Alice settings

Bob settings

Simulation

CHSH inequality:
S = E(a,b) − E(a,b') + E(a',b) + E(a',b')
Classical: |S| ≤ 2
Quantum: |S| ≤ 2√2 ≈ 2.828

Quantum correlation:
E(a,b) = −cos(a−b) for singlet |Ψ-⟩

Optimal settings:
a=0°, a'=90°, b=45°, b'=135° gives S=2√2

Loophole-free:
Aspect 1982 → Hensen et al 2015 (NV centers, 1.3 km): S=2.42