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Merge pull request #91 from qiboteam/refactor-ham
Refactor molecular Hamiltonian code
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,7 +1 @@ | ||
| from qibochem.driver.hamiltonian import ( | ||
| fermionic_hamiltonian, | ||
| parse_pauli_string, | ||
| qubit_hamiltonian, | ||
| symbolic_hamiltonian, | ||
| ) | ||
| from qibochem.driver.molecule import Molecule |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,97 +1,68 @@ | ||
| """ | ||
| Functions for obtaining and transforming the molecular Hamiltonian | ||
| """ | ||
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| import openfermion | ||
| from qibo import hamiltonians | ||
| from qibo.symbols import X, Y, Z | ||
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| def fermionic_hamiltonian(oei, tei, constant): | ||
| """ | ||
| Build molecular Hamiltonian as an InteractionOperator using the 1-/2- electron integrals | ||
| Args: | ||
| oei: 1-electron integrals in the MO basis | ||
| tei: 2-electron integrals in 2ndQ notation and MO basis | ||
| constant: Nuclear-nuclear repulsion, and inactive Fock energy if HF embedding used | ||
| Returns: | ||
| Molecular Hamiltonian as an InteractionOperator | ||
| """ | ||
| oei_so, tei_so = openfermion.ops.representations.get_tensors_from_integrals(oei, tei) | ||
| # tei_so already multiplied by 0.5, no need to include in InteractionOperator | ||
| return openfermion.InteractionOperator(constant, oei_so, tei_so) | ||
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| def qubit_hamiltonian(fermion_hamiltonian, ferm_qubit_map): | ||
| """ | ||
| Converts the molecular Hamiltonian to a QubitOperator | ||
| Args: | ||
| fermion_hamiltonian: Molecular Hamiltonian as a InteractionOperator/FermionOperator | ||
| ferm_qubit_map: Which Fermion->Qubit mapping to use | ||
| Returns: | ||
| qubit_operator : Molecular Hamiltonian as a QubitOperator | ||
| """ | ||
| # Map the fermionic molecular Hamiltonian to a QubitHamiltonian | ||
| if ferm_qubit_map == "jw": | ||
| q_hamiltonian = openfermion.jordan_wigner(fermion_hamiltonian) | ||
| elif ferm_qubit_map == "bk": | ||
| q_hamiltonian = openfermion.bravyi_kitaev(fermion_hamiltonian) | ||
| else: | ||
| raise KeyError("Unknown fermion->qubit mapping!") | ||
| q_hamiltonian.compress() # Remove terms with v. small coefficients | ||
| return q_hamiltonian | ||
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| def parse_pauli_string(pauli_string, coeff): | ||
| """ | ||
| Helper function: Converts a single Pauli string to a Qibo Symbol | ||
| Args: | ||
| pauli_string (tuple of tuples): Indicate what gates to apply onto which qubit | ||
| e.g. ((0, 'Z'), (2, 'Z')) | ||
| coeff (float): Coefficient of the Pauli string | ||
| Returns: | ||
| qibo.symbols.Symbol for a single Pauli string, e.g. -0.04*X0*X1*Y2*Y3 | ||
| """ | ||
| # Dictionary for converting | ||
| xyz_to_symbol = {"X": X, "Y": Y, "Z": Z} | ||
| # Check that pauli_string is non-empty | ||
| if pauli_string: | ||
| # pauli_string format: ((0, 'Y'), (1, 'Y'), (3, 'X')) | ||
| qibo_pauli_string = 1.0 | ||
| for p_letter in pauli_string: | ||
| qibo_pauli_string *= xyz_to_symbol[p_letter[1]](p_letter[0]) | ||
| # Include coefficient after all symbols | ||
| qibo_pauli_string = coeff * qibo_pauli_string | ||
| else: | ||
| # Empty word, i.e. constant term in Hamiltonian | ||
| qibo_pauli_string = coeff | ||
| return qibo_pauli_string | ||
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| def symbolic_hamiltonian(q_hamiltonian): | ||
| """ | ||
| Converts a OpenFermion QubitOperator to a Qibo SymbolicHamiltonian | ||
| Args: | ||
| q_hamiltonian: QubitOperator | ||
| Returns: | ||
| qibo.hamiltonians.SymbolicHamiltonian | ||
| """ | ||
| # Sums over each individual Pauli string in the QubitOperator | ||
| symbolic_ham = sum( | ||
| parse_pauli_string(pauli_string, coeff) | ||
| # Iterate over all operators | ||
| for operator in q_hamiltonian.get_operators() | ||
| # .terms gives one operator as a dictionary with one entry | ||
| for pauli_string, coeff in operator.terms.items() | ||
| ) | ||
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| # Map the QubitHamiltonian to a Qibo SymbolicHamiltonian and return it | ||
| return hamiltonians.SymbolicHamiltonian(symbolic_ham) | ||
| """ | ||
| Functions for obtaining and transforming the molecular Hamiltonian | ||
| """ | ||
|
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| from functools import reduce | ||
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| import openfermion | ||
| from qibo import symbols | ||
| from qibo.hamiltonians import SymbolicHamiltonian | ||
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|
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||
| def fermionic_hamiltonian(oei, tei, constant): | ||
| """ | ||
| Build molecular Hamiltonian as an InteractionOperator using the 1-/2- electron integrals | ||
| Args: | ||
| oei: 1-electron integrals in the MO basis | ||
| tei: 2-electron integrals in 2ndQ notation and MO basis | ||
| constant: Nuclear-nuclear repulsion, and inactive Fock energy if HF embedding used | ||
| Returns: | ||
| Molecular Hamiltonian as an InteractionOperator | ||
| """ | ||
| oei_so, tei_so = openfermion.ops.representations.get_tensors_from_integrals(oei, tei) | ||
| # tei_so already multiplied by 0.5, no need to include in InteractionOperator | ||
| return openfermion.InteractionOperator(constant, oei_so, tei_so) | ||
|
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||
|
|
||
| def qubit_hamiltonian(fermion_hamiltonian, ferm_qubit_map): | ||
| """ | ||
| Converts the molecular Hamiltonian to a QubitOperator | ||
| Args: | ||
| fermion_hamiltonian: Molecular Hamiltonian as a InteractionOperator/FermionOperator | ||
| ferm_qubit_map: Which Fermion->Qubit mapping to use | ||
| Returns: | ||
| qubit_operator : Molecular Hamiltonian as a QubitOperator | ||
| """ | ||
| # Map the fermionic molecular Hamiltonian to a QubitHamiltonian | ||
| if ferm_qubit_map == "jw": | ||
| q_hamiltonian = openfermion.jordan_wigner(fermion_hamiltonian) | ||
| elif ferm_qubit_map == "bk": | ||
| q_hamiltonian = openfermion.bravyi_kitaev(fermion_hamiltonian) | ||
| else: | ||
| raise KeyError("Unknown fermion->qubit mapping!") | ||
| q_hamiltonian.compress() # Remove terms with v. small coefficients | ||
| return q_hamiltonian | ||
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| def qubit_to_symbolic_hamiltonian(q_hamiltonian): | ||
| """ | ||
| Converts a OpenFermion QubitOperator to a Qibo SymbolicHamiltonian | ||
| Args: | ||
| q_hamiltonian: QubitOperator | ||
| Returns: | ||
| qibo.hamiltonians.SymbolicHamiltonian | ||
| """ | ||
| symbolic_ham = sum( | ||
| reduce(lambda x, y: x * y, (getattr(symbols, pauli_op)(qubit) for qubit, pauli_op in pauli_string), coeff) | ||
| # Sums over each individual Pauli string in the QubitOperator | ||
| for operator in q_hamiltonian.get_operators() | ||
| # .terms gives one operator as a single-item dictionary, e.g. {((1: "X"), (2: "Y")): 0.33} | ||
| for pauli_string, coeff in operator.terms.items() | ||
| ) | ||
| return SymbolicHamiltonian(symbolic_ham) |
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