Photon-number correlation for quantum enhanced imaging and sensing

TLDR

Photon‑number correlations in the quantum regime are readily produced and remain robust against experimental losses and noise, unlike entanglement which can be destroyed by losing a single photon. This review surveys the potential and achievements of non‑classical photon‑number correlations in twin‑beam states for imaging and metrology, emphasizing phase‑insensitive intensity measurements that probe transmission or absorption and enable target detection in strong backgrounds. The authors exploit twin‑beam sources that emit many pairwise correlated modes, which can be independently accessed by camera pixels to perform parallel photon‑counting, enabling sub‑shot‑noise wide‑field imaging and quantum‑enhanced ghost imaging. Non‑classical correlations open new avenues in quantum radiometry, such as absolute calibration of spatially resolving detectors from the single‑photon to the linear regime within a single experimental setup.

Abstract

In this review we present the potentialities and the achievements of the use of non-classical photon number correlations in twin beams (TWB) states for many applications, ranging from imaging to metrology. Photon number correlations in the quantum regime are easy to be produced and are rather robust against unavoidable experimental losses, and noise in some cases, if compared to the entanglement, where loosing one photon can completely compromise the state and its exploitable advantage. Here, we will focus on quantum enhanced protocols in which only phase-insensitive intensity measurements (photon number counting) are performed, which allow probing transmission/absorption properties of a system, leading for example to innovative target detection schemes in a strong background. In this framework, one of the advantages is that the sources experimentally available emit a wide number of pairwise correlated modes, which can be intercepted and exploited separately, for example by many pixels of a camera, providing a parallelism, essential in several applications, like wide field sub-shot-noise imaging and quantum enhanced ghost imaging. Finally, non-classical correlation enables new possibilities in quantum radiometry, e.g. the possibility of absolute calibration of a spatial resolving detector from the on-off- single photon regime to the linear regime, in the same setup.