Lab: D^2+V^2 in a Real Interferometer with Eraser

This paper is the third paper after Synthesis II, and the lab paper promised in 2026i, 2026o, 2026p, 2026q. In 2026a (Ch. 124), we proved no unital map T → E for H = S^1. In 2026b (Ch. 125), we generalized to the triple (dim H^n, dim C^n, 1). In 2026c (Ch. 138), we defined the Bridge Conjecture. In 2026d (Ch. 139), we proved the eraser must be CPTP. In 2026e (Ch. 140), we proved all four follow from one Unifier Axiom: [x,y] = 1. In 2026f (Ch. 141), we categorified H. In 2026g (Ch. 142), we proved the Unifier survives in characteristic p. In 2026h (Ch. 143), we proved it survives for infinite H. In 2026i (Ch. 144), we gave the lab falsifier D^2 + V^2 ≤ 1. In 2026j (Ch. 145), we proved the nine papers are one theorem. In 2026k (Ch. 146), we proved the Unifier survives for any A with [x,y] = 1. In 2026l (Ch. 147), we constructed H(M) for M Lorentzian. In 2026m (Ch. 148), we defined causal homotopy, π1^causal, and H1^causal. In 2026n (Ch. 149), we defined H^n_causal(H(M)) for all n. In 2026o (Ch. 150), we proved the fourteen papers are one theorem. In 2026p (Ch. 151), we proved Einstein + NEC + Bridge ⇒ no CTC, and NEC violation still forces erasure. In 2026q (Ch. 152), we proved quantum M still forces erasure, branch + interference. Here we give the concrete lab protocol that tests all seventeen papers in one interferometer. Setup: Mach-Zehnder interferometer, single photons, which-way marker W, quantum eraser E. Define D = distinguishability from W, V = fringe visibility at output. We prove: (1) D^2+V^2 ≤ 1 is exactly the lab shadow of no unital T → E preserving [x,y], (2) eraser E is CPTP by 2026d, and restores V only by erasing D, (3) delayed-choice eraser does not retro-cause: erasure acts on H(M) causal history, not on past M, (4) a repeatable run with D ≈ 1, V ≈ 1, no eraser, at >3σ, falsifies 2026i and hence 2026o/p/q and the whole arc, (5) a run with D → 1 forcing V → 0, and eraser restoring V → 1 forcing D → 0, confirms the One Theorem in lab. This is a protocol paper, not a data paper. No data is claimed. The protocol is falsifiable, cheap, and doable with existing photonics. Tseglin 2026r = Ch. 153. Cites Tseglin 2026a DOI 10.5281/zenodo.23977165, 2026b DOI 10.5281/zenodo.23980498, 2026c DOI 10.5281/zenodo.23980738, 2026d DOI 10.5281/zenodo.23981860, 2026e DOI 10.5281/zenodo.23982063, 2026f DOI 10.5281/zenodo.23982359, 2026g DOI 10.5281/zenodo.23985216, 2026h DOI 10.5281/zenodo.23991367, 2026i DOI 10.5281/zenodo.23991442, 2026j DOI 10.5281/zenodo.23991535, 2026k DOI 10.5281/zenodo.23991603, 2026l DOI 10.5281/zenodo.23991665, 2026m DOI 10.5281/zenodo.23991998, 2026n DOI 10.5281/zenodo.23992083, 2026o DOI 10.5281/zenodo.23992187, 2026p DOI 10.5281/zenodo.23992267, 2026q DOI 10.5281/zenodo.23992317.