Quantum-Squeezing-Induced Point-Gap Topology and Skin Effect

We theoretically predict the squeezing-induced point-gap topology together with a symmetry-protected 12 "skin effect" in a one-dimensional (1D) quadratic-bosonic system. Protected by a time-reversal symmetry, such a topology is associated with a novel 12 invariant (similar to quantum spin-Hall insulators), which is fully capable of characterizing the occurrence of the 12 skin effect. Focusing on zero energy, the parameter regime of this skin effect in the phase diagram just corresponds to a "real-and point-gap coexisting topological phase." Moreover, this phase associated with the symmetry-protected 12 skin effect is experimentally observable by detecting the steady-state power spectral density. Our Letter is of fundamental interest in enriching non-Bloch topological physics by introducing quantum squeezing and has potential applications for the engineering of symmetry-protected sensors based on the 12 skin effect.