Phase-matching Quantum Key Distribution Research Articles

Improving the performance of practical phase-matching quantum key distribution with advantage distillation

Improving the performance of practical phase-matching quantum key distribution with advantage distillation

Phase-Matching quantum key distribution with the single-photon-added coherent source

Phase-Matching quantum key distribution with the single-photon-added coherent source

Improved statistical fluctuation analysis for two decoy-states phase matching quantum key distribution

Abstract Phase matching quantum key distribution is a promising scheme for remote quantum key distribution, breaking through the traditional linear key-rate bound. In practical applications, finite data size can cause significant system performance deterioration when data size is below 1010. In this paper, an improved statistical fluctuation analysis method is applied for the first time to two decoy-states phase matching quantum key distribution, offering new insights and potential solutions for improving the key generation rate and the maximum transmission distance while maintaining security. Moreover, we also compares the impacts of the proposed improved statistical fluctuation analysis method to those of the Gaussian approximation and Chernoff-Hoeffding boundary methods on system performance. The simulation results show that the proposed scheme significantly improves key generation rate and maximum transmission distance compared to the Chernoff-Hoeffding approach, and approaches the results obtained when the Gaussian approximation is employed. At the same time, the proposed scheme retains the same security level as the Chernoff-Hoeffding method, and is even more secure than the Gaussian approximation.

Asymmetric Channel Phase Matching Quantum Key Distribution

The phase-matching protocol is a practical and promising protocol that can surpass the linear key generation rate boundary. However, classical phase-matching quantum key distribution requires symmetry in channel attenuation between communicating parties. In practice, channels used are often asymmetric due to geographical reasons in a quantum key distribution network. To enhance the practicality of phase-matching, this paper proposes an asymmetric phase-matching protocol based on the classical framework and establishes a relevant mathematical simulation model to study the impact of channel asymmetry on its performance. The simulation results show that channel asymmetry significantly affects the count rate, error rate, gain, and quantum bit error rate (QBER), ultimately affecting system performance. As the channel attenuation difference increases, the system performance decreases, and the rate of decrease accelerates. Key generation becomes impossible when the channel attenuation difference exceeds 4dB. Although the decoy-state scheme cannot change the system's tolerance to channel attenuation differences, increasing the number of decoy states significantly improves system performance with a three-decoy-state phase-matching protocol outperforming a two-decoy-state protocol when the channel attenuation difference is large. Considering the limited data length, the system performance improves as the data length increases, and the tolerance to channel attenuation differences gradually increases. When the data length exceeds 10<sup>12</sup>, this improvement does not continue. The system cannot break through the boundary of linear key generation rate when the channel attenuation difference is 2dB and the data length is less than 10<sup>12</sup>. Compared to symmetric channels, the system performance improvement is more significant under asymmetric channel conditions as the data length increases.

Phase-matching quantum key distribution based on heralded pair-coherent source

Phase-matching quantum key distribution based on heralded pair-coherent source

Analysis of an injection-locking-loophole attack from an external source for quantum key distribution

Many security loopholes exist in quantum key distribution (QKD) due to the imperfections of realistic devices. On the source side, the decoy-state method can defend against the most severe photon-number-splitting (PNS) attack and improve the performance of QKD. Measurement-device-independent QKD and twin-field QKD have further closed all loopholes on the detection side. In this paper, we propose a valuable optical injection-locking loophole for the case when the internal isolator inside the laser is removed. We first introduce the effects of the injection locking with different injection intensities on the source frequency. Through the successive responses of adjacent pulses from frequency ports of the dense wavelength division multiplexer, the decoy state and the signal state can be partially distinguished. The specific injection-locking-loophole analysis of the isolatorless decoy phase-encoding Bennet-Brassard 1984 QKD and decoy phase-matching QKD protocols with external optical injection has been deeply studied. Simulation results show that, if we maintain the same observed gain statistics as normal after an external optical injection locking, the loophole cannot be exploited for a PNS attack when the QKD distance is short. As the QKD distance increases, a PNS attack at a medium distance using the optical injection-locking loophole does not threaten the security; the security is still valid. With the further increase of the QKD distance, the lower-bound secure key rate is higher than the upper-bound secure key rate given by a PNS attack at a long distance, some of the keys must be insecure, and information will be leaked.

