Continuous-variable Measurement Device Independent MIMO Quantum Key Distribution for THz Communications

TL;DR

This paper proposes a secure MIMO CVQKD system for THz communications that leverages measurement-device independence to eliminate detector vulnerabilities, using beamforming and protocol analysis to optimize key rates.

Contribution

It introduces a MIMO CVQKD protocol at THz frequencies with measurement-device independence, enhancing practical security and analyzing performance with various antenna and detection configurations.

Findings

Measurement-device independence eliminates detector attack vulnerabilities.

Optimal key rates achieved at lower THz frequencies for long-range links.

System performance improves with multiple antennas and efficient homodyne detection.

Abstract

Although multiple-input multiple-output (MIMO) terahertz (THz) continuous-variable quantum key distribution (CVQKD) is theoretically secure, practical vulnerabilities may arise due to detector imperfections. This paper explores a CV measurement-device-independent (MDI) QKD system operating at THz frequencies within a MIMO framework. In this system, measurement is delegated to an untrusted third party, Charlie, rather than the receiver, eliminating all detector attacks and significantly enhancing the system's practical security. Using transmit-receive beamforming techniques, the system transforms MIMO channels into multiple parallel lossy quantum channels, enabling robust key distribution between Alice and Bob. This study examines entanglement-based and prepare-and-measure protocols, deriving secret key rates for both asymptotic and finite code scenarios. Simulations reveal the critical role of multiple antenna configurations and efficient homodyne detection in mitigating free-space path loss and maximizing key rates. Results indicate that system performance is optimized at lower THz frequencies for long-range transmissions and higher frequencies for short-range applications. The proposed protocol offers a scalable solution for secure quantum communications in next-generation wireless networks, demonstrating potential for deployment in both indoor and outdoor environments.