  We present an analysis of magnetic traps for ultracold atoms based on
current-carrying wires with sub-micron dimensions. We analyze the physical
limitations of these conducting wires, as well as how such miniaturized
magnetic traps are affected by the nearby surface due to tunneling to the
surface, surface thermal noise, electron scattering within the wire, and the
Casimir-Polder force. We show that wires with cross sections as small as a few
tens of nanometers should enable robust operating conditions for coherent atom
optics (e.g. tunneling barriers for interferometry). In particular, trap sizes
on the order of the deBroglie wavelength become accessible, based solely on
static magnetic fields, thereby bringing the atomchip a step closer to
fulfilling its promise of a compact device for complex and accurate quantum
optics with ultracold atoms.
