Nonlinear Decoherence — Theoretical Predictions and Experimental Test of the Information Bottleneck Theorem

The quantum–classical boundary is one of the deepest unsolved problems in physics. The Information Bottleneck Theorem of the Order Parameter Spacetime Theory provides a precise criterion: when the total information dissipation coefficient Υ=0, the system resides in the quantum sector (unitary evolution, entanglement conservation); when Υ>0, irreversible classicality emerges. How can this binary criterion be tested experimentally? This paper reveals that the binary nature of the Information Bottleneck Theorem—the transition of entanglement from "strict conservation" to "onset of decay"—does not manifest as a discontinuous jump of entanglement, but rather as a nonlinear signature in the decoherence rate. This nonlinearity originates from complex metric back-reaction: information dissipation alters the spacetime geometry, and the geometry in turn modifies the dissipation rate, forming an information–geometry closed loop. Specifically, for a two-qubit entangled state evolving under a pure dephasing channel, the standard Lindblad theory predicts that log C(t) is a straight line; the complex metric back-reaction predicts that log C(t) bends upward—the decay rate slows down as entanglement decreases, i.e., entanglement is protected. At the critical coupling α=1/r₀², the theory predicts exact protection of entanglement (C(t)=constant); in the strong-coupling regime α>1/r₀², the theory predicts that in the initial stage entanglement exceeds its maximum value (C>1). This paper provides a complete theoretical prediction and data analysis scheme to test these predictions using existing experimental data. The decision logic is binary: either log C(t) is a straight line (α=0, complex metric back-reaction falsified), or it is not (α>0, information–geometry closed loop verified).