def test_multi_thread(self):
"""Test that multi-threaded queuing works correctly"""
n_qubits = 4
n_batches = 5
dev = qml.device("default.qubit", wires=n_qubits)
def circuit(inputs, weights):
for index, input in enumerate(inputs):
qml.RY(input, wires=index)
for index in range(n_qubits - 1):
qml.CNOT(wires=(index, index + 1))
for index, weight in enumerate(weights):
qml.RX(weight, wires=index)
return [qml.expval(qml.PauliZ(wires=i)) for i in range(n_qubits)]
weight_shapes = {"weights": (n_qubits)}
try:
qnode = QNodeCollection(
[QNode(circuit, dev) for _ in range(n_batches)])
except Exception as e:
pytest.fail("QNodeCollection cannot be instantiated")
x = np.random.rand(n_qubits).astype(np.float64)
p = np.random.rand(weight_shapes["weights"]).astype(np.float64)
try:
for _ in range(10):
qnode(x, p, parallel=True)
except:
pytest.fail("Multi-threading on QuantumTape failed")
def test_error_backprop_wrong_interface(self, interface, tol):
"""Tests that an error is raised if diff_method='backprop' but not using
the Autograd interface"""
dev = qml.device("default.qubit.autograd", wires=1)
def circuit(x, w=None):
qml.RZ(x, wires=w)
return qml.expval(qml.PauliX(w))
with pytest.raises(
qml.QuantumFunctionError,
match="default.qubit.autograd only supports diff_method='backprop' when using the autograd interface",
):
qml.qnode(dev, diff_method="backprop", interface=interface)(circuit)
def test_error_backprop_wrong_interface(self, interface, tol):
"""Tests that an error is raised if diff_method='backprop' but not using
the Jax interface"""
dev = qml.device("default.qubit.jax", wires=1)
def circuit(x, w=None):
qml.RZ(x, wires=w)
return qml.expval(qml.PauliX(w))
error_type = qml.QuantumFunctionError if qml.tape_mode_active(
) else ValueError
with pytest.raises(
error_type,
match=
"default.qubit.jax only supports diff_method='backprop' when using the jax interface",
):
qml.qnode(dev, diff_method="backprop",
interface=interface)(circuit)
def test_operator_all_wires(self, monkeypatch, tol):
"""Test that an operator that must act on all wires
does, or raises an error."""
monkeypatch.setattr(qml.RX, "num_wires", qml.operation.AllWires)
def circuit(x):
qml.RX(x, wires=0)
return qml.expval(qml.PauliZ(0))
dev = qml.device("default.qubit", wires=2)
qnode = QNode(circuit, dev)
with pytest.raises(qml.QuantumFunctionError, match="Operator RX must act on all wires"):
qnode(0.5)
dev = qml.device("default.qubit", wires=1)
qnode = QNode(circuit, dev)
assert np.allclose(qnode(0.5), np.cos(0.5), atol=tol, rtol=0)
def test_no_jax_interface_applied(self):
"""Tests that the JAX interface is not applied and no error is raised if qml.probs is used with the Jax
interface when diff_method='backprop'
When the JAX interface is applied, we can only get the expectation value and the variance of a QNode.
"""
dev = qml.device("default.qubit.jax", wires=1, shots=None)
def circuit():
return qml.probs(wires=0)
qnode = qml.qnode(dev, diff_method="backprop", interface="jax")(circuit)
assert jnp.allclose(qnode(), jnp.array([1, 0]))
