Entanglement Entropy — The Ebit Curve
cos θ|00⟩ + sin θ|11⟩ — drag θ from product state to Bell state; watch the entropy curve and the subsystem Bloch ball shrink.
Schmidt angle θ
θ = 0° (product)
Mode
Symmetric: cos²θ, sin²θ
Asymmetric: α², 1−α²
α
α = 0.500
θ =
0.0
°
λ₁ =
1.000
λ₂ =
0.000
S_E =
0.000
ebits
Purity =
1.000