Physics Colloquium

(Mostly) Quantum Optics with Structured Light
Prof. Robert Fickler
_{Experimental Quantum Optics, Tampere University of Applied Sciences}

Abstract:
Structured light, i.e. light fields with a non-trivial shape in time, space, and polarization, has become a versatile approach to explore fundamental optics effects and develop novel applications in fields such as microscopy, imaging, optical communications, and quantum technologies, to name a few. In this talk, I will first introduce the field of structured light along with some of its applications in classical and quantum optics. Following this introduction, I will focus on two of our recent quantum optics experiments exploring nonlinear optical processes and structured light. In the first experiment, we test the fundamental law of angular momentum conservation commonly assumed for photons in nonlinear frequency conversion processes. We show that the angular momentum conservation still holds on the single photon level and outline a scheme to leverage it for the generation of high-dimensional multi-photon quantum states. In second experiment, I will present so-called quantum frequency conversion process which we control using structured light. In our approach a single photon is not only converted from one frequency to another, but its entanglement with a partner photon is simultaneously changed from being in polarization to the spatial profile of the photon. We show that the preservation of entanglement (non-local) during this process is conditioned upon the classical non-separability (local) of the structured field that drives the process. Not only show our results an interesting link between classical and quantum non-separability but they will also enable novel studies in open quantum systems and quantum nonlinear optical applications.

Date: Tuesday, October 14, 2025
Institute of Physics, University of Graz, Universitaetsplatz 5
Lecture: 4:15 p.m. Lecture Hall 05.01, ground floor

Host: Peter Banzer

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