Thermally induced losses in ultra-cold atoms magnetically trapped near room-temperature surfaces

We have measured magnetic trap lifetimes of ultra-cold Rb-87 atoms at distances of 5-1000 mum from surfaces of conducting metals with varying resistivity. Good agreement is found with a theoretical model for losses arising from near-field magnetic thermal noise, confirming the complications associated with holding trapped atoms close to conducting surfaces. A dielectric surface (silicon) was found in contrast to be so benign that we are able to evaporatively cool atoms to a Bose-Einstein condensate by using the surface to selectively adsorb higher energy atoms.