def test_invalid_n_mean(self):
"""Test if function raises a ``ValueError`` when the mean photon number is specified to
be negative."""
g = nx.complete_graph(5)
with pytest.raises(ValueError,
match="Mean photon number must be non-negative"):
similarity.prob_orbit_exact(g, [1, 1, 1, 1], n_mean=-1)
def test_invalid_loss(self):
"""Test if function raises a ``ValueError`` when the loss parameter is specified outside
of range."""
g = nx.complete_graph(5)
with pytest.raises(
ValueError,
match="Loss parameter must take a value between zero and one"):
similarity.prob_orbit_exact(g, [1, 1, 1, 1], loss=2)
def test_known_result(self):
"""Tests if the probability for known cases is correctly
reproduced."""
g = nx.complete_graph(3)
p = similarity.prob_orbit_exact(g, [1, 1], 2)
assert np.allclose(p, 0.24221526825385403)
s = similarity._get_state(g, 2)
temp = s.fock_prob([1, 1, 0]) + s.fock_prob([1, 0, 1]) + s.fock_prob(
[0, 1, 1])
assert np.allclose(p, temp)
assert np.allclose(similarity.prob_orbit_exact(g, [4], 1), 0)
def test_known_result(self):
"""Tests if the probability for known cases is correctly
reproduced."""
graph = nx.complete_graph(4)
p1 = similarity.prob_event_exact(graph, 2, 2, 1)
p2 = similarity.prob_event_exact(graph, 2, 1, 1)
p3 = similarity.prob_orbit_exact(graph, [1, 1], 1)
p4 = similarity.prob_event_exact(graph, 2, 2, 4)
assert np.allclose(p1 - p2, 0)
assert np.allclose(p2, p3)
assert np.allclose(p4, 0.21087781178526066)
def test_correct_result_returned(self, monkeypatch):
"""Tests if the call to _get_state function is performed correctly and probabilities over all
permutations of the given orbit are summed correctly. The test monkeypatches the fock_prob
function so that the probability is the same for each sample permutation and
is equal to 1/8. For a 4-mode graph, [1, 1] has 6 possible permutations."""
graph = nx.complete_graph(4)
with monkeypatch.context() as m:
m.setattr(
"strawberryfields.backends.BaseGaussianState.fock_prob",
lambda *args, **kwargs: 1 / 8,
)
assert similarity.prob_orbit_exact(graph, [1, 1]) == 6 / 8
def test_calls_exact_for_zero_samples(self):
"""Test if function calls the exact function for zero samples"""
g = nx.complete_graph(5)
assert similarity.feature_vector_orbits(
g, [[1, 1]], samples=0) == similarity.prob_orbit_exact(g, [1, 1])
def test_odd_photon_numbers(self, k):
"""Test if function returns zero probability for odd number of total photons."""
graph = nx.complete_graph(10)
assert similarity.prob_orbit_exact(graph, [k]) == 0.0
def test_prob_vacuum_orbit(self):
"""Tests if the function gives the right probability for the empty orbit when the GBS
device has been configured to have zero mean photon number."""
graph = nx.complete_graph(5)
assert similarity.prob_orbit_exact(graph, [], 0) == 1.0
