Experimental investigation of Lee-Yang criticality using non-Hermitian quantum system

Abstract

Lee-Yang theory clearly demonstrate where the phase transition of many-body systems occurs and the asymptotic behavior near the phase transition using the partition function under complex parameters. The complex parameters make the direct investigation of Lee-Yang theory in practical systems challenging. Here we construct a non-Hermitian quantum system that can correspond to the one-dimensional Ising model with imaginary parameters through the equality of partition functions. By adjusting the non-Hermitian parameter, we successfully obtained the partition function under different imaginary magnetic fields and observed the Lee-Yang zeros. We also observe the critical behavior of free energy in vicinity of Lee-Yang zero that is consistent with theoretical prediction. Our work provides a protocol to study Lee-Yang zeros of the one-dimensional Ising model using a single-qubit non-Hermitian system.