def to_autograd(self):
"""Apply the Autograd interface to the internal quantum tape."""
self.interface = "autograd"
self.dtype = AutogradInterface.dtype
if self.qtape is not None:
AutogradInterface.apply(self.qtape)
def cost(a, b, device):
with AutogradInterface.apply(QuantumTape()) as tape:
qml.RY(a, wires=0)
qml.RX(b, wires=0)
expval(qml.PauliZ(0))
assert tape.trainable_params == {0}
return tape.execute(device)
def cost(x, device):
with AutogradInterface.apply(QuantumTape()) as tape:
qml.Hadamard(wires=[0])
qml.CNOT(wires=[0, 1])
sample(qml.PauliZ(0))
sample(qml.PauliX(1))
return tape.execute(device)
def test_interface_str(self):
"""Test that the interface string is correctly identified as autograd"""
with AutogradInterface.apply(QuantumTape()) as tape:
qml.RX(0.5, wires=0)
expval(qml.PauliX(0))
assert tape.interface == "autograd"
assert isinstance(tape, AutogradInterface)
def cost(a, device):
with AutogradInterface.apply(QuantumTape()) as qtape:
qml.RY(a[0], wires=0)
qml.RX(a[1], wires=0)
expval(qml.PauliZ(0))
qtape.jacobian_options = {"h": 1e-8, "order": 2}
return qtape.execute(dev)
def cost(x, y, device):
with AutogradInterface.apply(QuantumTape()) as tape:
qml.RX(x, wires=[0])
qml.RY(y, wires=[1])
qml.CNOT(wires=[0, 1])
expval(qml.PauliZ(0))
probs(wires=[1])
return tape.execute(device)
def test_get_parameters(self):
"""Test that the get_parameters function correctly sets and returns the
trainable parameters"""
a = np.array(0.1, requires_grad=True)
b = np.array(0.2, requires_grad=False)
c = np.array(0.3, requires_grad=True)
d = np.array(0.4, requires_grad=False)
with AutogradInterface.apply(QuantumTape()) as tape:
qml.Rot(a, b, c, wires=0)
qml.RX(d, wires=1)
qml.CNOT(wires=[0, 1])
expval(qml.PauliX(0))
assert tape.trainable_params == {0, 2}
assert np.all(tape.get_parameters() == [a, c])
def cost_fn(a, p, device):
tape = QuantumTape()
with tape:
qml.RX(a, wires=0)
U3(*p, wires=0)
expval(qml.PauliX(0))
tape = AutogradInterface.apply(tape.expand())
assert tape.trainable_params == {1, 2, 3, 4}
assert [i.name
for i in tape.operations] == ["RX", "Rot", "PhaseShift"]
assert np.all(
np.array(tape.get_parameters()) ==
[p[2], p[0], -p[2], p[1] + p[2]])
return tape.execute(device=device)
def test_reusing_quantum_tape(self, tol):
"""Test re-using a quantum tape by passing new parameters"""
a = np.array(0.1, requires_grad=True)
b = np.array(0.2, requires_grad=True)
dev = qml.device("default.qubit", wires=2)
with AutogradInterface.apply(QuantumTape()) as tape:
qml.RY(a, wires=0)
qml.RX(b, wires=1)
qml.CNOT(wires=[0, 1])
expval(qml.PauliZ(0))
expval(qml.PauliY(1))
assert tape.trainable_params == {0, 1}
def cost(a, b):
tape.set_parameters([a, b])
return tape.execute(dev)
jac_fn = qml.jacobian(cost)
jac = jac_fn(a, b)
a = np.array(0.54, requires_grad=True)
b = np.array(0.8, requires_grad=True)
res2 = cost(2 * a, b)
expected = [np.cos(2 * a), -np.cos(2 * a) * np.sin(b)]
assert np.allclose(res2, expected, atol=tol, rtol=0)
jac_fn = qml.jacobian(lambda a, b: cost(2 * a, b))
jac = jac_fn(a, b)
expected = [
[-2 * np.sin(2 * a), 0],
[2 * np.sin(2 * a) * np.sin(b), -np.cos(2 * a) * np.cos(b)],
]
assert np.allclose(jac, expected, atol=tol, rtol=0)