Photons are neutral particles and do not interact with each other. An
effective photon-photon interaction can be created by employing
light-matter interactions in a nonlinear optical medium. Nonlinear
photon-photon interaction at single-photon level is essential for
photonic devices and photonic quantum gates. However single-photon
nonlinearities are tiny because the electric field of a photon is many
orders of magnitude smaller than the binding field of electrons in
matter. Recently a new approach has been demonstrated to create strong
photon-photon interactions by coupling a bare two-level emitter with
photons in an open one-dimensional (1D) waveguide without using an
optical cavity. In this talk I will first introduce the basics of
strongly interacting photons in 1D free space. Next I will explain a
theoretical method to study correlated photons in such physical
systems. Finally I will discuss some proposed all-optical quantum
devices along this direction and their current experimental status.
|