Multi-emitter cavity QED with color centers

R. Mark Wilson

Marina Radulaski, Victoria A. Norman, Sridhar Majety +5 more

Color centers integrated into nanophotonic devices offer functionalities applied in quantum communication, simulation and computation. We explore various regimes of single-emitter and multi-emitter cavity quantum electrodynamics for applications in quantum information hardware.

Ravi Naik, David C. McKay, David Schuster

Daniil M. Lukin, Melissa A. Guidry, J. Joshua Yang +6 more

An outstanding challenge for color center-based quantum information processing technologies is the integration of optically-coherent emitters into scalable thin-film photonics. Here, we report on the integration of near-transform-limited silicon vacancy (V$_{\text{Si}}$) defects into microdisk resonators fabricated in a CMOS-compatible 4H-Silicon Carbide-on-Insulator platform. We demonstrate a single-emitter cooperativity of up to 0.8 as well as optical superradiance from a pair of color centers coupled to the same cavity mode. We investigate the effect of multimode interference on the photon scattering dynamics from this multi-emitter cavity quantum electrodynamics system. These results are crucial for the development of quantum networks in silicon carbide and bridge the classical-quantum photonics gap by uniting optically-coherent spin defects with wafer-scalable, state-of-the-art photonics.

Hannah C. Kleidermacher, Bennet Windt, Miguel Bello +2 more

A central obstacle in realizing color center cavity-QED-based quantum technologies is inhomogeneity, or disorder, among individual emitters. As the number of emitters increases, so does the complexity of the experimental data, making it difficult to quantify the present physical mechanisms of disorder. Here we introduce an artificial intelligence-driven model discovery framework in which a large language model (LLM)-based agent, equipped with tools and a structured workflow, proposes candidate Hamiltonian and Lindbladian models, generates computational tools, and quantitatively evaluates competing physical hypotheses. We apply the workflow to three previously published experimental cavity-QED datasets collected from color centers in diamond and silicon carbide. Across the experiments, the agent successfully identifies physical models for the system and characterizes the disorder. In assessing reproducibility, we find that run-to-run variability is concentrated primarily in the research plan generation step, while the computational analysis itself is substantially more consistent. Our results suggest that structured LLM agent workflows can support model discovery from quantum optical experimental data while simultaneously allowing for human expert supervision and collaboration.

Alex Holt Rubin

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 them a leading candidate for building quantum computers, networks, and sensors, but realizing that promise 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 integrated into 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 model on both a superconducting and a trapped-ion processor. Platform-specific compilation and error mitigation yield population dynamics in close agreement with exact solutions, providing a recipe for 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.