Image-Plane Detection of Spatially Entangled Photon Pairs with a CMOS Camera

TL;DR

This paper demonstrates the detection of spatially entangled photon pairs using a standard CMOS camera at mesoscopic light levels, enabling efficient quantum imaging beyond photon-counting limitations.

Contribution

It introduces a method to observe biphoton correlations with conventional CMOS cameras at higher photon flux, bypassing the need for photon-counting detectors and deep photon-sparse operation.

Findings

Successful measurement of position and momentum correlations in image and pupil planes.

Correlation analysis suppresses artifacts and reduces frame requirements.

Quantum imaging can be extended with standard imaging hardware.

Abstract

Spatially entangled photon pairs (biphotons) generated by spontaneous parametric down-conversion offer unique opportunities for quantum imaging, but image-plane biphoton correlations are difficult to observe with camera-based detectors. Previous camera-based biphoton imaging experiments have relied on photon-counting detection, which necessitates operation deep in the photon-sparse regime and requires extremely low dark rates. Here, we demonstrate the detection of spatial biphoton joint probability distributions in both the image plane and the pupil plane (also termed "near-field plane" and "far-field plane" respectively) using a conventional scientific CMOS camera operated in linear mode. We work at mesoscopic intensity levels, corresponding to a photon flux approximately four orders of magnitude higher than typical photon-counting approaches. From the measured image- and pupil plane correlations, we observe position and momentum correlations consistent with an EPR-type entanglement witness. A tailored correlation analysis suited for image plane imaging suppresses detector artifacts and intensity fluctuations, enabling acquisition with significantly fewer frames. Our results demonstrate that spatially entangled-light imaging can be performed efficiently with standard imaging hardware, extending quantum imaging techniques beyond the photon-counting regime.