Strong Coupling Achieved in Hybrid Quantum System with Three-Mode Avoided Crossing

The pursuit of strong interactions between multiple quantum systems represents a significant step towards advanced quantum technologies, and researchers are now demonstrating genuine tripartite strong coupling within a novel solid-state platform. Yingqiu Mao, Han-Yu Ren, and Zi-Yi Liu, working with colleagues including Yi-Zheng Zhen, Tao Rong, and Tao Jiang, have successfully created a hybrid quantum system integrating a superconducting transmon, a microwave resonator, and the quantum spins of nitrogen-vacancy centres in diamond. Their experiments reveal a coherent sharing of energy between all three components, a key indicator of strong coupling, and open up access to complex quantum behaviours previously difficult to observe. This achievement establishes a new architecture for hybrid quantum systems, promising a versatile platform for exploring fundamental quantum dynamics and developing interfaces between different quantum technologies. Researchers employed frequency-domain spectroscopy to reveal a characteristic three-mode avoided crossing, confirming coherent sharing of single excitations across all three subsystems and establishing a new architecture for exploring complex quantum behaviours. To accurately capture the system’s behavior, the team developed a stepwise parameter estimation strategy, beginning with a simplified model to determine key parameters like resonant frequencies and qubit decay rates. These initial values were then combined with pre-fitted parameters characterizing the NV centers to simulate the full spectrum, bridging experimental observations with theoretical descriptions. To interpret complex spectral features, scientists accounted for the hyperfine structure of the NV centers, recognizing that the electron spin interacts with the nuclear spin of nitrogen atoms, effectively creating subensembles within the NV center ensemble.

The team constructed a Hamiltonian to model this system, incorporating the coupling strength between the resonator, transmon, and these subensembles, allowing for numerical solutions of the eigenvalue problem within the manifold of no more than two excitations. This detailed modeling enabled the identification of dressed states, classifying them into sets with one or two total excitations, and explaining the observed patterns in the experimental data. Further investigation into nonlinear responses involved probing the system with varying power levels, generating heat maps displaying transmission coefficients as a function of probe frequency and transmon flux. These measurements revealed multiphoton transitions and signatures of transmon-nuclear-spin interactions, highlighting accessibility to higher-excitation manifolds within this architecture. By numerically solving the Hamiltonian, researchers mapped the energies of one- and two-excitation dressed states as a function of detuned transmon frequency, identifying avoided crossings and bright-dark-bright lines that correspond to the main patterns observed in the experimental spectra. This innovative approach establishes a new regime of hybrid cavity quantum electrodynamics, providing a platform for exploring complex multicomponent dynamics and developing hybrid quantum interfaces.,.

Hybrid Qubit System, Strong Coupling Demonstrated Researchers have demonstrated strong coupling between a superconducting transmon qubit, a microwave cavity resonator, and an ensemble of nitrogen-vacancy (NV) centers in diamond. This achievement establishes a novel platform for exploring interactions between disparate quantum components, integrating superconducting circuits with spin-based quantum systems. Experiments revealed a characteristic three-mode interaction, confirming that energy is coherently shared among all three subsystems, and opening avenues for complex quantum dynamics. The research provides detailed characterization of the system, including parameter estimation and spectroscopic data, alongside a comprehensive theoretical model to understand the observed results.

The team investigated the hyperfine structure of the NV centers and its impact on the observed spectra, incorporating these interactions into their model. The research also explored nonlinear effects at higher energy levels, including multiphoton transitions and interactions between the transmon and the nuclear spins of the diamond, demonstrating access to more complex quantum behaviours within this hybrid system. This work establishes a foundation for developing hybrid quantum interfaces and exploring phenomena such as photon-mediated entanglement and novel modes of quantum computation.,. Three-System Quantum Coupling and Nonlinear Dynamics Researchers have demonstrated strong coupling between a superconducting transmon qubit, a microwave cavity resonator, and an ensemble of nitrogen-vacancy (NV) centers in diamond. This achievement establishes a novel platform for exploring interactions between disparate quantum components, integrating superconducting circuits with spin-based quantum systems. Experiments revealed a characteristic three-mode interaction, confirming that energy is coherently shared among all three subsystems, and opening avenues for complex quantum dynamics. The research provides detailed characterization of the system, including parameter estimation and spectroscopic data, alongside a comprehensive theoretical model to understand the observed results.

The team investigated the hyperfine structure of the NV centers and its impact on the observed spectra, incorporating these interactions into their model. The research also explored nonlinear effects at higher energy levels, including multiphoton transitions and interactions between the transmon and the nuclear spins of the diamond, demonstrating access to more complex quantum behaviours within this hybrid system. This work establishes a foundation for developing hybrid quantum interfaces and exploring phenomena such as photon-mediated entanglement and novel modes of quantum computation. 👉 More information 🗞 Genuine Tripartite Strong Coupling in a Superconducting-Spin Hybrid Quantum System 🧠 ArXiv: https://arxiv.org/abs/2512.13129 Tags: