A tomographic measurement is a ubiquitous tool for estimating the properties of quantum states, and its application is known as quantum state tomography (QST). The process involves manipulating single photons in a sequence of projective measurements, often to construct a density matrix from which other information can be inferred, and is as laborious as it is complex. Here we unravel the steps of a QST and outline how it may be demonstrated in a fast and simple manner with intense (classical) light. We use scalar beams in a time reversal approach to simulate the outcome of a QST and exploit non-separability in classical vector beams as a means to treat the latter as a “classically entangled” state for illustrating QSTs directly. We provide a complete do-it-yourself resource for the practical implementation of this approach, complete with tutorial video, which we hope will facilitate the introduction of this core quantum tool into teaching and research laboratories alike. Our work highlights the value of using intense classical light as a means to study quantum systems and in the process provides a tutorial on the fundamentals of QSTs.

中文翻译：

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量子态断层扫描的概念和强光下的经典实现：教程

断层扫描测量是一种普遍存在的用于估计量子态特性的工具，其应用被称为量子态断层扫描 (QST)。该过程涉及在一系列投影测量中操纵单个光子，通常是为了构建一个密度矩阵，从中可以推断出其他信息，并且既费力又复杂。在这里，我们解开 QST 的步骤，并概述如何使用强（经典）光以快速而简单的方式进行演示。我们以时间反转方法使用标量光束来模拟 QST 的结果，并利用经典矢量光束的不可分离性作为将后者视为“经典纠缠”状态以直接说明 QST 的一种手段。我们为这种方法的实际实施提供了一个完整的 DIY 资源，完整的教程视频，我们希望这将有助于将这一核心量子工具引入教学和研究实验室。我们的工作强调了使用强经典光作为研究量子系统的手段的价值，并在此过程中提供了有关 QST 基础知识的教程。