class TestReset:
"""Unit tests for the method `reset()`"""
def test_reset_basis(self, nr_wires, tol):
dev = qml.device("default.mixed", wires=nr_wires)
dev._state = dev._create_basis_state(1)
dev.reset()
assert np.allclose(dev._state,
dev._create_basis_state(0),
atol=tol,
rtol=0)
@pytest.mark.parametrize("op", [CNOT, CZ])
def test_reset_after_twoqubit(self, nr_wires, op, tol):
"""Tests that state is correctly reset after applying two-qubit operations on the first
wires"""
dev = qml.device("default.mixed", wires=nr_wires)
dev.apply([op(wires=[0, 1])])
dev.reset()
assert np.allclose(dev._state,
dev._create_basis_state(0),
atol=tol,
rtol=0)
@pytest.mark.parametrize(
"op",
[
AmplitudeDamping(0.5, wires=[0]),
DepolarizingChannel(0.5, wires=[0]),
ResetError(0.1, 0.5, wires=[0]),
PauliError("X", 0.5, wires=0),
PauliError("ZY", 0.3, wires=[1, 0]),
],
)
def test_reset_after_channel(self, nr_wires, op, tol):
"""Tests that state is correctly reset after applying a channel on the first
wires"""
dev = qml.device("default.mixed", wires=nr_wires)
dev.apply([op])
dev.reset()
assert np.allclose(dev._state,
dev._create_basis_state(0),
atol=tol,
rtol=0)
@pytest.mark.parametrize("op", [PauliX, PauliZ, Hadamard])
def test_reset_after_channel(self, nr_wires, op, tol):
"""Tests that state is correctly reset after applying gates on the first
wire"""
dev = qml.device("default.mixed", wires=nr_wires)
dev.apply([op(wires=0)])
dev.reset()
assert np.allclose(dev._state,
dev._create_basis_state(0),
atol=tol,
rtol=0)
def test_max_mixed_state(self, nr_wires, tol):
"""Tests that applying damping channel on all qubits to the state |11...1> produces a
maximally mixed state"""
dev = qml.device("default.mixed", wires=nr_wires)
flips = [PauliX(i) for i in range(nr_wires)]
damps = [AmplitudeDamping(0.5, wires=i) for i in range(nr_wires)]
ops = flips + damps
dev.apply(ops)
assert np.allclose(dev.state, max_mixed_state(nr_wires), atol=tol, rtol=0)
class TestKrausOps:
"""Unit tests for the method `_get_kraus_ops()`"""
unitary_ops = [
(PauliX, np.array([[0, 1], [1, 0]])),
(Hadamard, np.array([[INV_SQRT2, INV_SQRT2], [INV_SQRT2,
-INV_SQRT2]])),
(CNOT,
np.array([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 0, 1], [0, 0, 1, 0]])),
]
@pytest.mark.parametrize("ops", unitary_ops)
def test_unitary_kraus(self, ops, tol):
"""Tests that matrices of non-diagonal unitary operations are retrieved correctly"""
dev = qml.device("default.mixed", wires=2)
assert np.allclose(dev._get_kraus(ops[0]), [ops[1]], atol=tol, rtol=0)
diagonal_ops = [
(PauliZ(wires=0), np.array([1, -1])),
(CZ(wires=[0, 1]), np.array([1, 1, 1, -1])),
]
@pytest.mark.parametrize("ops", diagonal_ops)
def test_diagonal_kraus(self, ops, tol):
"""Tests that matrices of non-diagonal unitary operations are retrieved correctly"""
dev = qml.device("default.mixed", wires=2)
assert np.allclose(dev._get_kraus(ops[0]), ops[1], atol=tol, rtol=0)
p = 0.5
K0 = np.sqrt(1 - p) * np.eye(2)
