Function fidelity_kernel 

pub fn fidelity_kernel(
    ideal: &HilbertState,
    actual: &HilbertState,
) -> Result<f64, PhysicsError>

Calculates Quantum Fidelity: $F = |\langle \psi_{\text{ideal}} | \psi_{\text{actual}} \rangle|^2$.

Arguments

• ideal - Ideal/Target state.
• actual - Actual/Noisy state.

Returns

• Result<f64, PhysicsError> - Fidelity $F$.