Helper functions in HadaMAG.jl

build_tmp!(tmp1, tmp2, X)

Compute tmp1 = real(X)+imag(X), tmp2 = imag(X)-real(X) in place. X is the complex state vector (length = 2^L).

call_fht!(vec::Vector{Float64}, L::Int32)

In-place fast Hadamard transform using the currently active backend.

fht_backend()

Return the currently active FHT backend.

haar_random_unitary(q::Int, n_qudits::Integer, rng::AbstractRNG = Random.GLOBAL_RNG)

Generate a Haar-distributed random unitary matrix of size q^nqudits × q^nqudits.

Arguments

• q::Int: local dimension (2 for qubits, 3 for qutrits).
• n_qudits::Integer: number of qubits; the output U lives in U(2^n_qubits).
• rng::AbstractRNG: random number generator (defaults to GLOBAL_RNG).

integrate_simpson_uniform(x, y) -> Float64

Simpson's rule on a uniform grid x. Requires an odd number of points.

use_default_fht()

Revert to whichever backend was auto-selected at load time.

use_fht_lib(path::String)

Use a custom .so that exports :fht_double. Overrides any other backend.

use_jll_fht()

Switch to the FastHadamardStructuredTransforms_jll backend (x86 only). Throws on unsupported platforms.

use_julia_fht()

Switch to the pure Julia + LoopVectorization backend (works on all platforms).