BosonicOperator

class BosonicOperator(h, basis)

Bases: object

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].

Methods

direct_mapping_filtering_criterion	Filters out the states of irrelevant symmetries
mapping	Maps a bosonic operator into a qubit operator.
number_occupied_modals_per_mode	A bosonic operator which can be used to evaluate the number of occupied modals in a given mode