Genuine Tripartite Strong Coupling in a Superconducting-Spin Hybrid Quantum System

TL;DR

This paper demonstrates a genuine tripartite strong coupling in a hybrid quantum system combining superconducting qubits, a resonator, and NV centers, enabling complex multicomponent quantum dynamics and interfaces.

Contribution

It introduces a new hybrid cavity QED regime with tripartite strong coupling, integrating superconducting and spin systems for advanced quantum exploration.

Findings

Observation of three-mode avoided crossing indicating coherent sharing of excitations.

Detection of nonlinear multiphoton transitions and nuclear-spin interactions.

Establishment of a platform for complex multicomponent quantum dynamics.

Abstract

We demonstrate genuine tripartite strong coupling in a solid-state hybrid quantum system comprising a superconducting transmon qubit, a fixed-frequency coplanar-waveguide resonator, and an ensemble of NV$^-$ centers in diamond. Frequency-domain spectroscopy reveals a characteristic three-mode avoided crossing, indicating that single excitations are coherently shared across all three subsystems. At higher probe powers, we observe nonlinear features including multiphoton transitions and signatures of transmon-${}^{14}\mathrm{N}$ nuclear-spin interactions, highlighting the accessibility of higher-excitation manifolds in this architecture. These results establish a new regime of hybrid cavity QED that integrates superconducting and spin degrees of freedom, providing a platform for exploring complex multicomponent dynamics and developing hybrid quantum interfaces.