Measurement of temporal correlations of the overhauser field in a double quantum dot.
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.
Reilly
D J
DJ
Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
Taylor
J M
JM
Laird
E A
EA
Petta
J R
JR
Marcus
C M
CM
Hanson
M P
MP
Gossard
A C
AC