Quantum logic readout and cooling of a single dark electron spin.

We study a single dark N2 electron spin defect in diamond, which is magnetically coupled to a nearby nitrogen-vacancy (NV) center. We perform pulsed electron spin resonance on this single spin by mapping its state to the NV center spin and optically reading out the latter. Moreover, we show that the NV center's spin polarization can be transferred to the electron spin by combined two decoupling control-NOT gates. These two results allow us to extend the NV center's two key properties-optical spin polarization and detection—to any electron spin in its vicinity. This enables dark electron spins to be used as local quantum registers and engineerable memories. [ABSTRACT FROM AUTHOR]