Structured Photons – Their Application in Quantum Photonics

Abstract: Photons, the quanta of light, possess several different degrees of freedom, e.g. frequency, polarisation, spatial and temporal modes, which can be used as platforms for quantum information applications. Polarisation, corresponding to the vectorial nature of light, is bi-dimensional, and thus can represent ‘0’ and ‘1’ in the digital world. Unlike polarisation, transverse and temporal modes would provide an unbonded vector space and could be used to extend the alphabet beyond the ‘0’s and ‘1’s to any arbitrary integer numbers. Photons in superposition states of these different degrees of freedom are known as Structured Photons. In the classical regime, structured light has found tremendous applications, e.g., overcoming the diffraction limit (STED microscopy), for optical spanners, communication multiplexing, and generating non-trivial 3D topologies such as Möbius and Knots. In the quantum domain, structured photons may be used to realise higher- dimensional states, and thus are employed in quantum communication, computation, and simulation applications.

The recent progress, challenges, and applications of structured photons in modern photonics will be the subject of my talk. In particular, I will discuss their applications in high-dimensional quantum key distribution, quantum hacking, and simulating complex quantum systems.