Quantum Systems

An optically pumped magnetometer (OPM) is presented which is dedicated to sensitive measurements on mobile platforms within the Earth’s magnetic field. It features omnidirectional sensitivity based on amplitude-modulated optical pumping of two cesium vapor cells in perpendicular arrangement. The sensor’s heading error is remarkably suppressed in a differential scheme using two well-balanced circularly polarized laser beams of opposite helicity for each of the cells. In addition, a modulation of the spin-driving frequency eliminates potential systematic errors in sensor read-out due to demodulation phase shifts and instabilities. Within shielded environment, we demonstrate the omnidirectional sensing characteristics, on average a maximum heading error of 0.4 nT for arbitrary sensor orientation, and a noise-limited magnetic flux density resolution of 1.8 pT/√Hz within a sensor 3-dB bandwidth of 1 kHz..