Vector EIT magnetometer for highly sensitive measurements.

We experimentally develop a novel and highly sensitive approach to measuring a vector magnetic fields using electromagnetically induced transparency (EIT) resonances. When an atom interacts with a bi-chromatic field in a two-photon configuration, the medium becomes transparent if the frequency difference between the fields is close to the energy separation between two Zeeman sublevels. As a result, a narrow transition peak appears in the transmission spectrum for all the allowed resonances. The magnitude of the magnetic field determines the separation between EIT spectrum peaks, and its orientation modifies the resonance amplitudes, making this system capable of vector measurements. Here we report our evaluation of the short-term stability and sensitivity of our prototype: we were able to achieve scalar stability below 10 pT/rtHz in the 10Hz-100Hz bandwidth using a 100mm³ vapor cell of hot ⁸⁷Rb atoms, and sensitivity better than 1° for azimuthal magnetic field angle detection.