Event Date
Title: Cavity Quantum Electrodynamics and Nanophotonic Integration for Quantum Light–Matter Interfaces
Abstract: Color centers are optically active point defects in semiconductor materials, many of them carrying a spin degree of freedom that couples coherently to emitted photons. This makes thema leading candidate for building quantum computers, networks, and sensors, but realizing thatpromise depends on the interface between the emitter and light. Color centers must be integrated into nanophotonic structures, such as nanopillars that collect their emission efficiently and optical cavities that couple them to a single mode. This dissertation studies the physics of quantum emitters inside such structures along two complementary threads: the direct cryogenic spectroscopy of color centers integrated into silicon carbide nanostructures, and the study of the physics of many-body cavity quantum electrodynamics (CQED) through simulation on superconducting and trapped-ion quantum hardware.
The first thread concerns the nitrogen-vacancy (NV) center in 4H silicon carbide integratedinto nanopillars. We show that the sub-wavelength geometry of a nanopillar reshapes the local electromagnetic environment, granting optical access to transitions that selection rules forbid in bulk material: emission from the PL3 divacancy, nearly absent in planar devices, becomes pronounced in nanopillars through a polarization transformation of the excitation field, and the orientation dependent collection of the pillar resolves the previously ambiguous NV4′ line, establishing nanophotonic integration as a symmetry-sensitive probe of defect structure. We then take up the complementary problem of quantifying how many emitters a device contains, adapting the number-and-brightness technique from fluorescence microscopy to solid-state emitters. This calibration-free method counts dense NV ensembles in silicon carbide nanopillars, a regime beyond the reach of existing optical techniques, and extracts their areal density and formation yield.
The second thread turns to many-body cavity QED, in which placing N emitters in a common cavity enhances the light-matter coupling by√N and gives rise to collective effects that are central to strong-coupling applications yet difficult to achieve in solid-state devices based on defects. We realize one such effect on a superconducting circuit, demonstrating photon blockade, the conversion of a coherent drive into a stream of single photons, in a Tavis–Cummings system of N = 1,2,3 transmon qubits coupled to a common resonator. To study the open-system dynamics that govern these systems, we digitally simulate the dissipative Tavis–Cummings modelon both a superconducting and a trapped-ion processor. Platform specific compilation and errormitigation yield population dynamics in close agreement with exact solutions, providing a recipefor simulating cavity-emitter systems on contemporary quantum computers.
Together, the two threads connect the fabrication and characterization of color- center devices to the many-body cavity-QED physics that will ultimately govern their performance.