High-speed free-space optical continuous-variable quantum key distribution enabled by three-dimensional multiplexing

Abstract

A high-speed four-state continuous-variable quantum key distribution (CV-QKD) system, enabled by wavelength-division multiplexing, polarization multiplexing, and orbital angular momentum (OAM) multiplexing, is studied in the presence of atmospheric turbulence. The atmospheric turbulence channel is emulated by two spatial light modulators (SLMs) on which two randomly generated azimuthal phase patterns yielding Andrews' spectrum are recorded. The phase noise is mitigated by the phase noise cancellation (PNC) stage, and channel transmittance can be monitored directly by the D.C. level in our PNC stage. After the system calibration, a total SKR of >1.68 Gbit/s can be reached in the ideal system, featured with lossless channel and free of excess noise. In our experiment, based on commercial photodetectors, the minimum transmittances of 0.21 and 0.29 are required for OAM states of 2 (or −2) and 6 (or −6), respectively, to guarantee the secure transmission, while a total SKR of 120 Mbit/s can be obtained in case of mean transmittances.

Continuous variable quantum key distribution with multi-mode signals for noisy detectors

“…Here, we propose a new scheme for CV-QKD with a multi-mode Gaussian modulated protocol [2,4] that exhibits higher SNR compared to a conventional high-bandwidth CV-QKD system. Multi-mode signals in CV-QKD have been considered in [16,17,18] for Gaussian as well as in [19,20] for discrete modulation protocols. The basic feature of our scheme involves the transmission of multi-mode, mutually incoherent signals prepared by Alice and their joint measurement at once using a coherent detector by Bob.…”

Secret key rates of free‐space optical continuous‐variable quantum key distribution

“…Free‐space optical (FSO) quantum links provide a tool to implement quantum communications via wireless telecommunication network infrastructures. As an integrated component of future quantum Internet and long‐distance quantum communications, the FSO quantum channels could play a significant role in the global‐scale practical implementations of quantum communications and quantum key distribution (QKD) . QKD systems allow us to utilize the fundamentals of quantum mechanics to realize unconditionally secure communications for legal users.…”

“…As an integrated component of future quantum Internet 11-16 and long-distance quantum communications, 11,17-29 the FSO quantum channels could play a significant role in the global-scale practical implementations of quantum communications and quantum key distribution (QKD). [1][2][3][30][31][32][33][34][35][36][44][45][46][47][48][49] QKD systems allow us to utilize the fundamentals of quantum mechanics to realize unconditionally secure communications for legal users. QKD protocols can be decomposed into discrete-variable (DV) and continuous-variable (CV) counterparts.…”

Comment on “Quantum-to-the-Home: Achieving Gbits/s Secure Key Rates via Commercial Off-the-Shelf Telecommunication Equipment”

“…The article titled "Quantum-to-the-Home: Achieving Gbits/s Secure Key Rates via Commercial Off-the-Shelf Telecommunication Equipment" [1] copied substantial parts of our previous publications without properly citing the source. In our previous publications we clearly described the mathematical model of our RF-subcarrier-assisted four-state continuousvariable QKD (CV-QKD) system, as well as the phase noise cancellation (PNC) stage [2,3]. While the article [1] copied our work without properly citing it, they cited one of our articles in an unremarkable position in Section 3 and put the core mathematical model and PNC model in the appendix, like their creative work.…”

“…As an illustration, Figure 2 in their article can be found as Figure 1 of [2]. However, they attributed the PNC stage to their previous conference paper [4], which was presented in June 2017, well after the articles [2,3] were published. Further, the derivations in Appendices A and B are copied from [2] with some small changes.…”