Collapse is Relational: Testing the Temporal Structure of Decoherence

Wave-function collapse is usually regarded as independent of a detector’s temporal resolution. In this Rapid Communication that view is challenged. I derive the Temporal-Binding Collapse Theorem and show that coarse-grained measurements introduce a universal decoherence channel proportional to 1 ⁄ τ, where τ is the detector’s temporal binding window. The theorem predicts  tc(τ) = tc(E) + τ,so the measured coherence time grows linearly with detector timescale—behavior absent from standard decoherence theory and objective-collapse models. This relation is placed in a unified context with the quantum-Zeno effect, existing CSL bounds, and recent photonic experiments that employ variable-jitter superconducting detectors. Finally, a falsifiable protocol is proposed: the coherence time of entangled photons will be measured across a bank of SNSPDs spanning τ = 5–500 ps. Observation of a unit-slope tc – τ relationship would demonstrate that collapse is relational, governed by the observer’s timescale; any deviation would either falsify the theorem or establish a lower bound on intrinsic collapse mechanisms.