A beam of atoms, each a real charge with a magnetic moment, passes through an inhomogeneous field. The
deflection is ordinary magnetostatics — a real moment in a real gradient feels a force
F=μzG — so the spot separation is classical and native to RealQM,
Δz ∝ G. What is quantum is only which values μz takes:
a classical moment gives a continuous band; the real experiment gives two spots with no middle
(±μB), the signature of the topological/spinorial closure discussed in the text.
Source → magnet (gradient G) → screen. Dots = atoms; the screen
histogram builds up on the right.
modequantum
spot separation Δz (∝ G)0
hits: up / mid / down0 / 0 / 0
fraction in the middle0%
Quantum: two spots, the middle stays empty at any G. Turn G up and the two
dots march apart (Δz∝G) — the absent middle only grows more conspicuous.
Sequential mode shows the standard quantum result: the
↑ beam, re-measured on a rotated axis, splits again into two — the non-commutativity a
fixed classical orientation cannot give. RealQM's deterministic account of this (the measurement
statistics) is the open frontier, not a settled result.