Full-mode characterization of correlated photon pairs generated in spontaneous downconversion

Spontaneous parametric downconversion is the primary source to generate entangled photon pairs in quantum photonics laboratories. Depending on the experimental design, the generated photon pairs can be correlated in the frequency spectrum, polarization, position-momentum, and spatial modes. Exploring the spatial modes' correlation has hitherto been limited to the polar coordinates' azimuthal angle, and a few attempts to study Walsh mode's radial states. Here, we study the full-mode correlation, on a Laguerre-Gauss basis, between photon pairs generated in a type-I crystal. Furthermore, we explore the effect of a structured pump beam possessing different spatial modes onto bi-photon spatial correlation. Finally, we use the capability to project over arbitrary spatial mode superpositions to perform the bi-photon state's full quantum tomography in a 16-dimensional subspace. (C) 2021 Optical Society of America

Automated summary

This study focuses on the spatial mode correlation between photon pairs generated through spontaneous parametric downconversion, including research on full-mode correlation on a Laguerre-Gauss basis and the impact of a structured pump beam on the bi-photon spatial correlation. Experimental results demonstrate successful implementation of full quantum tomography of the bi-photon state in a 16-dimensional subspace.