qiskit.chemistry.BosonicOperator
class BosonicOperator(h, basis)
A set of functions to map bosonic Hamiltonians to qubit Hamiltonians.
References:
- Veis Libor, et al., International Journal of Quantum Chemistry 116.18 (2016): 1328-1336.
- McArdle Sam, et al., Chemical science 10.22 (2019): 5725-5735.
- Ollitrault Pauline J., Chemical science 11 (2020): 6842-6855.
The Bosonic operator in this class is written in the n-mode second quantization format (Eq. 10 in Ref. Ollitrault Pauline J., Chemical science 11 (2020): 6842-6855.) The second quantization operators act on a given modal in a given mode. self._degree is the truncation degree of the expansion (n).
Parameters
- h (
List[List[Tuple[List[List[int]],float]]]) – Matrix elements for the n-body expansion. The format is as follows: h is a self._degree (n) dimensional array. For each degree n, h[n] contains the list [[indices, coeff]_0, [indices, coeff]_1, …] where the indices is a n-entry list and each entry is of the shape [mode, modal1, modal2] which define the indices of the corresponding raising (mode, modal1) and lowering (mode, modal2) operators. - basis (
List[int]) – Is a list defining the number of modals per mode. E.g. for a 3 modes system with 4 modals per mode basis = [4,4,4].
__init__
__init__(h, basis)
The Bosonic operator in this class is written in the n-mode second quantization format (Eq. 10 in Ref. Ollitrault Pauline J., Chemical science 11 (2020): 6842-6855.) The second quantization operators act on a given modal in a given mode. self._degree is the truncation degree of the expansion (n).
Parameters
- h (
List[List[Tuple[List[List[int]],float]]]) – Matrix elements for the n-body expansion. The format is as follows: h is a self._degree (n) dimensional array. For each degree n, h[n] contains the list [[indices, coeff]_0, [indices, coeff]_1, …] where the indices is a n-entry list and each entry is of the shape [mode, modal1, modal2] which define the indices of the corresponding raising (mode, modal1) and lowering (mode, modal2) operators. - basis (
List[int]) – Is a list defining the number of modals per mode. E.g. for a 3 modes system with 4 modals per mode basis = [4,4,4].
Methods
__init__(h, basis) | The Bosonic operator in this class is written in the n-mode second quantization format (Eq. |
direct_mapping_filtering_criterion(state, value) | Filters out the states of irrelevant symmetries |
mapping([qubit_mapping, threshold]) | Maps a bosonic operator into a qubit operator. |
number_occupied_modals_per_mode(mode) | A bosonic operator which can be used to evaluate the number of occupied modals in a given mode |
direct_mapping_filtering_criterion
direct_mapping_filtering_criterion(state, value, aux_values=None)
Filters out the states of irrelevant symmetries
Parameters
- state (
Union[List,ndarray]) – the statevector - value (
float) – the energy - aux_values (
Optional[List[float]]) – the auxiliary energies
Return type
bool
Returns
True if the state is has one and only one modal occupied per mode meaning that the direct mapping symmetries are respected and False otherwise
mapping
mapping(qubit_mapping='direct', threshold=1e-08)
Maps a bosonic operator into a qubit operator.
Parameters
- qubit_mapping (
str) – a string giving the type of mapping (only the ‘direct’ mapping is implemented at this point) - threshold (
float) – threshold to chop the low contribution paulis
Return type
WeightedPauliOperator
Returns
A qubit operator
Raises
ValueError – If requested mapping is not supported
number_occupied_modals_per_mode
number_occupied_modals_per_mode(mode)
A bosonic operator which can be used to evaluate the number of occupied modals in a given mode
Parameters
mode (int) – the index of the mode
Returns
the corresponding bosonic operator
Return type