Abstract
We perform security analysis of a passive continuous-variable quantum key distribution (CV-QKD) protocol by considering the finite-size effect. In the passive CV-QKD scheme, Alice utilizes thermal sources to passively make preparation of quantum state without Gaussian modulations. With this technique, the quantum states can be prepared precisely to match the high transmission rate. Here, both asymptotic regime and finite-size regime are considered to make a comparison. In the finite-size scenario, we illustrate the passive CV-QKD protocol against collective attacks. Simulation results show that the performance of passive CV-QKD protocol in the finite-size case is more pessimistic than that achieved in the asymptotic case, which indicates that the finite-size effect has a great influence on the performance of the single-mode passive CV-QKD protocol. However, we can still obtain a reasonable performance in the finite-size regime by enhancing the average photon number of the thermal state.
Highlights
Quantum key distribution (QKD) solves the problem of sharing secure keys between two distant authenticated users (Alice and Bob)
It is noteworthy that the excess noise caused by the quantum state preparation has an important effect on the performance of the passive continuous-variable quantum key distribution (CV-QKD) protocol; the mutual information between Alice and Bob is associated with Alice’s uncertainties on the quadrature of the outgoing mode
We show the calculation of the asymptotic secret key rate of the passive CV-QKD protocol based on an assumption that Alice and Bob can take advantage of infinitely many signals to make the exchange
Summary
Quantum key distribution (QKD) solves the problem of sharing secure keys between two distant authenticated users (Alice and Bob). A passive-state preparation scheme in view of single-mode thermal source rather than high extinction ratio modulators has been proposed, whose aim is to simplify the implementation of CV-QKD [26]. By assuming that Alice’s QKD transmitter is trusted, it can take advantage of the well-established security proofs directly for Gaussianmodulated CV-QKD into passive CV-QKD protocol This passive-state preparation scheme has been applied in CV quantum secret sharing [27] and measurement-device-independent. Compared to a direct Gaussian modulation CV-QKD protocol, the passive CV-QKD scheme with practical implementations of a thermal source has its own advantages, namely, this protocol waives the necessity of utilizing high-extinction ratio amplitude and phase modulators, which may yield significant reductions in cost. We perform security analysis of single-mode passive CV-QKD protocol by considering finite-size effect.
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