Research
A cavity quantum electrodynamics (QED) system, in which an atom is coupled to the quantized electromagnetic fields (light) of an optical cavity, can be described with three characteristic parameters: g, the rate of coherent exchange of energy between the atom and cavity fields, γ, the rate of the decay of the atomic dipole, and κ, the rate of the decay of the cavity field. When the cavity has extremely high finesse and small mode volume, the condition of strong coupling, g >> γ , κ , can be achieved. In the strong coupling regime, coherent interaction of the cavity field and the atom dominates the dissipation of the system, and a single atom gives rise to a strong nonlinearity in optical responses and nonclassical statistics for light at the single-photon level, while a single photon appreciably affects the quantum state of the atom. In such a system, it is possible to generate highly quantum (nonclassical) states or to observe novel phenomena that are normally hampered by dissipation in other systems. This is applicable to quantum information science (e.g., nonclassical light sources, scalable quantum logic with photons, quantum networks connected with light), ultra-low threshold optical devices, and single atom/molecule detecting devices.
Progress in the research of cavity QED has been made with systems of single atoms coupled to Fabry-Perot cavities. In order to overcome the inherent limitation of these conventional cavities for scaling to large numbers and for coupling to single-mode optical fibers with high efficiency, the development of alternative types of cavities has been pursued.
In our current research, we utilize nanofiber cavities to build all-fiber cavity QED systems. With our technologies for fabricating low-loss optical nanofibers and low-loss fiber Bragg gratings, nanofiber cavities with finesse exceeding 1000 can be fabricated. We are currently working to build scalable multiple cavity QED systems and are seeking for applications to quantum information science with light.