High impedance circuit quantum electrodynamics with hole spins

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This project will experimentally and theoretically investigate hybrid quantum systems consisting of hole spins in semiconductor nanostructures that are embedded into high-impedance superconducting resonators. The combination of the long spin coherence times of holes in silicon and germanium (SiGe) with their dilute nuclear spin system on the one hand, and high-impedance granular aluminum (grAl) resonators on the other, represents a unique platform to investigate the strong coupling of individual spins to a single boson mode in the sense of cavity quantum electrodynamics (QED). In this context, it is an interesting open question whether and to what extent the strong spin-orbit interaction in the valence band of germanium can give rise to an induced electric dipole coupling of the spin to the electric field of the superconducting resonator. A near-term goal will be to achieve dispersive readout of single hole spins with the help of the grAl superconducting resonator, which is realistic with moderate spin-photon coupling. Towards the end of the project, we aim at reaching the strong coupling regime of cavity QED between a hole spin and a single photon. We will develop a theoretical model that describes the hybrid system consisting of holes in SiGe quantum dots coupled to a high-impedance resonator, and calculate the microwave cavity transmission that contains information about the spin-photon coupling. A long-term goal is to investigate the possibility of coupling two remote hole spins via the exchange of virtual microwave photons in the superconducting resonator.