quri_parts.chem.transforms package#

class quri_parts.chem.transforms.FermionCreationTerm(indices: Sequence[int], coef: complex = 1.0)#

Bases: object

Represents a term for creating a single Fermionic Fock state with a coefficient.

indices specify indices of occupied spin orbitals. The orbitals should be indexed in an alternating order of up and down spins (especially important when using symmetry-conserving Bravyi-Kitaev mapping). The order of indices in indices corresponds to the order of Fermionic creation operators. Therefore this class also contains information about a sign coming from ordering of creation operators.

quri_parts.chem.transforms.FermionQubitStateMapper#

Interface for a function that maps a collection of occupied spin orbital indices to a computational basis state of qubits. Note that the mapping does not depend on the order of the occupied indices. A computational basis state with a positive sign should always be returned.

alias of Callable[[Collection[int]], ComputationalBasisState]

quri_parts.chem.transforms.QubitFermionStateMapper#

Interface for a function that maps a computational basis state of qubits to a collection of occupied spin orbital indices.

alias of Callable[[ComputationalBasisState], Collection[int]]

class quri_parts.chem.transforms.FermionQubitMapping(*args, **kwargs)#

Bases: Protocol

Mapping from Fermionic states to qubit states.

abstract n_qubits_required(n_spin_orbitals: int) → int#: Returns a number of qubits the mapping requires for a given number of spin orbitals.

abstract n_spin_orbitals(n_qubits: int) → int#: Returns a number of spin orbitals that the mapping can represent with a given number of qubits.

abstract get_state_mapper(n_spin_orbitals: int, n_fermions: int | None = None) → Callable[[Collection[int]], ComputationalBasisState]#

Returns a function that maps occupied spin orbital indices to a computational basis state of qubits.

Parameters:

n_spin_orbitals – The number of spin orbitals to be mapped to qubits.
n_fermions – When specified, restrict the mapping to a subspace spanned by states containing the fixed number of Fermions. Some mappings require this argument (e.g. symmetry-conserving Bravyi-Kitaev transformation) while the others ignore it.

abstract get_inv_state_mapper(n_spin_orbitals: int, n_fermions: int | None = None, n_up_spins: int | None = None) → Callable[[ComputationalBasisState], Collection[int]]#

Returns a function that maps a computational basis state of qubits to the set of occupied spin orbital indices.

Parameters:

n_spin_orbitals – The number of spin orbitals.
n_fermions – The number of fermions considered when the qubit state is mapped. Some mappings require this argument (e.g. symmetry-conserving Bravyi-Kitaev transformation) while the others ignore it.
n_up_spins – The number of spin-up electrons.

class quri_parts.chem.transforms.JordanWigner(*args, **kwargs)#

Bases: FermionQubitMapping, ABC

Jordan-Wigner transformation.

n_qubits_required(n_spin_orbitals: int) → int#: Returns a number of qubits the mapping requires for a given number of spin orbitals.

n_spin_orbitals(n_qubits: int) → int#: Returns a number of spin orbitals that the mapping can represent with a given number of qubits.

class quri_parts.chem.transforms.BravyiKitaev(*args, **kwargs)#

Bases: FermionQubitMapping, ABC

Bravyi-Kitaev transformation.

n_qubits_required(n_spin_orbitals: int) → int#: Returns a number of qubits the mapping requires for a given number of spin orbitals.

n_spin_orbitals(n_qubits: int) → int#: Returns a number of spin orbitals that the mapping can represent with a given number of qubits.

class quri_parts.chem.transforms.SymmetryConservingBravyiKitaev(*args, **kwargs)#

Bases: FermionQubitMapping, ABC

Symmetry-conserving Bravyi-Kitaev transformation described in arXiv:1701.08213.

Note that in this mapping the spin orbital indices are first reordered to all spin-up orbitals, then all spin-down orbitals. Bravyi-Kitaev transoformation is applied after the reordering and then two qubits are dropped using conservation of particle number and spin.

n_qubits_required(n_spin_orbitals: int) → int#: Returns a number of qubits the mapping requires for a given number of spin orbitals.

n_spin_orbitals(n_qubits: int) → int#: Returns a number of spin orbitals that the mapping can represent with a given number of qubits.