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freeze_orbitals reflects the prune flag #803

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merged 5 commits into from
Aug 7, 2023
Merged

freeze_orbitals reflects the prune flag #803

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870ad07
Update operator_tapering.py
mafaldaramoa Sep 23, 2022
c469caf
Update operator_tapering.py
mafaldaramoa Sep 23, 2022
b47ceec
Update operator_tapering.py
mafaldaramoa Sep 23, 2022
53c1346
Merge branch 'master' into master
mpharrigan Aug 4, 2023
b1509f7
Merge branch 'master' into master
mpharrigan Aug 7, 2023
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15 changes: 9 additions & 6 deletions src/openfermion/transforms/repconversions/operator_tapering.py
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Original file line number Diff line number Diff line change
Expand Up @@ -21,16 +21,18 @@
def freeze_orbitals(fermion_operator, occupied, unoccupied=None, prune=True):
"""Fix some orbitals to be occupied and others unoccupied.

Removes all operators acting on the specified orbitals, and renumbers the
remaining orbitals to eliminate unused indices. The sign of each term
is modified according to the ladder uperator anti-commutation relations in
order to preserve the expectation value of the operator.
Removes all operators acting on the specified orbitals, and optionally
renumbers the remaining orbitals to eliminate unused indices. The sign of
each term is modified according to the ladder operator anti-commutation
relations in order to preserve the expectation value of the operator.

Args:
occupied: A list containing the indices of the orbitals that are to be
assumed to be occupied.
unoccupied: A list containing the indices of the orbitals that are to
be assumed to be unoccupied.
prune: A flag that determines whether the orbitals will be renumbered to
eliminate unused indices.
"""
new_operator = fermion_operator
frozen = [(index, 1) for index in occupied]
Expand Down Expand Up @@ -81,8 +83,9 @@ def freeze_orbitals(fermion_operator, occupied, unoccupied=None, prune=True):
if op[0] > index:
new_operator.terms[term] *= -1

# Renumber indices to remove frozen orbitals
new_operator = prune_unused_indices(new_operator)
if prune:
# Renumber indices to remove frozen orbitals
new_operator = prune_unused_indices(new_operator)

return new_operator

Expand Down