Description
The continuous-variable (CV) quantum key distribution (QKD) has attracted considerable attention in recent years due to its high key-rate performance, compatibility with telecom-wavelength infrastructure, and cost-effective use of photodetectors. However, CV QKD is sensitive to transmission loss and noise, limiting its operation length to the metropolitan level. A recent approach of optical parametric amplification (OPA) provides a new path for loss-tolerant CV quantum information processing. Here, we combine CV QKD with the OPA method to extend its operational range and key rate. Theoretical analysis is conducted using the entanglement-based (EB) scheme, with a two-mode squeezed state as the resource, followed by two OPAs on the state. Preliminary analysis shows that with OPA, CV QKD can tolerate much higher losses and detection inefficiencies, thus potentially enabling longer transmission lengths. Specifically, when the OPA gain is sufficiently large, e.g., 30dB, the key rate improves by approximately a factor of 3 compared to that without OPA, even when system noise and detection inefficiency are quite large.
Meanwhile, the maximum transmission length can be increased by about 25km. We study system performance by varying parameters, including OPA gains, transmission length (loss), and squeezing values. Further, we propose a multi-user CV QKD scheme, in which an OPA is placed before each receiver. The overall key rate is analyzed, demonstrating robustness to loss with OPAs. Similarly, the key rate can be significantly improved with OPA under large noise and transmission loss, compared to that without OPA. The proposed scheme provides a promising path for extending the operational scale of present CV QKD protocols and lays the foundation for subsequent experimental implementations.
| I am the presenting author | Yes |
|---|