Abstract
Twin-field quantum key distribution (TF-QKD) has attracted considerable attention and developed rapidly due to its ability to surpass the fundamental rate-distance limit of QKD. However, the device imperfections may compromise its practical implementations. The goal of this paper is to make it robust against the state preparation flaws (SPFs) and side channels at the light source. We adopt the sending or not-sending (SNS) TF-QKD protocol to accommodate the SPFs and multiple optical modes in the emitted states. We analyze that the flaws of the phase modulation can be overcome by regarding the deviation of the phase as phase noise and eliminating it with the post-selection of phase. To overcome the side channels, we extend the generalized loss-tolerant (GLT) method to the four-intensity decoy-state SNS protocol. Remarkably, by decomposing of the two-mode single-photon states, the phase error rate can be estimated with only four parameters. The practical security of the SNS protocol with flawed and leaky source can be guaranteed. Our results might constitute a crucial step towards guaranteeing the practical implementation of the SNS protocol.
Highlights
Quantum key distribution (QKD) promises to share a common secret key with its security guaranteed by the principles of quantum physics [1]
We take into account the imperfections at the light source and enhance the practical implementation of the sending or not-sending (SNS) protocol
We analyze that the flaws of phase modulation can be overcome by regarding the deviation of the phase as phase noise and eliminating it with the method of the post-selection of phase
Summary
Quantum key distribution (QKD) promises to share a common secret key with its security guaranteed by the principles of quantum physics [1]. The decoy-state method [4,5,6] allows the use of the practical sources while maintaining the secret key rate (SKR) at a level comparable to that of the perfect single-photon source. In this paper, according to the characteristic of the states in SNS protocol, we modify the decomposition of the two-mode single-photon states In this way, only two groups of parameters (two for each group) need to be calculated. Only two groups of parameters (two for each group) need to be calculated To make it more practical, we consider the coherent states as the light sources and analyze how to apply the method in the four-intensity decoy-state SNS protocol.
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