  We demonstrate bias control of the hyperfine coupling between a single
electron in an InAs quantum dot and the surrounding nuclear spins monitored
through the positively charged exciton X+ emission. In applied longitudinal
magnetic fields we vary simultaneously the correlation time of the hyperfine
interaction and the nuclear spin relaxation time and thereby the amplitude of
the achieved dynamic nuclear polarization under optical pumping conditions. In
applied transverse magnetic fields a change in the applied bias allows to
switch from the anomalous Hanle effect to the standard electron spin
depolarization curves.
