pub fn parameter_shift_gradient(
circuit: &QaoaCircuit,
gamma: &[f64],
beta: &[f64],
) -> QcResult<(Vec<f64>, Vec<f64>)>Expand description
Compute analytic gradients of the QAOA objective using the parameter-shift rule.
d/dθ E(θ) = 0.5 * [E(θ + π/2) - E(θ - π/2)]
Returns (d_gamma, d_beta) where each vector has length p.