Function parameter_shift_gradient 

pub fn parameter_shift_gradient<F>(
    evaluate: F,
    params: &[f64],
    shift: f64,
) -> Vec<f64>
where
    F: Fn(&[f64]) -> f64,

Compute parameter-shift gradient for a quantum circuit.

Arguments

• evaluate - Function that evaluates the circuit at given parameters
• params - Current parameter values
• shift - Shift amount (typically π/2)

Returns

Gradient vector computed via parameter-shift rule.