Quantum entanglement is at the heart of quantum information sciences and quantum technologies. In the optical domain, the most common type of quantum entanglement is polarization entanglement, which is usually created in a postselection manner involving destructive photon detection and thus hindering further applications which require readily available entanglement resources. In this work, we propose a scheme to prepare multipartite entangled states of polarized photons in a heralded manner, i.e., without postselection. We exploit the quantum scissors technique to truncate a given continuous-variable entanglement into the target entangled states which are of hybrid discrete-continuous or solely discrete types. We consider two implementations of the quantum scissors: one modified from the original quantum scissors [Pegg et al., Phys. Rev. Lett. 81, 1604 (1998)] using single photons and linear optics and the other designed here using a type-II two-mode squeezer. We clarify the pros and cons of these two implementations as well as discussing practical aspects of the entanglement preparation. Our work illustrates an interface between various types of optical entanglement and the proposed quantum scissors techniques could serve as alternative methods for heralded generation of polarization entanglement.

中文翻译：

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通过量子剪刀预示极化纠缠的制备

量子纠缠是量子信息科学和量子技术的核心。在光学领域，最常见的量子纠缠类型是偏振纠缠，它通常以涉及破坏性光子检测的后选择方式产生，因此阻碍了需要现成纠缠资源的进一步应用。在这项工作中，我们提出了一种方案，以预兆的方式准备偏振光子的多部分纠缠态，即没有后选择。我们利用量子剪刀技术将给定的连续变量纠缠截断为混合离散连续或单独离散类型的目标纠缠态。我们考虑量子剪刀的两种实现方式：一种是从原始量子剪刀 [Pegg等。，物理。牧师莱特。 81 , 1604 (1998)] 使用单光子和线性光学器件，另一个在这里设计使用 II 型双模挤压器。我们阐明了这两种实现的优缺点，并讨论了纠缠准备的实际方面。我们的工作说明了各种类型的光学纠缠之间的界面，并且所提出的量子剪刀技术可以作为预示产生偏振纠缠的替代方法。