random_bitstring_xeb.py

def random_bitstrings(n_qubits, n_programs):
    dim = 2**n_qubits
    # keep track of probability of sampling (randomly) chosen bitstring
    probs_bitstring = []
    # simulate many Haar-random circuits
    for _ in range(n_programs):
        unitary = random_unitary(dim)
        bitstring = np.random.choice(dim, p=[np.abs(unitary[b,0])**2 for b in range(dim)])
        prob = np.abs(unitary[bitstring,0])**2
        probs_bitstring.append(prob)
    return probs_bitstring