目前实验上所用的单光子源，主要有两类。

Currently, there are two main ways to prepare a single-photon source.

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纠缠光子源对于量子密钥分发系统至关重要。

Entangled photon pairs are the critical resources in quantum key distribution (QKD) system.

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使用光学分束器和单光子源，利用单光子态和真空态制备出了纠缠单光子态。

A method of generating the single-photon entangled states of a single photon state and a vacuum state through utilizing optical beam-splitter and single-photon source is described.

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Intensity, if we increase the intensity, we're not increasing the energy in each photon, we're just increasing the number of photons that we're shooting out of our laser, whatever our light source is.

强度，如果我们增加强度，我们增加的不是,每个光子的能量，我们增加的仅仅是,从我们激光源射出的光子数，无论我们的光源是什么。

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