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arXiv:cond-mat/0603675 · Physical Review Letters

Resonator-Aided Single-Atom Detection on a Microfabricated Chip

Igor Teper, Y.-J. Lin, Vladan Vuletić

Published Jul 14, 2006• 71 citations
arXivHTMLPDF

Abstract

We use an optical cavity to detect single atoms magnetically trapped on an atom chip. We implement the detection using both fluorescence into the cavity and atom-induced reduction in cavity transmission. In fluorescence, we register 2.0(2) photon counts per atom, which allows us to detect single atoms with 75% efficiency in 250 micros. In absorption, we measure transmission attenuation of 3.3(3)% per atom, which allows us to count small numbers of atoms with a resolution of about 1 atom.

DOI
10.1103/physrevlett.97.023002

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We use an optical cavity to detect single atoms magnetically trapped on an atom chip. We implement the detection using both fluorescence into the cavity and atom-induced reduction in cavity transmission. In fluorescence, we register 2.0(2) photon counts per atom, which allows us to detect single atoms with 75% efficiency in 250 micros. In absorption, we measure transmission attenuation of 3.3(3)% per atom, which allows us to count small numbers of atoms with a resolution of about 1 atom.
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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.
We explore the feasibility of single atom detection on an atom chip by using a tiny fluorescence detector mounted on the chip. Resonant fluorescence from a trapped ultracold atom will be collected with a miniature aspheric lens and taken out of a vacuum chamber through a fiber. During detection, the atom can be held at the focus of the detector with a dipole trapping beam introduced through the same fiber. We have experimentally determined the optical performance of such a detector, taking into account effects such as stray light from the dipole trapping beam and chromatic aberration. The collection efficiency for isotropically emitted radiation is experimentally obtained to be 2.5%. From this, it is estimated that the fluorescence emitted from a single Rb atom will produce a photon count rate of 4.7x10(4) Hz, which is much larger than the shot noise limited background fluctuations.
The subject of this thesis is the miniaturization and integration of detectors for the detection of single rubidium atoms on an atom chip. For this purpose three different detectors were developed for atom detection by absorption or fluorescence: i) A fluorescence detector was realized by mounting a tapered lensed fiber perpendicular to a collection fiber. ii) An absorption detector was built by placing a multi-mode fiber in-line with a tapered lensed fiber. iii) A tunable cavity detector was built from two single mode fibers mounted on the chip surface. To mount the detectors on the planar surface of the atom chip retaining structures by means of lithographical techniques were developed. Those structures allow a very accurate and stable passive fiber alignment. To test the individual detectors an atomic ensemble of thermal rubidium atoms was prepared in a magneto-optical trap. Then the atoms were transferred into magnetic micro-traps of the atom chip and were guided to one of the detectors. Each integrated detector has been evaluated by several characterization measurements. With the fluorescence detector the highest single atom detection efficiency of 54\\% was attained. Thereby it was possible to perform quantitative measurements for the magnetically guided atoms on a single atom level and to study fundamental properties of the confined atoms.
Abstract 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.
A single atom strongly coupled to a cavity mode is stored by three-dimensional confinement in blue-detuned cavity modes of different longitudinal and transverse order. The vanishing light intensity at the trap center reduces the light shift of all atomic energy levels. This is exploited to detect a single atom by means of a dispersive measurement with 95% confidence in 10 micros, limited by the photon-detection efficiency. As the atom switches resonant cavity transmission into cavity reflection, the atom can be detected while scattering about one photon.