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Physical Review Research

Source monitoring twin-field quantum key distribution assisted with Hong-Ou-Mandel interference

Ming-Shuo Sun, Wenlin Wang, Xingyu Zhou, Chunhui Zhang, Qin Wang

Published Nov 27, 2023• 8 citations
Publisher

Abstract

Twin-field quantum key distribution (TF-QKD) can change the channel-loss dependence of key rates from $O(\ensuremath{\eta})$ to $O(\sqrt{\ensuremath{\eta}})$ and thus significantly increase the secure key rate compared with other existing quantum key distribution protocols. However, it does not take the source security into account in most present TF-QKD protocols. Here, we propose to employ the Hong-Ou-Mandel interference to characterize the source security, i.e., to use the interference visibility to quantify the information leakage from detectable side channels of sources. Furthermore, we establish a corresponding theoretical model and calculate the final key rate, by using the three-intensity decoy-state method and taking finite-data-size effects into account. Consequently, by employing our present scheme, the secure transmission distance can be longer than 100 km under current experimental conditions, significantly surpassing present device-independent QKD systems.

DOI
10.1103/physrevresearch.5.043179

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Twin-field quantum key distribution (TF-QKD) can change the channel-loss dependence of key rates from O(\ensuremathη)O(\ensuremath{\eta})O(\ensuremathη) to O(\ensuremathη)O(\sqrt{\ensuremath{\eta}})O(\ensuremathη​) and thus significantly increase the secure key rate compared with other existing quantum key distribution protocols. However, it does not take the source security into account in most present TF-QKD protocols. Here, we propose to employ the Hong-Ou-Mandel interference to characterize the source security, i.e., to use the interference visibility to quantify the information leakage from detectable side channels of sources. Furthermore, we establish a corresponding theoretical model and calculate the final key rate, by using the three-intensity decoy-state method and taking finite-data-size effects into account. Consequently, by employing our present scheme, the secure transmission distance can be longer than 100 km under current experimental conditions, significantly surpassing present device-independent QKD systems.
Quantum key distribution (QKD) allows the transmission of keys with unconditional security. Nevertheless, a discrepancy remains between the theoretical framework and the practical implementation, as device imperfections are frequently neglected in most QKD protocols. Some previous works proposed to use Hong-Ou-Mandel interference to quantify information leakage from side-channels. However, the security bound was relatively loose, resulting in poor performance. In this paper, we present an improved method for the security analysis of practical QKD protocols and provide a more precise parameter estimation. Furthermore, we apply it to several important QKD protocols, including BB84, measurement-device-independent, and twin-field, and carry out corresponding numerical simulations. Our work demonstrates significant improvements in both the key rate and the transmission distance compared to previous methods, representing a crucial step towards the practical implementation of QKD.
Side-channel attacks on practical quantum key distribution systems compromise its security. Although some of these attacks can be taken into account, the general recipe of how to eliminate all side-channel flaws is still missing. In this work, we propose a method for estimation of the total passive side-channel information leakage from the Alice's light source. The method relies on Hong-Ou-Mandel interference between different signals emitted by Alice, which reveals their overall mode mismatch without the necessity to measure all individual degrees of freedom independently. We include experimental values of interference visibility in the security proof for the decoy-state BB84 protocol, and lower-bound the secure key rate for realistic light sources. The obtained results provide a tool that can be used for certification of the current QKD systems and pave the way towards the loophole-free design of the future ones.
Twin-field quantum key distribution (TF-QKD) can overcome the fundamental rate-loss limit in the point-to-point QKD without a quantum repeater and achieve high key rates over long distances. However, TF-QKD protocol and its variants commonly use weak coherent pulses (WCPs) as light sources. The vacuum part of WCP accounts for a large proportion, resulting in the lower photon detection rate of the communication receiver, which leads to a shorter transmission distance of the secret key. In this paper, we propose an active-decoy TF-QKD protocol with heralded single-photon source (HSPS), which can achieve higher key rate and longer transmission distance than the active-decoy TF-QKD protocol with WCPs. Also, in order to resist the side channel attacks caused by actively modulating intensity of the pulses, we propose a passive-decoy TF-QKD protocol with HSPS to enhance the security, which can perform almost as good as the active-decoy TF-QKD protocol with WCPs.
Passive side-channel attacks in quantum key distribution (QKD) aim at obtaining information about the quantum signals without disturbing them and hence compromise real-world QKD security. Currently, there are no reliable tools for the assessment of QKD signal generation imperfections. In this work we propose a generic experimental method which allows to upper-bound QKD light-source imperfections and directly integrate them into the modern security proofs. The method relies on Hong-Ou-Mandel interference between different emitted signals: the maximum interference visibility reveals overall signal distinguishability that could lead to passive side-channel information leakage. We apply it for the standard decoy-state BB84 protocol and calculate a lower bound on the secret key rate for realistic values of interference visibility. The method can be readily implemented in practical QKD setups and is especially relevant for multiple-laser QKD systems such as the one installed on the Micius satellite.
Abstract Twin-Field quantum key distribution (TF-QKD) and its variants, e.g. phase-maching QKD, sending-or-not-sending QKD, and no phase post-selection TFQKD promise high key rates at long distance to beat the rate distance limit without a repeater. The security proof of these protocols are based on decoy-state method, which is usually performed by actively modulating a variable optical attenuator together with a random number generator in practical experiments, however, active-decoy schemes like this may lead to side channel and could open a security loophole. To enhance the source security of TF-QKD, in this paper, we propose passive-decoy based TF-QKD, in which we combine TF-QKD with the passive-decoy method. And we present a simulation comparing the key generation rate with that in active-decoy, the result shows our scheme performs as good as active decoy TF-QKD, and our scheme could reach satisfactory secret key rates with just a few photon detectors. This shows our work is meaningful in practice.
Abstract Quantum key distribution (QKD) holds the potential to establish secure keys over long distances. The distance of point-to-point QKD secure key distribution is primarily impeded by the transmission loss inherent to the channel. In the quest to realize a large-scale quantum network, increasing the QKD distance under current technology is of great research interest. Here we adopt the 3-intensity sending-or-not-sending twin-field QKD (TF-QKD) protocol with the actively-odd-parity-pairing method. The experiment demonstrates the feasibility of secure QKD over a 1002 km fibre channel considering the finite size effect. The secure key rate is 3.11×10−123.11\times 10^{-12}3.11×10−12 3.11 × 10 − 12 per pulse at this distance. Furthermore, by optimizing parameters for shorter fiber distances, we conducted performance tests on key distribution for fiber lengths ranging from 202 km to 505 km. Notably, the secure key rate for the 202 km, the normal distance between major cities, reached 111.74 kbps.