Hamiltonian split by stabilizers #545
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| raise TypeError('Input stabilizers must be QubitOperator or list.') | ||
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| stabilizer_list = list(copy.deepcopy(stabilizers)) | ||
| ham = copy.deepcopy(hamiltonian) |
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Why is it necessary to copy these two objects? It doesn't appear to me that you modify them anywhere.
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Hi Kevin,
Thanks for reviewing the PR, sorry that it took a while for me to update it.
Indeed, these objects are never modified, and hence there is no need to deepcopy them.
I'm going to remove the additional variable name as it is also redundant, but I'm happy to put it back.
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| def _check_stabilizer_overlap(pauli_op, stabilizer): | ||
| """ | ||
| Auxiliar function of get Hamiltonian subsets. |
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Corrected! Sorry about this.
| overlap = False | ||
| if qp[0] in qbts_in_stab: | ||
| overlap = True | ||
| return overlap |
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You can rewrite this function as
indices_in_pauli_op = {index for (index, _) in list(pauli_op.terms.keys())[0]}
indices_in_stabilizer = {index for (index, _) in list(stabilizer.terms.keys())[0]}
return not indices_in_pauli_op.isdisjoint(indices_in_stabilizer_op)
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Thanks for this piece of code, very simple and does the job. Changed!
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| def _check_missing_paulis(hamiltonian, subsets): | ||
| """ | ||
| Auxiliar function of Hamiltonian subset splitting. |
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Corrected! Sorry about this.
| from openfermion.ops import QubitOperator | ||
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| def _check_stabilizer_overlap(pauli_op, stabilizer): |
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This function doesn't really have anything to do with stabilizers. So rename it to _has_overlapping_indices(op1, op2), and remove references to stabilizers in the docstring.
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Indeed, the functions only aims to check if two Pauli operators have common qubits.
Updated name and docstring.
| op2(QubitOperator): Single Pauli string. | ||
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| Returns: | ||
| overlap (Boolean): True if the operator and stabilizer overlap. |
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This needs to be updated. "True if the operators have disjoint indices, False otherwise."
| """ | ||
| Auxiliary function of get Hamiltonian subsets. | ||
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| Check if two QubitOperators have any qubit in common. |
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This needs to be updated. I think a one-liner "Check if two operators have disjoint indices." is sufficient. Put it on the same line as the triple quotes.
| # Initialize subset | ||
| ham_subset = QubitOperator() | ||
| for pauli in hamiltonian: | ||
| if _has_disjoint_indices(pauli, stab) is True: |
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is True is unnecessary; remove it.
| try: | ||
| remaining_paulis.terms.pop(list(pauli.terms.keys())[0]) | ||
| except: | ||
| continue |
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Why is the try-except necessary? Isn't the Pauli here guaranteed to be inside `remaining_paulis'?
| return indices_in_op1.isdisjoint(indices_in_op2) | ||
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| def get_hamiltonian_subsets(hamiltonian, stabilizers): |
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These needs a more descriptive name
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Decided to close PR in last OF sync. Functional will be marginally useful. |
Hi all,
I split the PR that I submitted a couple of weeks ago.
Here I add a module that allows one to find the subsets of Pauli operators of a Hamiltonian that have support on a set of stabilizers.
The code comes fully documented and tested as requested by OpenFermion guidelines.
Best,
Xavi