Photons, the particles of light, are ideal carriers of quantum and classical information. Various emerging synthetic platforms enable the unconventional manipulation of photons in their intrinsic degrees of freedom, from polarization to spatial modes to frequency. In this talk, I will summarize some progress on two such platforms.

The first part of the talk will be on nanostructured metasurfaces for quantum photonics. I will show our experimental results that use metasurfaces for the interference, tomographic measurement, and nontrivial transformation of multiphoton quantum states encoded in the polarization degree of freedom.

The second part will focus on non-Hermitian topological photonics in synthetic dimensions. I will show how we implement lattice Hamiltonians with great flexibility using discrete frequency modes of photons in a dynamically modulated system. I will show how we judiciously use losses to achieve non-Hermitian topological invariants, from nontrivial winding numbers to braids/knots formed by the complex-energy non-Hermitian bands.

 Short bio: Kai Wang is a postdoctoral scholar at Stanford University and an incoming assistant professor and MEI chair in quantum photonics in the department of physics at McGill University in Canada. He received his PhD from The Australian National University in 2019. Prior to that, he obtained MSc from Friedrich-Schiller-Universität Jena and BE from Tianjin University. His research interests include quantum photonics, topological photonics, metasurfaces and metamaterials, nanophotonics, and nonlinear optics.