Control and manipulation of the nuclear spin bath via continuous measurement and feedback

The detailed control of the electron and surrounding nuclear spins of the nitrogen vacancy (NV) defect in diamond is of interest both for sensing applications as well as for quantum information processing. Detailed control of these spins is hampered by decoherence from the extended surrounding nuclear spin bath consisting of ¹³C nuclear spins. Researchers have previously shown that it is possible to control quantum systems via pulsed measurements and feedback in optomechanics. We theoretically describe how a similar protocol can be implemented in the solid-state spin to allow the NV to manipulate the surrounding nuclear spin bath to achieve a complete purification of the bath, to prepare the bath in a fully polarized state or to prepare highly spin squeezed states of the bath. By achieving detail control over the surrounding nuclear spins allows for greatly extended spin dephasing times for the electron spin of the NV and the potential use of the spin squeezed bath for improved sensing.