Quantum CDMA-based Continuous Variable Quantum Key Distribution using Chaotic Phase Shifters

TL;DR

This paper introduces a multiuser continuous-variable quantum key distribution system using chaotic phase shifters for encoding and decoding, enabling scalable secure quantum communication over shared channels.

Contribution

It proposes a novel q-CDMA framework with chaotic phase shifters for multiuser CV-QKD, including theoretical modeling and performance analysis under various noise conditions.

Findings

Achieves secure key distribution with multiple users over shared channels.

Derives input-output relations for multiuser q-CDMA CV-QKD system.

Analyzes secret key rates considering environmental and system noise.

Abstract

We present a quantum code-division multiple-access (q-CDMA) framework for multiuser continuous-variable quantum key distribution (CV-QKD) over a shared quantum channel. The proposed architecture employs chaotic phase shifters to encode and decode quantum states, enabling efficient multiplexing and demultiplexing of signals generated by multiple transmitters. In this scheme, quantum states from different users are chaotically phase-encoded and combined through a beam splitter network before transmission. At the receiver, synchronized chaotic phase shifters are used for decoding, followed by an inverse beam splitter structure to recover the individual user signals. This chaotic synchronization allows reliable state recovery and secure key establishment between each sender-receiver pair. For an arbitrary number of users, we derive the input-output quadrature relations describing the multiuser q-CDMA CV-QKD system. Using this model, we evaluate the achievable secret key rate under collective attacks with reverse reconciliation. We further investigate the impact of key system parameters including the correction factor, multiuser interference noise, environmental noise, and channel transmittance. A comparison between the asymptotic and finite-size regimes is also presented to highlight the associated performance trade-offs. These results provide a theoretical framework for assessing the performance of q-CDMA-based CV-QKD and support the development of scalable and secure multiuser quantum communication networks.