Flake in test_decompose_to_diagonal_and_circuit

[dabacon]

v = array([[-0.61070603+0.1365783j , -0.5391698 -0.27113172j, -0.13448845+0.33649975j, 0.07048975+0.3284511j ],
[-...[-0.144254 +0.16332075j, 0.23525491+0.0989278j , -0.29602534+0.62655133j, -0.28742015-0.56971717j]], dtype=complex64)
@pytest.mark.parametrize(
"v",
[
cirq.unitary(random_two_qubit_circuit_with_czs(3)),
cirq.unitary(random_two_qubit_circuit_with_czs(2)),
np.diag(np.exp(1j * np.pi * np.random.random(4))),
],
)
deftest_decompose_to_diagonal_and_circuit(v):
b, c = cirq.LineQubit.range(2)
diagonal, ops = two_qubit_matrix_to_diagonal_and_cz_operations(b, c, v, atol=1e-6)
assert cirq.is_diagonal(diagonal)
combined_circuit = cirq.Circuit(cirq.MatrixGate(diagonal)(b, c), ops)
circuit_unitary = combined_circuit.unitary(qubits_that_should_be_present=[b, c])

  cirq.testing.assert_allclose_up_to_global_phase(circuit_unitary, v, atol=1e-5)

E AssertionError:
E Not equal to tolerance rtol=1e-07, atol=1e-05
E
E Mismatched elements: 16 / 16 (100%)
E Max absolute difference: 6.1219725e-05
E Max relative difference: 0.00010682
E x: array([[ 0.384335+4.938793e-01j, -0.014804+6.033021e-01j, 0.361728-2.215727e-02j, 0.266857-2.040258e-01j],
E [ 0.619436-1.967203e-01j, -0.672573-1.093492e-01j, -0.196227+1.505381e-01j, -0.16237 -1.604927e-01j],
E [-0.215903+3.031191e-01j, -0.21768 +2.428720e-01j, -0.19194 -5.389726e-01j, -0.650181-7.116976e-02j],
E [ 0.209275+6.065131e-02j, -0.011074-2.549549e-01j, 0.692938-5.960464e-08j, -0.392396+5.032529e-01j]], dtype=complex64)
E y: array([[ 0.384375+4.938332e-01j, -0.014821+6.033215e-01j, 0.361702-2.214911e-02j, 0.266861-2.040445e-01j],
E [ 0.619446-1.967466e-01j, -0.672537-1.093988e-01j, -0.196237+1.505618e-01j, -0.162392-1.604833e-01j],
E [-0.215881+3.031079e-01j, -0.217704+2.428641e-01j, -0.191879-5.389693e-01j, -0.650208-7.117966e-02j],
E [ 0.209292+6.066049e-02j, -0.011051-2.549695e-01j, 0.692963+5.960464e-08j, -0.392335+5.032508e-01j]], dtype=complex64)
cirq-core/cirq/transformers/analytical_decompositions/two_qubit_to_cz_test.py:268: AssertionError

[tanujkhattar]

xref #5533

[vtomole]

Similar flake https://github.com/quantumlib/Cirq/runs/7027217455?check_suite_focus=true

[dabacon]

__________________ test_decompose_to_diagonal_and_circuit[v1] __________________
E         
E         v = array([[-0.04917413+0.31887117j, -0.21023309-0.17613545j,  0.03311536-0.84780866j, -0.29627275-0.11413992j],
E                [-...[-0.00090575+0.2908945j ,  0.29029933+0.5300961j ,  0.33330664-0.02012963j, -0.33348376+0.5721835j ]], dtype=complex64)
E         
E             @pytest.mark.parametrize(
E                 "v",
E                 [
E                     cirq.unitary(random_two_qubit_circuit_with_czs(3)),
E                     cirq.unitary(random_two_qubit_circuit_with_czs(2)),
E                     np.diag(np.exp(1j * np.pi * np.random.random(4))),
E                 ],
E             )
E             def test_decompose_to_diagonal_and_circuit(v):
E                 b, c = cirq.LineQubit.range(2)
E                 diagonal, ops = two_qubit_matrix_to_diagonal_and_cz_operations(b, c, v, atol=1e-6)
E                 assert cirq.is_diagonal(diagonal)
E                 combined_circuit = cirq.Circuit(cirq.MatrixGate(diagonal)(b, c), ops)
E                 circuit_unitary = combined_circuit.unitary(qubits_that_should_be_present=[b, c])
E         >       cirq.testing.assert_allclose_up_to_global_phase(circuit_unitary, v, atol=1e-5)
E         E       AssertionError: 
E         E       Not equal to tolerance rtol=1e-07, atol=1e-05
E         E       
E         E       Mismatched elements: 5 / 16 (31.2%)
E         E       Max absolute difference: 2.4261433e-05
E         E       Max relative difference: 4.014266e-05
E         E        x: array([[-0.320549-3.669657e-02j,  0.167792-2.169474e-01j,  0.848454-8.940697e-08j,  0.102486-3.005073e-01j],
E         E              [ 0.226037-4.611170e-01j,  0.028327-5.401294e-01j,  0.107656+7.426675e-02j, -0.561706+3.333432e-01j],
E         E              [ 0.366648-6.427520e-01j, -0.10464 +5.059708e-01j,  0.192138-3.385318e-01j,  0.075745-1.680024e-01j],
E         E              [-0.290706+1.045696e-02j, -0.518354+3.107907e-01j,  0.03313 +3.322693e-01j, -0.584769-3.108764e-01j]], dtype=complex64)
E         E        y: array([[-0.320[547](https://github.com/quantumlib/Cirq/runs/7044934576?check_suite_focus=true#step:5:548)-3.669108e-02j,  0.167796-2.169475e-01j,  0.848455+4.097819e-08j,  0.102489-3.005019e-01j],
E         E              [ 0.226045-4.611138e-01j,  0.02834 -5.401317e-01j,  0.107655+7.426722e-02j, -0.[561](https://github.com/quantumlib/Cirq/runs/7044934576?check_suite_focus=true#step:5:562)709+3.333324e-01j],
E         E              [ 0.366656-6.427467e-01j, -0.104649+5.059704e-01j,  0.192147-3.385260e-01j,  0.075747-1.680016e-01j],
E         E              [-0.290708+1.044859e-02j, -0.518362+3.107679e-01j,  0.033123+3.322670e-01j, -0.584763-3.108972e-01j]], dtype=complex64)
E         
E         cirq-core/cirq/transformers/analytical_decompositions/two_qubit_to_cz_test.py:268: AssertionError

[dabacon]

We have rolled back the change in default #5636 so these should no longer be occurring