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Physical Review A

Security and gain improvement of a practical quantum key distribution using a gated single-photon source and probabilistic photon-number resolution

Tomoyuki Horikiri, Hideki Sasaki, Haibo Wang, Takayoshi Kobayashi

Published Jul 13, 2005• 4 citations
Publisher

Abstract

We propose a high security quantum key distribution (QKD) scheme utilizing one mode of spontaneous parametric downconversion gated by a photon number resolving detector. This photon number measurement is possible by using single-photon detectors operating at room temperature and optical fibers. By post selection, the multiphoton probability in this scheme can be reduced to lower than that of a scheme using an attenuated coherent light resulting in improvement of security. Furthermore, if distillation protocol (error correction and privacy amplification) is performed, the gain will be increased. Hence a QKD system with higher security and bit rate than the laser-based QKD system can be attained using present available technologies.

DOI
10.1103/physreva.72.012312

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Acta Physica Sinica•Jan 1, 2024•1 citation
We propose a high security quantum key distribution (QKD) scheme utilizing one mode of spontaneous parametric downconversion gated by a photon number resolving detector. This photon number measurement is possible by using single-photon detectors operating at room temperature and optical fibers. By post selection, the multiphoton probability in this scheme can be reduced to lower than that of a scheme using an attenuated coherent light resulting in improvement of security. Furthermore, if distillation protocol (error correction and privacy amplification) is performed, the gain will be increased. Hence a QKD system with higher security and bit rate than the laser-based QKD system can be attained using present available technologies.
We have suppressed multiphoton probability of a heralded-photon source, which is vital for quantum key distribution with a higher secure key generation rate. It is accomplished by utilizing a practical photon-number-resolving detector for triggering resulting in an important step for improved practical quantum key distribution. Heralded-photon source and a practical photon-number-resolving detector capable of real-time processed multiphoton rejection are stably operable at room temperature and enable us to generate a secure key at a distance as long as an ideal single photon source is used.
Recently, a long-distance and high-key-rate quantum key distribution (QKD) has become possible by the idea of the decoy state method. We show that a longer distance QKD is possible by utilizing a heralded single-photon source (HSPS) utilizing spontaneous parametric down-conversion as a source instead of a weak coherent pulse (WCP) as proposed in the original decoy state method. Moreover, the key rate is improved by utilizing a presently available photon number resolving detector as a trigger detector of the HSPS, and it is shown to approach the key rate of the WCP.
Recently a long distance and high key rate quantum key distribution (QKD) has become possible by the idea of the decoy state method. We show that a longer distance QKD is possible by utilizing a heralded single photon source (utilizing spontaneous parametric down-conversion) as a source instead of a weak coherent pulse (WCP) as proposed in the original decoy state method. Moreover, the key rate is improved by utilizing a presently available photon number resolving detector as a trigger detector of the heralded single photon source and it is shown to approach the key rate of the WCP.
Photon number resolving monitoring is a practical light source monitoring scheme in quantum key distribution (QKD) systems and can, effectively, reduce the risks due to the effects of untrusted sources. This scheme requires a single-photon detector, normally working at low temperature to suppress its dark count rate. In this paper, we use a room-temperature detector and show that the dark count rate is nearly irrelevant to the monitoring performance in our scheme, thus can sufficiently reduce the afterpulsing effect of the detectors as well as relax the requirements on their working conditions and integration complexity, which would be highly desirable for practical high-speed QKD systems with imperfect sources. Furthermore, the influences of parameter drifts at room temperature are analyzed, and the monitoring scheme is testified in a real QKD system.
A highly attenuated laser pulse which gives a weak coherent state is widely used in quantum key distribution (QKD) experiments. A weak coherent state has multi-photon components, which opens up a security loophole to the sophisticated eavesdropper. With a small adjustment of the hardware, we prove that the decoy state method can close this loophole and substantially improve the QKD performance. We also propose a few practical decoy state protocols, study statistical fluctuations and perform experimental demonstrations. Moreover, we apply the methods from entanglement distillation protocols based on two-way classical communication to improve the decoy state QKD performance. Furthermore, we study the decoy state methods for other single photon sources, such as triggering parametric down-conversion (PDC) source. We propose a model and post-processing scheme for the entanglement-based QKD with a PDC source. Although the model is proposed to study the entanglement-based QKD, we emphasize that our generic model may also be useful for other non-QKD experiments involving a PDC source. By simulating a real PDC experiment, we show that the entanglement-based QKD can achieve longer maximal secure distance than the single-photon-based QKD schemes. We present a time-shift attack that exploits the efficiency mismatch of two single photon detectors in a QKD system. This eavesdropping strategy can be realized by current technology. We also discuss counter measures against the attack and study the security of a QKD system with efficiency mismatch detectors.
The security of quantum key distribution (QKD) is based on the basic principles of quantum mechanics, and therefore has unconditional security in theory. In existing quantum key distribution systems, weakly coherent sources (WCSs) are often used as light sources due to a high probability of vacuum pulses in these sources, resulting in limited transmission distances. Besides, there inevitably exist equipment defects in actual QKD systems, such as certain defects in phase modulators and intensity modulators, which lead to distinguishability of quantum states in higher dimensions and result in side-channel vulnerabilities. An eavesdropper can carry out corresponding attacks, thereby threatening the actual security of QKD systems. To overcome the above limitations, we propose an improved protocol on quantum key distribution based on monitoring heralded single-photon sources. Due to the simultaneity of parametric down-conversion photon pairs, we can accurately predict the arrival of one photon by measuring the arrival time of another photon. Through this way, we can greatly reduce the probability of vacuum states in the signal light, and increase the longest transmission distance of the QKD system. Moreover, a light source monitoring module is inserted into the sender’s side. By randomly selecting a certain period of time through the source monitoring module to measure the Hong-Ou-Mandel interference between the signal light and the idle light , we can estimate the side-channel information leakage of the source and then obtain the key generation rate. Compared with the QKD protocol based on monitoring weak coherent sources, our present protocol can give a better performance in either the transmission distance or the key generation rate, especially when the interference error is large. In addition, in principle, our present protocol can also be extended to other quantum key distribution protocols, such as the measurement-device-independent protocols, to further improve the security and practicability of QKD systems. Therefore, our present work can provide valuable references for realizing the large-scale application of quantum communication networks in the near future.