Yingqiu Mao

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

  1. Yingqiu Mao,
  2. Han-Yu Ren,
  3. Zi-Yi Liu,
  4. Yi-Zheng Zhen,
  5. Tao Rong,
  6. Tao Jiang,
  7. Zhuo Chen,
  8. Zhe-Heng Yuan,
  9. Wen-Hua Qin,
  10. Xiaoran Zhang,
  11. Xiaobing Liu,
  12. Ming Gong,
  13. Kae Nemoto,
  14. William J. Munro,
  15. and Johannes Majer
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-14N 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.
arxiv pdf

Perspective on witnessing entanglement in hybrid quantum systems

  1. Yingqiu Mao,
  2. Ming Gong,
  3. Kae Nemoto,
  4. William J. Munro,
  5. and Johannes Majer
Hybrid quantum systems aim at combining the advantages of different physical systems and to produce novel quantum devices. In particular, the hybrid combination of superconducting circuits
and spins in solid-state crystals is a versatile platform to explore many quantum electrodynamics problems. Recently, the remote coupling of nitrogen-vacancy center spins in diamond via a superconducting bus was demonstrated. However, a rigorous experimental test of the quantum nature of this hybrid system and in particular entanglement is still missing. We review the theoretical ideas to generate and detect entanglement, and present our own scheme to achieve this.
arxiv pdf