Biphoton Waveforms of Photon Pair from Velocity‐Selective Atoms in a Doppler‐Broadened Atomic Ensemble

Telecom band photonic quantum states generated from atomic systems are critical quantum resources for long‐distance and scalable quantum communication networks. Here, the beat phenomenon in the autocorrelation function of the telecom‐wavelength photon due to the velocity‐selective classes of the atoms in a Doppler‐broadened atomic ensemble of the cascade‐type 5S 1/2 –5P 3/2 –4D 5/2 transition of 87 Rb is reported. Although the signal (1529 nm) and idler (780 nm) photons are emitted from a single‐atomic ensemble, the autocorrelation functions of the signal and idler photons exhibit significantly different features, with temporal widths of 7 and 0.13 ns, respectively. Furthermore, the biphoton spectral waveform of the telecom band photon pair is measured using a stimulated emission method. The biphoton waveforms of the telecom‐wavelength biphoton source demonstrate good agreement with the magnitude of the Fourier components of the measured biphoton temporal and spectral waveforms.