Possibilities of integrating micro-optics on top of an atom chip by standard fiber technology are investigated. In particular, the study is interested in single-atom detection with minimal spontaneous scattering.
We investigate the optical detection of single atoms held in a microscopic atom trap close to a surface. Laser light is guided by optical fibers or optical microstructures via the atom to a photodetector. Our results suggest that with present-day technology microcavities can be built around the atom with sufficiently high finesse to permit unambiguous detection of a single atom in the trap with $10\ensuremath{\mu}\mathrm{s}$ of integration. We compare resonant and nonresonant detection schemes and discuss the requirements for detecting an atom without causing it to undergo spontaneous emission.
Abstract: 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. 1.
Detecting single atoms (qubits) is a key requirement for implementing quantum information processing on an atom chip. The detector should ideally be integrated on the chip. Here we present and compare different methods capable of detecting neutral atoms on an atom chip. After a short introduction to fluorescence and absorption detection we discuss cavity enhanced detection of single atoms. In particular we concentrate on optical fiber based detectors such as fiber cavities and tapered fiber dipole traps. We discuss the various constraints in building such detectors in detail along with the current implementations on atom chips. Results from experimental tests of fiber integration are also described. In addition we present a pilot experiment for atom detection using a concentric cavity to verify the required scaling.