LMI Seminar: Quantum Vortices of Propagating Photons

Abstract:

In optics, vortices appear as phase twists of the electromagnetic field, traditionally arising from interactions between light and matter. Our lab investigates an extreme regime of optical nonlinearity in which quantum vortices emerge from strong, effective interactions between individual photons. We observe structured phase singularities in the few-photon wavefunction, including vortex lines and rings forming inside the optical medium. Crucially, the nonlinearity breaks the symmetry between a photon pair propagating behind or ahead of a single photon, which allows us to use three photons to generate and directly observe freely propagating quantum vortices of light. Extending beyond co-propagating geometries, we find that counter-propagating photons exhibit longer-range and richer vortex interactions, opening new avenues for studying interacting quantum light.