88 lines
4.5 KiB
Plaintext
88 lines
4.5 KiB
Plaintext
---
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title: plot_state_city (v1.2)
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description: API reference for qiskit.visualization.plot_state_city in qiskit v1.2
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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_city
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---
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<span id="qiskit-visualization-plot-state-city" />
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# qiskit.visualization.plot\_state\_city
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<Function id="qiskit.visualization.plot_state_city" isDedicatedPage={true} github="https://github.com/Qiskit/qiskit/tree/stable/1.2/qiskit/visualization/state_visualization.py#L360-L608" signature="qiskit.visualization.plot_state_city(state, title='', figsize=None, color=None, alpha=1, ax_real=None, ax_imag=None, *, filename=None)">
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Plot the cityscape of quantum state.
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Plot two 3d bar graphs (two dimensional) of the real and imaginary part of the density matrix rho.
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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*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)")) – a string that represents the plot title
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* **figsize** ([*tuple*](https://docs.python.org/3/library/stdtypes.html#tuple "(in Python v3.13)")) – Figure size in inches.
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* **color** ([*list*](https://docs.python.org/3/library/stdtypes.html#list "(in Python v3.13)")) – A list of len=2 giving colors for real and imaginary components of matrix elements.
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* **alpha** ([*float*](https://docs.python.org/3/library/functions.html#float "(in Python v3.13)")) – Transparency value for bars
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* **ax\_real** ([*matplotlib.axes.Axes*](https://matplotlib.org/stable/api/_as_gen/matplotlib.axes.Axes.html#matplotlib.axes.Axes "(in Matplotlib v3.9.2)")) – An optional Axes object to be used for the visualization output. If none is specified a new matplotlib Figure will be created and used. If this is specified without an ax\_imag only the real component plot will be generated. Additionally, if specified there will be no returned Figure since it is redundant.
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* **ax\_imag** ([*matplotlib.axes.Axes*](https://matplotlib.org/stable/api/_as_gen/matplotlib.axes.Axes.html#matplotlib.axes.Axes "(in Matplotlib v3.9.2)")) – An optional Axes object to be used for the visualization output. If none is specified a new matplotlib Figure will be created and used. If this is specified without an ax\_real only the imaginary component plot will be generated. 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_real` and `ax_imag` kwargs are not set
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**Return type**
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[`matplotlib.figure.Figure`](https://matplotlib.org/stable/api/_as_gen/matplotlib.figure.Figure.html#matplotlib.figure.Figure "(in Matplotlib v3.9.2)")
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**Raises**
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* [**MissingOptionalLibraryError**](exceptions#qiskit.exceptions.MissingOptionalLibraryError "qiskit.exceptions.MissingOptionalLibraryError") – Requires matplotlib.
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* [**ValueError**](https://docs.python.org/3/library/exceptions.html#ValueError "(in Python v3.13)") – When ‘color’ is not a list of len=2.
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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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**Examples**
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```python
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# You can choose different colors for the real and imaginary parts of the density matrix.
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from qiskit import QuantumCircuit
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from qiskit.quantum_info import DensityMatrix
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from qiskit.visualization import plot_state_city
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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 = DensityMatrix(qc)
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plot_state_city(state, color=['midnightblue', 'crimson'], title="New State City")
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```
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```python
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# You can make the bars more transparent to better see the ones that are behind
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# if they overlap.
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import numpy as np
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from qiskit.quantum_info import Statevector
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from qiskit.visualization import plot_state_city
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from qiskit import QuantumCircuit
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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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state = Statevector(qc)
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plot_state_city(state, alpha=0.6)
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```
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</Function>
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