MUT v5.8.20.1: Supplement XVIII: Testing Effective Background Scalar Field Phase-Locking via Single-Photon Interferometry

This supplement proposes a deterministic experimental test of the Effective Background Scalar Field (ΦA) introduced in MUT v5.8. A single-photon Mach–Zehnder interferometer configuration is developed to detect phase-locking interactions between the quantum system and the effective background scalar field.The analysis predicts a quartic deviation in interference visibility relative to standard decoherence models under weak measurement coupling. A full perturbative derivation of the visibility correction as a function of coupling strength and interaction time is presented, along with the crossover regime in which MUT-specific effects become experimentally observable.This work provides a concrete interferometric pathway for empirical testing of the MUT v5.8 framework at the quantum scale.