Magnetic field gradiometer

A magnetic field gradiometer for determining a magnetic field gradient, the magnetic field gradiometer comprising:

• at least one excitation light source for emitting excitation light,
• two spatially spaced-apart measurement regions for magnetic field measurement, the two measurement regions comprising color centers in a diamond, which emit fluorescence upon excitation by the excitation light,
• a first detector for detecting the fluorescence from a first measurement region of the two measurement regions,
• a second detector for detecting the fluorescence from a second measurement region of the two measurement regions,
• a first microwave emitter for applying a first microwave field to the first measurement region,
• a second microwave emitter for applying a second microwave field to the second measurement region,
• an evaluation device configured to determine the magnetic field gradient based on the detected fluorescence from the first measurement region and the detected fluorescence from the second measurement region, and
• a signal generator unit configured to generate a first microwave signal for the first microwave emitter, the first microwave signal comprising at least two frequency components with a phase offset of π with respect to one another, and a second microwave signal for the second microwave emitter, the second microwave signal comprising at least two frequency components with a phase offset of π with respect to one another.