The benefit of the CDSM magnetometer is its ‘alloptical’ measurement of the magnetic field strength. Its working principle is based on a quantum optical phenomenon, the Coherent Population Trapping (CPT) effect. This effect causes a trapping of atomic population in so-called dark states. The stringent preparation conditions of the CPT effect results in very narrow dark resonance features. These resonances are suited for measuring the magnetic field dependent (Zeeman-) energy level shift within the 87Rb D1 and D2 - hyperfine structure.
The combination of several of these dark state resonances enables an omni-directional (i.e. dead-zone free) measurement of the magnetic field and additionally reduces line shift effects (light shift, buffer gas induced temperature shift) which increases the measurement accuracy.