Frequency nondegenerate entangled photon pairs have been employed in quantum communication, imaging, and sensing. To characterize quantum entangled states with long-wavelength [infrared (IR) or even terahertz (THz)] photons, one needs to either develop the single-photon detectors at the corresponding wavelengths or use a novel tomography technique that does not rely on single-photon detections, such as stimulated emission tomography (SET). We use standard quantum state tomography and SET to measure the density matrix of entangled photon pairs, with one photon at 1550 nm and the other one at 810 nm, and obtain highly consistent results, showing the reliability of SET. Our work paves the way for efficient measurement of entangled photons with highly dissimilar frequencies, even to the frequencies where single-photon detections are not available.

中文翻译：

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具有不同检测光谱范围的纠缠光子对的受激发射体层摄影术

频率非简并纠缠光子对已用于量子通信，成像和传感中。为了表征具有长波[红外（IR）甚至太赫兹（THz）]光子的量子纠缠态，需要开发相应波长的单光子探测器，或者使用不依赖于单光子的新型层析技术光子检测，例如受激发射体层摄影（SET）。我们使用标准量子态层析成像和SET来测量纠缠光子对的密度矩阵，其中一个光子在1550 nm，另一个光子在810 nm，并获得高度一致的结果，表明SET的可靠性。我们的工作为有效测量频率高度不同的纠缠光子铺平了道路，甚至可以解决无法使用单光子检测的频率。