Photons do not interact with each other directly. Here, we make photons more interesting by generating strong interactions between them. We coherently couple slowly propagating photons to strongly-interacting atomic Rydberg states in a cold, dense atomic gas. In the dissipative regime, one photon scatters the neighboring photons . In the dispersive regime, photons are attracted to form a two-photon bound state . These results open up the possibility for realizing all-optical switching, deterministic photonic quantum logic, and strongly interacting photonic many-body systems. In particular, we are investigating novel quantum states resulting from three or more interacting photons, as well as a single-photon CNOT gate based on flip-flop dipole-dipole interactions.
- T. Peyronel, et al., Quantum nonlinear optics with single photons enabled by strongly interacting atoms, Nature, 488 (2012) 57-60.
- O. Firstenberg, et al., Attractive Photons in a Quantum Nonlinear Medium, Nature, 502 (2013) 71-75.