UC San Diego

In recent years, nitrogen-vacancy (NV) centers, optically active spin defects in diamond, have emerged as a promising platform for quantum sensing, computing and communications applications. These defects exhibit remarkable properties, including single-spin addressability, excellent quantum coherence, and functionality over a broad temperature range, making them well-suited for realizing quantum information science technologies.

This doctoral dissertation explores the complementary techniques of quantum sensing and qubit control using NV centers in diamond. The relevant background and physics of NV-based quantum sensing and control are first introduced. The NV center measurement platforms are also presented, including the experimental realizations in confocal and widefield microscopes, as well as the NV magnetometry and qubit control measurement protocols.

NV magnetometry techniques are applied to probe the relationship between the microscopic magnetic structure and material properties of novel non-collinear antiferromagnets Mn3Sn. Nanoscale imaging of both spin-orbit-torque-induced deterministic magnetic switching and chiral spin rotation in Mn3Sn films using NV centers is reported. Furthermore, direct evidence of the off-resonance dipole-dipole coupling between the spin dynamics in Mn3Sn and proximate NV centers is presented through NV relaxometry measurements. These results demonstrate the unique capabilities of NV centers in accessing the local information about the magnetic order and dynamics in emergent quantum materials.

Furthermore, we address the challenges of realizing scalable and local control of individual NV spin qubits via integration into NV-based hybrid quantum systems. Magnetic tunnel junction (MTJ) devices are introduced to establish electrically driven coherent coupling between single and multiple NV centers and a resonant MTJ with voltage controlled magnetic anisotropy. The oscillating magnetic stray fields produced by a resonant micromagnet are shown to effectively modulate and drive coherent NV spin rotations when the NV electron spin resonance frequency matches the resonance conditions of the MTJ. This demonstrated NV-based quantum operational platform offers a new pathway for achieving all-electric control of NV spin qubits, with significant advantages in scalability, device compatibility, and energy efficiency, further expanding the potential role of NV centers in a broad range of quantum computing, sensing, and communications applications.