Quantum squeezing operators have no single 'natural' version

When a squeezing operator in quantum optics has its free-field term dialed to zero, you might expect it to settle on one natural mathematical form — but it doesn't. Using a mix of discrete WKB methods and Airy-function asymptotics, the authors show that different ways of taking this limit select different self-adjoint extensions, with no single physically preferred one emerging. This matters practically: it means the squeezing operator's behavior isn't pinned down by the limit, and any calculation assuming a canonical choice may be making an implicit, unjustified assumption.