86 lines
3.6 KiB
Plaintext
86 lines
3.6 KiB
Plaintext
---
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title: plot_state_paulivec
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description: API reference for qiskit.visualization.plot_state_paulivec
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in_page_toc_min_heading_level: 1
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python_api_type: function
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python_api_name: qiskit.visualization.plot_state_paulivec
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---
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# qiskit.visualization.plot\_state\_paulivec
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<Function id="qiskit.visualization.plot_state_paulivec" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.23/qiskit/visualization/state_visualization.py" signature="plot_state_paulivec(state, title='', figsize=None, color=None, ax=None, *, rho=None, filename=None)">
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Plot the paulivec representation of a quantum state.
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Plot a bargraph of the density matrix of a quantum state using as a basis all possible tensor products of Pauli operators and identities, that is, $\{\bigotimes_{i=0}^{N-1}P_i\}_{P_i\in \{I,X,Y,Z\}}$, where $N$ is the number of qubits.
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**Parameters**
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* **state** ([*Statevector*](qiskit.quantum_info.Statevector "qiskit.quantum_info.Statevector") *or*[*DensityMatrix*](qiskit.quantum_info.DensityMatrix "qiskit.quantum_info.DensityMatrix") *or ndarray*) – an N-qubit quantum state.
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* **title** (*str*) – a string that represents the plot title
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* **figsize** (*tuple*) – Figure size in inches.
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* **color** (*list or str*) – Color of the coefficient value bars.
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* **ax** (*matplotlib.axes.Axes*) – An optional Axes object to be used for the visualization output. If none is specified a new matplotlib Figure will be created and used. Additionally, if specified there will be no returned Figure since it is redundant.
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**Returns**
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The matplotlib.Figure of the visualization if the `ax` kwarg is not set
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**Return type**
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matplotlib.Figure
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**Raises**
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* **MissingOptionalLibraryError** – Requires matplotlib.
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* [**VisualizationError**](qiskit.visualization.VisualizationError "qiskit.visualization.VisualizationError") – if input is not a valid N-qubit state.
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**Examples**
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```python
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# You can set a color for all the bars.
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from qiskit import QuantumCircuit
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from qiskit.quantum_info import Statevector
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from qiskit.visualization import plot_state_paulivec
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qc = QuantumCircuit(2)
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qc.h(0)
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qc.cx(0, 1)
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state = Statevector(qc)
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plot_state_paulivec(state, color='midnightblue', title="New PauliVec plot")
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```
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([Source code](qiskit-visualization-plot_state_paulivec-1.py), [png](qiskit-visualization-plot_state_paulivec-1.png), [hires.png](qiskit-visualization-plot_state_paulivec-1.hires.png), [pdf](qiskit-visualization-plot_state_paulivec-1.pdf))
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```python
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# If you introduce a list with less colors than bars, the color of the bars will
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# alternate following the sequence from the list.
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import numpy as np
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from qiskit.quantum_info import DensityMatrix
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from qiskit import QuantumCircuit
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from qiskit.visualization import plot_state_paulivec
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qc = QuantumCircuit(2)
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qc.h(0)
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qc.cx(0, 1)
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qc = QuantumCircuit(2)
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qc.h([0, 1])
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qc.cz(0, 1)
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qc.ry(np.pi/3, 0)
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qc.rx(np.pi/5, 1)
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matrix = DensityMatrix(qc)
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plot_state_paulivec(matrix, color=['crimson', 'midnightblue', 'seagreen'])
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```
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([Source code](qiskit-visualization-plot_state_paulivec-2.py), [png](qiskit-visualization-plot_state_paulivec-2.png), [hires.png](qiskit-visualization-plot_state_paulivec-2.hires.png), [pdf](qiskit-visualization-plot_state_paulivec-2.pdf))
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</Function>
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