If a picture tells a thousand words, then we might ask ourselves how many photons does it take to form a picture? In terms of the transmission of the picture information, then the multiple degrees of freedom (e.g., wavelength, polarization, and spatial mode) of the photon mean that high amounts of information can be encoded such that the many pixel values of an image can, in principle, be communicated by a single photon. However, the number of photons required to transmit the image information is not necessarily, at least technically, the same as the number of photons required to image an object. Therefore, another equally important question is how many photons does it take to measure an unknown image?

中文翻译：

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形成一幅图像需要多少光子？

如果一张图片讲述了一千个单词，那么我们可能会问自己，形成一张图片需要多少光子？就图片信息的传输而言，光子的多个自由度（例如，波长、偏振和空间模式）意味着可以对大量信息进行编码，使得图像的许多像素值可以，原则上，通过单个光子进行通信。然而，传输图像信息所需的光子数量不一定与成像物体所需的光子数量相同，至少在技术上是这样。因此，另一个同样重要的问题是测量一张未知图像需要多少光子？