K1 = np.sqrt(p / 3) * np.array([[0, 1], [1, 0]])
K2 = np.sqrt(p / 3) * np.array([[0, -1j], [1j, 0]])
K3 = np.sqrt(p / 3) * np.array([[1, 0], [0, -1]])
channel_ops = [
(
AmplitudeDamping(p, wires=0),
[
np.diag([1, np.sqrt(1 - p)]),
np.sqrt(p) * np.array([[0, 1], [0, 0]])
],
),
(DepolarizingChannel(p, wires=0), [K0, K1, K2, K3]),
]
@pytest.mark.parametrize("ops", channel_ops)
def test_channel_kraus(self, ops, tol):
"""Tests that kraus matrices of non-unitary channels are retrieved correctly"""
dev = qml.device("default.mixed", wires=1)
assert np.allclose(dev._get_kraus(ops[0]), ops[1], atol=tol, rtol=0)
class TestState:
"""Tests for the method `state()`, which retrieves the state of the system"""
def test_shape(self, nr_wires):
"""Tests that the state has the correct shape"""
dev = qml.device("default.mixed", wires=nr_wires)
assert (2**nr_wires, 2**nr_wires) == np.shape(dev.state)
def test_init_state(self, nr_wires, tol):
"""Tests that the state is |0...0><0...0| after initialization of the device"""
rho = np.zeros((2**nr_wires, 2**nr_wires))
rho[0, 0] = 1
dev = qml.device("default.mixed", wires=nr_wires)
assert np.allclose(rho, dev.state, atol=tol, rtol=0)
@pytest.mark.parametrize("op", [CNOT, CZ])
def test_state_after_twoqubit(self, nr_wires, op, tol):
"""Tests that state is correctly retrieved after applying two-qubit operations on the
first wires"""
dev = qml.device("default.mixed", wires=nr_wires)
dev.apply([op(wires=[0, 1])])
current_state = np.reshape(dev._state, (2**nr_wires, 2**nr_wires))
assert np.allclose(dev.state, current_state, atol=tol, rtol=0)
@pytest.mark.parametrize(
"op",
[
AmplitudeDamping(0.5, wires=0),
DepolarizingChannel(0.5, wires=0),
ResetError(0.1, 0.5, wires=0),
PauliError("X", 0.5, wires=0),
PauliError("ZY", 0.3, wires=[1, 0]),
],
)
def test_state_after_channel(self, nr_wires, op, tol):
"""Tests that state is correctly retrieved after applying a channel on the first wires"""
dev = qml.device("default.mixed", wires=nr_wires)
dev.apply([op])
current_state = np.reshape(dev._state, (2**nr_wires, 2**nr_wires))
assert np.allclose(dev.state, current_state, atol=tol, rtol=0)
@pytest.mark.parametrize("op", [PauliX, PauliZ, Hadamard])
def test_state_after_gate(self, nr_wires, op, tol):
"""Tests that state is correctly retrieved after applying operations on the first wires"""
dev = qml.device("default.mixed", wires=nr_wires)
dev.apply([op(wires=0)])
current_state = np.reshape(dev._state, (2**nr_wires, 2**nr_wires))
assert np.allclose(dev.state, current_state, atol=tol, rtol=0)
class TestApplyChannel:
"""Unit tests for the method `_apply_channel()`"""
x_apply_channel_init = [
[1, PauliX, basis_state(1, 1)],
[
1, Hadamard,
np.array([[0.5 + 0.0j, 0.5 + 0.0j], [0.5 + 0.0j, 0.5 + 0.0j]])
],
[2, CNOT, basis_state(0, 2)],
[1, AmplitudeDamping(0.5, wires=0),
basis_state(0, 1)],
[
1,
DepolarizingChannel(0.5, wires=0),
np.array([[2 / 3 + 0.0j, 0.0 + 0.0j], [0.0 + 0.0j, 1 / 3 + 0.0j]]),
],
[
1,
