def test_pt_tempo():
start_time = -0.3
end_time = 0.84
system = tempo.System(0.5 * tempo.operators.sigma("x"))
correlation_function = lambda t: (np.cos(6.0*t)+1j*np.sin(6.0*t)) \
* np.exp(-12.0*t)
correlations = tempo.CustomCorrelations(correlation_function,
max_correlation_time=0.5)
bath = tempo.Bath(0.5 * tempo.operators.sigma("z"), correlations)
initial_state = tempo.operators.spin_dm("z+")
tempo_param_A = tempo.PtTempoParameters(0.1, 5, 1.0e-5, name="rough-A")
pt_tempo_sys_A = tempo.PtTempo(bath=bath,
parameters=tempo_param_A,
start_time=start_time,
end_time=end_time)
assert pt_tempo_sys_A.dimension == 2
pt_tempo_sys_A.compute()
pt_A = pt_tempo_sys_A.get_process_tensor()
assert len(pt_A.times) == 12
tempo_param_B = tempo.PtTempoParameters(0.1, None, 1.0e-5, name="rough-B")
pt_tempo_sys_B = tempo.PtTempo(bath=bath,
parameters=tempo_param_B,
start_time=start_time,
end_time=end_time)
pt_B = pt_tempo_sys_B.get_process_tensor()
def test_tempo_bad_input():
start_time = -0.3
end_time = 0.84
system = tempo.System(0.5 * tempo.operators.sigma("x"))
correlation_function = lambda t: (np.cos(6.0*t)+1j*np.sin(6.0*t)) \
* np.exp(-12.0*t)
correlations = tempo.CustomCorrelations(correlation_function,
max_correlation_time=0.5)
bath = tempo.Bath(0.5 * tempo.operators.sigma("z"), correlations)
initial_state = tempo.operators.spin_dm("z+")
tempo_param_A = tempo.TempoParameters(0.1, 5, 1.0e-5, name="rough-A")
with pytest.raises(AssertionError):
tempo_sys_A = tempo.Tempo(system=system,
bath=bath,
parameters=tempo_param_A,
initial_state="bla",
start_time=start_time)
with pytest.raises(AssertionError):
tempo_sys_A = tempo.Tempo(system=system,
bath=bath,
parameters=tempo_param_A,
initial_state=initial_state,
start_time="bla")
tempo_sys_A = tempo.Tempo(system=system,
bath=bath,
parameters=tempo_param_A,
initial_state=initial_state,
start_time=start_time)
with pytest.raises(AssertionError):
tempo_sys_A.compute(end_time="bla", progress_type="bar")
def test_process_tensor_backends(backend, backend_config):
initial_state = tempo.operators.spin_dm("y+")
initial_tensor = initial_state.flatten().reshape((1, -1))
system = tempo.System(tempo.operators.sigma("z"))
pt = tempo.ProcessTensor(times=None,
tensors=[],
initial_tensor=None,
backend=backend,
backend_config=backend_config)
pt.export(TEMP_FILE, overwrite=True)
pt.get_bond_dimensions()
pt = tempo.ProcessTensor(times=None,
tensors=[],
initial_tensor=initial_tensor,
backend=backend,
backend_config=backend_config)
pt.export(TEMP_FILE, overwrite=True)
pt.get_bond_dimensions()
pt.compute_final_state_from_system(system=system)
pt.compute_dynamics_from_system(system=system)
tensor = tempo.operators.identity(4).reshape((1, 1, 4, 4))
pt = tempo.ProcessTensor(times=None,
tensors=[tensor],
initial_tensor=initial_tensor,
backend=backend,
backend_config=backend_config)
pt.export(TEMP_FILE, overwrite=True)
pt.get_bond_dimensions()
pt.compute_final_state_from_system(system=system)
pt.compute_dynamics_from_system(system=system)
def test_tempo():
start_time = -0.3
end_time1 = 0.4
end_time2 = 0.6
end_time3 = 0.84
system = tempo.System(0.5 * tempo.operators.sigma("x"))
correlation_function = lambda t: (np.cos(6.0*t)+1j*np.sin(6.0*t)) \
* np.exp(-12.0*t)
correlations = tempo.CustomCorrelations(correlation_function,
max_correlation_time=0.5)
bath = tempo.Bath(0.5 * tempo.operators.sigma("z"), correlations)
