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Optics Express

Fully reference-frame-independent measurement-device-independent quantum key distribution

Jian-Rong Zhu, Chunmei Zhang, Rong Wang

Published Jul 13, 2026• 0 citations
Publisher

Abstract

The reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) protocol is immune to both the slow drift of the reference frame and the potential attacks aimed at the measurement device. However, its reference-frame-independent behavior in terms of performance relies on the assumption that the key-generation basis is well aligned, which may not always be satisfied in practice. In this work, to address this limitation in RFI-MDI-QKD, we propose a fully RFI-MDI-QKD (FRFI-MDI-QKD) protocol by harnessing the quantum discord resource, and prove its security against collective attacks in the asymptotic case. With a 3 × 3 matrix whose singular values are independent of the reference frame, the information obtained by the eavesdropper in FRFI-MDI-QKD is completely irrelevant to the reference frame. Simulation results show that, in the case of a misaligned key-generation basis, FRFI-MDI-QKD can yield more positive keys compared with previous RFI-MDI-QKD; in the case of a well-calibrated key-generation basis, the key rate performance of FRFI-MDI-QKD can be reduced to that of previous RFI-MDI-QKD.

DOI
10.1364/oe.603442

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The reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) protocol is immune to both the slow drift of the reference frame and the potential attacks aimed at the measurement device. However, its reference-frame-independent behavior in terms of performance relies on the assumption that the key-generation basis is well aligned, which may not always be satisfied in practice. In this work, to address this limitation in RFI-MDI-QKD, we propose a fully RFI-MDI-QKD (FRFI-MDI-QKD) protocol by harnessing the quantum discord resource, and prove its security against collective attacks in the asymptotic case. With a 3 × 3 matrix whose singular values are independent of the reference frame, the information obtained by the eavesdropper in FRFI-MDI-QKD is completely irrelevant to the reference frame. Simulation results show that, in the case of a misaligned key-generation basis, FRFI-MDI-QKD can yield more positive keys compared with previous RFI-MDI-QKD; in the case of a well-calibrated key-generation basis, the key rate performance of FRFI-MDI-QKD can be reduced to that of previous RFI-MDI-QKD.
Abstract Reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) can remove all potential detector side-channel attacks and the requirement of real-time alignment of reference frames. However, all previous RFI-MDI-QKD implementations assume the perfect state preparation in sources, which is impractical and may lead to security loopholes. Here, we propose an RFI-MDI-QKD protocol which is robust against state preparation flaws. Comparing to the conventional six-state RFI-MDI-QKD, our scheme can be realized with only four flawed states, which improves the practical security of RFI-MDI-QKD and simplifies the experimental implementation. In addition, simulation results demonstrate that source flaws in Z basis have adverse effect on the performance of RFI-MDI-QKD while the source flaws in X and Y bases have almost no effect. We hope that this work could provide a valuable reference for practical implementations of RFI-MDI-QKD.
Abstract Reference-frame-independent measurement-device-independent QKD (RFI-MDI-QKD), immune to both the slow unknown drift of reference frames and detector side channel attacks, can generate information-theoretic secure keys. Despite its natural resistance to the slow drift of reference frames, the performance of practical RFI-MDI-QKD systems descends with the increasing drift of reference frames. In this paper, we demonstrate the worst relative rotation of reference frames for practical RFI-MDI-QKD systems, and investigate their performance against the worst-case scenario, both of which are unclear to date. Simulation results show that, practical RFI-MDI-QKD systems can achieve quite good performance even against the worst-case scenario, which clearly demonstrates that it is possible to implement practical MDI-QKD systems with freely drifting reference frames.
Reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) eliminates detector side-channel attacks and avoids reference-frame calibration. While its feasibility has been widely demonstrated, existing implementations typically assume fixed or slowly drifting reference-frame misalignment, conditions rarely satisfied outside the laboratory. In realistic environments, rapid and free-running reference-frame variations can severely degrade both the key rate and transmission distance of conventional RFI-MDI-QKD. Here we propose a free-running RFI-MDI-QKD protocol that maintains high-rate key generation under rapid reference-frame variations. By introducing a classification-distillation method that reclassifies total detection events, secure keys can be extracted without modifying the experimental setup. Our protocol achieves a key rate more than nine times higher than the best previous RFI-MDI-QKD scheme and tolerates channel losses exceeding 24 dB, where earlier approaches fail. These results enable practical quantum key distribution on mobile platforms, including satellite-to-ground links and airborne nodes.
Reference-frame-independent quantum key distribution (RFI-QKD) can generate secure keys between two remote peers with an unknown and slowly drifted reference frame. It adopts a statistical quantity C independent of the rotation of the reference frame to estimate the eavesdropper’s knowledge. However, in practical scenarios, the estimation of C should be completed with data collected in a short period of time, since the variation of the reference frame during the run will smear its correlations. In this paper, we propose to improve the performance of RFI-QKD with a new, to the best of our knowledge, statistical quantity R , which is less sensitive to statistical fluctuations and more robust to the variation of the reference frame, and obtain an analytical bound to estimate the eavesdropper’s knowledge. Simulation results show that the performance of RFI-QKD in the non-asymptotic case can be significantly promoted, which is very promising in practical QKD systems. Furthermore, we apply the new statistical quantity R to the RFI measurement-device-independent QKD (RFI-MDI-QKD) protocol and demonstrate that significant improvement can also be obtained in RFI-MDI-QKD.
Reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) is proposed to remove all possible detector side channel attacks without the alignment of reference frames. Due to unavoidable multiphoton events in practical sources, the decoy-state method is always adopted in real-life QKD systems. Unlike original MDI-QKD (O-MDI-QKD), the characterization on practical decoy-state RFI-MDI-QKD is still absent to date. In this paper, we investigate the performance of practical decoy-state RFI-MDI-QKD at different misalignments of reference frames with full parameter optimization when considering statistical fluctuations, and provide a clear comparison between decoy-state RFI-MDI-QKD and O-MDI-QKD. Simulation results demonstrate that decoy-state RFI-MDI-QKD can exhibit performance comparable to that of O-MDI-QKD in practical scenarios, which is very robust in QKD systems.
Reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) is a novel protocol that eliminates all possible attacks on the detector side and the necessity of reference-frame alignment in source sides. However, its performance may degrade notably due to statistical fluctuations since more parameters, e.g., yields and error rates for mismatched-basis events, must be accumulated to monitor the security. In this work, we find that the original decoy states method estimates these yields overpessimistically since it ignores the potential relations between different bases. Through jointly processing parameters of different bases, the performance of RFI-MDI-QKD is greatly improved in terms of the secret key rate and achievable distance when statistical fluctuations are considered (the statistical fluctuation analysis is the first step to the final analysis of the finite key size effect). Our results pave an avenue towards practical RFI-MDI-QKD.