Robert Maiwald

Stylus ion trap for enhanced access and sensing

Small, controllable, highly accessible quantum systems can serve as probes at the single quantum level to study multiple physical e ects, for example in quantum optics or for electric and magnetic eld sensing. The applicability of trapped atomic ions as probes is highly dependent on the measurement situation at hand and thus calls for specialized traps. Previous approaches for ion traps with enhanced optical access included traps consisting of a single ring electrode [1, 2] or two opposing endcap electrodes [2, 3]. Other possibilities are planar trap geometries, which have been investigated for Penning traps [4, 5] and rf-trap arrays [6, 7, 8]. By not having the electrodes lie in a common plane the optical access in the latter cases can be substantially increased. Here, we discuss the fabrication and experimental characterization of a novel radio-frequency (rf) ion trap geometry. It has a relatively simple structure and provides largely unrestricted optical and physical access to the ion, of up to 96% of the total 4π solid angle in one of the three traps tested. We also discuss potential applications in quantum optics and eld sensing. As a force sensor, we estimate sensitivity to forces smaller than 1 yN Hz−1/2.

Design of a mode converter for efficient light-atom coupling in free space

In this article, we describe how to develop a mode converter that transforms a plane electromagnetic wave into an inward-moving dipole wave. The latter one is intended to bring a single atom or ion from its ground state to an excited state by absorption of a single photon wave packet with near-100% efficiency.

A new 4π geometry optimized for focusing on an atom with a dipole-like radiation pattern

Focusing electromagnetic radiation efficiently onto an atom requires an open geometry, which is as close to the full solid angle as possible. Additionally, the radiant intensity should be as close as possible to a dipole radiation in order to have a similar field distribution as in the emission process. Here, we propose to make use of a novel combination of a parabolic mirror and a diffractive optical element.

Efficient saturation of an ion in free space

Abstract We report on the demonstration of a light-matter interface coupling light to a single

Resonant photo-ionization of Yb+ to Yb2+

^{174}\hbox {Yb}^+

A Single Ion Headlight

174Yb+ ion in free space. The interface is realized through a parabolic mirror partially surrounding the ion. It transforms a Laguerre–Gaussian beam into a linear dipole wave converging at the mirror’s focus. By measuring the non-linear response of the atomic transition, we deduce the power required for reaching an upper-level population of

Ions inside a parabolic mirror - Surrounding absorbers with reflective geometry allows for efficient free space-coupling

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