High dimensional measurement device independent quantum key distribution on two dimensional subspaces

TL;DR

This paper demonstrates that high-dimensional encoding in measurement device independent quantum key distribution enhances secret key rates and security, even with realistic imperfections, compared to traditional two-dimensional systems.

Contribution

The authors introduce a high-dimensional (qudit-based) mdi-QKD scheme that improves key rates and maintains unconditional security under practical conditions.

Findings

High-dimensional encoding increases secret key rate compared to 2D systems.

The scheme remains secure with weak coherent pulses and decoy states.

Performance improvements are robust against system imperfections.

Abstract

Quantum key distribution (QKD) provides ultimate cryptographic security based on the laws of quantum mechanics. For point-to-point QKD protocols, the security of the generated key is compromised by detector side channel attacks. This problem can be solved with measurement device independent QKD (mdi-QKD). However, mdi-QKD has shown limited performances in terms of the secret key generation rate, due to post-selection in the Bell measurements. We show that high dimensional (Hi-D) encoding (qudits) improves the performance of current mdi-QKD implementations. The scheme is proven to be unconditionally secure even for weak coherent pulses with decoy states, while the secret key rate is derived in the single photon case. Our analysis includes phase errors, imperfect sources and dark counts to mimic real systems. Compared to the standard bidimensional case, we show an improvement in the key generation rate.