def test_fenwick_tree_ancestor_children(self):
"""Ancestor children test. Checks get_remainder_set(j) on 8 qubit
register.
Tests: Checks the example given in the paper."""
f = FenwickTree(16)
self.assertEqual(f.get_remainder_set(9)[0].index, 7)
def test_parity_set(self):
"""Test getting the parity set."""
f = FenwickTree(16)
for j in range(1, 16):
parity_set_nodes = f.get_parity_set(j)
parity_set = [node.index for node in parity_set_nodes]
correct = _parity_set(j - 1)
self.assertEqual(set(parity_set), set(correct))
print(parity_set)
def bravyi_kitaev(operator, n_qubits=None):
"""Apply the Bravyi-Kitaev transform and return qubit operator.
(arxiv1701.07072)
Args:
operator (openfermion.ops.FermionOperator):
A FermionOperator to transform.
n_qubits (int|None):
Can force the number of qubits in the resulting operator above the
number that appear in the input operator.
Returns:
transformed_operator: An instance of the QubitOperator class.
Raises:
ValueError: Invalid number of qubits specified.
"""
# Compute the number of qubits.
from openfermion.utils import count_qubits
if n_qubits is None:
n_qubits = count_qubits(operator)
if n_qubits < count_qubits(operator):
raise ValueError('Invalid number of qubits specified.')
# Build the Fenwick tree.
fenwick_tree = FenwickTree(n_qubits)
# Compute transformed operator.
transformed_terms = (_transform_operator_term(
term=term, coefficient=operator.terms[term], fenwick_tree=fenwick_tree)
for term in operator.terms)
return inline_sum(seed=QubitOperator(), summands=transformed_terms)
def test_fenwick_tree_structure(self):
"""A lookup test on 5-qubit fenwick tree.
Test: Verifies structure of the Fenwick Tree on 5 sites."""
f = FenwickTree(5)
self.assertEqual(f.root.children[0].index, 2)
self.assertEqual(f.root.children[1].index, 3)
self.assertEqual(f.root.children[0].children[0].index, 1)
self.assertEqual(f.root.children[0].children[0].children[0].index, 0)
def test_fenwick_tree_children(self):
"""Children test. Checks get_F(j) on 8 qubit register.
Test: Verifies integrity of child nodes of the root."""
f = FenwickTree(8)
self.assertEqual(f.get_node(7).children[0], f.get_node(3))
self.assertEqual(f.get_node(7).children[1], f.get_node(5))
self.assertEqual(f.get_node(7).children[2], f.get_node(6))
self.assertEqual(len(f.get_children_set(7)), 3)
def bravyi_kitaev_tree(operator, n_qubits=None):
"""Apply the "tree" Bravyi-Kitaev transform.
Implementation from arxiv:1701.07072
Note that this implementation is different from the one described in
arXiv:quant-ph/0003137. In particular, it gives different results
when the total number of modes is not a power of 2. The one described
in arXiv:quant-ph/0003137 is the same as the one described in
arXiv:1208.5986, and it is implemented in OpenFermion under the name
`bravyi_kitaev`.
Args:
operator (openfermion.ops.FermionOperator):
A FermionOperator to transform.
n_qubits (int|None):
Can force the number of qubits in the resulting operator above the
number that appear in the input operator.
Returns:
transformed_operator: An instance of the QubitOperator class.
Raises:
ValueError: Invalid number of qubits specified.
"""
# Compute the number of qubits.
from openfermion.utils import count_qubits
if n_qubits is None:
n_qubits = count_qubits(operator)
if n_qubits < count_qubits(operator):
raise ValueError('Invalid number of qubits specified.')
# Build the Fenwick tree.
fenwick_tree = FenwickTree(n_qubits)
# Compute transformed operator.
transformed_terms = (
_transform_operator_term(term=term,
coefficient=operator.terms[term],
fenwick_tree=fenwick_tree)
for term in operator.terms
)
return inline_sum(seed=QubitOperator(), summands=transformed_terms)
def test_fenwick_tree_ancestors(self):
"""Ancestor test. Check validity of the get_update_set(j) method on 8
qubit register. Note that root is the last node.
Test: Verifies integrity of ancestors of nodes within the tree."""
f = FenwickTree(8)
self.assertEqual(len(f.get_update_set(7)), 0)
# Is the parent of the middle child the root?
self.assertEqual(f.get_update_set(3)[0], f.root)
# Are the ancestors chained correctly?
self.assertEqual(f.get_update_set(0)[0], f.get_node(1))
self.assertEqual(f.get_update_set(0)[1], f.get_node(3))