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Register a new userLong term performance of the SwissQuantum quantum key distribution network in a field environment
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In this paper, we report on the performance of the SwissQuantum quantum key distribution (QKD) network. The network was installed in the Geneva metropolitan area and run for more than one and a half years, from the end of March 2009 to the beginning of January 2011. The main goal of this experiment was to test the reliability of the quantum layer over a long period of time in a production environment. A key management layer has been developed to manage the key between the three nodes of the network. This QKD-secure network was used by end-users through an application layer.
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A novel secure communication network with quantum key distribution in a metropolitan area is reported. Different QKD schemes are integrated to demonstrate secure TV conferencing over a distance of 45km, stable long-term operation, and application to secure mobile phones.
Twin-Field (TF) quantum key distribution (QKD) is a major candidate to be the new benchmark for far-distance QKD implementations, since its secret key rate can overcome the repeaterless bound by means of a simple interferometric measurement. Many variants of the original protocol have been recently proven to be secure. Here, we focus on the TF-QKD type protocol proposed by Curty et al [preprint arXiv:1807.07667], which can provide a high secret key rate and whose practical feasibility has been demonstrated in various recent experiments. The security of this protocol relies on the estimation of certain detection probabilities (yields) through the decoy-state technique. Analytical bounds on the relevant yields have been recently derived assuming that both parties use the same set of decoy intensities, thus providing sub-optimal key rates in asymmetric-loss scenarios. Here we derive new analytical bounds when the parties use either three or four independent decoy intensity settings each. With the new bounds we optimize the protocols performance in asymmetric-loss scenarios and show that the protocol is robust against uncorrelated intensity fluctuations affecting the parties lasers.
Twin-Field Quantum Key Distribution(TF-QKD) protocol and its variants, such as Phase-Matching QKD(PM-QKD), sending or not QKD(SNS-QKD) and No Phase Post-Selection TF-QKD(NPP-TFQKD), are very promising for long-distance applications. However, there are still some gaps between theory and practice in these protocols. Concretely, a finite-key size analysis is still missing, and the intensity fluctuations are not taken into account. To address the finite-key size effect, we first give the key rate of NPP-TFQKD against collective attack in finite-key size region and then prove it can be against coherent attack. To deal with the intensity fluctuations, we present an analytical formula of 4-intensity decoy state NPP-TFQKD and a practical intensity fluctuation model. Finally, through detailed simulations, we show NPP-TFQKD can still keep its superiority of high key rate and long achievable distance.
Quantum key distribution (QKD) permits information-theoretically secure transmission of digital encryption keys, assuming that the behaviour of the devices employed for the key exchange can be reliably modelled and predicted. Remarkably, no assumptions have to be made on the capabilities of an eavesdropper other than that she is bounded by the laws of Nature, thus making the security of QKD unconditional. However, unconditional security is hard to achieve in practice. For example, any experimental realisation can only collect finite data samples, leading to vulnerabilities against coherent attacks, the most general class of attacks, and for some protocols the theoretical proof of robustness against these attacks is still missing. For these reasons, in the past many QKD experiments have fallen short of implementing an unconditionally secure protocol and have instead considered limited attacking capabilities by the eavesdropper. Here, we explore the security of QKD against coherent attacks in the most challenging environment: the long-distance transmission of keys. We demonstrate that the BB84 protocol can provide positive key rates for distances up to 240 km without multiplexing of conventional signals, and up to 200 km with multiplexing. Useful key rates can be achieved even for the longest distances, using practical thermo-electrically cooled single-photon detectors.
Twin-field quantum key distribution (TF-QKD), which is immune to all possible detector side channel attacks, enables two remote legitimate users to perform secure communications without quantum repeaters. With the help of a central node, TF-QKD is expected to overcome the linear key-rate constraint using current technologies. However, the security of the former TF-QKD protocols relies on the hypothesis of infinite-key and stable sources. In this paper, we present the finite-key analysis of a practical decoy-state twin-field quantum key distribution with variant statistical fluctuation models. We examine the composable security of the protocol with intensity fluctuations of unstable sources employing Azumas inequality. Our simulation results indicate that the secret key rate is able to surpass the linear key-rate bound with limited signal pulses and intensity fluctuations. In addition, the effect of intensity fluctuations is extremely significant for small size of total signals.
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