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.
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.
Abstract A mode-pairing quantum key distribution based on heralded pair-coherent source with passive decoy-states is proposed, named HPCS-PDS-MP-QKD protocol, where the light sources at Alice and Bob sides are changed to heralded pair-coherent sources, and devices designed to implement passive decoy states are included at the transmitter sides to generate the decoy state pulses in the decoy-state window passively. With the defined efficient events and the designed pairing strategy, the key bits and bases can be obtained by data post-processing. Numerical simulation results verify the feasibility of the proposed protocol. The results show that the proposed protocol can exceed PLOB when the pairing interval setting is greater than 103, and the transmission distance exceeds 200 km. When the key transmission distance reaches 300 km and the maximum pairing interval is equivalent to 1, its performance is improved by nearly 1.8 times compared to the original MP-QKD protocol with a weak coherent source (WCS-MP-QKD), and by 6.8 times higher than that of WCS-MP-QKD with passive decoy states (WCS-PDS-MP-QKD). Meanwhile, the key transmission distance can reach 480 km, and surpasses the WCS-PDS-MP-QKD protocol by nearly 40 km. When the total pulse length is greater than 1011, the key generation rate is almost equal to that of infinite pulses. It is a promising QKD protocol that breaks the PLOB bound without requiring phase tracking and locking, has a longer transmission distance and a higher key generation rate, and eliminates the potential of side channel attack.
The performance of active decoy-state quantum key distribution (QKD) system with a practical light source is compared with that of passive decoy-state QKD. The effect of statistical fluctuation due to a finite data size on final secret key rate is analyzed. This procedure is based on the standard error analysis on the assumption that all the variables measured in the experiment fluctuate around their asymptotic values. The relation between key generation rate and secure transmission distance is shown with exchanged quantum efficiency of threshold detector (d=1 and d=0.4) under the condition of active decoy-state (or passive decoy-state ) QKD which we pick the data size to be N=6.0109. This analysis will provide important parameters for practical QKD experiment.
Decoy states have recently been proposed as a useful protocol for substantially improving the performance of quantum key distribution (QKD). The passive decoy-state protocol has the advantage of easier implementation, higher transmission rate and better security compared with the active decoy-state protocol. This paper analyzes the passive decoy-state protocol with different light sources, including the lastest passive state protocol with weak coherent state (WCS) and the simple passive state protocol (AYKI) with heralded single photon source (HSPS). Based on the theoretic discussion and numerical simulation, we obtain the conclusion that the passive decoy-state protocol with HSPS is easier to implement than the passive decoy-state protocol with WCS because the latter need a hardware change but the former dose not involve any hardware change on the statnard QKD scheme. The key generation rate of the passive decoy-state protocol with WCS is better than that of the passive decoy-state protocol with HSPS, but the transmission distance is less than the latter. Anyhow, the performance of the passive scheme with a threshold detector is close to the active one.
The performance of active decoy-state quantum key distribution (QKD) system with an untrusted source is compared with that of passive decoy-state QKD. The key generation rate with the change of the secure transmission distance is shown under the condition of active decoy-state (or passive decoy-state) QKD where we pick the data size to be N=1012. The security characteristics of the passive scheme are studied with statistical fluctuation of the counting rate and the intensity of the practical source. At communication wavelength 1310 nm or 1550 nm, The security range of communication distance is [73.2 km, 96.5 km] or [104.5 km, 137.9 km] respectively. This analysis will provide important theoretical parameters for practical QKD experiment.
Decoy states have been proven to be a very useful method for significantly enhancing the performance of quantum key distribution systems with practical light sources. Although active modulation of the intensity of the laser pulses is an effective way of preparing decoy states in principle, in practice passive preparation might be desirable in some scenarios. Typical passive schemes involve parametric down-conversion. More recently, it has been shown that phase-randomized weak coherent pulses (WCP) can also be used for the same purpose [M. Curty et al., Opt. Lett. 34, 3238 (2009).] This proposal requires only linear optics together with a simple threshold photon detector, which shows the practical feasibility of the method. Most importantly, the resulting secret key rate is comparable to the one delivered by an active decoy-state setup with an infinite number of decoy settings. In this article we extend these results, now showing specifically the analysis for other practical scenarios with different light sources and photodetectors. In particular, we consider sources emitting thermal states, phase-randomized WCP, and strong coherent light in combination with several types of photodetectors, like, for instance, threshold photon detectors, photon number resolving detectors, and classical photodetectors. Our analysis includes as well the effect that detection inefficiencies and noise in the form of dark counts shown by current threshold detectors might have on the final secret key rate. Moreover, we provide estimations on the effects that statistical fluctuations due to a finite data size can have in practical implementations.
A nonorthogonal passive decoy-state method is presented with a reconstructive weak coherent state source. The method dose not prepare decoy states actively and divides the receiver detection events into two groups, i.e., triggered components and nontriggered components, according to triggering situation of the sender detector. Both triggered and nontriggered components, as signal states and decoy states, are used to do some estimations and to generate secure key. The simulation results show that a better key generation rate and a longer secure transmission distance can be obtained with the nonorthogonal passive decoy-state method than with the existing passive methods, and that the performance is comparable to the theoretical limit of an active infinite decoy-state protocol. Furthermore, the nontriggered component contribution to key generation offsets the limitation of the detector low efficiency, and the performance of the method dose not depend on the detector efficiency of sender. Because decoy states need not be prepared actively, and our protocol is easy to implement and apply to quantum key distribution at high transmission rates.