关键词: 量子光学, 双光子光谱仪, 联合频谱强度, 量子纠缠, 色散光纤

Abstract: The single-photon-level two-dimensional fiber spectrometer can efficiently measure the joint spectral distribution of biphotons produced by spontaneous parametric down-conversion processes, and has been widely used in quantum information technology in the 1550 nm band. However, this instrument is currently not suitable for use in the 800 nm band due to the lack of low-loss dispersion fibers. To overcome this limitation, we constructed a single-photon-level two-dimensional fiber spectrometer for the 800 nm band by employing two single-mode fibers of 0.544 km length designed for the 800 nm band, two silicon-based single-photon detectors, and a time interval analyzer, expanding the application of the twodimensional fiber spectrometer from 1550 nm band to 800 nm band. After measurement and calibration, the resolution of the spectrometer was confirmed to be 7.8 nm. And then, utilizing this spectrometer, we measured the joint spectral distribution of biphotons with a center wavelength of 810 nm generated from a periodically poled potassium titanyl phosphate crystal, verifying the resolution and applicability of the spectrometer. This work is expected to promote the advancement of time-frequency measurement techniques with single-photon level in the visible and near-infrared spectral regions.

Key words: quantum optics, biphoton spectrometer, joint spectral intensity, quantum entanglement; dispersive fiber