Experimental long-distance decoy-state quantum key distribution based on polarization encoding
ABSTRACT We demonstrate the decoy-state quantum key distribution (QKD) with one-way quantum communication in polarization space over 102 km. Further, we simplify the experimental setup and use only one detector to implement the one-way decoy-state QKD over 75 km, with the advantage to overcome the security loopholes due to the efficiency mismatch of detectors. Our experimental implementation can really offer the unconditionally secure final keys. We use 3 different intensities of 0, 0.2, and 0.6 for the light sources in our experiment. In order to eliminate the influences of polarization mode dispersion in the long-distance single-mode optical fiber, an automatic polarization compensation system is utilized to implement the active compensation.
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ABSTRACT: A novel counterfactual quantum key distribution scheme was proposed by T.-G. Noh and a strict security analysis has been given by Z.-Q. Yin, in which two legitimate geographical separated couples may share se-cret keys even when the key carriers are not traveled in the quantum channel. However, there are still plenty of practical details in this protocol that haven't been discussed yet, which are of significant importance in physical implementation. In this paper, we will give a practical analysis on such kind of counterfactual quantum cryptography in the aspects of quantum bit error rate (QBER) and stabilization. Furthermore, modi-fied schemes are proposed, which can obtain lower QBER and will be much more robust on stabilization in physical implementation.
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ABSTRACT: In general, quantum key distribution (QKD) has been proved unconditionally secure for perfect devices due to quantum uncertainty principle, quantum noncloning theorem and quantum nondividing principle which means that a quantum cannot be divided further. However, the practical optical and electrical devices used in the system are imperfect, which can be exploited by the eavesdropper to partially or totally spy the secret key between the legitimate parties. In this article, we first briefly review the recent work on quantum hacking on some experimental QKD systems with respect to imperfect devices carried out internationally, then we will present our recent hacking works in details, including passive faraday mirror attack, partially random phase attack, wavelength-selected photon-number-splitting attack, frequency shift attack, and single-photon-detector attack. Those quantum attack reminds people to improve the security existed in practical QKD systems due to imperfect devices by simply adding countermeasure or adopting a totally different protocol such as measurement-device independent protocol to avoid quantum hacking on the imperfection of measurement devices [Lo, et al., Phys. Rev. Lett., 2012, 108: 130503].Frontiers of Physics 10/2014; 9(5):613-628. DOI:10.1007/s11467-014-0420-6 · 1.36 Impact Factor
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ABSTRACT: We propose an alignment-free photonic qubit transmission scheme and apply it in quantum key distribution schemes, in which the authorized parties do not have to calibrate their Cartesian reference frames in advance. The polarization states are labeled by time, and the receiver can obtain the original state in his own coordinate by postselecting a determinate time of arrival. The scheme does not resort to decoherence-free subspace based on multiple photon states, and it can be implemented with only passive linear optics, which make it efficient and practical with current technology. We demonstrate its application in quantum key distributions, and the scheme should find applications in long-distance quantum communication without frame alignment.Journal of the Optical Society of America B 10/2014; 31(10). DOI:10.1364/JOSAB.31.002334 · 1.81 Impact Factor