Quantum Light with a Twist: When Single-Photon Topology Meets Nanophotonics

The fields of quantum optics, nanophotonics and topological photonics have advanced rapidly over the past decade, albeit mostly along separate paths. Bringing those fields together could enable quantum light that carries information in robust topological textures, generated and controlled on a chip. Beyond its technological advantages, confining light on a chip gives rise to intriguing physics. When concentrated to sub-wavelength dimensions, light becomes a three-dimensional vector field whose degrees of freedom are locked together. While this locking results in some loss of information, it opens new opportunities for shaping light and creating new quantum states.

In this talk I will present our progress in turning this locking into a resource for quantum light, carried in the total angular momentum (TAM) of single photons. I will start with the first observation of non-classical correlations between two photons in the near-field regime, entangled in their TAM. On the fundamental side, I will describe how we traced the evolution of quantum information in heralded single photons as they couple into and out of the near field of a nanophotonic system, and show that the TAM qubit in the near field becomes a free-space qudit entangled in its spin and orbital angular momentum. I will then present optical skyrmions, topological textures of the optical field that our group was the first to observe, and show how, by bringing the two together, single photons in confined TAM states become quantum Stokes skyrmions, which are known to carry quantum information robustly. Finally, I will touch upon twisted light in the form of skyrmion bags - single textures that carry several topological integers that can underpin topological secret sharing protocol on a chip.