Add test for PT-TEBD with site dissipation

Author: gefux

tests/physics/example_H_test.py

@@ -0,0 +1,101 @@
+# Copyright 2020 The TEMPO Collaboration
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+Tests for the time_evovling_mpo.backends.tensor_network modules.
+"""
+import sys
+sys.path.insert(0,'.')
+
+import pytest
+import numpy as np
+
+import oqupy
+
+# -----------------------------------------------------------------------------
+# -- Test F: Test Lindblad dissipation for PT-TEBD  ---------------------------
+
+# --- Parameters --------------------------------------------------------------
+
+# -- time steps --
+dt = 0.1
+num_steps = 10
+
+# -- bath --
+alpha = 0.3
+omega_cutoff = 3.0
+temperature = 0.8
+pt_dkmax = 10
+pt_epsrel = 1.0e-6
+
+# -- chain --
+N = 5
+Omega = 1.0
+eta = 0.3
+Delta = 1.2
+h = np.array(
+    [[1.0, 0.0, 0.0],
+     [2.0, 0.0, 0.0],
+     [3.0, 0.0, 0.0],
+     [4.0, 0.0, 0.0],
+     [5.0, 0.0, 0.0]]) * np.pi / 10
+J = np.array([[Delta, 1.0+eta, 1.0-eta]]*(N-1))
+up_dm = oqupy.operators.spin_dm("z+")
+down_dm = oqupy.operators.spin_dm("z-")
+tebd_order = 2
+tebd_epsrel = 1.0e-7
+
+
+def test_pt_tebd_site_dissipation_H1():
+    # -- initial state --
+    initial_augmented_mps = oqupy.AugmentedMPS([up_dm, down_dm, down_dm])
+
+    # -- add single site dissipation --
+    system_chain = oqupy.SystemChain(hilbert_space_dimensions=[2,2,2])
+    # lowering operator on site 0:
+    system_chain.add_site_dissipation(0,[[0,0],[1,0]])
+    # identity cross raising operator on sites 1 and 2:
+    system_chain.add_nn_dissipation(1,np.identity(2),[[0,1],[0,0]])
+
+    # -- PT-TEBD parameters --
+    pt_tebd_params = oqupy.PtTebdParameters(
+        dt=dt,
+        order=tebd_order,
+        epsrel=tebd_epsrel)
+
+    num_steps = int(1.0/pt_tebd_params.dt)
+
+    pt_tebd = oqupy.PtTebd(
+        initial_augmented_mps=initial_augmented_mps,
+        system_chain=system_chain,
+        process_tensors=[None]*3,
+        parameters=pt_tebd_params,
+        dynamics_sites=[0,1,2],
+        chain_control=None)
+
+    r = pt_tebd.compute(num_steps, progress_type="silent")
+
+    np.testing.assert_almost_equal(
+        r['dynamics'][0].states[-1],
+        [[np.exp(-1),0],[0,1-np.exp(-1)]],
+        decimal=4)
+    np.testing.assert_almost_equal(
+        r['dynamics'][1].states[-1],
+        [[0,0],[0,1]],
+        decimal=4)
+    np.testing.assert_almost_equal(
+        r['dynamics'][2].states[-1],
+        [[1-np.exp(-1),0],[0,np.exp(-1)]],
+        decimal=4)
+
+# -----------------------------------------------------------------------------