A quantum key distribution protocol for optical fiber systems that does not require the adjustment of the receiving optical system has been proposed. It significantly simplifies the practical implementation of the system and ensures stable operation even at the imbalance of the receiving optical system. The robustness of the protocol has been explicitly proven taking into account side channels of information leakage.
A quantum key distribution protocol for optical fiber systems that does not require the adjustment of the receiving optical system has been proposed. It significantly simplifies the practical implementation of the system and ensures stable operation even at the imbalance of the receiving optical system. The robustness of the protocol has been explicitly proven taking into account side channels of information leakage.
Abstract The robustness of a quantum cryptography system is considered that uses a protocol with phase–time coding on attenuated coherent states. This protocol admits an effective fiber optic implementation, which does not require a phase modulator on the receiver side and adjusting the polarization state at the input of the receiver side. The absence of a phase modulator on the receiver side excludes a side channel of information leakage associated with the active probing of the phase modulator at the receiving station, thus making the system more robust against such attacks compared to other systems. The nonstrict single-photon nature of information states, as well as information leakage through side channels, is considered by the generalized decoy state method, which takes into account joint collective measurements of information quantum states and quantum states in side channels. An estimate for the secret key length is obtained that is expressed only in terms of observed quantities at the receiving station and the parameters of quantum states in side channels.
We present a three-party reference frame independent quantum key distribution protocol which can be implemented without any alignment of reference frames between the sender and the receiver. The protocol exploits entangled states to establish a secret key among three communicating parties. We derive the asymptotic key rate for the proposed protocol against collective attacks and perform a finite-size key security analysis against general attacks in the presence of statistical fluctuations. We investigate the impact of reference frame misalignment on the stability of our protocol, and we obtain a transmission distance of 180 km, 200 km, and 230 km for rotation of reference frames β = π/6, β = π/8 and β = 0, respectively. Remarkably, our results demonstrate that our proposed protocol is not heavily affected by an increase in misalignment of reference frames as the achievable transmission distances are still comparable to the case where there is no misalignment in reference frames (when β = 0). We also simulate the performance of our protocol for a fixed number of signals. Our results demonstrate that the protocol can achieve an effective key generation rate over a transmission distance of about 120 km with realistic 107 finite data signals and approximately achieve 195 km with 109 signals. Moreover, our proposed protocol is robust against noise in the quantum channel and achieves a threshold error rate of 22.7%.
Reference-frame-independent measurement-device-independent quantum key distribution is a promising candidate for building star-type quantum secure networks because it does not require reference alignment and removes all detector-side-channel attacks. However, prior works considered only a symmetric case in which the channels of both users have the same loss. In a realistic quantum secure network, the losses of various channels are likely to be different owing to their geographical locations. In this study, we present an asymmetric protocol for scalable reference-frame-independent measurement-device-independent quantum key distribution networks. By allowing independent adjustments of signal intensities of both users, our protocol provides a higher key rate than previous symmetric protocols in a realistic quantum secure network. The simulation results demonstrate that our protocol works well under realistic experimental conditions and obtains a key rate that is approximately one order of magnitude higher than that of previous methods. Our study paves the way for high-rate quantum secure communication network development.
Quantum key distribution (QKD) enables the establishment of shared keys between two distant users, Alice and Bob, based on the fundamental principles of quantum mechanics, and it has proven to possess information-theoretic security. In most of QKD systems, Alice and Bob require a shared reference frame, and real-time calibration of the reference frame increases system costs and reduces its performance. Fortunately, the reference-frame-independent QKD protocol has been proposed, overcoming reference-frame drift issues and receiving widespread attention. However, in practical QKD systems, the non-ideal characteristics of realistic devices introduce certain inconsistency between the theory and the practice. In real-world quantum key distribution systems, device imperfections can lead to security vulnerabilities, thereby reducing system security. For example, imperfections in the encoding apparatus at the source end may result in errors in the quantum states. The inherent defects in the detection part may cause after-pulse effects and dead-time effects, thus reducing the key rate. Therefore, in this work, we propose a practical state-preparation error tolerant reference-frame-independent quantum key distribution protocol by taking imperfections in both the source and the detectors into account. Moreover, a three-intensity decoy-state scheme for modeling analysis and numerical simulations is employed. In this protocol, we reduce the influence of state-preparation errors on the key rate by utilizing virtual state methods to precisely estimate the phase-error rate. Furthermore, by characterizing the effects of after-pulses and dead-time on the key rate, our protocol exhibits higher robustness and can effectively address issues related to detector imperfections. This approach can also be extended to other quantum key distribution protocols with higher security levels, such as measurement-device-independent quantum key distribution protocol and twin-field quantum key distribution, further mitigating the influence of device imperfections on practical implementation of QKD system. Therefore, our present work provide important reference value for putting the quantum key distributions into practical application.
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.
Side-channel attacks currently constitute the main challenge for quantum key distribution (QKD) to bridge theory with practice. So far two main approaches have been introduced to address this problem, (full) device-independent QKD and measurement-device-independent QKD. Here we present a third solution that might exceed the performance and practicality of the previous two in circumventing detector side-channel attacks, which arguably is the most hazardous part of QKD implementations. Our proposal has, however, one main requirement: the legitimate users of the system need to ensure that their labs do not leak any unwanted information to the outside. The security in the low-loss regime is guaranteed, while in the high-loss regime we already prove its robustness against some eavesdropping strategies.