initial_state = tempo.operators.spin_dm("z+")
tempo_param_A = tempo.TempoParameters(0.1, 5, 1.0e-5, name="rough-A")
tempo_sys_A = tempo.Tempo(system=system,
bath=bath,
parameters=tempo_param_A,
initial_state=initial_state,
start_time=start_time)
assert tempo_sys_A.dimension == 2
tempo_sys_A.compute(end_time=end_time1, progress_type="bar")
tempo_sys_A.compute(end_time=end_time2, progress_type="silent")
tempo_sys_A.compute(end_time=end_time3, progress_type="simple")
dyn_A = tempo_sys_A.get_dynamics()
assert len(dyn_A.times) == 13
def test_tensor_network_tempo_backend_non_diag(backend):
Omega = 1.0
omega_cutoff = 5.0
alpha = 0.3
sx = tempo.operators.sigma("x")
sy = tempo.operators.sigma("y")
sz = tempo.operators.sigma("z")
bases = [{"sys_op":sx, "coupling_op":sz, \
"init_state":tempo.operators.spin_dm("y+")},
{"sys_op":sy, "coupling_op":sx, \
"init_state":tempo.operators.spin_dm("z+")},
{"sys_op":sz, "coupling_op":sy, \
"init_state":tempo.operators.spin_dm("x+")}]
results = []
for i, base in enumerate(bases):
system = tempo.System(0.5 * base["sys_op"])
correlations = tempo.PowerLawSD(alpha=alpha,
zeta=1,
cutoff=omega_cutoff,
cutoff_type='exponential',
max_correlation_time=8.0)
bath = tempo.Bath(0.5 * base["coupling_op"], correlations)
tempo_parameters = tempo.TempoParameters(dt=0.1,
dkmax=30,
epsrel=10**(-5))
dynamics = tempo.tempo_compute(system=system,
bath=bath,
initial_state=base["init_state"],
start_time=0.0,
end_time=1.0,
parameters=tempo_parameters,
backend=backend)
_, s_x = dynamics.expectations(0.5 * tempo.operators.sigma("x"),
real=True)
_, s_y = dynamics.expectations(0.5 * tempo.operators.sigma("y"),
real=True)
_, s_z = dynamics.expectations(0.5 * tempo.operators.sigma("z"),
real=True)
if i == 0:
results.append(np.array([s_x, s_y, s_z]))
elif i == 1:
results.append(np.array([s_y, s_z, s_x]))
elif i == 2:
results.append(np.array([s_z, s_x, s_y]))
assert np.allclose(results[0], results[1], atol=tempo_parameters.epsrel)
assert np.allclose(results[0], results[2], atol=tempo_parameters.epsrel)
def test_tempo_compute():
start_time = -0.3
end_time = 0.84
system = tempo.System(0.5 * tempo.operators.sigma("x"))
correlation_function = lambda t: (np.cos(6.0*t)+1j*np.sin(6.0*t)) \
* np.exp(-12.0*t)
correlations = tempo.CustomCorrelations(correlation_function,
max_correlation_time=0.5)
bath = tempo.Bath(0.5 * tempo.operators.sigma("z"), correlations)
initial_state = tempo.operators.spin_dm("z+")
with pytest.warns(UserWarning):
dyn_A = tempo.tempo_compute(system=system,
bath=bath,
initial_state=initial_state,
start_time=start_time,
end_time=end_time)
def test_tempo_dynamics_reference():
system = tempo.System(0.5 * tempo.operators.sigma("x"))
correlations = tempo.PowerLawSD(alpha=0.1,
zeta=1,
cutoff=1.0,
cutoff_type='exponential',
max_correlation_time=0.5)
bath = tempo.Bath(0.5 * tempo.operators.sigma("z"), correlations)
tempo_parameters = tempo.TempoParameters(dt=0.1, dkmax=10, epsrel=10**(-4))
tempo_A = tempo.Tempo(system=system,
bath=bath,
parameters=tempo_parameters,
initial_state=tempo.operators.spin_dm("up"),
start_time=0.0)
dynamics_1 = tempo_A.compute(end_time=0.2)
t_1, sz_1 = dynamics_1.expectations(tempo.operators.sigma("z"))
tempo_A.compute(end_time=0.4)
dynamics_2 = tempo_A.get_dynamics()
t_2, sz_2 = dynamics_2.expectations(tempo.operators.sigma("z"))
assert dynamics_1 == dynamics_2
assert len(t_2) > len(t_1)
