Integration of light and atom optics on an atom chip

The whole business of quantum computing with neutral atoms requires accurate preparation and control of their quantum states. The envisioned procedureof preparing and operating an atom chip quantum processor involves two main tools at all its stages: quasi-static electro-magnetic fields to provide taylored potentials for trapping and guiding atomic qubits and light optical elements for initialisation, gate operation, and read-out. Our vision is to implement microoptics directly on the atomchip. A large scale quantum processor will probably involve microscale structures such as waveguides or photonic crystals. As a final goal even the light sources themselves (diode lasers) might beintegrated on the chip. The miniaturisation of optical elements already is a rapidly growing field driven by the telecommunication boom. We hope to adapt these techniques to develope an atomoptical toolbox for Quantum Information Processing. Our first experiments aim at the detection of few or even single atoms in miniaturized traps using optical fibres. Two single mode fibres will be mounted on an atom chip with a small gap between the facets. Light that is sent through the fibres will be absorbed by the atoms leading to a decreasedoutput intensity. In order to enhance the coupling between lightand atom, the two fibres should form a cavity. Each time an atom enters the cavity, the output intensity will decrease. Here we present our ongoing experiments, where we tryto build a fibre cavity on a chip serving asa single atom detector. The concepts will be introduced, theoretical estimates for expectable signals will be presented and first setups will be shown. Beyond this we will discuss future perspectivesof this technology.