## `eigenkit.core.draw_mpl` Matplotlib drawer for `CircuitSpec`, which does not depend on the provider. It draws a circuit diagram: gates as boxes with labels, controls as filled dots, the targets of controlled-NOT (`CNOT`) and multi-controlled `X` (`MCX`) gates as `⊕`, `SWAP` gates as crossed wires and, optionally, measurement meters at the end of the wires that the observables act on. Like the text drawer in `draw.py`, the picture is built from the `CircuitSpec` intermediate representation (IR) and the observables of the circuit, never from the compiled backend object. The drawing is therefore the same whichever provider ran the circuit. It uses `draw._layout` to place the gates in columns, so the matplotlib and the text drawings stay consistent. matplotlib is an optional dependency, and it is imported only when `draw_mpl` is called. A core installation does not install it. Install it with `eigenkit[viz]`. The styles come in light and dark pairs, selected by name: - `"default"`: black on white. - `"eigen"`: the brand palette. Each gate is coloured by its kind: violet for rotations, cyan for `H` and the block gates, and blue for the meters. - `"roles"`: the outline of each gate is coloured by its role (encoding, trainable or fixed), with a legend. Each of them has a `"-dark"` variant (`"default-dark"`, `"eigen-dark"`, `"roles-dark"`) for dark backgrounds. These variants have a transparent canvas and light strokes, so they work on any dark shade. There is also `"eigen-universal"`: a single transparent image of filled gate chips, which can be read on both light and dark pages. The styles are plain dictionaries in `_STYLES`, where a new theme can be added. The wires are drawn only in the gaps between gates, so no wire shows through the label of a gate. ### `draw_mpl(spec, *, observables=None, decimals=3, show_params=True, show_measurements=True, fontsize=_DEFAULT_FONTSIZE, style='default', legend=True, ax=None)` Draw `spec` as a matplotlib circuit diagram. Parameters: | Name | Type | Description | Default | | ------------------- | -------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------- | | `spec` | `CircuitSpec` | The circuit to draw. | *required* | | `observables` | `Optional[Sequence[Observable]]` | The observables whose Pauli support sets the wires that end with a measurement meter. Pass None, or show_measurements=False, to draw no meters. Default: None. | `None` | | `decimals` | `int` | The number of significant digits of constant gate angles. Default: 3. | `3` | | `show_params` | `bool` | If True, the angle of each parametrised gate is written in its box (for example RX above w_0). Default: True. | `True` | | `show_measurements` | `bool` | If True and observables is given, a meter is drawn on each measured wire. Default: True. | `True` | | `fontsize` | `float` | The font size of the gate names. The angle labels are smaller. Default: 13.0. | `_DEFAULT_FONTSIZE` | | `style` | `str` | The name of a style: "default" (black on white), "eigen" (the brand palette, where gates are coloured by kind: rotations, H and block gates, and meters), "roles" (gate outlines coloured by role: encoding, trainable or fixed) or "eigen-universal" (one image for light and dark pages). Each of them except the last has a "-dark" variant (for example "eigen-dark") for dark backgrounds. A style dictionary can also be passed. Default: "default". | `'default'` | | `legend` | `bool` | If True, the "roles" styles draw a legend that maps each colour to its role. Styles that do not colour gates by role ignore it. Default: True. | `True` | | `ax` | `'Optional[Axes]'` | An existing matplotlib Axes to draw into. If it is not given, a new figure and axes are created, with a size that fits the circuit. The background of a style is applied only to a figure that draw_mpl creates. When you pass your own ax, set the face colour of its figure yourself: the "-dark" styles draw in light colours and need a dark background to be readable. Default: None. | `None` | Returns: | Type | Description | | ----------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `'tuple[Figure, Axes]'` | The (figure, axes) pair. Save the figure with figure.savefig(...). A figure that draw_mpl creates is not registered with pyplot, so plt.show() does not display it. | ### `measured_qubits(observables)` Return every qubit that any of `observables` acts on (their Pauli support). Parameters: | Name | Type | Description | Default | | ------------- | ---------------------- | --------------------------- | ---------- | | `observables` | `Sequence[Observable]` | The observables to measure. | *required* | Returns: | Type | Description | | ---------- | ----------------------------------------------------- | | `set[int]` | The index of every qubit that the observables act on. |