Subcarrier Domain of Multicarrier Continuous-Variable Quantum Key Distribution

TL;DR

This paper introduces the subcarrier domain for multicarrier continuous-variable quantum key distribution, providing a new physical model that enhances understanding and implementation of multicarrier CVQKD systems, including multiuser scenarios.

Contribution

It proposes the subcarrier domain as a natural representation for multicarrier CVQKD, extending it to multiuser settings and demonstrating its utility in adaptive schemes.

Findings

Validates the subcarrier domain model through AMQD schemes

Extends the framework to multiuser multicarrier CVQKD

Provides a general apparatus for various multicarrier CVQKD scenarios

Abstract

We propose the subcarrier domain of multicarrier continuous-variable (CV) quantum key distribution (QKD). In a multicarrier CVQKD scheme, the information is granulated into Gaussian subcarrier CVs and the physical Gaussian link is divided into Gaussian sub-channels. The sub-channels are dedicated for the conveying of the subcarrier CVs. The angular domain utilizes the phase-space angles of the Gaussian subcarrier CVs to construct the physical model of a Gaussian sub-channel. The subcarrier domain injects physical attributes to the description of the subcarrier transmission. We prove that the subcarrier domain is a natural representation of the subcarrier-level transmission in a multicarrier CVQKD scheme. We also extend the subcarrier domain to a multiple-access multicarrier CVQKD setting. We demonstrate the results through the adaptive multicarrier quadrature-division (AMQD) CVQKD scheme and the AMQD-MQA (multiuser quadrature allocation) multiple-access multicarrier scheme. The subcarrier domain representation provides a general apparatus that can be utilized for an arbitrary multicarrier CVQKD scenario. The framework is particularly convenient for experimental multicarrier CVQKD scenarios.