Abstract
Discrete-modulated continuous-variable quantum key distribution with homodyne detection is widely recognized for its ease of implementation, efficiency with respect to error correction, and its compatibility with modern optical communication devices. However, recent studies report that the application of homodyne detection obtains poor tolerance to excess noise and insufficient transmission distance, hence seriously restricting the large-scale deployment of quantum secure communication networks. In this paper, we propose a homodyne detection protocol using the quadrature phase shift keying technique. By limiting information leakage, our proposed protocol enhances excess noise tolerance to a high level. Furthermore, we demonstrate that homodyne detection performs better than heterodyne detection in quaternary-modulated continuous-variable quantum key distribution under the untrusted detector noise scenario. The security is analyzed using the tight numerical method against collective attacks in the asymptotic regime. Our results imply that the current protocol can distribute keys in nearly intercity area and, thus, paves the way for constructing low-cost quantum secure communication networks.
- Received 2 May 2021
- Revised 15 July 2021
- Accepted 21 October 2021
DOI:https://doi.org/10.1103/PRXQuantum.2.040334
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Using quantum states which obey the uncertainty relation, quantum key distribution is a fundamental communication protocol to generate identical and secret keys between two users. The key is used for information encryption and, thus, guarantees that only users possessing the key can decrypt the information, which is the essence of secure communication tasks. Protocols where one user sends a few kinds of signals and the other user measures them in the observables with continuous eigenvalues is called discrete-modulated continuous-variable quantum key distribution. These protocols can be realized with low experimental cost, which is suitable for the large-scale deployment of secure communication networks. However, the longest distribution distance allowed is limited under the general experimental environment, leading to impracticality.
In this work, we design a protocol that the sender randomly sends four kinds of special states and announces nothing about the sending states. Through our protocol, we can realize quantum key distribution in a significantly long distribution distance with simple and efficient apparatuses, which satisfies the requirements of deploying large-scale secure communication networks. Considering the intrinsic reason for improvement, we find that it is the unnecessary announcement of the sender in protocols that leaks extra information, resulting in the short distribution distance.
In future work, an experimental demonstration is necessary, and the security analysis can be further researched considering tougher attacks. Moreover, the thought of avoiding unnecessary announcements may help other cryptographic missions limit information leakage and improve their performance.
