Sensing electric and magnetic fields with Bose-Einstein condensates

We experimentally demonstrate that one-dimensional Bose-Einstein condensates brought close to microfabricated wires on an atom chip are a very sensitive sensor for magnetic and electric fields reaching a sensitivity to potential variations of similar to 10(-14) eV at 3 mu m spatial resolution. We measure a two-dimensional magnetic field map 10 mu m above a 100-mu m-wide wire and show how the transverse current-density component inside the wire can be reconstructed. The relation between the field sensitivity and the spatial resolution is discussed and further improvements utilizing Feshbach-resonances are outlined.