def test_equality():
q0 = cirq.NamedQubit('q0')
obj1a = cirq.ProjectorString({q0: 0})
obj1b = cirq.ProjectorString({q0: 0})
obj2 = cirq.ProjectorString({q0: 1})
obj3 = cirq.ProjectorString({q0: 1}, coefficient=0.20160913)
eq = cirq.testing.EqualsTester()
eq.add_equality_group(obj1a, obj1b)
eq.add_equality_group(obj2)
eq.add_equality_group(obj3)
def test_projector_matrix():
q0 = cirq.NamedQubit('q0')
zero_projector = cirq.ProjectorString({q0: 0})
one_projector = cirq.ProjectorString({q0: 1})
coeff_projector = cirq.ProjectorString({q0: 0}, 1.23 + 4.56j)
np.testing.assert_allclose(zero_projector.matrix().toarray(),
[[1.0, 0.0], [0.0, 0.0]])
np.testing.assert_allclose(one_projector.matrix().toarray(),
[[0.0, 0.0], [0.0, 1.0]])
np.testing.assert_allclose(coeff_projector.matrix().toarray(),
[[1.23 + 4.56j, 0.0], [0.0, 0.0]])
def test_expectation_higher_dims():
qubit = cirq.NamedQid('q0', dimension=2)
qutrit = cirq.NamedQid('q1', dimension=3)
with pytest.raises(ValueError, match="Only qubits are supported"):
cirq.ProjectorString({qutrit: 0})
d = cirq.ProjectorString({qubit: 0})
with pytest.raises(ValueError, match="Only qubits are supported"):
_ = (d.expectation_from_state_vector(np.zeros(2 * 3), {
qubit: 0,
qutrit: 0
}), )
def test_get_values():
q0 = cirq.NamedQubit('q0')
d = cirq.ProjectorString({q0: 0}, 1.23 + 4.56j)
assert len(d.projector_dict) == 1
assert d.projector_dict[q0] == 0
assert d.coefficient == 1.23 + 4.56j
def test_expectation_from_density_matrix_basis_states_empty():
q0 = cirq.NamedQubit('q0')
d = cirq.ProjectorString({})
np.testing.assert_allclose(
d.expectation_from_density_matrix(np.array([[1.0, 0.0], [0.0, 0.0]]),
{q0: 0}), 1.0)
def test_projector_repr():
q0 = cirq.NamedQubit('q0')
assert (
repr(cirq.ProjectorString({q0: 0})) ==
"cirq.ProjectorString(projector_dict={cirq.NamedQubit('q0'): 0},coefficient=(1+0j))"
)
def test_expectation_from_state_vector_basis_states_single_qubits():
q0 = cirq.NamedQubit('q0')
d = cirq.ProjectorString({q0: 0})
np.testing.assert_allclose(
d.expectation_from_state_vector(np.array([1.0, 0.0]), {q0: 0}), 1.0)
np.testing.assert_allclose(
d.expectation_from_state_vector(np.array([0.0, 1.0]), {q0: 0}), 0.0)
def test_projector_matrix_missing_qid():
q0, q1 = cirq.LineQubit.range(2)
proj = cirq.ProjectorString({q0: 0})
proj_with_coefficient = cirq.ProjectorString({q0: 0}, 1.23 + 4.56j)
np.testing.assert_allclose(proj.matrix().toarray(), np.diag([1.0, 0.0]))
np.testing.assert_allclose(
proj.matrix([q0]).toarray(), np.diag([1.0, 0.0]))
np.testing.assert_allclose(
proj.matrix([q1]).toarray(), np.diag([1.0, 1.0]))
np.testing.assert_allclose(
proj.matrix([q0, q1]).toarray(), np.diag([1.0, 1.0, 0.0, 0.0]))
np.testing.assert_allclose(
proj.matrix([q1, q0]).toarray(), np.diag([1.0, 0.0, 1.0, 0.0]))
np.testing.assert_allclose(
proj_with_coefficient.matrix([q1, q0]).toarray(),