Phase-matching quantum key distribution with imperfect sources

The huge discrepancies between actual devices and theoretical assumptions severely threaten the security of quantum key distribution. Recently, a general new framework called the reference technique has attracted wide attention in defending against the imperfect sources of quantum key distribution. Here, the state preparation flaws, the side channels of mode dependencies, the Trojan horse attacks, and the pulse classical correlations are studied by using the reference technique on the phase-matching protocol. Our simulation results highlight the importance of the actual secure parameters choice for transmitters, which is necessary to achieve secure communication. Increasing the single actual secure parameter will reduce the secure key rate. However, as long as the parameters are set properly, the secure key rate is still high. Considering the influences of multiple actual secure parameters will significantly reduce the secure key rate. These actual secure parameters must be considered when scientists calibrate transmitters. This work is an important step towards the practical and secure implementation of phase-matching protocol. In the future, it is essential to study the main parameters, find out their maximum and general values, classify the multiple parameters as the same parameter, and give countermeasures.

Satellite-based phase-matching quantum key distribution

Satellite-based phase-matching quantum key distribution

Numerical method for finite-size security analysis of quantum key distribution

Quantum key distribution (QKD) enables secure information exchange with untrusted quantum links between remote communication parties. A central task in the studies of QKD protocols is security analysis, which aims at deriving the length of the final key such that it is secure regardless of the eavesdropper's computational power. In literature, the security analysis has been done both analytically and numerically. Compared to analytical methods which tend to require techniques specific to each QKD protocol, numerical ones are more general since they can be directly applied to many QKD protocols with little adaptation. However, current numerical methods are carried out based on some assumptions such as working in the asymptotic limit and collective attacks from eavesdroppers. In this work, we remove these assumptions and develop a numerical finite-size security analysis against general attacks for a large class of QKD protocols. We also give an example of applying the method to the recent phase-matching QKD protocol with a simplified protocol design. Our result shows that the finite-size key rate can surpass the linear key-rate bound with a practical QKD system operated for only several hours.

Phase-matching quantum key distribution based on orbital angular momentum under atmospheric turbulence

We propose a phase-matching quantum key distribution (PM-QKD) protocol based on orbital angular momentum (OAM) to exceed the linear key-rate bound without quantum repeater in the paper, named OAM-PM-QKD protocol, where the coherent state consisting of OAM with opposite topological charges is used as the information carrier. With the equivalent entanglement distillation model, we analyze its security and then derive its key generation rate. The numerical simulation results show that the proposed OAM-PM-QKD protocol is able to exceed the linear key-rate bound when the transmission distance exceeds 230 km, and the maximum secure transmission distance is also longer than those of original PM-QKD protocol due to no misalignment in the basis. Furthermore, the influence of the atmospheric turbulence (AT) on the key generation rate is also discussed. The stronger the strength of AT is, the shorter the transmission distance is.

Phase-matching quantum key distribution with advantage distillation

Phase-matching quantum key distribution (PM-QKD) provides a promising solution to surpass the fundamental rate–distance bound without quantum repeaters. In this paper, we insert an additional advantage distillation (AD) step after quantum communication to improve the performance of PM-QKD. Simulation results show that, by splitting the raw key into blocks of only a few bits so as to identify highly correlated bit pairs, the AD method can tolerate high system misalignment errors and improve the secret key rate and transmission distance significantly, which is very promising in current PM-QKD systems.

Performance of phase-matching quantum key distribution based on wavelength division multiplexing technology

Quantum key distribution (QKD) generates information-theoretical secure keys between two parties based on the physical laws of quantum mechanics. The phase-matching (PM) QKD protocol allows the key rate to break the quantum channel secret key capacity limit without quantum repeaters, and the security of the protocol is demonstrated by using equivalent entanglement. In this paper, the wavelength division multiplexing (WDM) technique is applied to the PM-QKD protocol considering the effect of crosstalk noise on the secret key rate. The performance of PM-QKD protocol based on WDM with the influence of adjacent classical channels and Raman scattering is analyzed by numerical simulations to maximize the total secret key rate of the QKD, providing a reference for future implementations of QKD based on WDM techniques.

Passive decoy state phase matching quantum key distribution

In this paper, a passive decoy state phase matching quantum key distribution scheme is proposed based on the heralded pair coherent state light source to make the protocol more practical and safe. Without changing the intensity of the light source, we can derive four different data sets by dividing the raw key data into four groups according to the combined results of detectors in source end. The scheme can make use of the different data sets to estimate the parameters and extract the secret key. The key generation rate formula is derived after the parameter estimation. The performance of the proposed scheme is analyzed with and without taking statistical fluctuation into consideration. The simulation results show that compared with the existing active decoy-state method, the proposed passive method has slightly lower key rate when the transmission distance is short, and has obviously higher key rate when the transmission distance exceeds 406[Formula: see text]km. The maximum safety transmission distance of the proposed scheme is 452[Formula: see text]km which is relatively further. According to the influence of statistical fluctuation, the performance of the proposed scheme declines as the length of the data falls. Even though the data size is [Formula: see text], the max safety transmission distance is also more than 400[Formula: see text]km.

