Toward Practical Entanglement-Based Satellite FSO/QKD Systems Using Dual-Threshold/ Direct Detection

Abstract

We propose a new implementation of the BBM92 protocol for satellite continuous-variable quantum key distribution (CV-QKD) systems using the dual-threshold/direct detection (DT/DD) scheme. The proposed system is less complex and therefore possibly cheaper than current discrete-variable (DV) and CV-QKD ones using coherent detection receivers. We model and analyze the performance of the proposed system in the context that a satellite distributes secret keys to two legitimate users. The analytical results are derived by considering channel loss, atmospheric turbulence-induced fading, and receiver noises. The Gaussian beam model is considered to evaluate the impact of geometric spread on the signal received by legitimate users and the possibility of being eavesdropped. Based on the design criteria for the system and analytical results, we investigate the feasibility of a case study for the Japan QKD network using the existing low-Earth orbit (LEO) satellite constellation.

Enhancing Design and Performance Analysis of Satellite Entanglement-Based CV-QKD/FSO Systems

“…Using a small value of divergence angle results in not only low QBER CAB but also P E error . As reported in [15], the P E error of 0.1 is high enough for entanglement-based QKD transmitter design. Therefore, with the divergence angle of 0.4 mrad, the safe zone for our proposed QKD system is 140 m around Alice/Bob, where P E error is higher than 0.1.…”

“…As shown in Fig. 3, depending on the geography area, an existing minimum elevation angle of the base station can be determined to see satellites in LEO orbit, e.g., the range of the elevation angle in Japan from 30 • to 150 • [15]. In the tracking zone, the entanglement-based QKD system performance is evaluated by taking into account three main effects, including atmospheric attenuation, h a , geometric spreading loss, h g , and turbulence-induced fading, h t .…”

“…However, investigations on satellite EB/CV-QKD/FSO have been relatively limited, despite the potential advantages of the entanglement-based QKD implementation and continuous-variable QKD. In a very recent study, a design concept for satellite EB/CV-QKD/FSO has explored using subcarrier intensity modulation/binary phase-shift keying (SIM/BPSK) and dual-threshold/direct detection (DT/DD) receiver [15]. However, it is worth noting that SIM/BPSK requires the use of additional RF subcarriers and large modulation depths, which can introduce issues of complexity and feasibility.…”

“…Another important issue is that the performance of satellite QKD/FSO systems is significantly influenced by various channel impairments, including atmospheric attenuation, atmospheric turbulence, and receiver noise. However, previous works on performance analysis in this context suffer from several limitations [10], [13], [15], [16]. Firstly, the impact of atmospheric attenuation is typically only considered within the troposphere layer, which extends up to an altitude of less than 20 km.…”

Low-complexity conjugate homodyne detection scheme for SPAD-free DV-QKD

“…In 3 , the authors demonstrate the feasibility of using homodyne detection to perform photon number statistics, which suggests the possibility of using the same detection scheme on a DV-QKD protocol. In addition, the advantages of using post-selection to save computational effort while guaranteeing the communication security has been approached in CV-QKD systems [4][5][6] .…”