable quantum key distribution (QKD) protocols, based on exchanging single-photon signals between the trusted parties, can provide its users with only very low key generation rates. One of the potential solutions for this problem, that can be adapted for the case of entanglement-based QKD schemes using broadband photon-pair sources, is to utilize wavelength-division-multiplexing (WDM) modules in order to split the photons with different wavelengths to separate detection channels and generate multiple keys in parallel. Here, we theoretically investigate this idea in the case of pulsed laser used to pump spontaneous parametric down-conversion source. We optimize the effective phase-matching function width of the nonlinear crystal, and the intensity and duration of the pump laser pulses in order to maximize the advantage of the overall key generation rate provided by the WDM-based QKD scheme over the traditional no-WDM scenario. The results of our analysis show that the considered method can significantly accelerate the production of cryptographic keys, but proper optimization of the photon-pair source is needed to exploit its full potential.