Coupling Creates Information: A channel-specific trade-off thesis for gravity-sensitive interferometry

A lab-ready note proposing a diagnostic pattern for gravity-sensitive interferometry: when the same physical channel both writes the geometric phase and induces dephasing, scanning a single control parameter yields a channel-specific curve between accessible information (Fisher/QFI) and visibility V. In a minimal two-path model the QFI reduces to F_θ = V(θ)^2[∂_θφ(θ)]^2 + [∂_θ V(θ)]^2/(1−V(θ)^2); in the pure-phase case F/F0 = V^2. The proposal is compatible with standard QM/GR and is falsifiable via one-knob scans, null checks, and echo/eraser controls.