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32###############################################################################
33"""
34Unit tests for QuTiP partial transpose functions.
35"""
36
37import numpy as np
38from numpy.testing import assert_, run_module_suite
39
40from qutip import Qobj, partial_transpose, tensor, rand_dm
41from qutip.partial_transpose import _partial_transpose_reference
42
43
44def test_partial_transpose_bipartite():
45    """partial transpose of bipartite systems"""
46
47    rho = Qobj(np.arange(16).reshape(4, 4), dims=[[2, 2], [2, 2]])
48
49    # no transpose
50    rho_pt = partial_transpose(rho, [0, 0])
51    assert_(np.abs(np.max(rho_pt.full() - rho.full())) < 1e-12)
52
53    # partial transpose subsystem 1
54    rho_pt = partial_transpose(rho, [1, 0])
55    rho_pt_expected = np.array([[0, 1,  8,  9],
56                                [4, 5, 12, 13],
57                                [2, 3, 10, 11],
58                                [6, 7, 14, 15]])
59    assert_(np.abs(np.max(rho_pt.full() - rho_pt_expected)) < 1e-12)
60
61    # partial transpose subsystem 2
62    rho_pt = partial_transpose(rho, [0, 1])
63    rho_pt_expected = np.array([[0, 4, 2, 6],
64                                [1, 5, 3, 7],
65                                [8, 12, 10, 14],
66                                [9, 13, 11, 15]])
67    assert_(np.abs(np.max(rho_pt.full() - rho_pt_expected)) < 1e-12)
68
69    # full transpose
70    rho_pt = partial_transpose(rho, [1, 1])
71    assert_(np.abs(np.max(rho_pt.full() - rho.trans().full())) < 1e-12)
72
73
74def test_partial_transpose_comparison():
75    """partial transpose: comparing sparse and dense implementations"""
76
77    N = 10
78    rho = tensor(rand_dm(N, density=0.5), rand_dm(N, density=0.5))
79
80    # partial transpose of system 1
81    rho_pt1 = partial_transpose(rho, [1, 0], method="dense")
82    rho_pt2 = partial_transpose(rho, [1, 0], method="sparse")
83    np.abs(np.max(rho_pt1.full() - rho_pt1.full())) < 1e-12
84
85    # partial transpose of system 2
86    rho_pt1 = partial_transpose(rho, [0, 1], method="dense")
87    rho_pt2 = partial_transpose(rho, [0, 1], method="sparse")
88    np.abs(np.max(rho_pt1.full() - rho_pt2.full())) < 1e-12
89
90
91def test_partial_transpose_randomized():
92    """partial transpose: randomized tests on tripartite system"""
93
94    rho = tensor(rand_dm(2, density=1),
95                 rand_dm(2, density=1),
96                 rand_dm(2, density=1))
97
98    mask = np.random.randint(2, size=3)
99
100    rho_pt_ref = _partial_transpose_reference(rho, mask)
101
102    rho_pt1 = partial_transpose(rho, mask, method="dense")
103    np.abs(np.max(rho_pt1.full() - rho_pt_ref.full())) < 1e-12
104
105    rho_pt2 = partial_transpose(rho, mask, method="sparse")
106    np.abs(np.max(rho_pt2.full() - rho_pt_ref.full())) < 1e-12
107
108
109if __name__ == "__main__":
110    run_module_suite()
111