def test_guess_tempo_parameters():
system = tempo.System(0.5 * tempo.operators.sigma("x"))
correlation_function = lambda t: (np.cos(t) + 1j * np.sin(6.0 * t)
) * np.exp(-2.0 * t)
correlations = tempo.CustomCorrelations(correlation_function,
max_correlation_time=10.0)
bath = tempo.Bath(0.5 * tempo.operators.sigma("z"), correlations)
with pytest.warns(UserWarning):
param = tempo.guess_tempo_parameters(bath=bath,
start_time=0.0,
end_time=15.0)
with pytest.raises(AssertionError): # bad start time input
param = tempo.guess_tempo_parameters(bath=bath,
start_time="bla",
end_time=15.0)
with pytest.raises(AssertionError): # bad end time input
param = tempo.guess_tempo_parameters(bath=bath,
start_time=0.0,
end_time="bla")
with pytest.raises(ValueError): # bad start/end time (swapped)
param = tempo.guess_tempo_parameters(bath=bath,
start_time=10.0,
end_time=0.0)
with pytest.raises(AssertionError): # bad tollerance
param = tempo.guess_tempo_parameters(bath=bath,
start_time=0.0,
end_time=15.0,
tollerance="bla")
with pytest.raises(AssertionError): # bad tollerance (negative)
param = tempo.guess_tempo_parameters(bath=bath,
start_time=0.0,
end_time=15.0,
tollerance=-0.2)
with pytest.warns(UserWarning): # reach MAX_DKMAX
param = tempo.guess_tempo_parameters(bath=bath,
start_time=0.0,
end_time=15.0,
tollerance=1.0e-12)
+ y_plus * tempo.operators.spin_dm("y+")
return dm
rho_E = exact_result(t_end_E)
correlations_E = tempo.PowerLawSD(alpha=alpha_E,
zeta=3.0,
cutoff=cutoff_E,
cutoff_type="exponential",
temperature=temperature_E,
name="superohmic",
)
bath_E = tempo.Bath(coupling_operator_E,
correlations_E,
name="superohmic phonon bath")
system_E = tempo.System(h_sys_E)
# -----------------------------------------------------------------------------
@pytest.mark.parametrize('backend,backend_config',
[("tensor-network", {"backend":"numpy"}),])
def test_tensor_network_tempo_backend_E(backend, backend_config):
tempo_params_E = tempo.TempoParameters(dt=0.4,
dkmax=5,
epsrel=1.0e-6)
tempo_E = tempo.Tempo(system_E,
bath_E,
tempo_params_E,
initial_state_E,
start_time=t_start_E,
backend=backend,
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Tests for the time_evovling_mpo.process_tensor module.
"""
import pytest
import time_evolving_mpo as tempo
TEMP_FILE = "tests/data/temp.processTensor"
# -- prepare a process tensor -------------------------------------------------
system = tempo.System(tempo.operators.sigma("x"))
initial_state = tempo.operators.spin_dm("z+")
correlations = tempo.PowerLawSD(alpha=0.3,
zeta=1.0,
cutoff=5.0,
cutoff_type="exponential",
temperature=0.2,
name="ohmic")
bath = tempo.Bath(0.5*tempo.operators.sigma("z"),
correlations,
name="phonon bath")
tempo_params = tempo.PtTempoParameters(dt=0.1,
dkmax=5,
epsrel=10**(-5))
pt = tempo.pt_tempo_compute(bath,
start_time=0.0,
# * A.1: The Model and its Parameters
# * A.2: Create System, Spectral Density and Bath Objects
# * A.3: The TEMPO Computation
# -------------------------------------------------
# ## Example A - The Spin Boson Model
#
# As a first example let's try to reconstruct one of the lines in figure 2a of [Strathearn2018] ([Nat. Comm. 9, 3322 (2018)](https://doi.org/10.1038/s41467-018-05617-3) / [arXiv:1711.09641v3](https://arxiv.org/abs/1711.09641)). In this example we compute the time evolution of a spin which is strongly coupled to an ohmic bath (spin-boson model). Before we go through this step by step below, let's have a brief look at the script that will do the job - just to have an idea where we are going:
# In[3]:
Omega = 1.0
