109 lines
6.3 KiB
Plaintext
109 lines
6.3 KiB
Plaintext
---
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title: BosonicOperator
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description: API reference for qiskit.chemistry.BosonicOperator
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.chemistry.BosonicOperator
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---
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# qiskit.chemistry.BosonicOperator
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<Class id="qiskit.chemistry.BosonicOperator" isDedicatedPage={true} github="https://github.com/qiskit-community/qiskit-aqua/tree/stable/0.9/qiskit/chemistry/bosonic_operator.py" signature="BosonicOperator(h, basis)" modifiers="class">
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A set of functions to map bosonic Hamiltonians to qubit Hamiltonians.
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References:
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* *Veis Libor, et al., International Journal of Quantum Chemistry 116.18 (2016): 1328-1336.*
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* *McArdle Sam, et al., Chemical science 10.22 (2019): 5725-5735.*
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* *Ollitrault Pauline J., Chemical science 11 (2020): 6842-6855.*
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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).
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**Parameters**
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* **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.
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* **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].
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### \_\_init\_\_
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<Function id="qiskit.chemistry.BosonicOperator.__init__" signature="__init__(h, basis)">
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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).
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**Parameters**
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* **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.
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* **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].
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</Function>
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## Methods
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| | |
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| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------- |
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| [`__init__`](#qiskit.chemistry.BosonicOperator.__init__ "qiskit.chemistry.BosonicOperator.__init__")(h, basis) | The Bosonic operator in this class is written in the n-mode second quantization format (Eq. |
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| [`direct_mapping_filtering_criterion`](#qiskit.chemistry.BosonicOperator.direct_mapping_filtering_criterion "qiskit.chemistry.BosonicOperator.direct_mapping_filtering_criterion")(state, value) | Filters out the states of irrelevant symmetries |
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| [`mapping`](#qiskit.chemistry.BosonicOperator.mapping "qiskit.chemistry.BosonicOperator.mapping")(\[qubit\_mapping, threshold]) | Maps a bosonic operator into a qubit operator. |
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| [`number_occupied_modals_per_mode`](#qiskit.chemistry.BosonicOperator.number_occupied_modals_per_mode "qiskit.chemistry.BosonicOperator.number_occupied_modals_per_mode")(mode) | A bosonic operator which can be used to evaluate the number of occupied modals in a given mode |
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### direct\_mapping\_filtering\_criterion
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<Function id="qiskit.chemistry.BosonicOperator.direct_mapping_filtering_criterion" signature="direct_mapping_filtering_criterion(state, value, aux_values=None)">
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Filters out the states of irrelevant symmetries
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**Parameters**
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* **state** (`Union`\[`List`, `ndarray`]) – the statevector
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* **value** (`float`) – the energy
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* **aux\_values** (`Optional`\[`List`\[`float`]]) – the auxiliary energies
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**Return type**
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`bool`
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**Returns**
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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
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</Function>
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### mapping
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<Function id="qiskit.chemistry.BosonicOperator.mapping" signature="mapping(qubit_mapping='direct', threshold=1e-08)">
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Maps a bosonic operator into a qubit operator.
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**Parameters**
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* **qubit\_mapping** (`str`) – a string giving the type of mapping (only the ‘direct’ mapping is implemented at this point)
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* **threshold** (`float`) – threshold to chop the low contribution paulis
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**Return type**
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`WeightedPauliOperator`
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**Returns**
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A qubit operator
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**Raises**
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**ValueError** – If requested mapping is not supported
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</Function>
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### number\_occupied\_modals\_per\_mode
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<Function id="qiskit.chemistry.BosonicOperator.number_occupied_modals_per_mode" signature="number_occupied_modals_per_mode(mode)">
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A bosonic operator which can be used to evaluate the number of occupied modals in a given mode
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**Parameters**
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**mode** (`int`) – the index of the mode
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**Returns**
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the corresponding bosonic operator
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**Return type**
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[BosonicOperator](#qiskit.chemistry.BosonicOperator "qiskit.chemistry.BosonicOperator")
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</Function>
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</Class>
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