Magnetic Microtraps, Microguides, and Mirrors:
New tools for cavity QED, BECs, and atom optics

Background

The primary aim of this research is to develop new experimental techniques for studying the dynamics of open quantum systems under continuous measurement. Microfabricated atom chips combined with laser cooling and trapping have found successful application in creating atom optical elements, novel atom traps, and in investigations of Bose-Einstein condensates.

Cavity QED with Magnetic Microtraps

The system comprised of an atom strongly coupled to photons, known as cavity quantum electrodynamics, provides a rich experimental setting for quantum information processing, both in the implementation of quantum logic gates and in the development of quantum networks [1]. Moreover, studies of cavity QED will help elucidate the dynamics of continuously observed open quantum systems with quantum-limited feedback.

To achieve these goals in cavity QED, a neutral atom must be tightly confined inside a high-finesse cavity with small mode volume for long periods of time. Microfabricated wires on a substrate---known as an atom chip---can create a sufficiently high-curvature magnetic potential to trap atoms in the Lamb-Dicke regime [2]. These micron-sized wires can position an atom inside the mode of a Fabry-Perot cavity, and perhaps enable the coupling of atoms to more exotic resonators such as microsphere, microdisk, or photonic bandgap cavities. We are currently investigating the integration of magnetic microtraps with microdisk and photonic bandgap cavities to form robust and scalable atom-cavity chips [3].

In collaboration with the Reichel and Hansch group at the MPQ/LMU in Munich, we have recently magnetically guided atoms into the mode of an on-chip optical fiber-gap cavity and are pursuing single atom detection with this system.

Hard Drive Atom Mirrors

We fabricated and demonstrated a specular atom mirror formed from a standard computer hard drive [4]. Magnetization periodicity of 3 um has been achieved, and we believe it would be straightforward to reduce this to 2 um with photolithography and to 1 um using a large area electron-beam writer. The hard drive atom mirror is compact, passive, relatively simple to fabricate, and possesses a large remanent magnetic field. Moreover, it has several desirable properties for applications beyond reflection of thermal atoms or an atom laser. The hard drive’s large coercivity should allow one to use wires fabricated directly on its surface to augment the mirror’s ability to manipulate atoms. Likewise, electric pads could be printed on the surface (see below). These pads would allow state-independent forces to act in concert with the state-dependent forces from the mirror’s magnetic field to perform quantum logic gates necessary for quantum computation. The mirror can trap cold atom gases in two dimensions, and can act as an adjustable grating when used in conjunction with a magnetic bias field. Large area mirrors can be fabricated, and it seems possible that these mirrors could be useful for guiding or confining cold neutrons. As hard drive platters are expected to have good surface flatness and substrate rigidity, it may be possible to create two-dimensional waveguides and other devices by holding an opposing pair of atom mirrors a few microns apart.

1D Magnetoelectrostatic Ring Trap in collaboration with Asa Hopkins

The hard drive atom mirror, in conjunction with micron-sized charged circular pads, can create a 1-D ring trap which may prove useful for studying Tonks gases in a ring geometry and for creating devices such as a SQUID-like system for neutral atoms [5]. We are currently fabricating these ring traps, and are building a vacuum chamber and laser set-up to begin testing them.

Interferometry and Josephson Effects with Bose-Einstein Condensates

In collaboration with the Hansch and Reichel group at the MPQ/LMU in Munich, we fabricated and are currently testing an atom chip for the purpose of splitting a BEC with a double well potential. We hope to use such a device for atom interferometry and for studying Josephson phenomena in this double well system.

(last updated November 18, 2004)

Group Publications

References