In this talk, Prof. Firstenberg provides insights into his research on quantum vortices and discusses the theory and experimental realization of the photon-photon interaction

Have you ever tried dragging a plate through the surface of a water pool? Quite excitingly, you would form a pair of vortex and antivortex, propagating steadily on the water’s surface!

In optics, vortices manifest as phase twists of the electromagnetic field, usually formed by interaction with matter. Vortex formation due to light interacting with light requires strong optical nonlinearity. Recently, we have reached a new extreme regime of photon-photon interactions in which quantum vortices – phase dislocations in the few-body wavefunction – are formed.

We will discuss the theory and experimental realization of this effective photon-photon interaction in a quantum nonlinear medium based on ultracold Rydberg atoms. Similarly to a plate pushing water, the excess phase accumulating due to the interaction produces vortex pairs, lines, and rings.

The “conditional” phase localized between these vortices can be used for deterministic quantum logic operations.