219 lines
9.0 KiB
Plaintext
219 lines
9.0 KiB
Plaintext
---
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title: Z2Symmetries
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description: API reference for qiskit.opflow.primitive_ops.Z2Symmetries
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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.opflow.primitive_ops.Z2Symmetries
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---
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# Z2Symmetries
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<Class id="qiskit.opflow.primitive_ops.Z2Symmetries" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.24/qiskit/opflow/primitive_ops/tapered_pauli_sum_op.py" signature="Z2Symmetries(symmetries, sq_paulis, sq_list, tapering_values=None, tol=1e-14)" modifiers="class">
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Bases: `object`
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Deprecated: Z2 Symmetries
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<Admonition title="Deprecated since version 0.24.0" type="danger">
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The class `qiskit.opflow.primitive_ops.tapered_pauli_sum_op.Z2Symmetries` is deprecated as of qiskit-terra 0.24.0. It will be removed no earlier than 3 months after the release date. For code migration guidelines, visit [https://qisk.it/opflow\_migration](https://qisk.it/opflow_migration).
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</Admonition>
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**Parameters**
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* **symmetries** (*List\[*[*Pauli*](qiskit.quantum_info.Pauli "qiskit.quantum_info.operators.symplectic.pauli.Pauli")*]*) – the list of Pauli objects representing the Z\_2 symmetries
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* **sq\_paulis** (*List\[*[*Pauli*](qiskit.quantum_info.Pauli "qiskit.quantum_info.operators.symplectic.pauli.Pauli")*]*) – the list of single - qubit Pauli objects to construct the Clifford operators
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* **sq\_list** (*List\[int]*) – the list of support of the single-qubit Pauli objects used to build the Clifford operators
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* **tapering\_values** (*List\[int] | None*) – values determines the sector.
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* **tol** (*float*) – Tolerance threshold for ignoring real and complex parts of a coefficient.
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**Raises**
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[**OpflowError**](qiskit.opflow.OpflowError "qiskit.opflow.OpflowError") – Invalid paulis
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## Methods Defined Here
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<span id="qiskit-opflow-primitive-ops-z2symmetries-consistent-tapering" />
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### consistent\_tapering
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<Function id="qiskit.opflow.primitive_ops.Z2Symmetries.consistent_tapering" signature="Z2Symmetries.consistent_tapering(operator)">
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Tapering the operator with the same manner of how this tapered operator is created. i.e., using the same Cliffords and tapering values.
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**Parameters**
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**operator** ([*PauliSumOp*](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.pauli_sum_op.PauliSumOp")) – the to-be-tapered operator
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**Returns**
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The tapered operator
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**Raises**
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[**OpflowError**](qiskit.opflow.OpflowError "qiskit.opflow.OpflowError") – The given operator does not commute with the symmetry
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**Return type**
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[*OperatorBase*](qiskit.opflow.OperatorBase "qiskit.opflow.operator_base.OperatorBase")
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</Function>
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<span id="qiskit-opflow-primitive-ops-z2symmetries-convert-clifford" />
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### convert\_clifford
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<Function id="qiskit.opflow.primitive_ops.Z2Symmetries.convert_clifford" signature="Z2Symmetries.convert_clifford(operator)">
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This method operates the first part of the tapering. It converts the operator by composing it with the clifford unitaries defined in the current symmetry.
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**Parameters**
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**operator** ([*PauliSumOp*](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.pauli_sum_op.PauliSumOp")) – to-be-tapered operator
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**Returns**
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[`PauliSumOp`](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.PauliSumOp") corresponding to the converted operator.
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**Raises**
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[**OpflowError**](qiskit.opflow.OpflowError "qiskit.opflow.OpflowError") – Z2 symmetries, single qubit pauli and single qubit list cannot be empty
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**Return type**
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[*OperatorBase*](qiskit.opflow.OperatorBase "qiskit.opflow.operator_base.OperatorBase")
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</Function>
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<span id="qiskit-opflow-primitive-ops-z2symmetries-copy" />
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### copy
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<Function id="qiskit.opflow.primitive_ops.Z2Symmetries.copy" signature="Z2Symmetries.copy()">
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Get a copy of self. :returns: copy
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**Return type**
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[*Z2Symmetries*](qiskit.opflow.primitive_ops.Z2Symmetries "qiskit.opflow.primitive_ops.tapered_pauli_sum_op.Z2Symmetries")
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</Function>
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<span id="qiskit-opflow-primitive-ops-z2symmetries-find-z2-symmetries" />
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### find\_Z2\_symmetries
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<Function id="qiskit.opflow.primitive_ops.Z2Symmetries.find_Z2_symmetries" signature="Z2Symmetries.find_Z2_symmetries(operator)" modifiers="classmethod">
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Finds Z2 Pauli-type symmetries of an Operator.
