def test_fidelity_product_states():
a, b = cirq.LineQubit.range(2)
np.testing.assert_allclose(
cirq.fidelity(cirq.KET_ZERO(a) * cirq.KET_ZERO(b), cirq.KET_ZERO(a) * cirq.KET_ZERO(b)), 1.0
)
np.testing.assert_allclose(
cirq.fidelity(cirq.KET_ZERO(a) * cirq.KET_ZERO(b), cirq.KET_ZERO(a) * cirq.KET_ONE(b)),
0.0,
atol=1e-7,
)
np.testing.assert_allclose(
cirq.fidelity(cirq.KET_ZERO(a) * cirq.KET_ZERO(b), cirq.KET_ZERO(a) * cirq.KET_PLUS(b)), 0.5
)
np.testing.assert_allclose(
cirq.fidelity(cirq.KET_ONE(a) * cirq.KET_ONE(b), cirq.KET_MINUS(a) * cirq.KET_PLUS(b)), 0.25
)
np.testing.assert_allclose(
cirq.fidelity(cirq.KET_MINUS(a) * cirq.KET_PLUS(b), cirq.KET_MINUS(a) * cirq.KET_PLUS(b)),
1.0,
)
np.testing.assert_allclose(
cirq.fidelity(cirq.KET_MINUS(a) * cirq.KET_PLUS(b), cirq.KET_PLUS(a) * cirq.KET_MINUS(b)),
0.0,
atol=1e-7,
)
with pytest.raises(ValueError, match='Mismatched'):
_ = cirq.fidelity(cirq.KET_MINUS(a), cirq.KET_PLUS(a) * cirq.KET_MINUS(b))
with pytest.raises(ValueError, match='qid shape'):
_ = cirq.fidelity(
cirq.KET_MINUS(a) * cirq.KET_PLUS(b),
cirq.KET_PLUS(a) * cirq.KET_MINUS(b),
qid_shape=(4,),
)
def test_tp_projector():
q0, q1 = cirq.LineQubit.range(2)
p00 = (cirq.KET_ZERO(q0) * cirq.KET_ZERO(q1)).projector()
rho = cirq.final_density_matrix(cirq.Circuit(cirq.I.on_each(q0, q1)))
np.testing.assert_allclose(rho, p00)
p01 = (cirq.KET_ZERO(q0) * cirq.KET_ONE(q1)).projector()
rho = cirq.final_density_matrix(cirq.Circuit([cirq.I.on_each(q0, q1), cirq.X(q1)]))
np.testing.assert_allclose(rho, p01)
ppp = (cirq.KET_PLUS(q0) * cirq.KET_PLUS(q1)).projector()
rho = cirq.final_density_matrix(
cirq.Circuit(
[
cirq.H.on_each(q0, q1),
]
)
)
np.testing.assert_allclose(rho, ppp, atol=1e-7)
ppm = (cirq.KET_PLUS(q0) * cirq.KET_MINUS(q1)).projector()
rho = cirq.final_density_matrix(cirq.Circuit([cirq.H.on_each(q0, q1), cirq.Z(q1)]))
np.testing.assert_allclose(rho, ppm, atol=1e-7)
pii = (cirq.KET_IMAG(q0) * cirq.KET_IMAG(q1)).projector()
rho = cirq.final_density_matrix(cirq.Circuit(cirq.rx(-np.pi / 2).on_each(q0, q1)))
np.testing.assert_allclose(rho, pii, atol=1e-7)
pij = (cirq.KET_IMAG(q0) * cirq.KET_MINUS_IMAG(q1)).projector()
rho = cirq.final_density_matrix(cirq.Circuit(cirq.rx(-np.pi / 2)(q0), cirq.rx(np.pi / 2)(q1)))
np.testing.assert_allclose(rho, pij, atol=1e-7)
def test_max_weight_state():
q0, q1 = cirq.LineQubit.range(2)
states = [cirq.KET_PLUS(q0), cirq.KET_PLUS(q1)]
assert _max_weight_state(states) == cirq.KET_PLUS(q0) * cirq.KET_PLUS(q1)
states = [cirq.KET_PLUS(q0), cirq.KET_PLUS(q1), cirq.KET_MINUS(q1)]
assert _max_weight_state(states) is None
def test_product_state_equality():
q0, q1, q2 = cirq.LineQubit.range(3)
assert cirq.KET_PLUS(q0) == cirq.KET_PLUS(q0)
assert cirq.KET_PLUS(q0) != cirq.KET_PLUS(q1)
assert cirq.KET_PLUS(q0) != cirq.KET_MINUS(q0)
assert cirq.KET_PLUS(q0) * cirq.KET_MINUS(q1) == cirq.KET_PLUS(q0) * cirq.KET_MINUS(q1)
assert cirq.KET_PLUS(q0) * cirq.KET_MINUS(q1) != cirq.KET_PLUS(q0) * cirq.KET_MINUS(q2)
assert hash(cirq.KET_PLUS(q0) * cirq.KET_MINUS(q1)) == hash(
cirq.KET_PLUS(q0) * cirq.KET_MINUS(q1)
)
assert hash(cirq.KET_PLUS(q0) * cirq.KET_MINUS(q1)) != hash(
cirq.KET_PLUS(q0) * cirq.KET_MINUS(q2)
)
assert cirq.KET_PLUS(q0) != '+X(0)'