Abstract
Establishing high-rate secure communications is a potential application of continuous-variable quantum key distribution (CVQKD) but still challenging for the long-distance transmission technology compatible with modern optical communication systems. Here, we propose a photon subtraction-induced plug-and-play scheme for enhancing CVQKD with discrete-modulation (DM), avoiding the traditional loopholes opened by the transmission of local oscillator. A photon subtraction operation is involved in the plug-and-play scheme for detection while resisting the extra untrusted source noise of the DM-CVQKD system. We analyze the relationship between secret key rate, channel losses, and untrusted source noise. The simulation result shows that the photon-subtracted scheme enhances the performance in terms of the maximal transmission distance and make up for the deficiency of the original system effectively. Furthermore, we demonstrate the influence of finite-size effect on the secret key rate which is close to the practical implementation.
Highlights
Motivated by the characteristics of photon subtraction (PS) operation, which is a mature technology in implementation, in this paper, we propose an approach for enhancing the PP
We find that the secret key rate of DM-continuous-variable quantum key distribution (CVQKD) in a finite-size scenario is lower than that of the asymptotic case whether it performs the PS operation or not
The proposed scheme can tolerate more channel losses compared with the original scheme so that it extends the maximal transmission distances
Summary
Quantum key distribution (QKD) [1,2,3] is a primary application of quantum cryptography, which enables two remote legitimate communication parties, Alice and Bob, to share random secret key sequences [4,5,6] in public channel preventing the eavesdropper Eve by physical laws [7,8,9,10]. The reconciliation efficiency of Gaussian modulated CVQKD (GM-CVQKD), whose secret keys are modulated following Gaussian distribution, is sensitive to channel losses [23], so that this scheme is unsuitable in long distance situations To solve this problem, CVQKD with discrete modulation (DM-CVQKD) has been proposed by A. An improved scheme called real local oscillator in which the LO is generated on the receiver’s side without transmitting through the quantum channel has been proposed [35,36,37,38] In this scheme, the loopholes resulted by the transmission of LO are closed, but its performance would be poor because of the incidental frequency out-sync between two independent laser sources.
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