def test_evolve_obc(self, order, dt, tol):
n = 10
tf = 2
psi0 = qtn.MPS_neel_state(n)
H_int = qu.ham_heis(2, cyclic=False)
if dt and tol:
with pytest.raises(ValueError):
qtn.TEBD(psi0, H_int, dt=dt, tol=tol)
return
tebd = qtn.TEBD(psi0, H_int, dt=dt, tol=tol)
tebd.split_opts['cutoff'] = 0.0
if (dt is None and tol is None):
with pytest.raises(ValueError):
tebd.update_to(tf, order=order)
return
tebd.update_to(tf, order=order)
assert tebd.t == approx(tf)
assert not tebd._queued_sweep
dpsi0 = psi0.to_dense()
dham = qu.ham_heis(n=n, sparse=True, cyclic=False)
evo = qu.Evolution(dpsi0, dham)
evo.update_to(tf)
assert qu.expec(evo.pt, tebd.pt.to_dense()) == approx(1, rel=1e-5)
def test_at_times(self, dt, tol):
n = 10
psi0 = qtn.MPS_neel_state(n)
H_int = qu.ham_heis(2, cyclic=False)
tebd = qtn.TEBD(psi0, H_int, dt=dt, tol=tol)
assert tebd.H.special_sites == set()
for pt in tebd.at_times([0.1, 0.2, 0.3, 0.4, 0.5]):
assert pt.H @ pt == approx(1, rel=1e-5)
assert tebd.err <= 1e-5
def test_setup_and_sweep(self):
n = 10
H_int = qu.ham_heis(n=2, cyclic=False)
psi0 = qtn.MPS_neel_state(n, dtype=complex)
tebd = qtn.TEBD(psi0, H_int, dt=0.05)
assert tebd.pt.bond_size(0, 1) == 1
tebd.sweep('right', 1 / 2)
assert tebd.pt.count_canonized() == (n - 1, 0)
tebd.sweep('left', 1 / 2)
assert tebd.pt.count_canonized() == (0, n - 1)
assert tebd.pt.bond_size(0, 1) > 1
assert not tebd._queued_sweep
def test_NNI_and_single_site_terms_heis(self):
n = 10
psi0 = qtn.MPS_neel_state(n)
H_nni = qtn.NNI_ham_heis(n, j=(0.7, 0.8, 0.9), bz=0.337)
tebd = qtn.TEBD(psi0, H_nni)
tebd.update_to(1.0, tol=1e-5)
assert abs(psi0.H @ tebd.pt) < 1.0
assert tebd.pt.entropy(5) > 0.0
psi0_dns = qu.neel_state(n)
H_dns = qu.ham_heis(10, j=(0.7, 0.8, 0.9), b=0.337, cyclic=False)
evo = qu.Evolution(psi0_dns, H_dns)
evo.update_to(1.0)
assert qu.expec(tebd.pt.to_dense(), evo.pt) == pytest.approx(1.0)
def test_NNI_and_single_site_terms(self):
n = 10
psi0 = qtn.MPS_neel_state(n)
H_nni = qtn.NNI_ham_XY(n, bz=0.9)
assert H_nni.special_sites == {(8, 9)}
tebd = qtn.TEBD(psi0, H_nni)
tebd.update_to(1.0, tol=1e-5)
assert abs(psi0.H @ tebd.pt) < 1.0
assert tebd.pt.entropy(5) > 0.0
psi0_dns = qu.neel_state(n)
H_dns = qu.ham_XY(10, jxy=1.0, bz=0.9, cyclic=False)
evo = qu.Evolution(psi0_dns, H_dns)
evo.update_to(1.0)
assert qu.expec(tebd.pt.to_dense(), evo.pt) == pytest.approx(1.0)