np.diag([1.23 + 4.56j, 0.0, 1.23 + 4.56j, 0.0]),
)
def test_expectation_with_coefficient():
q0 = cirq.NamedQubit('q0')
d = cirq.ProjectorString({q0: 0}, coefficient=(0.6 + 0.4j))
np.testing.assert_allclose(
d.expectation_from_state_vector(np.array([[1.0, 0.0]]),
qid_map={q0: 0}), 0.6 + 0.4j)
np.testing.assert_allclose(
d.expectation_from_density_matrix(np.array([[1.0, 0.0], [0.0, 0.0]]),
{q0: 0}), 0.6 + 0.4j)
def test_consistency_state_vector_and_density_matrix():
q0 = cirq.NamedQubit('q0')
q1 = cirq.NamedQubit('q1')
q2 = cirq.NamedQubit('q2')
state_vector = cirq.testing.random_superposition(8)
state = np.einsum('i,j->ij', state_vector, np.conj(state_vector))
for proj_qubit in q0, q1, q2:
for proj_idx in [0, 1]:
d = cirq.ProjectorString({proj_qubit: proj_idx})
np.testing.assert_allclose(
d.expectation_from_state_vector(state_vector, {
q0: 0,
q1: 1,
q2: 2
}),
d.expectation_from_density_matrix(state, {
q0: 0,
q1: 1,
q2: 2
}),
)
def test_projector_from_np_array():
q0 = cirq.NamedQubit('q0')
zero_projector = cirq.ProjectorString({q0: 0})
np.testing.assert_allclose(zero_projector.matrix().toarray(),
[[1.0, 0.0], [0.0, 0.0]])
def test_expectation_from_density_matrix_three_qubits():
q0 = cirq.NamedQubit('q0')
q1 = cirq.NamedQubit('q1')
q2 = cirq.NamedQubit('q2')
d_1qbit = cirq.ProjectorString({q1: 1})
d_2qbits = cirq.ProjectorString({q0: 0, q1: 1})
state = cirq.testing.random_density_matrix(8)
# If the mapping of state is {q0: 0, q1: 1, q2: 2}, then the coefficients are:
# 0: (q0, q1, q2) = (0, 0, 0)
# 1: (q0, q1, q2) = (0, 0, 1)
# 2: (q0, q1, q2) = (0, 1, 0) -> Projected on
# 3: (q0, q1, q2) = (0, 1, 1) -> Projected on
# 4: (q0, q1, q2) = (1, 0, 0)
# 5: (q0, q1, q2) = (1, 0, 1)
# 6: (q0, q1, q2) = (1, 1, 0)
# 7: (q0, q1, q2) = (1, 1, 1)
np.testing.assert_allclose(
d_2qbits.expectation_from_density_matrix(state, {
q0: 0,
q1: 1,
q2: 2
}),
sum(state[i][i].real for i in [2, 3]),
)
# Same as above except it's only for q1=1, which happens for indices 2, 3, 6, and 7:
np.testing.assert_allclose(
d_1qbit.expectation_from_density_matrix(state, {
q0: 0,
q1: 1,
q2: 2
}),
sum(state[i][i].real for i in [2, 3, 6, 7]),
)
# Here we have a different mapping, but the idea is the same.
# 0: (q0 ,q2, q1) = (0, 0, 0)
# 1: (q0, q2, q1) = (0, 0, 1) -> Projected on
# 2: (q0, q2, q1) = (0, 1, 0)
# 3: (q0, q2, q1) = (0, 1, 1) -> Projected on
# 4: (q0, q2, q1) = (1, 0, 0)
# 5: (q0, q2, q1) = (1, 0, 1)
# 6: (q0, q2, q1) = (1, 1, 0)
# 7: (q0, q2, q1) = (1, 1, 1)
np.testing.assert_allclose(
d_2qbits.expectation_from_density_matrix(state, {
q0: 0,
q1: 2,
q2: 1
}),
sum(state[i][i].real for i in [1, 3]),
)
# Same as above except it's only for q1=1, which happens for indices 1, 3, 5, and 7:
np.testing.assert_allclose(
d_1qbit.expectation_from_density_matrix(state, {
q0: 0,
q1: 2,
q2: 1
}),
sum(state[i][i].real for i in [1, 3, 5, 7]),
)
