def test_partial_trace_of_state_vector_as_mixture_mixed_result():
state = np.array([1, 0, 0, 1]) / np.sqrt(2)
truth = ((0.5, np.array([1, 0])), (0.5, np.array([0, 1])))
for q1 in [0, 1]:
mixture = cirq.partial_trace_of_state_vector_as_mixture(state, [q1], atol=1e-8)
assert mixtures_equal(mixture, truth)
state = np.array([0, 1, 1, 0, 1, 0, 0, 0]).reshape((2, 2, 2)) / np.sqrt(3)
truth = ((1 / 3, np.array([0.0, 1.0])), (2 / 3, np.array([1.0, 0.0])))
for q1 in [0, 1, 2]:
mixture = cirq.partial_trace_of_state_vector_as_mixture(state, [q1], atol=1e-8)
assert mixtures_equal(mixture, truth)
state = np.array([1, 0, 0, 0, 0, 0, 0, 1]).reshape((2, 2, 2)) / np.sqrt(2)
truth = ((0.5, np.array([1, 0])), (0.5, np.array([0, 1])))
for q1 in [0, 1, 2]:
mixture = cirq.partial_trace_of_state_vector_as_mixture(state, [q1], atol=1e-8)
assert mixtures_equal(mixture, truth)
truth = (
(0.5, np.array([1, 0, 0, 0]).reshape((2, 2))),
(0.5, np.array([0, 0, 0, 1]).reshape((2, 2))),
)
for (q1, q2) in [(0, 1), (0, 2), (1, 2)]:
mixture = cirq.partial_trace_of_state_vector_as_mixture(state, [q1, q2], atol=1e-8)
assert mixtures_equal(mixture, truth)
def test_partial_trace_of_state_vector_as_mixture_mixed_result_qudits():
state = np.array([[1, 0, 0], [0, 0, 0], [0, 0, 1]]) / np.sqrt(2)
truth = ((0.5, np.array([1, 0, 0])), (0.5, np.array([0, 0, 1])))
for q1 in [0, 1]:
mixture = cirq.partial_trace_of_state_vector_as_mixture(state, [q1],
atol=1e-8)
assert mixtures_equal(mixture, truth)
def test_deprecated():
a = np.arange(4) / np.linalg.norm(np.arange(4))
with cirq.testing.assert_logs('subwavefunction', 'sub_state_vector',
'deprecated'):
_ = cirq.subwavefunction(a, [0, 1], atol=1e-8)
with cirq.testing.assert_logs('wavefunction', 'state_vector',
'deprecated'):
# pylint: disable=unexpected-keyword-arg,no-value-for-parameter
_ = cirq.sub_state_vector(wavefunction=a,
keep_indices=[0, 1],
atol=1e-8)
with cirq.testing.assert_logs(
'wavefunction_partial_trace_as_mixture',
'partial_trace_of_state_vector_as_mixture',
'deprecated',
):
_ = cirq.wavefunction_partial_trace_as_mixture(a, [0])
with cirq.testing.assert_logs('wavefunction', 'state_vector',
'deprecated'):
# pylint: disable=unexpected-keyword-arg,no-value-for-parameter
_ = cirq.partial_trace_of_state_vector_as_mixture(wavefunction=a,
keep_indices=[0])
def get_state(self, resolver: cirq.ParamResolver, trace_dims: list = None, max_traced: bool = True):
state_vector = cirq.final_state_vector(cirq.resolve_parameters(self.circuit, resolver))
if trace_dims and len(trace_dims) < self.get_circuit_size():
state_vector = cirq.partial_trace_of_state_vector_as_mixture(state_vector, trace_dims)
if max_traced:
prob, state_vector = max(state_vector, key=lambda el: el[0])
print(f"Max probability state after tracing has probability: {prob}")
return state_vector, abs(state_vector)
return state_vector, abs(state_vector)
def test_partial_trace_of_state_vector_as_mixture_invalid_input():
with pytest.raises(ValueError, match='7'):
cirq.partial_trace_of_state_vector_as_mixture(np.arange(7), [1, 2],
atol=1e-8)
with pytest.raises(ValueError, match='normalized'):
cirq.partial_trace_of_state_vector_as_mixture(np.arange(8), [1],
atol=1e-8)
state = np.arange(8) / np.linalg.norm(np.arange(8))
with pytest.raises(ValueError, match='repeated axis'):
cirq.partial_trace_of_state_vector_as_mixture(state, [1, 2, 2],
atol=1e-8)
state = np.array([1, 0, 0, 0]).reshape((2, 2))
with pytest.raises(IndexError, match='out of range'):
cirq.partial_trace_of_state_vector_as_mixture(state, [5], atol=1e-8)
with pytest.raises(IndexError, match='out of range'):
cirq.partial_trace_of_state_vector_as_mixture(state, [0, 1, 2],
atol=1e-8)
def test_partial_trace_of_state_vector_as_mixture_pure_result_qudits():
a = cirq.testing.random_superposition(2)
b = cirq.testing.random_superposition(3)
c = cirq.testing.random_superposition(4)
state = np.kron(np.kron(a, b), c).reshape((2, 3, 4))
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [0], atol=1e-8),
((1.0, a), ),
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [1], atol=1e-8),
((1.0, b), ),
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [2], atol=1e-8),
((1.0, c), ),
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [0, 1],
atol=1e-8),
((1.0, np.kron(a, b).reshape((2, 3))), ),
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [0, 2],
atol=1e-8),
((1.0, np.kron(a, c).reshape((2, 4))), ),
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [1, 2],
atol=1e-8),
((1.0, np.kron(b, c).reshape((3, 4))), ),
)
def test_partial_trace_of_state_vector_as_mixture_pure_result():
a = cirq.testing.random_superposition(4)
b = cirq.testing.random_superposition(8)
c = cirq.testing.random_superposition(16)
state = np.kron(np.kron(a, b), c).reshape((2,) * 9)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [0, 1], atol=1e-8),
((1.0, a.reshape(2, 2)),),
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [2, 3, 4], atol=1e-8),
((1.0, b.reshape(2, 2, 2)),),
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [5, 6, 7, 8], atol=1e-8),
((1.0, c.reshape(2, 2, 2, 2)),),
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [0, 1, 2, 3, 4], atol=1e-8),
((1.0, np.kron(a, b).reshape((2, 2, 2, 2, 2))),),
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [0, 1, 5, 6, 7, 8], atol=1e-8),
((1.0, np.kron(a, c).reshape((2, 2, 2, 2, 2, 2))),),
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [2, 3, 4, 5, 6, 7, 8], atol=1e-8),
((1.0, np.kron(b, c).reshape((2, 2, 2, 2, 2, 2, 2))),),
)
# Shapes of states in the output mixture conform to the input's shape.
state = state.reshape(2 ** 9)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [0, 1], atol=1e-8), ((1.0, a),)
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [2, 3, 4], atol=1e-8), ((1.0, b),)
)
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [5, 6, 7, 8], atol=1e-8), ((1.0, c),)
)
# Return mixture will defer to numpy.linalg.eigh's builtin tolerance.
state = np.array([1, 0, 0, 1]) / np.sqrt(2)
truth = ((0.5, np.array([1, 0])), (0.5, np.array([0, 1])))
assert mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [1], atol=1e-20), truth, atol=1e-15
)
assert not mixtures_equal(
cirq.partial_trace_of_state_vector_as_mixture(state, [1], atol=1e-20), truth, atol=1e-16
)
def test_partial_trace_of_state_vector_as_mixture_invalid_input():
with pytest.raises(ValueError, match='7'):
cirq.partial_trace_of_state_vector_as_mixture(np.arange(7), [1, 2], atol=1e-8)
bad_shape = np.arange(16).reshape((2, 4, 2))
with pytest.raises(ValueError, match='shaped'):
cirq.partial_trace_of_state_vector_as_mixture(bad_shape, [1], atol=1e-8)
bad_shape = np.arange(16).reshape((16, 1))
with pytest.raises(ValueError, match='shaped'):
cirq.partial_trace_of_state_vector_as_mixture(bad_shape, [1], atol=1e-8)
with pytest.raises(ValueError, match='normalized'):
cirq.partial_trace_of_state_vector_as_mixture(np.arange(8), [1], atol=1e-8)
state = np.arange(8) / np.linalg.norm(np.arange(8))
with pytest.raises(ValueError, match='2, 2'):
cirq.partial_trace_of_state_vector_as_mixture(state, [1, 2, 2], atol=1e-8)
state = np.array([1, 0, 0, 0]).reshape((2, 2))
with pytest.raises(ValueError, match='invalid'):
cirq.partial_trace_of_state_vector_as_mixture(state, [5], atol=1e-8)
with pytest.raises(ValueError, match='invalid'):
cirq.partial_trace_of_state_vector_as_mixture(state, [0, 1, 2], atol=1e-8)
