Tomonaga A, Stassi R, Mukai H, Nori F, Yoshihara F, Tsai J S
Department of Physics, Tokyo University of Science, Shinjuku, Tokyo, Japan.
Center for Quantum Computing, RIKEN, Wakoshi, Saitama, Japan.
Nat Commun. 2025 Jun 17;16(1):5294. doi: 10.1038/s41467-025-60589-5.
We experimentally investigate a superconducting circuit composed of two flux qubits ultrastrongly coupled to a common LC resonator. Owing to the large anharmonicity of the flux qubits, the system can be described well by a generalized Dicke Hamiltonian containing spin-spin interaction terms. In the experimentally measured spectrum, we observed two key phenomena. First, an avoided level crossing provides evidence of the exotic interaction that allows the simultaneous excitation of two artificial atoms by absorbing one photon from the resonator. Second, we identified a pronounced spectral asymmetry that is a clear signature of light-matter decoupling. This multi-atom ultrastrongly coupled system opens the door to studying novel processes for quantum optics and quantum-information tasks on a chip.
我们通过实验研究了一个由两个与一个公共LC谐振器超强耦合的磁通量子比特组成的超导电路。由于磁通量子比特的大非谐性，该系统可以用一个包含自旋-自旋相互作用项的广义迪克哈密顿量很好地描述。在实验测量的光谱中，我们观察到两个关键现象。第一，一个避免能级交叉提供了奇异相互作用的证据，这种相互作用允许通过从谐振器吸收一个光子同时激发两个人造原子。第二，我们识别出一种明显的光谱不对称性，这是光与物质解耦的明确标志。这个多原子超强耦合系统为在芯片上研究量子光学和量子信息任务的新过程打开了大门。
