Function apply_rz_simd 

pub fn apply_rz_simd(
    state: &mut Vec<Complex64>,
    theta: f64,
    target: usize,
    n_qubits: usize,
)

Apply the RZ(theta) rotation gate to qubit target using SIMD.

RZ(θ) = [[exp(−iθ/2), 0], [0, exp(iθ/2)]]