def test_matrix_mixture_repr():
mix = [
(0.5, np.array([[1, 0], [0, 1]], dtype=np.complex64)),
(0.5, np.array([[0, 1], [1, 0]], dtype=np.complex64)),
]
half_flip = cirq.MixedUnitaryChannel(mix, key='flip')
assert (repr(half_flip) == """\
cirq.MixedUnitaryChannel(mixture=[\
(0.5, np.array([[(1+0j), 0j], [0j, (1+0j)]], dtype=np.complex64)), \
(0.5, np.array([[0j, (1+0j)], [(1+0j), 0j]], dtype=np.complex64))], \
key='flip')""")
def test_matrix_mixture_str():
mix = [(0.5, np.array([[1, 0], [0, 1]])), (0.5, np.array([[0, 1], [1,
0]]))]
half_flip = cirq.MixedUnitaryChannel(mix)
assert (str(half_flip) == """MixedUnitaryChannel([(0.5, array([[1, 0],
[0, 1]])), (0.5, array([[0, 1],
[1, 0]]))])""")
half_flip_keyed = cirq.MixedUnitaryChannel(mix, key='flip')
assert (
str(half_flip_keyed) == """MixedUnitaryChannel([(0.5, array([[1, 0],
[0, 1]])), (0.5, array([[0, 1],
[1, 0]]))], key=flip)""")
def test_validate():
mix = [
(0.5, np.array([[1, 0], [0, 0]])),
(0.5, np.array([[0, 0], [0, 1]])),
]
with pytest.raises(ValueError, match='non-unitary'):
_ = cirq.MixedUnitaryChannel(mixture=mix, key='m', validate=True)
def test_mix_mismatch_fails():
op2 = np.zeros((4, 4))
op2[1][1] = 1
mix = [(0.5, np.array([[1, 0], [0, 0]])), (0.5, op2)]
with pytest.raises(ValueError, match='Inconsistent unitary shapes'):
_ = cirq.MixedUnitaryChannel(mixture=mix, key='m')
def test_nonqubit_mixture_fails():
mix = [
(0.5, np.array([[1, 0, 0], [0, 1, 0]])),
(0.5, np.array([[0, 1, 0], [1, 0, 0]])),
]
with pytest.raises(ValueError, match='Input mixture'):
_ = cirq.MixedUnitaryChannel(mixture=mix, key='m')
def test_measured_mixture():
# This behaves like an X-basis measurement.
mm = cirq.MixedUnitaryChannel(mixture=((0.5, np.array([[1, 0], [0, 1]])),
(0.5, np.array([[0, 1], [1, 0]]))),
key='flip')
q0 = cirq.LineQubit(0)
circuit = cirq.Circuit(mm.on(q0), cirq.measure(q0, key='m'))
sim = cirq.Simulator(seed=0)
results = sim.run(circuit, repetitions=100)
assert results.histogram(key='flip') == results.histogram(key='m')
def test_matrix_mixture_from_unitaries():
q0 = cirq.LineQubit(0)
mix = [(0.5, np.array([[1, 0], [0, 1]])), (0.5, np.array([[0, 1], [1, 0]]))]
half_flip = cirq.MixedUnitaryChannel(mix, key='flip')
assert cirq.measurement_key_name(half_flip) == 'flip'
circuit = cirq.Circuit(half_flip.on(q0), cirq.measure(q0, key='m'))
sim = cirq.Simulator(seed=0)
results = sim.simulate(circuit)
assert 'flip' in results.measurements
assert results.measurements['flip'] == results.measurements['m']
def test_matrix_mixture_equality():
dp_pt1 = cirq.depolarize(0.1)
dp_pt2 = cirq.depolarize(0.2)
mm_a1 = cirq.MixedUnitaryChannel.from_mixture(dp_pt1, key='a')
mm_a2 = cirq.MixedUnitaryChannel.from_mixture(dp_pt2, key='a')
mm_b1 = cirq.MixedUnitaryChannel.from_mixture(dp_pt1, key='b')
# Even if their effect is the same, MixedUnitaryChannels are not treated
# as equal to other channels defined in Cirq.
assert mm_a1 != dp_pt1
assert mm_a1 != mm_a2
assert mm_a1 != mm_b1
assert mm_a2 != mm_b1
mix = [(0.5, np.array([[1, 0], [0, 1]])), (0.5, np.array([[0, 1], [1, 0]]))]
half_flip = cirq.MixedUnitaryChannel(mix)
mix_inv = list(reversed(mix))
half_flip_inv = cirq.MixedUnitaryChannel(mix_inv)
# Even though these have the same effect on the circuit, their measurement
# behavior differs, so they are considered non-equal.
assert half_flip != half_flip_inv
def test_mix_bad_prob_fails():
mix = [(0.5, np.array([[1, 0], [0, 0]]))]
with pytest.raises(ValueError,
match='Unitary probabilities must sum to 1'):
_ = cirq.MixedUnitaryChannel(mixture=mix, key='m')
def test_mix_no_unitaries_fails():
with pytest.raises(ValueError, match='must have at least one unitary'):
_ = cirq.MixedUnitaryChannel(mixture=[], key='m')
