标题： 合成任意双光子偏振混合态 显示英文标题

标题： Synthesizing arbitrary two-photon polarization mixed states

摘要： 引入了两种创建任意双光子偏振纯态的方法。 基于这些方法，提出了四种创建双光子偏照混合态的方案并进行了分析。 前两种方案可以合成完全任意的两量子比特混合态，即控制所有15个自由参数：方案I需要多个晶体组，而方案II只需要一个晶体组，但依赖于对泵浦光束进行退相干。 此外，我们描述了另外两种更容易实现的方案。 尽管这些方案的总体能力仍在研究中，但我们展示了它们可以合成所有的两量子比特Werner态、最大纠缠混合态、Collins-Gisin态和任意Bell对角态。 显示英文摘要

摘要： Two methods for creating arbitrary two-photon polarization pure states are introduced. Based on these, four schemes for creating two-photon polarization mixed states are proposed and analyzed. The first two schemes can synthesize completely arbitrary two-qubit mixed states, i.e., control all 15 free parameters: Scheme I requires several sets of crystals, while Scheme II requires only a single set, but relies on decohering the pump beam. Additionally, we describe two further schemes which are much easier to implement. Although the total capability of these is still being studied, we show that they can synthesize all two-qubit Werner states, maximally entangled mixed states, Collins-Gisin states, and arbitrary Bell-diagonal states.