This project will study interactions of light with matter that are so strongly enhanced that single photons can alter the propagation of other photons. This strong enhancement will be achieved by injecting Rubidium atoms into the core of special hollow fibers, known as photonic crystal fibers, which can tightly confine the light over distances much longer than could be achieved in free space. Various interactions will be studied which could have important applications to quantum information science and could be used for highly secure communications and for quantum computing. In particular, successful realization of the three projects making up the effort could lead to a number of important quantum devices including scalable single-photon sources, deterministic quantum logic gates, and quantum repeaters.
Photonic band-gap fibers (PBGF) guide light via diffraction rather than by total internal reflection and allow for simultaneous high confinement of light and gases in a hollow-core region. As a result, PBGF's offer a unique advantage over free-space, focused geometries for atom-light interactions due to their unmatched ratio of path length to cross-sectional core area. The proposed effort will consist of three projects that build on the principal investigator's recent results. The first project will explore nonlinear phase shifts induced by single photons and its use for quantum non-demolition measurements. The second project entails demonstration at sub-milliwatt powers of frequency translation of a light field and its quantum properties using the process of frequency translation via the nonlinear process of Bragg scattering four-wave mixing. The third project will investigate the process of coherent photon conversion in which three quantum fields undergo a strong nonlinear interaction that is mediated by a strong pump field. These projects will address not only fundamental issues, such as whether large nonlinear phase shifts per photon are possible, but also will explore whether the Rubidium-based PBGF system can fulfill its promise as a platform for quantum information applications.
