Single-pixel quantum imaging via induced coherence in warm atomic ensemble

Induced coherence is a phenomenon where coherence appears without stimulated emission. It is hard to explain well with only classical optics, and a quantum-mechanical explanation is needed. Induced coherence allows the two photon states to become indistinguishable by erasing the which-path information carried by the conjugate photon of the detected photon. With induced coherence, we can obtain information about an object without directly detecting the photon that interacts with it. We then detect the correlated photon and extract the object's information from the measured signal. This principle has motivated extensive research in quantum sensing, including quantum imaging, quantum holography, and spectroscopy. In this work, we generate photon pairs in a single warm atomic vapor cell using two spontaneous four-wave mixing (SFWM) processes and observe induced-coherence interference. Based on this setup, we are extending the setup to a single-pixel imaging scheme using a spatial light modulator (SLM). The SLM programs the spatial phase to control the spatial mode in the interferometer. By sequentially projecting spatial patterns such as Hadamard masks, we can reconstruct an image from the single-pixel detection signal.