  Dynamic nuclear polarization (DNP) is used in nuclear magnetic resonance
(NMR) to transfer polarization from electron spins to nuclear spins. The
resulting nuclear polarization enhancement can, in theory, be two or three
orders of magnitude depending on the sample. In solid state systems, however,
there are competing mechanisms of DNP, which, when occurring simultaneously,
reduce the net polarization enhancement of the nuclear spin. We present a
simple quantum description of DNP and apply optimal control theory (OCT) with
an open quantum system framework to design pulses that select one DNP process
and suppress the others. We demonstrate experimentally an order of magnitude
improvement in the DNP enhancement using OCT pulses.
