def get_qwc_group(H: QubitOperator):
'''
Return a list of qubit-wise commuting fragments of H
'''
# Preparing all terms in H into a list
qubit_ops = []
for pw, val in H.terms.items():
qubit_ops.append(QubitOperator(term=pw, coefficient=val))
n = len(qubit_ops)
# Making commutation matrix
comm_matrix = np.zeros((n, n))
for i in range(n):
for j in range(i + 1, n):
comm_matrix[i, j] = qubit_wise_commuting(qubit_ops[i],
qubit_ops[j])
# Compute commuting fragments
comm_matrix = np.identity(n) + comm_matrix + comm_matrix.T
colors = largest_first(1 - comm_matrix)
# Collect commuting fragments into a list of QubitOperators
qwc_list = []
qwc_list_idx = 0
for key, indices in colors.items():
qwc_list.append(QubitOperator.zero())
for idx in indices:
qwc_list[qwc_list_idx] += qubit_ops[idx]
qwc_list_idx += 1
return qwc_list
def get_commuting_group(H: QubitOperator):
'''
Get a dictionary of mutually commuting groups with terms in Hp
'''
n = get_number_qubit(H)
pws = []
pws_val = []
for pw, val in H.terms.items():
pws.append(pw)
pws_val.append(val)
binvecs = pauli2binvec(pws, n)
tnum = len(binvecs)
comm_matrix = np.zeros((tnum, tnum))
for i in range(tnum):
for j in range(i + 1, tnum):
comm_matrix[i, j] = 1 - anticommute(binvecs[i], binvecs[j])
comm_matrix = np.identity(tnum) + comm_matrix + comm_matrix.T
colors = largest_first(1 - comm_matrix)
dict = {}
for key, indices in colors.items():
dict[key] = QubitOperator.zero()
for idx in indices:
dict[key] += QubitOperator(term=pws[idx], coefficient=pws_val[idx])
return dict
def map_qubits(self, qubit_map: dict):
"""
E.G. X(1)Y(2) --> X(3)Y(1) with qubit_map = {1:3, 2:1}
Parameters
----------
qubit_map
a dictionary which maps old to new qubits
Returns
-------
the Hamiltonian with mapped qubits
"""
mapped_terms = {}
for k, v in self.qubit_operator.terms.items():
mk = tuple([(qubit_map[x[0]], x[1]) for x in k])
mapped_terms[mk] = v
mapped = QubitOperator.zero()
mapped.terms = mapped_terms
return QubitHamiltonian(qubit_operator=mapped)
def remove_complex(H: QubitOperator, tiny=1e-8):
'''
Removing near-zero complex coefficient
'''
real_h = QubitOperator.zero()
for term, val in H.terms.items():
if np.imag(val) < tiny:
val = np.real(val)
real_h += QubitOperator(term=term, coefficient=val)
return real_h
def benchmark_linear_qubit_operator(n_qubits, n_terms, processes=None):
"""Test speed with getting a linear operator from a Qubit Operator.
Args:
n_qubits: The number of qubits, implying the dimension of the operator
is 2 ** n_qubits.
n_terms: The number of terms in a qubit operator.
processes: The number of processors to use.
Returns:
runtime_operator: The time it takes to get the linear operator.
runtime_matvec: The time it takes to perform matrix multiplication.
"""
# Generates Qubit Operator with specified number of terms.
map_int_to_operator = {
0: 'X',
1: 'Y',
2: 'Z',
}
qubit_operator = QubitOperator.zero()
for _ in range(n_terms):
tuples = []
for i in range(n_qubits):
operator = numpy.random.randint(4)
# 3 is 'I', so just skip.
if operator > 2:
continue
tuples.append((i, map_int_to_operator[operator]))
if tuples:
qubit_operator += QubitOperator(tuples, 1.00)
# Gets an instance of (Parallel)LinearQubitOperator.
start = time.time()
if processes is None:
linear_operator = LinearQubitOperator(qubit_operator, n_qubits)
else:
linear_operator = ParallelLinearQubitOperator(
qubit_operator, n_qubits,
LinearQubitOperatorOptions(processes=processes))
end = time.time()
runtime_operator = end - start
vec = numpy.random.rand(2**n_qubits)
# Performs matrix multiplication.
start = time.time()
_ = linear_operator * vec
end = time.time()
runtime_matvec = end - start
return runtime_operator, runtime_matvec
def __init__(self, qubit_hamiltonian: typing.Union[QubitOperator, str, numbers.Number] = None):
"""
Initialize from string or from a preexisting OpenFermion QubitOperator instance
:param qubit_hamiltonian: string or openfermion.QubitOperator
if string: Same conventions as openfermion
if None: The Hamiltonian is initialized as identity operator
if Number: initialized as scaled unit operator
"""
if isinstance(qubit_hamiltonian, str):
self._qubit_operator = self.from_string(string=qubit_hamiltonian)._qubit_operator
elif qubit_hamiltonian is None:
self._qubit_operator = QubitOperator.zero()
elif isinstance(qubit_hamiltonian, numbers.Number):
self._qubit_operator = qubit_hamiltonian * QubitOperator.identity()
else:
self._qubit_operator = qubit_hamiltonian
assert (isinstance(self._qubit_operator, QubitOperator))