Quantum computing in diamond

Our approach for quantum computing is to use spectral hole-burning (SHB) materials for which a large number of individual atoms can be selectively addressed using lasers. However, the qubits are the spins of individual active atoms, which are known to have long coherence lifetimes in these materials. Qubit initialization and single-qubit manipulations can be performed using laser excited Raman transitions. Because of the large optical Rabi frequencies, we anticipate being able to perform >1000 single-qubit operations within the coherence lifetime. Two-qubit, nonlinear operations will be performed using either cavity QED or optical dipole coupling in conjunction with laser excited Raman transitions. The most promising candidate material is NV-Diamond, for which the optical matrix elements are large, thereby enabling fast qubit manipulation and efficient detection of the final state. Here, we present the details of ours studies of single qubits in this medium. Specifically, Raman excited spin coherences were experimentally observed in N-V diamond color centers via nondegenerate four-wave mixing (NDFWM) and electromagnetically induced transparency (EIT). The maximal absorption suppression was found to be 17%, which corresponds to 70% of what is possible given the random geometric orientation of the N-V center in diamond. In the context of quantum computing, this level of transparency represents the efficient preparation of quantum bits (qubits), as well as ability to perform arbitrary single qubit rotations.