Ultrasensitive optomechanical magnetometry.

A cavity optomechanical magneto-meter operating in the 100 pT range is reported. The device operates at earth field, achieves tens of megahertz bandwidth with 60 µm spatial resolution and microwatt optical-power requirements. These unique capabilities may have a broad range of applications including cryogen-free and microfluidic magnetic resonance imaging (MRI), and investigation of spin-physics in condensed matter systems.