High-Resolution Magnetometry with a Spinor Bose-Einstein Condensate
We demonstrate a precise magnetic microscope based on direct imaging of the Larmor precession of a $^{87}\mathrm{Rb}$ spinor Bose-Einstein condensate. This magnetometer attains a field sensitivity of $8.3\text{ }\text{ }\mathrm{pT}/{\mathrm{Hz}}^{1/2}$ over a measurement area of $120\text{ }\text{ }\ensuremath{\mu}{\mathrm{m}}^{2}$, an improvement over the low-frequency field sensitivity of modern SQUID magnetometers. The achieved phase sensitivity is close to the atom shot-noise limit, estimated as $0.15\text{ }\text{ }\mathrm{pT}/{\mathrm{Hz}}^{1/2}$ for a unity duty cycle measurement, suggesting the possibilities of spatially resolved spin-squeezed magnetometry. This magnetometer marks a significant application of degenerate atomic gases to metrology.