omega_cutoff = 5.0
alpha = 0.3
system = tempo.System(0.5 * Omega * tempo.operators.sigma("x"))
correlations = tempo.PowerLawSD(alpha=alpha,
zeta=1,
cutoff=omega_cutoff,
cutoff_type='exponential',
max_correlation_time=8.0)
bath = tempo.Bath(0.5 * tempo.operators.sigma("z"), correlations)
tempo_parameters = tempo.TempoParameters(dt=0.1, dkmax=30, epsrel=10**(-4))
dynamics = tempo.tempo_compute(system=system,
bath=bath,
initial_state=tempo.operators.spin_dm("up"),
start_time=0.0,
end_time=15.0,
parameters=tempo_parameters)
t, s_z = dynamics.expectations(0.5 * tempo.operators.sigma("z"), real=True)
rho_C = np.array(
[[ 0.12576653+0.j ,-0.11739956-0.14312036j, 0.12211454-0.05963583j],
[-0.11739956+0.14312036j, 0.61315893+0.j ,-0.06636825+0.26917271j],
[ 0.12211454+0.05963583j,-0.06636825-0.26917271j, 0.26107455+0.j ]])
correlations_C = tempo.PowerLawSD(alpha=alpha_C,
zeta=1.0,
cutoff=cutoff_C,
cutoff_type="exponential",
temperature=temperature_C,
name="ohmic")
bath_C = tempo.Bath(coupling_operator_C,
correlations_C,
name="phonon bath")
system_C = tempo.System(h_sys_C,
gammas=[gamma_C_1, gamma_C_2],
lindblad_operators=[lindblad_operators_C_1,
lindblad_operators_C_2])
# -----------------------------------------------------------------------------
@pytest.mark.parametrize('backend',["tensor-network"])
def test_tensor_network_tempo_backend_C(backend):
tempo_params_C = tempo.TempoParameters(dt=0.05,
dkmax=11,
epsrel=10**(-7))
tempo_C = tempo.Tempo(system_C,
bath_C,
tempo_params_C,
initial_state_C,
start_time=0.0,
t_end_A = 1.0
# result obtained with release code (made hermitian):
rho_A = np.array([[0.7809559 + 0.j, -0.09456333 + 0.16671419j],
[-0.09456333 - 0.16671419j, 0.2190441 + 0.j]])
correlations_A = tempo.PowerLawSD(alpha=alpha_A,
zeta=1.0,
cutoff=cutoff_A,
cutoff_type="exponential",
temperature=temperature_A,
name="ohmic")
bath_A = tempo.Bath(coupling_operator_A, correlations_A, name="phonon bath")
system_A = tempo.System(h_sys_A,
gammas=[gamma_A_1, gamma_A_2],
lindblad_operators=[
tempo.operators.sigma("-"),
tempo.operators.sigma("z")
])
# -----------------------------------------------------------------------------
@pytest.mark.parametrize('backend,backend_config', [("tensor-network", {
"backend": "numpy"
}), ("tensor-network", None)])
def test_tensor_network_tempo_backend_A(backend, backend_config):
tempo_params_A = tempo.TempoParameters(dt=0.05,
dkmax=None,
epsrel=10**(-7))
tempo_A = tempo.Tempo(system_A,
bath_A,
os.environ['NUMEXPR_NUM_THREADS'] = '1'
import time_evolving_mpo as tempo
import numpy as np
import matplotlib.pyplot as plt
from scipy import constants
Omega = 0.0 # 1.0
# omega_cutoff = 3.0
# alpha = 0.1
omega_cutoff = 2.0e-3 * constants.electron_volt * 1e-12 / constants.hbar
alpha = constants.hbar * 11.2e-3 * omega_cutoff**2 * 1e12/ \
(2 * constants.pi * constants.Boltzmann)
system = tempo.System(0.0 * Omega * tempo.operators.sigma("x"))
initial_state = tempo.operators.spin_dm("y+")
def generate_pt(temp):
start_time = 0.0
end_time = 10.0
correlations = tempo.PowerLawSD(alpha=alpha,
zeta=3,
cutoff=omega_cutoff,
cutoff_type='gaussian',
temperature=temp)
bath = tempo.Bath(0.5 * tempo.operators.sigma("z"), correlations)
