Practical reference-frame-independent quantum key distribution systems against the worst relative rotation of reference frames

Abstract

Reference-frame-independent quantum key distribution (RFI-QKD) can generate secret keys with the slow drift of reference frames. However, the performance of practical RFI-QKD systems deteriorates with the increasing drift of reference frames. In this paper, we mathematically demonstrate the worst relative rotation of reference frames for practical RFI-QKD systems, and investigate the corresponding performance with optimized system parameters. Simulation results show that practical RFI-QKD systems can achieve quite good performance against the worst relative rotation of reference frames, which exhibit the feasibility of practical QKD systems with free drifting reference frames. Furthermore, we propose a universal estimation method of the secret key rate in practical RFI-QKD systems, which conforms to the nature of RFI-QKD more well than the usual estimation method.

Tripartite Quantum Key Distribution Implemented with Imperfect Sources

“…In particular, we determine the error rates by employing the security proof introduced by Koashi [44,45] based on the complementarity of conjugate observables. The effect of misalignment of reference frames is incorporated in the measurement results from the X and the Y bases by following the method introduced in [46]. In order to estimate the secret key rate of the three-party RFI QKD, we consider a biased basis choice decoy-state QKD protocol [39,47,48] with three intensity settings.…”

“…While these parameters are derived in similar fashion to the bipartite case, the formulae are generalized to a tripartite case. Furthermore, the estimation of the decoy parameters for simulation is based on the channel model proposed in [41,46]. In our analysis, it is assumed that the detection probabilities of photons are independently determined by the channel transmittance, t = 10 −0.02l , where l is the channel length, and the detection efficiencies, η B and η C , of Bob and Charlie's respective detection systems.…”

Free-Running Long-Distance Reference-Frame-Independent Quantum Key Distribution

“…The blue dash lines in FIG. 4 illustrate the simulated results with N t = 10 13 [5,10,18,25]. In principle, the C value and the secure key rate reach the maximum value with θ ∈ {0, π/2, π, 3π/2} and drop to the minimum value with θ ∈ {π/4, 3π/4, 7π/4}.…”

“…Reference-frame-independent (RFI) QKD protocol, proposed in 2010, is robust for the slowly varying reference frames and suitable to the satellite-to-ground and drone-based systems [17]. The secure key rate of RFI QKD systems varies a lot with given misalignment (θ 0 ) of reference frames [18]. Furthermore, F. Wang et al shows the valid condition of RFI-QKD is that the misalignment variation ∆θ ≤ π [19].…”

“…The C value, secure key rate of merged sub-block and the simulated result with Nt = 10 12 and ∆θ = π/8. The C value and secure key rate varies with θ because the misalignment of reference frame affects the leaked information[18].…”