Quantum Optics with Diamond Color Centers Coupled to Nanophotonic Devices

Abstract

Solid-state quantum systems based on Josephson junctions, electronic spins and nuclear spins are among the leading candidates for realizing quantum bits (qubits) in a scalable manner. Despite recent demonstrations of few-qubit quantum registers with these systems, efficient photon-mediated entanglement generation between remote quantum registers remains an outstanding challenge. In this thesis, we develop a platform based on diamond color centers coupled to nanophotonic devices to address this challenge. To realize coherent atom-photon interactions, we first develop an improved understanding of the impact of the solid-state environment on the optical transitions of nitrogen-vacancy (NV) and silicon-vacancy (SiV) color centers in diamond. By investigating the interaction of defect orbitals with phonons and electric fields, we identify the necessary symmetry and temperature conditions at which atom-like, transform-limited optical transitions can be achieved. We show that the inversion symmetry of the SiV center results in a vanishing static electric dipole moment and protects optical transitions from electric field fluctuations arising from the solid-state environment. The reduced sensitivity to electric field noise results in spectrally-stable optical transitions for SiV centers, even in nanostructures. We use these properties and bright zero-phonon line emission to efficiently generate indistinguishable photons from separate SiV centers. These results establish SiV centers as superior optical emitters compared with NV centers both in terms of brightness and spectral stability. We next integrate SiV centers into diamond nanophotonic structures and demonstrate strong atom-photon interactions in the high-cooperativity regime of cavity quantum electrodynamics. We use ion implantation to create SiV centers with coherent optical transitions in diamond photonic crystal cavities. The strongly coupled SiV-cavity system is used to realize a quantum-optical switch that is nonlinear at the single-photon level. Finally, we demonstrate entanglement generation between two SiV centers in a single diamond waveguide based on detection of indistinguishable photons.