Performance analysis of an optically pumped magnetometer in Earth’s magnetic field Gregor Oelsner, Volkmar Schultze, Rob IJsselsteijn and Ronny Stolz EPJ Quantum Technol., 6 1 (2019) 6 Published online: 12 December 2019 DOI: 10.1140/epjqt/s40507-019-0076-9