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**Returns**
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a z2\_symmetries object contains symmetries, single-qubit X, single-qubit list.
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**Return type**
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[*Z2Symmetries*](qiskit.opflow.primitive_ops.Z2Symmetries "qiskit.opflow.primitive_ops.tapered_pauli_sum_op.Z2Symmetries")
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</Function>
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<span id="qiskit-opflow-primitive-ops-z2symmetries-is-empty" />
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### is\_empty
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<Function id="qiskit.opflow.primitive_ops.Z2Symmetries.is_empty" signature="Z2Symmetries.is_empty()">
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Check the z2\_symmetries is empty or not. :returns: Empty or not
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**Return type**
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bool
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</Function>
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<span id="qiskit-opflow-primitive-ops-z2symmetries-taper" />
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### taper
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<Function id="qiskit.opflow.primitive_ops.Z2Symmetries.taper" signature="Z2Symmetries.taper(operator)">
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Taper an operator based on the z2\_symmetries info and sector defined by tapering\_values. The tapering\_values will be stored into the resulted operator for a record.
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The tapering is a two-step algorithm which first converts the operator into a [`PauliSumOp`](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.PauliSumOp") with same eigenvalues but where some qubits are only acted upon with the Pauli operators I or X. The number M of these redundant qubits is equal to the number M of identified symmetries.
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The second step of the reduction consists in replacing these qubits with the possible eigenvalues of the corresponding Pauli X, giving 2^M new operators with M less qubits. If an eigenvalue sector was previously identified for the solution, then this reduces to 1 new operator with M less qubits.
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**Parameters**
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**operator** ([*PauliSumOp*](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.pauli_sum_op.PauliSumOp")) – the to-be-tapered operator
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**Returns**
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\[[`PauliSumOp`](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.PauliSumOp")]; otherwise, [`PauliSumOp`](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.PauliSumOp")
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**Return type**
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If tapering\_values is None
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**Raises**
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[**OpflowError**](qiskit.opflow.OpflowError "qiskit.opflow.OpflowError") – Z2 symmetries, single qubit pauli and single qubit list cannot be empty
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</Function>
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<span id="qiskit-opflow-primitive-ops-z2symmetries-taper-clifford" />
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### taper\_clifford
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<Function id="qiskit.opflow.primitive_ops.Z2Symmetries.taper_clifford" signature="Z2Symmetries.taper_clifford(operator)">
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This method operates the second part of the tapering. This function assumes that the input operators have already been transformed using [`convert_clifford()`](qiskit.opflow.primitive_ops.Z2Symmetries#convert_clifford "qiskit.opflow.primitive_ops.Z2Symmetries.convert_clifford"). The redundant qubits due to the symmetries are dropped and replaced by their two possible eigenvalues. The tapering\_values will be stored into the resulted operator for a record.
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**Parameters**
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**operator** ([*PauliSumOp*](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.pauli_sum_op.PauliSumOp")) – Partially tapered operator resulting from a call to [`convert_clifford()`](qiskit.opflow.primitive_ops.Z2Symmetries#convert_clifford "qiskit.opflow.primitive_ops.Z2Symmetries.convert_clifford")
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**Returns**
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\[[`PauliSumOp`](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.PauliSumOp")]; otherwise, [`PauliSumOp`](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.PauliSumOp")
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**Return type**
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If tapering\_values is None
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**Raises**
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[**OpflowError**](qiskit.opflow.OpflowError "qiskit.opflow.OpflowError") – Z2 symmetries, single qubit pauli and single qubit list cannot be empty
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</Function>
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## Attributes
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### cliffords
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<Attribute id="qiskit.opflow.primitive_ops.Z2Symmetries.cliffords">
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Get clifford operators, build based on symmetries and single-qubit X. :returns: a list of unitaries used to diagonalize the Hamiltonian.
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</Attribute>
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### settings
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<Attribute id="qiskit.opflow.primitive_ops.Z2Symmetries.settings">
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Return operator settings.
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</Attribute>
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### sq\_list
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<Attribute id="qiskit.opflow.primitive_ops.Z2Symmetries.sq_list">
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returns sq list
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</Attribute>
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### sq\_paulis
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<Attribute id="qiskit.opflow.primitive_ops.Z2Symmetries.sq_paulis">
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returns sq paulis
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</Attribute>
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### symmetries
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<Attribute id="qiskit.opflow.primitive_ops.Z2Symmetries.symmetries">
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return symmetries
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</Attribute>
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### tapering\_values
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<Attribute id="qiskit.opflow.primitive_ops.Z2Symmetries.tapering_values">
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returns tapering values
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</Attribute>
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### tol
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<Attribute id="qiskit.opflow.primitive_ops.Z2Symmetries.tol">
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Tolerance threshold for ignoring real and complex parts of a coefficient.
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</Attribute>
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</Class>
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