title: Measurement of temporal correlations of the overhauser field in a double quantum dot.
abstract: In quantum dots made from materials with nonzero nuclear spins, hyperfine coupling creates a fluctuating effective Zeeman field (Overhauser field) felt by electrons, which can be a dominant source of spin qubit decoherence. We characterize the spectral properties of the fluctuating Overhauser field in a GaAs double quantum dot by measuring correlation functions and power spectra of the rate of singlet-triplet mixing of two separated electrons. Away from zero field, spectral weight is concentrated below 10 Hz, with approximately 1/f2 dependence on frequency f. This is consistent with a model of nuclear spin diffusion, and indicates that decoherence can be largely suppressed by echo techniques.
authors.affiliation: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Reilly
authors.forename: J M
authors.initials: JM
authors.lastname: Taylor
authors.forename: E A
authors.initials: EA
authors.lastname: Laird
authors.forename: J R
authors.initials: JR
authors.lastname: Petta
authors.forename: C M
authors.initials: CM
authors.lastname: Marcus
authors.forename: M P
authors.initials: MP
authors.lastname: Hanson
authors.forename: A C
authors.initials: AC
authors.lastname: Gossard