Fig. 2: Verification of high-dimensional frequency entanglement.

a–d Theoretical simulation and e–h experimental observation of frequency anti-correlation by setting the relative path (time) delay at a, e 36 μm (τ₁ = 0.12 ps), b, f 60 μm (τ₁ = 0.2 ps), c, g 80 μm (τ₁ = 0.27 ps) and d, h 110 μm (τ₁ = 0.37 ps). The red lines represent the theoretical predictions, while the blue points represent the experimental results that are bounded by the standard deviation estimated by statistical methods assuming a Poisson distribution.