A team of researchers from Louisiana State University (LSU) and the National Autonomous University of Mexico (UNAM) demonstrates that the statistical fluctuations of the electromagnetic field, which define different kinds of light, can be modified upon propagation leading to the modification of its quantum properties of coherence (see Illustration).

The theoretical study entitled “Multiphoton quantum van Cittert-Zernike Theorem” involves collaborative research from Dr. Chenglong You, Dr. Ashe Miller, and Dr. Omar S. Magaña-Loaiza from the LSU Quantum Photonics Laboratory, and Dr. Roberto de J. León-Montiel from the UNAM’s Institute of Nuclear Sciences. Remarkably, the van Cittert-Zernike theorem has constituted one of the pillars of classical optics for almost a century. As such, this fundamental theorem provides the formalism to describe the modification of the classical coherence properties of optical fields upon propagation.  However, the description of the evolution of the quantum properties of coherence of optical systems through the van Cittert-Zernike theorem had remained elusive. 

The team applied their theoretical formalism to a multiphoton system. Interestingly, this kind of systems can host many complex forms of interference processes that are essential to perform operations that are intractable on classical systems. Notably, their article provides a theoretical formalism to describe the modification of the quantum fluctuations of multiphoton systems upon propagation in the absence of conventional light-matter interactions. Furthermore, this work uncovers the possibility of performing all-optical preparation of multiphoton systems with attenuated quantum statistics below the shot-noise limit. The attenuation of the quantum fluctuations of optical fields has enormous implications for the design of diverse quantum technologies ranging from quantum sensing to quantum information processing.

This work was supported by the Army Research Office (ARO), through the Early Career Program (ECP) under the grant no. W911NF-22010-088 and by DGAPA-UNAM under the Project UNAM-PAPIIT IN101623.