Orthogonal Frequency Division Multiplexed Quantum Key Distribution

TL;DR

This paper introduces an OFDM-based multiplexing approach for quantum key distribution in quantum networks, analyzing system imperfections and proposing active decoding to enhance bandwidth utilization and key rates.

Contribution

It presents novel OFDM multiplexing schemes for QKD, analyzes their performance considering imperfections, and proposes an active decoding setup to improve key rate scalability.

Findings

Passive OFDM decoders do not increase total secret key rate.

Active OFDM decoding with optical switches enables linear key rate scaling.

Bandwidth utilization surpasses traditional wavelength division multiplexing.

Abstract

We propose orthogonal frequency division multiplexing (OFDM), as a spectrally efficient multiplexing technique, for quantum key distribution (QKD) at the core of trustednode quantum networks. Two main schemes are proposed and analyzed in detail, considering system imperfections, specifically, time misalignment issues. It turns out that while multiple service providers can share the network infrastructure using the proposed multiplexing techniques, no gain in the total secret key generation rate is obtained if one uses conventional all-optical passive OFDM decoders. To achieve a linear increase in the key rate with the number of channels, an alternative active setup for OFDM decoding is proposed, which employs an optical switch in addition to conventional passive circuits. We show that by using our proposed decoder the bandwidth utilization is considerably improved as compared to conventional wavelength division multiplexing techniques.