qiskit/visualization/state_visualization.py
def plot_bloch_multivector(rho, title='', figsize=None):
    """Plot the Bloch sphere.

    Plot a sphere, axes, the Bloch vector, and its projections onto each axis.

    Args:
        rho (ndarray): Numpy array for state vector or density matrix.
        title (str): a string that represents the plot title
        figsize (tuple): Has no effect, here for compatibility only.

    Returns:
        Figure: A matplotlib figure instance if `ax = None`.

    Raises:
        ImportError: Requires matplotlib.
    """
    if not HAS_MATPLOTLIB:
        raise ImportError('Must have Matplotlib installed.')
    rho = _validate_input_state(rho)
    num = int(np.log2(len(rho)))
    width, height = plt.figaspect(1/num)
    fig = plt.figure(figsize=(width, height))
    for i in range(num):
        ax = fig.add_subplot(1, num, i + 1, projection='3d')
        pauli_singles = [
            Pauli.pauli_single(num, i, 'X'),
            Pauli.pauli_single(num, i, 'Y'),
            Pauli.pauli_single(num, i, 'Z')
        ]
        bloch_state = list(
            map(lambda x: np.real(np.trace(np.dot(x.to_matrix(), rho))),
                pauli_singles))
        plot_bloch_vector(bloch_state, "qubit " + str(i), ax=ax,
                          figsize=figsize)
    fig.suptitle(title, fontsize=16)
    plt.close(fig)
    return fig
def plot_bloch_multivector(rho, title='', figsize=None):
    """Plot the Bloch sphere.

    Plot a sphere, axes, the Bloch vector, and its projections onto each axis.

    Args:
        rho (ndarray): Numpy array for state vector or density matrix.
        title (str): a string that represents the plot title
        figsize (tuple): Has no effect, here for compatibility only.

    Returns:
        Figure: A matplotlib figure instance if `ax = None`.

    Raises:
        ImportError: Requires matplotlib.
    """
    if not HAS_MATPLOTLIB:
        raise ImportError('Must have Matplotlib installed.')
    rho = _validate_input_state(rho)
    num = int(np.log2(len(rho)))
    width, height = plt.figaspect(1/num)
    fig = plt.figure(figsize=(width, height))
    for i in range(num):
        ax = fig.add_subplot(1, num, i + 1, projection='3d')
        pauli_singles = [
            Pauli.pauli_single(num, i, 'X'),
            Pauli.pauli_single(num, i, 'Y'),
            Pauli.pauli_single(num, i, 'Z')
        ]
        bloch_state = list(
            map(lambda x: np.real(np.trace(np.dot(x.to_matrix(), rho))),
                pauli_singles))
        plot_bloch_vector(bloch_state, "qubit " + str(i), ax=ax,
                          figsize=figsize)
    fig.suptitle(title, fontsize=16)
    plt.close(fig)
    return fig
Plot the Bloch sphere.

    Plot a sphere, axes, the Bloch vector, and its projections onto each axis.

    Args:
        rho (ndarray): Numpy array for state vector or density matrix.
        title (str): a string that represents the plot title
        figsize (tuple): Has no effect, here for compatibility only.

    Returns:
        Figure: A matplotlib figure instance if `ax = None`.

    Raises:
        ImportError: Requires matplotlib.