def get_gate(self, dt_frac, sites=None):
"""Get the unitary (exponentiated) gate for fraction of timestep
``dt_frac`` and sites ``sites``, cached.
"""
if sites not in self.H.special_sites:
sites = None
try:
return self._U_ints[dt_frac, sites]
except KeyError:
U = qu.expm(-1.0j * self._dt * dt_frac * self.H(sites))
self._U_ints[dt_frac, sites] = U
return U
def test_eye(self, sparse, herm):
p = qu.expm(qu.eye(2, sparse=sparse), herm=herm)
assert_allclose((p.A if sparse else p) / np.e, qu.eye(2))
if sparse:
assert isinstance(p, sp.csr_matrix)
def test_zeros_dense(self, herm):
p = qu.expm(np.zeros((2, 2), dtype=complex), herm=herm)
assert_allclose(p, qu.eye(2))