title: High-sensitivity magnetometry based on quantum beats in diamond nitrogen-vacancy centers.
abstract: We demonstrate an absolute magnetometer based on quantum beats in the ground state of nitrogen-vacancy centers in diamond. We show that, by eliminating the dependence of spin evolution on the zero-field splitting D, the magnetometer is immune to temperature fluctuation and strain inhomogeneity. We apply this technique to measure low-frequency magnetic field noise by using a single nitrogen-vacancy center located within 500 nm of the surface of an isotopically pure (99.99% 12C) diamond. The photon-shot-noise limited sensitivity achieves 38  nT/sqrt[Hz] for 4.45 s acquisition time, a factor of sqrt[2] better than the implementation which uses only two spin levels. For long acquisition times (>10  s), we realize up to a factor of 15 improvement in magnetic sensitivity, which demonstrates the robustness of our technique against thermal drifts. Applying our technique to nitrogen-vacancy center ensembles, we eliminate dephasing from longitudinal strain inhomogeneity, resulting in a factor of 2.3 improvement in sensitivity.
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Kejie
authors.initials: K
authors.lastname: Fang
authors.forename: Victor M
authors.initials: VM
authors.lastname: Acosta
authors.forename: Charles
authors.initials: C
authors.lastname: Santori
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Huang
authors.forename: Kohei M
authors.initials: KM
authors.lastname: Itoh
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Watanabe
authors.forename: Shinichi
authors.initials: S
authors.lastname: Shikata
authors.forename: Raymond G
authors.initials: RG
authors.lastname: Beausoleil