Observation of a Superradiant Phase Transition with Emergent Cat States
Ri‐Hua Zheng, Wen Ning, Ye‐Hong Chen, Jiahao Lu, Li-Tuo Shen, Kai Xu, Yu-Ran Zhang, Da Xu, Hekang Li, Yan Xia, Fan Wu, Zhen‐Biao Yang, Adam Miranowicz, Neill Lambert, Dongning Zheng, Heng Fan, Franco Nori, Shi‐Biao Zheng
Abstract
Superradiant phase transitions (SPTs) are important for understanding light-matter interactions at the quantum level, and play a central role in criticality-enhanced quantum sensing. So far, SPTs have been observed in driven-dissipative systems, but the emergent light fields did not show any nonclassical characteristic due to the presence of strong dissipation. Here we report an experimental demonstration of the SPT featuring the emergence of a highly nonclassical photonic field, realized with a resonator coupled to a superconducting qubit, implementing the quantum Rabi model. We fully characterize the light-matter state by Wigner matrix tomography. The measured matrix elements exhibit quantum interference intrinsic of a photonic mesoscopic superposition, and reveal light-matter entanglement.