ResetError(0.1, 0.5, wires=0),
np.array([[0.5 + 0.0j, 0.0 + 0.0j], [0.0 + 0.0j, 0.5 + 0.0j]]),
],
]
@pytest.mark.parametrize("x", x_apply_channel_init)
def test_channel_init(self, x, tol):
"""Tests that channels are correctly applied to the default initial state"""
nr_wires = x[0]
op = x[1]
target_state = np.reshape(x[2], [2] * 2 * nr_wires)
dev = qml.device("default.mixed", wires=nr_wires)
kraus = dev._get_kraus(op)
if op == CNOT:
dev._apply_channel(kraus, wires=Wires([0, 1]))
else:
dev._apply_channel(kraus, wires=Wires(0))
assert np.allclose(dev._state, target_state, atol=tol, rtol=0)
x_apply_channel_mixed = [
[1, PauliX, max_mixed_state(1)],
[2, Hadamard, max_mixed_state(2)],
[2, CNOT, max_mixed_state(2)],
[
1,
AmplitudeDamping(0.5, wires=0),
np.array([[0.75 + 0.0j, 0.0 + 0.0j], [0.0 + 0.0j, 0.25 + 0.0j]]),
],
[
1,
DepolarizingChannel(0.5, wires=0),
np.array([[0.5 + 0.0j, 0.0 + 0.0j], [0.0 + 0.0j, 0.5 + 0.0j]]),
],
[
1,
ResetError(0.1, 0.5, wires=0),
np.array([[0.3 + 0.0j, 0.0 + 0.0j], [0.0 + 0.0j, 0.7 + 0.0j]]),
],
]
@pytest.mark.parametrize("x", x_apply_channel_mixed)
def test_channel_mixed(self, x, tol):
"""Tests that channels are correctly applied to the maximally mixed state"""
nr_wires = x[0]
op = x[1]
target_state = np.reshape(x[2], [2] * 2 * nr_wires)
dev = qml.device("default.mixed", wires=nr_wires)
max_mixed = np.reshape(max_mixed_state(nr_wires), [2] * 2 * nr_wires)
dev._state = max_mixed
kraus = dev._get_kraus(op)
if op == CNOT:
dev._apply_channel(kraus, wires=Wires([0, 1]))
else:
dev._apply_channel(kraus, wires=Wires(0))
assert np.allclose(dev._state, target_state, atol=tol, rtol=0)
x_apply_channel_root = [
[
1, PauliX,
np.array([[0.5 + 0.0j, -0.5 + 0.0j], [-0.5 - 0.0j, 0.5 + 0.0j]])
],
[
1, Hadamard,
np.array([[0.0 + 0.0j, 0.0 + 0.0j], [0.0 + 0.0j, 1.0 + 0.0j]])
],
[
2,
CNOT,
np.array([
[0.25 + 0.0j, 0.0 - 0.25j, 0.0 + 0.25j, -0.25],
[0.0 + 0.25j, 0.25 + 0.0j, -0.25 + 0.0j, 0.0 - 0.25j],
[0.0 - 0.25j, -0.25 + 0.0j, 0.25 + 0.0j, 0.0 + 0.25j],
[-0.25 + 0.0j, 0.0 + 0.25j, 0.0 - 0.25j, 0.25 + 0.0j],
]),
],
[
1,
AmplitudeDamping(0.5, wires=0),
np.array([[0.75 + 0.0j, -0.35355339 - 0.0j],
[-0.35355339 + 0.0j, 0.25 + 0.0j]]),
],
[
1,
DepolarizingChannel(0.5, wires=0),
np.array([[0.5 + 0.0j, -1 / 6 + 0.0j], [-1 / 6 + 0.0j,
0.5 + 0.0j]]),
],
[
1,
ResetError(0.1, 0.5, wires=0),
np.array([[0.3 + 0.0j, -0.2 + 0.0j], [-0.2 + 0.0j, 0.7 + 0.0j]]),
],
]
@pytest.mark.parametrize("x", x_apply_channel_root)
def test_channel_root(self, x, tol):
"""Tests that channels are correctly applied to root state"""
nr_wires = x[0]
op = x[1]
target_state = np.reshape(x[2], [2] * 2 * nr_wires)
dev = qml.device("default.mixed", wires=nr_wires)
root = np.reshape(root_state(nr_wires), [2] * 2 * nr_wires)
dev._state = root
kraus = dev._get_kraus(op)
if op == CNOT:
dev._apply_channel(kraus, wires=Wires([0, 1]))
else:
dev._apply_channel(kraus, wires=Wires(0))
assert np.allclose(dev._state, target_state, atol=tol, rtol=0)