Superconductor–semiconductor hybrid-circuit quantum electrodynamics

Abstract

Light–matter interactions at the single-particle level have generally been explored in the context of atomic, molecular and optical physics. Recent advances motivated by quantum information science have made it possible to explore coherent interactions between photons trapped in superconducting cavities and superconducting qubits. In the context of quantum information, the study of coherent interactions between single charges and spins in semiconductors and photons trapped in superconducting cavities is very relevant, as the spin degree of freedom has a coherence time that can potentially exceed that of superconducting qubits, and cavity photons can serve to effectively overcome the limitation of short-range interaction inherent to spin qubits. Here, we review recent advances in hybrid ‘super–semi’ quantum systems, which coherently couple superconducting cavities to semiconductor quantum dots. We first present an overview of the physics governing the behaviour of superconducting cavities, semiconductor quantum dots and their modes of interaction. We then survey experimental progress in the field, focusing on recent demonstrations of cavity quantum electrodynamics in the strong-coupling regime with a single charge and a single spin. Finally, we broadly discuss promising avenues of future research, including the use of super–semi systems to investigate phenomena in condensed-matter physics. The integration of gate-defined quantum dots with superconducting resonators results in a hybrid architecture that holds promise for quantum information processing. This Review discusses recent experimental results in the field, including the achievement of strong coupling between single microwave photons and the charge and spin degrees of freedom, and examines the underlying physics. Hybrid quantum systems integrate the most desirable properties of semiconductor spin qubits and superconducting quantum devices. Single electron charges can be coherently coupled to single microwave-frequency photons. Using spin–orbit interactions, a single electron spin can be coherently coupled to a single photon. Coherent charge–photon and spin–photon coupling may enable long-range qubit interactions that are mediated by microwave-frequency photons. Hybrid quantum devices are also finding utility as sensitive probes of Kondo and valley physics, and perhaps of Majorana fermions. Hybrid quantum systems integrate the most desirable properties of semiconductor spin qubits and superconducting quantum devices. Single electron charges can be coherently coupled to single microwave-frequency photons. Using spin–orbit interactions, a single electron spin can be coherently coupled to a single photon. Coherent charge–photon and spin–photon coupling may enable long-range qubit interactions that are mediated by microwave-frequency photons. Hybrid quantum devices are also finding utility as sensitive probes of Kondo and valley physics, and perhaps of Majorana fermions.