Fiber optics for quantum computers

We describe schemes for the integration of miniature optical components onto Atom Chips, for the manipulation and detection of ultra-cold atoms. Our intention is to build detectors sensitive enough to accurately detect single atoms. Two approaches are discussed: simple fluorescence detection and the use of a resonant cavity. Theory predicts that cavities with F>100 should be sufficient to obtain signal to noise ratios high enough to detect single atoms. The first micro cavities were demonstrated using mirrors formed by cleaved fiber ends coated with a stick-on dielectric coating to give F ~100. A more successful approach involves the full integration of the mirrors and fibers by using Bragg gratings written into the fiber core: it has been possible to form gap cavities with F ~ 150.