Abstract :

In entanglement distribution-based quantum repeaters, one of the key resources is optically mediated entanglement between distant qubits which can be addressed and controlled individually. In this context, on one hand, atomic defect centers in solid as single photon emitters are suitable candidates as they pos sess optically active spin qubits that can be controlled with high fidelity. On the other hand, nonlinear optical processes like spontaneous parametric down conversion (SPDC) have been demonstrated as efficient methods for generating entangled photon pairs. In this presentation, I will talk about quantum control sequences for initializing a quantum register associated with a single nitrogen vacancy (NV) center, a promising defect center for quantum network applications. I will also present methods for imaging charge states of ensembles of NV centers and their spectroscopic characterizations. Next, I will present the development of an alignment-free, frequency multiplexed photon pair source that is based on fiber-pigtailed, cavity-enhanced spontaneous parametric down-conversion (SPDC) in a nonlinear crystal and is easy to integrate with a practical quantum repeater. We show characterization of multiple pairs of spectrally-resolved modes, as required for a quantum repeater. We also demonstrate optical interface of our source with Tm-based quantum memory.