def test_expand_one(self):
"""Test that a 1 qubit gate correctly expands to 3 qubits."""
self.logTestName()
dev = DefaultQubit(wires=3)
# test applied to wire 0
res = dev.expand(U, [0])
expected = np.kron(np.kron(U, I), I)
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# test applied to wire 1
res = dev.expand(U, [1])
expected = np.kron(np.kron(I, U), I)
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# test applied to wire 2
res = dev.expand(U, [2])
expected = np.kron(np.kron(I, I), U)
self.assertAllAlmostEqual(res, expected, delta=self.tol)
def test_expand_two(self):
"""Test that a 2 qubit gate correctly expands to 3 qubits."""
self.logTestName()
dev = DefaultQubit(wires=4)
# test applied to wire 0+1
res = dev.expand(U2, [0, 1])
expected = np.kron(np.kron(U2, I), I)
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# test applied to wire 1+2
res = dev.expand(U2, [1, 2])
expected = np.kron(np.kron(I, U2), I)
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# test applied to wire 2+3
res = dev.expand(U2, [2, 3])
expected = np.kron(np.kron(I, I), U2)
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# CNOT with target on wire 1
res = dev.expand(CNOT, [1, 0])
rows = np.array([0, 2, 1, 3])
expected = np.kron(np.kron(CNOT[:, rows][rows], I), I)
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# test exception raised if unphysical subsystems provided
with self.assertRaisesRegex(ValueError, "Invalid target subsystems provided in 'wires' argument"):
dev.expand(U2, [-1, 5])
def test_expand_three(self):
"""Test that a 3 qubit gate correctly expands to 4 qubits."""
self.logTestName()
dev = DefaultQubit(wires=4)
# test applied to wire 0,1,2
res = dev.expand(U_toffoli, [0, 1, 2])
expected = np.kron(U_toffoli, I)
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# test applied to wire 1,2,3
res = dev.expand(U_toffoli, [1, 2, 3])
expected = np.kron(I, U_toffoli)
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# test applied to wire 0,2,3
res = dev.expand(U_toffoli, [0, 2, 3])
expected = np.kron(U_swap, np.kron(I, I)) @ np.kron(I, U_toffoli) @ np.kron(U_swap, np.kron(I, I))
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# test applied to wire 0,1,3
res = dev.expand(U_toffoli, [0, 1, 3])
expected = np.kron(np.kron(I, I), U_swap) @ np.kron(U_toffoli, I) @ np.kron(np.kron(I, I), U_swap)
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# test applied to wire 3, 1, 2
res = dev.expand(U_toffoli, [3, 1, 2])
# change the control qubit on the Toffoli gate
rows = np.array([0, 4, 1, 5, 2, 6, 3, 7])
expected = np.kron(I, U_toffoli[:, rows][rows])
self.assertAllAlmostEqual(res, expected, delta=self.tol)
# test applied to wire 3, 0, 2
res = dev.expand(U_toffoli, [3, 0, 2])
# change the control qubit on the Toffoli gate
rows = np.array([0, 4, 1, 5, 2, 6, 3, 7])
expected = np.kron(U_swap, np.kron(I, I)) @ np.kron(I, U_toffoli[:, rows][rows]) @ np.kron(U_swap, np.kron(I, I))
self.assertAllAlmostEqual(res, expected, delta=self.tol)