Minimal Assumptions for Phase-Referenced Interference Tests of Structured Phase-Dependent Deviations

This note identifies the minimal conditions required for a phase-referenced interferometric test of structured phase-dependent deviations. The test relies on the quadrature representation: \[ I(φ) = C + V[Acosφ + Bsinφ], \] which enables a deviation metric: \[ Δ_n = √(A_n - A_0)^2 + (B_n - B_0)^2. \] Three assumptions are required: quadrature decomposability of the interference signal; availability of a stable phase reference; and controlled phase-structure input. Without phase referencing, all deviations collapse into a phase offset: \[ Acosφ + Bsinφ = Vcos(φ - δ), \] making the test non-diagnostic. Under these conditions, the protocol reduces to a falsifiable signature: \[ Δ_0 ≈ 0, Δ_n ↑, phase-locked quadrature structure. \] The result is model-independent: the validity of the test depends only on measurement structure, not on any specific underlying theory.