We discuss the influence of radiation field on the secure key size and the maximum safety distance during QKD by using a set of photons produced via a spontaneous parametric-down conversion (SPDC) photon source. Four implementations that use multiple-photons and decoy states are discussed, these include nondecoy state, infinite active decoy state, passive decoy state with threshold detector and passive decoy state with perfect photon-number resolving detector. Results show that the radiation field significantly improves both the secure key size and the maximum secure communication distance. Therefore, the radiation field is found to be a good candidate to reduce unwanted interactions of photons with the quantum channel and hence, to increase the secure key rate and the maximum safety distance between legitimate users.

中文翻译：

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通过辐射场触发基于参数下变频的量子密钥分发

我们通过使用通过自发参量下转换 (SPDC) 光子源产生的一组光子，讨论了辐射场对 QKD 期间安全密钥大小和最大安全距离的影响。讨论了使用多光子和诱饵状态的四种实现方式，包括非诱饵状态、无限主动诱饵状态、具有阈值检测器的被动诱饵状态和具有完美光子数分辨检测器的被动诱饵状态。结果表明，辐射场显着提高了安全密钥大小和最大安全通信距离。因此，发现辐射场是减少光子与量子通道的有害相互作用的良好候选者，因此可以提高安全密钥率和合法用户之间的最大安全距离。