Quantum information processing with high-density diamond nitrogen-vacancy centers in strain and magnetic fields.

The long-sought scalable quantum information processor is a critical challenge since it requires long coherence time as well as full control and readout of every single qubit. Here we propose methods to use closely spaced diamond nitrogen-vacancy (NV) centers for realizing quantum information processing and quantum computing. The NV centers are coupled with their adjacent color centers by spin-spin interactions. By applying a strain gradient, the position of each NV center is encoded and hence more than 100 NV centers can be read out individually due to the narrow linewidths and the dispersive distributions of the optical transition frequencies. At the same time, the individual control of the spin states can be realized by a position-dependent magnetic field. The strain and magnetic field gradient provide the flexibility to independently manipulate and selectively couple the electron spins. We also present a universal set of quantum gates with high fidelity combined utilizing optimal control methods for this solid-state system.