Engineering quantum states of light with multimode parametric down-conversion: how about the loss?
Dr. Denis Kopylov (Universität Paderborn Comp. Optoelectronics and Photonics)

Currently, pulsed parametric down-conversion (PDC) in waveguides is one of the most promising platforms for non-classical light sources. PDC provides not only an efficient way to generate biphoton pairs and squeezed states but also can be used in more advanced circuits to prepare non-Gaussian states of light. However, waveguides typically possess surface imperfections that may cause significant scattering of the guided light, providing multimode mixed output states. In this talk, we discuss the properties of the multimode PDC in lossy waveguides and show how critical these losses are for the generation of biphoton, squeezed, and entangled states ([Quantum 9, 1621 (2025)] and [arXiv:2501.08917]).