Squeezed Displaced Cat States: A Signature of the PT‐Symmetry Phase Transition

ABSTRACT Harnessing parity–time symmetry with balanced gain and loss profiles has created a variety of opportunities in an electronic system from wireless energy transfer to telemetry sensing and topological defect engineering. However, it is difficult to capture the ‐symmetry phase transition in an electronic system due to the limitation of probing the virtual energy spectrum. Here, we proposed a scheme to probe the ‐symmetry phase transition in an Non‐Hermitian (NH) Su–Schrieffer–Heeger (SSH) electronic chain coupled to a cavity. We show that, when ‐symmetry is broken, the cavity ground state is a Squeezed Displaced Schrödinger cat (SDSc) state, which immediately disappears when the symmetry recovers. Thus, our proposal provides a platform for capturing ‐symmetry phase transition based on cavity ground state. Furthermore, we demonstrate that the generation of the SDSc state in our scheme is related to spontaneous symmetry breaking mechanism. Besides, we exploit the cavity ground state to estimate the phase in the optical interferometer, and show that the quantum Fisher information and nonclassicality will sharply decline when symmetry recovers. This suggests that the phase estimation is preferably performed in the broken PT‐symmetry phase near the exceptional‐points. Our proposal offers a scheme not only to manipulate but also to probe the properties of electronic materials based on quantum Floquet engineering, and improve the utilization of cavity ground states in quantum metrology.