Experimental Long-Distance Decoy-State Quantum Key Distribution Based on Polarization Encoding

Department of Physics, East China Normal University, Shanghai, Shanghai Shi, China
Physical Review Letters (Impact Factor: 7.51). 02/2007; 98(1):010505. DOI: 10.1103/PhysRevLett.98.010505
Source: PubMed


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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    • "(D2), we have ∆t ≈ 4 × 10 −6 ns. In a QKD implementation, the optical pulse is typically around 1 ns width [11] [12] [13] or 0.1 ns [14] [15] [47], thus ∆t ≪ 0.1 ns. Assuming that the optical pulse is Gaussian, ∆t corresponds to a fidelity of F (ρ 0 , ρ π ) ≈ 1 − 10 −8 between {0} and {π}. "
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    ABSTRACT: Decoy-state quantum key distribution (QKD) is a standard technique in current quantum cryptographic implementations. Unfortunately, existing experiments have two important drawbacks: the state preparation is assumed to be perfect without errors and the employed security proofs do not fully consider the finite-key effects for general attacks. These two drawbacks mean that existing experiments are not guaranteed to be secure in practice. Here, we perform an experiment that for the first time shows secure QKD with imperfect state preparations at long distances and achieves rigorous finite-key security bounds for decoy-state QKD against general quantum attacks in the universally composable framework. We implement both decoy-state BB84 and three-state protocol on top of a commercial QKD system and generate secure keys over 50 km standard telecom fiber based on a recent security analysis that is loss-tolerant to source flaws. Our work constitutes an important step towards secure QKD with imperfect devices.
    Full-text · Article · Aug 2014
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    • "The decoy-state method [7] [8] [9] [10] [11] has been proposed to close these photon source loopholes. It has been implemented in both optical fiber [12] [13] [14] [15] [16] [17] and free space channels [18] [19]. "
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    ABSTRACT: The decoy-state method is widely used in practical quantum key distribution systems to replace ideal single photon sources with realistic light sources by varying intensities. Instead of active modulation, the passive decoy-state method employs built-in decoy states in a parametric down-conversion photon source, which can decrease the side channel information leakage in decoy state preparation and hence increase the security. By employing low dark count up-conversion single photon detectors, we have experimentally demonstrated the passive decoy-state method over a 50-km-long optical fiber and have obtained a key rate of about 100 bit/s. Our result suggests that the passive decoy-state source is a practical candidate for future quantum communication implementation.
    Full-text · Article · May 2014 · Laser Physics Letters
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    • "Eve's attack will modify the statistical characteristics of the decoy states and/or signal state and will be detected. As practical experiments have shown for these protocols (as for the SARG04 protocol), the key rate and practical length of the channel is bigger than for BB84 protocols (Peng et al., 2007; Rosenberg et al., 2007; Zhao et al., 2006). Nevertheless, it is necessary to notice that using these protocols, as well as the others considered above, it is also impossible without users pre-authentication to construct the complete high-grade solution of the problem of key distribution. "

    Full-text · Chapter · Mar 2012
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