def METHOD_NAME(self):
    for s, dic in zip(("psi-", "psi+", "phi+", "phi-"),
                      ({"qtype": 'dop'}, {}, {"sparse": True}, {})):
        p = bell_state(s, **dic)
        assert_allclose(expec(p, p), 1.0)
        pa = ptr(p, [2, 2], 0)
        assert_allclose(expec(pa, pa), 0.5)