84 lines
4.3 KiB
Plaintext
84 lines
4.3 KiB
Plaintext
---
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title: plot_state_qsphere
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description: API reference for qiskit.visualization.plot_state_qsphere
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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_qsphere
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---
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<span id="qiskit-visualization-plot-state-qsphere" />
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# qiskit.visualization.plot\_state\_qsphere
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<Function id="qiskit.visualization.plot_state_qsphere" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.25/qiskit/visualization/state_visualization.py" signature="qiskit.visualization.plot_state_qsphere(state, figsize=None, ax=None, show_state_labels=True, show_state_phases=False, use_degrees=False, *, rho=None, filename=None)">
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Plot the qsphere representation of a quantum state. Here, the size of the points is proportional to the probability of the corresponding term in the state and the color represents the phase.
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<Admonition title="Deprecated since version 0.15.1" type="danger">
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`qiskit.visualization.state_visualization.plot_state_qsphere()`’s argument `rho` is deprecated as of qiskit-terra 0.15.1. It will be removed no earlier than 3 months after the release date. Instead, use the argument `state`, which behaves identically.
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</Admonition>
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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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* **figsize** ([*tuple*](https://docs.python.org/3/library/stdtypes.html#tuple "(in Python v3.12)")) – Figure size in inches.
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* **ax** ([*matplotlib.axes.Axes*](https://matplotlib.org/stable/api/_as_gen/matplotlib.axes.Axes.html#matplotlib.axes.Axes "(in Matplotlib v3.8.0)")) – 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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* **show\_state\_labels** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.12)")) – An optional boolean indicating whether to show labels for each basis state.
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* **show\_state\_phases** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.12)")) – An optional boolean indicating whether to show the phase for each basis state.
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* **use\_degrees** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.12)")) – An optional boolean indicating whether to use radians or degrees for the phase values in the plot.
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**Returns**
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A matplotlib figure instance if the `ax` kwarg is not set
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**Return type**
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[`matplotlib.figure.Figure`](https://matplotlib.org/stable/api/figure_api.html#matplotlib.figure.Figure "(in Matplotlib v3.8.0)")
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**Raises**
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* [**MissingOptionalLibraryError**](exceptions#qiskit.exceptions.MissingOptionalLibraryError "qiskit.exceptions.MissingOptionalLibraryError") – Requires matplotlib.
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* [**VisualizationError**](visualization#qiskit.visualization.VisualizationError "qiskit.visualization.VisualizationError") – if input is not a valid N-qubit state.
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* [**QiskitError**](exceptions#qiskit.exceptions.QiskitError "qiskit.exceptions.QiskitError") – Input statevector does not have valid dimensions.
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**Examples**
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```python
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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_qsphere
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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_qsphere(state)
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```
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```python
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# You can show the phase of each state and use
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# degrees instead of radians
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from qiskit.quantum_info import DensityMatrix
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import numpy as np
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from qiskit import QuantumCircuit
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from qiskit.visualization import plot_state_qsphere
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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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qc.z(1)
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matrix = DensityMatrix(qc)
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plot_state_qsphere(matrix,
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show_state_phases = True, use_degrees = True)
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```
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</Function>
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