def test_bravyi_kitaev_fast_number_excitation_operator(self):
# using hydrogen Hamiltonian and introducing some number operator terms
constant = 0
one_body = numpy.zeros((4, 4))
one_body[(0, 0)] = .4
one_body[(1, 1)] = .5
one_body[(2, 2)] = .6
one_body[(3, 3)] = .7
two_body = self.molecular_hamiltonian.two_body_tensor
# initiating number operator terms for all the possible cases
two_body[(1, 2, 3, 1)] = 0.1
two_body[(1, 3, 2, 1)] = 0.1
two_body[(1, 2, 1, 3)] = 0.15
two_body[(3, 1, 2, 1)] = 0.15
two_body[(0, 2, 2, 1)] = 0.09
two_body[(1, 2, 2, 0)] = 0.09
two_body[(1, 2, 3, 2)] = 0.11
two_body[(2, 3, 2, 1)] = 0.11
two_body[(2, 2, 2, 2)] = 0.1
molecular_hamiltonian = InteractionOperator(constant, one_body,
two_body)
# comparing the eigenspectrum of Hamiltonian
n_qubits = count_qubits(molecular_hamiltonian)
bravyi_kitaev_fast_H = bksf.bravyi_kitaev_fast(molecular_hamiltonian)
jw_H = jordan_wigner(molecular_hamiltonian)
bravyi_kitaev_fast_H_eig = eigenspectrum(bravyi_kitaev_fast_H)
jw_H_eig = eigenspectrum(jw_H)
bravyi_kitaev_fast_H_eig = bravyi_kitaev_fast_H_eig.round(5)
jw_H_eig = jw_H_eig.round(5)
evensector_H = 0
for i in range(numpy.size(jw_H_eig)):
if bool(
numpy.size(
numpy.where(jw_H_eig[i] == bravyi_kitaev_fast_H_eig))):
evensector_H += 1
# comparing eigenspectrum of number operator
bravyi_kitaev_fast_n = bksf.number_operator(molecular_hamiltonian)
jw_n = QubitOperator()
n_qubits = count_qubits(molecular_hamiltonian)
for i in range(n_qubits):
jw_n += jordan_wigner_one_body(i, i)
jw_eig_spec = eigenspectrum(jw_n)
bravyi_kitaev_fast_eig_spec = eigenspectrum(bravyi_kitaev_fast_n)
evensector_n = 0
for i in range(numpy.size(jw_eig_spec)):
if bool(
numpy.size(
numpy.where(
jw_eig_spec[i] == bravyi_kitaev_fast_eig_spec))):
evensector_n += 1
self.assertEqual(evensector_H, 2**(n_qubits - 1))
self.assertEqual(evensector_n, 2**(n_qubits - 1))
def test_bravyi_kitaev_fast_generate_fermions(self):
n_qubits = count_qubits(self.molecular_hamiltonian)
# test for generating two fermions
edge_matrix = bksf.bravyi_kitaev_fast_edge_matrix(
self.molecular_hamiltonian)
edge_matrix_indices = numpy.array(
numpy.nonzero(
numpy.triu(edge_matrix) - numpy.diag(numpy.diag(edge_matrix))))
fermion_generation_operator = bksf.generate_fermions(
edge_matrix_indices, 2, 3)
fermion_generation_sp_matrix = get_sparse_operator(
fermion_generation_operator)
fermion_generation_matrix = fermion_generation_sp_matrix.toarray()
bksf_vacuum_state_operator = bksf.vacuum_operator(edge_matrix_indices)
bksf_vacuum_state_sp_matrix = get_sparse_operator(
bksf_vacuum_state_operator)
bksf_vacuum_state_matrix = bksf_vacuum_state_sp_matrix.toarray()
vacuum_state = numpy.zeros((2**(n_qubits), 1))
vacuum_state[0] = 1.
