Channel Estimation and Secret Key Rate Analysis of MIMO Terahertz Quantum Key Distribution

TL;DR

This paper analyzes the secret key rate of a MIMO Terahertz quantum key distribution system, considering practical channel estimation, and demonstrates how estimation errors impact performance at various distances.

Contribution

It introduces a practical channel estimation scheme for THz MIMO CVQKD and evaluates its effect on secret key rate considering estimation errors and overhead.

Findings

SKR degrades significantly with channel estimation errors

Performance drops at larger transmission distances

Proposed estimation scheme enables beamforming in THz CVQKD

Abstract

We study the secret key rate (SKR) of a multiple-input multiple-output (MIMO) continuous variable quantum key distribution (CVQKD) system operating at terahertz (THz) frequencies, accounting for the effects of channel estimation. We propose a practical channel estimation scheme for the THz MIMO CVQKD system which is necessary to realize transmit-receive beamforming between Alice and Bob. We characterize the input-output relation between Alice and Bob during the key generation phase, by incorporating the effects of additional noise terms arising due to the channel estimation error and detector noise. Furthermore, we analyze the SKR of the system and study the effect of channel estimation error and overhead. Our simulation results reveal that the SKR may degrade significantly as compared to the SKR upper bound that assumes perfect channel state information, particularly at large transmission distances.