174 lines
4.3 KiB
Plaintext
174 lines
4.3 KiB
Plaintext
---
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title: CPhaseGate (v0.29)
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description: API reference for qiskit.circuit.library.CPhaseGate in qiskit v0.29
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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.circuit.library.CPhaseGate
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---
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# CPhaseGate
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<Class id="qiskit.circuit.library.CPhaseGate" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.18/qiskit/circuit/library/standard_gates/p.py" signature="CPhaseGate(theta, label=None, ctrl_state=None)" modifiers="class">
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Bases: `qiskit.circuit.controlledgate.ControlledGate`
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Controlled-Phase gate.
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This is a diagonal and symmetric gate that induces a phase on the state of the target qubit, depending on the control state.
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**Circuit symbol:**
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```python
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q_0: ─■──
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│λ
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q_1: ─■──
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```
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**Matrix representation:**
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$$
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\begin{split}CPhase =
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|0\rangle\langle 0| \otimes I + |1\rangle\langle 1| \otimes P =
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\begin{pmatrix}
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1 & 0 & 0 & 0 \\
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0 & 1 & 0 & 0 \\
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0 & 0 & 1 & 0 \\
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0 & 0 & 0 & e^{i\lambda}
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\end{pmatrix}\end{split}
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$$
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<Admonition title="See also" type="note">
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`CRZGate`: Due to the global phase difference in the matrix definitions of Phase and RZ, CPhase and CRZ are different gates with a relative phase difference.
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</Admonition>
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Create new CPhase gate.
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## Methods Defined Here
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<span id="qiskit-circuit-library-cphasegate-control" />
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### control
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<Function id="qiskit.circuit.library.CPhaseGate.control" signature="CPhaseGate.control(num_ctrl_qubits=1, label=None, ctrl_state=None)">
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Controlled version of this gate.
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**Parameters**
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* **num\_ctrl\_qubits** (*int*) – number of control qubits.
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* **label** (*str or None*) – An optional label for the gate \[Default: None]
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* **ctrl\_state** (*int or str or None*) – control state expressed as integer, string (e.g. ‘110’), or None. If None, use all 1s.
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**Returns**
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controlled version of this gate.
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**Return type**
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[ControlledGate](qiskit.circuit.ControlledGate "qiskit.circuit.ControlledGate")
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</Function>
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<span id="qiskit-circuit-library-cphasegate-inverse" />
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### inverse
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<Function id="qiskit.circuit.library.CPhaseGate.inverse" signature="CPhaseGate.inverse()">
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Return inverted CPhase gate ($CPhase(\lambda){\dagger} = CPhase(-\lambda)$)
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</Function>
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## Attributes
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### ctrl\_state
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<Attribute id="qiskit.circuit.library.CPhaseGate.ctrl_state">
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Return the control state of the gate as a decimal integer.
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**Return type**
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`int`
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</Attribute>
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### decompositions
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<Attribute id="qiskit.circuit.library.CPhaseGate.decompositions">
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Get the decompositions of the instruction from the SessionEquivalenceLibrary.
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</Attribute>
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### definition
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<Attribute id="qiskit.circuit.library.CPhaseGate.definition">
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Return definition in terms of other basic gates. If the gate has open controls, as determined from self.ctrl\_state, the returned definition is conjugated with X without changing the internal \_definition.
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**Return type**
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`List`
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</Attribute>
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### duration
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<Attribute id="qiskit.circuit.library.CPhaseGate.duration">
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Get the duration.
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</Attribute>
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### label
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<Attribute id="qiskit.circuit.library.CPhaseGate.label">
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Return instruction label
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**Return type**
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`str`
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</Attribute>
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### name
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<Attribute id="qiskit.circuit.library.CPhaseGate.name">
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Get name of gate. If the gate has open controls the gate name will become:
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> \<original\_name\_o\<ctrl\_state>
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where \<original\_name> is the gate name for the default case of closed control qubits and \<ctrl\_state> is the integer value of the control state for the gate.
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**Return type**
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`str`
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</Attribute>
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### num\_ctrl\_qubits
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<Attribute id="qiskit.circuit.library.CPhaseGate.num_ctrl_qubits">
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Get number of control qubits.
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**Returns**
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The number of control qubits for the gate.
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**Return type**
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int
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</Attribute>
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### params
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<Attribute id="qiskit.circuit.library.CPhaseGate.params">
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Get parameters from base\_gate.
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**Returns**
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List of gate parameters.
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**Return type**
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list
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**Raises**
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**CircuitError** – Controlled gate does not define a base gate
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</Attribute>
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### unit
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<Attribute id="qiskit.circuit.library.CPhaseGate.unit">
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Get the time unit of duration.
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</Attribute>
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</Class>
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