BCT Letter 201: The Atoms That Chose Their Path — ANU Momentum-Entangled Helium Atoms as a Test of BCT Wavefunction Collapse via Hopf Charge Quantisation

Sridhar, Hodgman et al. (ANU, Nature Communications 2026) demonstrated Bell correlations in momentum-entangled ultracold helium-4 atoms — the first quantum non-locality demonstration in external motion of massive particles. The BCT Superfluid Lattice Model provides a geometric mechanism: quantum superposition persists until the OHC Hopf charge of the entangled system reaches N_collapse = 1/α₀ = 135, at which point Josephson coupling to the vacuum ground state forces wavefunction collapse. BCT Prediction #245: Bell inequality violation will be suppressed for N ≥ 16 helium-4 pairs (total Hopf charge ≥ 128 ≈ N_collapse). The ANU apparatus scaled to N~16 pairs would be the first experiment to probe the BCT quantum-gravitational boundary directly. Zero free parameters.