Hybrid Quantum Systems: Coupling Diamond Color Centers to Superconducting Cavities

SPICE Workshop on Quantum Spinoptics, June 13th - 15th 2023

Johannes Majer

Hybrid quantum systems based on spin-ensembles coupled to superconducting microwave cavities are promising candidates for robust experiments in cavity quantum electrodynamics (QED) and for future technologies employing quantum mechanical effects. In particular the electron spins hosted by nitrogen-vacancy centers in diamond. We used this system to study a broad variety of effects, such as cavity protection effect and hole burning which can extend the coherence time and reduce dephasing. Furthermore, this platform allows to study superradiance and the coupling of spins over macroscopic distances.
We use a dispersive detection scheme based on cQED to observe the spin relaxation of the negatively charged nitrogen vacancy center in diamond. We observe exceptionally long longitudinal relaxation times T1 of up to 8h. To understand the fundamental mechanism of spin-phonon coupling in this system we develop a theoretical model and calculate the relaxation time ab-initio. The calculations confirm that the low phononic density of states at the NV− transition frequency enables the spin polarization to survive over macroscopic timescales.