title: Quantum nonlinear optics with single photons enabled by strongly interacting atoms.
abstract: The realization of strong nonlinear interactions between individual light quanta (photons) is a long-standing goal in optical science and engineering, being of both fundamental and technological significance. In conventional optical materials, the nonlinearity at light powers corresponding to single photons is negligibly weak. Here we demonstrate a medium that is nonlinear at the level of individual quanta, exhibiting strong absorption of photon pairs while remaining transparent to single photons. The quantum nonlinearity is obtained by coherently coupling slowly propagating photons to strongly interacting atomic Rydberg states in a cold, dense atomic gas. Our approach paves the way for quantum-by-quantum control of light fields, including single-photon switching, all-optical deterministic quantum logic and the realization of strongly correlated many-body states of light.
authors: Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors: Thibault
authors: T
authors: Peyronel
authors: Ofer
authors: O
authors: Firstenberg
authors: Qi-Yu
authors: QY
authors: Liang
authors: Sebastian
authors: S
authors: Hofferberth
authors: Alexey V
authors: AV
authors: Gorshkov
authors: Thomas
authors: T
authors: Pohl
authors: Mikhail D
authors: MD
authors: Lukin
authors: Vladan
authors: V
authors: Vuletić