Fidelity vs Squeezing Parameter
Protocol & Theory
Braunstein-Kimble (1998):
1. Create EPR pair: r = squeezing
2. Alice measures (x̂_in−x̂_a, p̂_in+p̂_a)
3. Bob displaces: D̂(x_m, p_m)|ψ⟩
Fidelity (coherent input):
F = 1/(1 + e^(−2r)) → 1 as r→∞
Classical limit: F_cl = 1/2 (r=0)
Squeezing r1.0
Fidelity F—
Classical bound0.500
Output noise Δx²—
EPR correlations—