Magnetic interactions of cold atoms with anisotropic conductors

TL;DR

This paper investigates how using electrically anisotropic materials in atom chip wires can significantly reduce magnetic noise, heating, and decoherence of ultra-cold atoms, improving trap stability and coherence times.

Contribution

It develops a theory for magnetic noise reduction via electrical anisotropy and identifies materials and conditions that optimize atom chip performance.

Findings

Electrical anisotropy reduces heating and decoherence rates by orders of magnitude.

Cooling the surface further decreases trap loss due to spin flips.

Anisotropy alters static potential corrugations and their angular dependence.

Abstract

We analyze atom-surface magnetic interactions on atom chips where the magnetic trapping potentials are produced by current carrying wires made of electrically anisotropic materials. We discuss a theory for time dependent fluctuations of the magnetic potential, arising from thermal noise originating from the surface. It is shown that using materials with a large electrical anisotropy results in a considerable reduction of heating and decoherence rates of ultra-cold atoms trapped near the surface, of up to several orders of magnitude. The trap loss rate due to spin flips is expected to be significantly reduced upon cooling the surface to low temperatures. In addition, the electrical anisotropy significantly suppresses the amplitude of static spatial potential corrugations due to current scattering within imperfect wires. Also the shape of the corrugation pattern depends on the electrical anisotropy: the preferred angle of the scattered current wave fronts can be varied over a wide range. Materials, fabrication, and experimental issues are discussed, and specific candidate materials are suggested.