The superradiant phase transition in thermal equilibrium, a fundamental concept bridging statistical physics and electrodynamics, has never been observed in real physical systems. This paper experimentally simulates this transition using nuclear magnetic resonance, overcoming challenges posed by a no-go theorem. Antisqueezing is introduced to recover the ground state singularity, leading to strongly entangled and squeezed Schrödinger cat states of spins, with potential applications in quantum theory testing and quantum metrology.

Xi Chen, Ze Wu, Min Jiang, Xin-You Lü, Xinhua Peng, Jiangfeng Du