30 research outputs found
Quantum vortices of strongly interacting photons
Vortices are a hallmark of topologically nontrivial dynamics in nonlinear
physics and arise in a huge variety of systems, from space and atmosphere to
condensed matter and quantum gases. In optics, vortices manifest as phase
twists of the electromagnetic field, commonly formed by the interaction of
light and matter. Formation of vortices by effective interaction of light with
itself requires strong optical nonlinearity and has therefore been confined,
until now, to the classical regime. Here we report on the realization of
quantum vortices resulting from a strong photon-photon interaction in a quantum
nonlinear optical medium. The interaction causes faster phase accumulation for
co-propagating photons. Similarly to a plate pushing water, the local phase
accumulation produces a quantum vortex-antivortex pair within the two-photon
wavefunction. For three photons, the formation of vortex lines and a central
vortex ring attests to a genuine three-photon interaction. The wavefunction
topology, governed by two- and three-photon bound states, imposes a conditional
phase shift of -per-photon, a potential resource for deterministic quantum
logic operations.Comment: The first two authors contributed equally to this wor