High precision Optical AC Magnetometry using Dynamical Decoupling

Abstract: We propose a magnetometer for the precise measurement of AC magnetic fields that uses a Terbium-doped optical fiber with half-waveplates built into it at specified distances. Our scheme uses an open-loop quantum control technique called dynamical decoupling to reduce the noise floor and thus increase the sensitivity. We show that dynamical decoupling is extremely effective in preserving the photon state evolution due to the external AC magnetic field from random birefringence in the fiber, even when accounting for errors in pulse timing. Hence we achieve high sensitivity. For a given inter-waveplate distance, the minimum detectable field is inversely proportional to fiber length, as is the bandwidth of detectable frequencies.