Prefixed-threshold real-time selection for free-space phase-matching quantum key distribution

Phase-matching quantum key distribution (PM-QKD), a practical version of twin-field quantum key distribution (TF-QKD), is able to surpass the linear bound without quantum repeaters. Implementing PM-QKD through free space can guarantee two parties to share unconditionally secure keys between ground stations and mobile platforms. However, atmospheric turbulence (AT) in the free-space channel would decrease the secure key rate (SKR) since it would cause fluctuations of transmittances. Two works we do are presented in this paper. First, for simplicity and generality, we derive the SKR for 4-intensity PM-QKD with asymmetric channel transmittances. Secondly, we apply the observable model of the prefixed-threshold real-time selection (P-RTS) method to mitigate the effect of AT in PM-QKD. Here, the authorized parties predetermine the threshold of transmittances and use it to select the signals while monitoring the real-time transmittances. The results show that the performance of PM-QKD in free space is severely degraded by AT, while P-RTS can reduce the impact of AT, making it transmit more than 3 times as long the distance and have a 3.37 times as large SKR at a distance of 50 km.

Extended single-photon entanglement-based phase-matching quantum key distribution

Extended single-photon entanglement-based phase-matching quantum key distribution

Phase-matching quantum key distribution with light source monitoring

The transmission loss of photons during quantum key distribution (QKD) process leads to the linear key rate bound for practical QKD systems without quantum repeaters. Phase matching quantum key distribution (PM-QKD) protocol, an novel QKD protocol, can overcome the constraint with a measurement-device-independent structure, while it still requires the light source to be ideal. This assumption is not guaranteed in practice, leading to practical secure issues. In this paper, we propose a modified PM-QKD protocol with a light source monitoring, named PM-QKD-LSM protocol, which can guarantee the security of the system under the non-ideal source condition. The results show that our proposed protocol performs almost the same as the ideal PM-QKD protocol even considering the imperfect factors in practical systems. PM-QKD-LSM protocol has a better performance with source fluctuation, and it is robust in symmetric or asymmetric cases.

Analysis of three-intensity decoy-state phase-matching quantum key distribution

Analysis of three-intensity decoy-state phase-matching quantum key distribution

Phase-matching quantum key distribution based on pulse-position modulation

In order to further improve the performance of the phase-matching quantum key distribution (PM-QKD) protocol, in this paper, a more efficient protocol named PPM-PM-QKD is proposed which adopts pulse-position modulation (PPM) to realize the high-dimensional encoding. PPM technology utilizes the empty pulses in the weak coherent source, and can improve the performance of the protocol. The simulation results show the improvement compared with the original PM-QKD protocol. Moreover, the protocol inherits the advantages of the original PM-QKD protocol, and it can not only exceed the PLOB bound, but also has a higher robust to noise and channel disturbance.

Reference-Frame-Independent Design of Phase-Matching Quantum Key Distribution

The recently proposed phase-matching quantum key distribution offers means to overcome the linear key rate--transmittance bound. Since the key information is encoded onto the phases of coherent states, the misalignment between the two remote reference frames would yield errors and significantly degrade the key generation rate from the ideal case. In this work, we propose a reference-frame-independent design of phase-matching quantum key distribution by introducing a high-dimensional key encoding space. With encoded phases spanning the unit circle, the error statistics at arbitrary fixed-phase-reference difference can be recovered and treated separately, from which the misalignment angle can be identified. By naturally extending the binary encoding symmetry and complementarity to high dimensions, we present a security proof of this high-dimensional phase-matching quantum key distribution and demonstrate with simulation that a 17-dimensional protocol is completely immune to any degree of fixed misalignment and robust to slow phase fluctuations. We expect the high-dimensional protocol to be a practical reference-frame-independent design for general phase-encoding schemes where high-dimensional encoding is relatively easy to implement.

Phase-Matching Quantum Key Distribution with Discrete Phase Randomization.

The twin-field quantum key distribution (TF-QKD) protocol and its variations have been proposed to overcome the linear Pirandola–Laurenza–Ottaviani–Banchi (PLOB) bound. One variation called phase-matching QKD (PM-QKD) protocol employs discrete phase randomization and the phase post-compensation technique to improve the key rate quadratically. However, the discrete phase randomization opens a loophole to threaten the actual security. In this paper, we first introduce the unambiguous state discrimination (USD) measurement and the photon-number-splitting (PNS) attack against PM-QKD with imperfect phase randomization. Then, we prove the rigorous security of decoy state PM-QKD with discrete phase randomization. Simulation results show that, considering the intrinsic bit error rate and sifting factor, there is an optimal discrete phase randomization value to guarantee security and performance. Furthermore, as the number of discrete phase randomization increases, the key rate of adopting vacuum and one decoy state approaches infinite decoy states, the key rate between discrete phase randomization and continuous phase randomization is almost the same.