bksf_vacuum_state = numpy.dot(bksf_vacuum_state_matrix, vacuum_state)
two_fermion_state = numpy.dot(fermion_generation_matrix,
bksf_vacuum_state)
# using total number operator to check the number of fermions generated
tot_number_operator = bksf.number_operator(self.molecular_hamiltonian)
number_operator_sp_matrix = get_sparse_operator(tot_number_operator)
number_operator_matrix = number_operator_sp_matrix.toarray()
tot_fermions = numpy.dot(
two_fermion_state.conjugate().T,
numpy.dot(number_operator_matrix, two_fermion_state))
# checking the occupation number of site 2 and 3
number_operator_2 = bksf.number_operator(self.molecular_hamiltonian, 2)
number_operator_3 = bksf.number_operator(self.molecular_hamiltonian, 3)
number_operator_23 = number_operator_2 + number_operator_3
number_operator_23_sp_matrix = get_sparse_operator(number_operator_23)
number_operator_23_matrix = number_operator_23_sp_matrix.toarray()
tot_23_fermions = numpy.dot(
two_fermion_state.conjugate().T,
numpy.dot(number_operator_23_matrix, two_fermion_state))
self.assertTrue(2.0 - float(tot_fermions.real) < 1e-13)
self.assertTrue(2.0 - float(tot_23_fermions.real) < 1e-13)
def test_bravyi_kitaev_fast_jw_number_operator(self):
# bksf algorithm allows for even number of particles. So, compare the
# spectrum of number operator from jordan-wigner and bksf algorithm
# to make sure half of the jordan-wigner number operator spectrum
# can be found in bksf number operator spectrum.
bravyi_kitaev_fast_n = bksf.number_operator(self.molecular_hamiltonian)
jw_n = QubitOperator()
n_qubits = count_qubits(self.molecular_hamiltonian)
for i in range(n_qubits):
jw_n += jordan_wigner_one_body(i, i)
jw_eig_spec = eigenspectrum(jw_n)
bravyi_kitaev_fast_eig_spec = eigenspectrum(bravyi_kitaev_fast_n)
evensector = 0
for i in range(numpy.size(jw_eig_spec)):
if bool(
numpy.size(
numpy.where(
jw_eig_spec[i] == bravyi_kitaev_fast_eig_spec))):
evensector += 1
self.assertEqual(evensector, 2**(n_qubits - 1))
def test_bravyi_kitaev_fast_excitation_terms(self):
# Testing on-site and excitation terms in Hamiltonian
constant = 0
one_body = numpy.array([[1, 2, 0, 3], [2, 1, 2, 0], [0, 2, 1, 2.5],
[3, 0, 2.5, 1]])
# No Coloumb interaction
two_body = numpy.zeros((4, 4, 4, 4))
molecular_hamiltonian = InteractionOperator(constant, one_body,
two_body)
n_qubits = count_qubits(molecular_hamiltonian)
# comparing the eigenspectrum of Hamiltonian
bravyi_kitaev_fast_H = bksf.bravyi_kitaev_fast(molecular_hamiltonian)
jw_H = jordan_wigner(molecular_hamiltonian)
bravyi_kitaev_fast_H_eig = eigenspectrum(bravyi_kitaev_fast_H)
jw_H_eig = eigenspectrum(jw_H)
bravyi_kitaev_fast_H_eig = bravyi_kitaev_fast_H_eig.round(5)
jw_H_eig = jw_H_eig.round(5)
evensector_H = 0
for i in range(numpy.size(jw_H_eig)):
if bool(
numpy.size(
numpy.where(jw_H_eig[i] == bravyi_kitaev_fast_H_eig))):
evensector_H += 1
# comparing eigenspectrum of number operator
bravyi_kitaev_fast_n = bksf.number_operator(molecular_hamiltonian)
jw_n = QubitOperator()
n_qubits = count_qubits(molecular_hamiltonian)
for i in range(n_qubits):
jw_n += jordan_wigner_one_body(i, i)
jw_eig_spec = eigenspectrum(jw_n)
bravyi_kitaev_fast_eig_spec = eigenspectrum(bravyi_kitaev_fast_n)
evensector_n = 0
for i in range(numpy.size(jw_eig_spec)):
if bool(
numpy.size(
numpy.where(
jw_eig_spec[i] == bravyi_kitaev_fast_eig_spec))):
evensector_n += 1
self.assertEqual(evensector_H, 2**(n_qubits - 1))
self.assertEqual(evensector_n, 2**(n_qubits - 1))