Source code for sympy.physics.quantum.circuitplot

"""Matplotlib based plotting of quantum circuits.

Todo:

* Optimize printing of large circuits.
* Get this to work with single gates.
* Do a better job checking the form of circuits to make sure it is a Mul of
  Gates.
* Get multi-target gates plotting.
* Get initial and final states to plot.
* Get measurements to plot. Might need to rethink measurement as a gate
  issue.
* Get scale and figsize to be handled in a better way.
* Write some tests/examples!
"""

from __future__ import print_function, division

from sympy import Mul
from sympy.core.compatibility import u, range
from sympy.external import import_module
from sympy.physics.quantum.gate import Gate, OneQubitGate, CGate, CGateS
from sympy.core.core import BasicMeta
from sympy.core.assumptions import ManagedProperties


__all__ = [
    'CircuitPlot',
    'circuit_plot',
    'labeller',
    'Mz',
    'Mx',
    'CreateOneQubitGate',
    'CreateCGate',
]

np = import_module('numpy')
matplotlib = import_module(
    'matplotlib', __import__kwargs={'fromlist': ['pyplot']},
    catch=(RuntimeError,))  # This is raised in environments that have no display.

if not np or not matplotlib:
    class CircuitPlot(object):
        def __init__(*args, **kwargs):
            raise ImportError('numpy or matplotlib not available.')

    def circuit_plot(*args, **kwargs):
        raise ImportError('numpy or matplotlib not available.')
else:
    pyplot = matplotlib.pyplot
    Line2D = matplotlib.lines.Line2D
    Circle = matplotlib.patches.Circle

    #from matplotlib import rc
    #rc('text',usetex=True)

    class CircuitPlot(object):
        """A class for managing a circuit plot."""

        scale = 1.0
        fontsize = 20.0
        linewidth = 1.0
        control_radius = 0.05
        not_radius = 0.15
        swap_delta = 0.05
        labels = []
        inits = {}
        label_buffer = 0.5

        def __init__(self, c, nqubits, **kwargs):
            self.circuit = c
            self.ngates = len(self.circuit.args)
            self.nqubits = nqubits
            self.update(kwargs)
            self._create_grid()
            self._create_figure()
            self._plot_wires()
            self._plot_gates()
            self._finish()

        def update(self, kwargs):
            """Load the kwargs into the instance dict."""
            self.__dict__.update(kwargs)

        def _create_grid(self):
            """Create the grid of wires."""
            scale = self.scale
            wire_grid = np.arange(0.0, self.nqubits*scale, scale, dtype=float)
            gate_grid = np.arange(0.0, self.ngates*scale, scale, dtype=float)
            self._wire_grid = wire_grid
            self._gate_grid = gate_grid

        def _create_figure(self):
            """Create the main matplotlib figure."""
            self._figure = pyplot.figure(
                figsize=(self.ngates*self.scale, self.nqubits*self.scale),
                facecolor='w',
                edgecolor='w'
            )
            ax = self._figure.add_subplot(
                1, 1, 1,
                frameon=True
            )
            ax.set_axis_off()
            offset = 0.5*self.scale
            ax.set_xlim(self._gate_grid[0] - offset, self._gate_grid[-1] + offset)
            ax.set_ylim(self._wire_grid[0] - offset, self._wire_grid[-1] + offset)
            ax.set_aspect('equal')
            self._axes = ax

        def _plot_wires(self):
            """Plot the wires of the circuit diagram."""
            xstart = self._gate_grid[0]
            xstop = self._gate_grid[-1]
            xdata = (xstart - self.scale, xstop + self.scale)
            for i in range(self.nqubits):
                ydata = (self._wire_grid[i], self._wire_grid[i])
                line = Line2D(
                    xdata, ydata,
                    color='k',
                    lw=self.linewidth
                )
                self._axes.add_line(line)
                if self.labels:
                    init_label_buffer = 0
                    if self.inits.get(self.labels[i]): init_label_buffer = 0.25
                    self._axes.text(
                        xdata[0]-self.label_buffer-init_label_buffer,ydata[0],
                        render_label(self.labels[i],self.inits),
                        size=self.fontsize,
                        color='k',ha='center',va='center')
            self._plot_measured_wires()

        def _plot_measured_wires(self):
            ismeasured = self._measurements()
            xstop = self._gate_grid[-1]
            dy = 0.04 # amount to shift wires when doubled
            # Plot doubled wires after they are measured
            for im in ismeasured:
                xdata = (self._gate_grid[ismeasured[im]],xstop+self.scale)
                ydata = (self._wire_grid[im]+dy,self._wire_grid[im]+dy)
                line = Line2D(
                    xdata, ydata,
                    color='k',
                    lw=self.linewidth
                )
                self._axes.add_line(line)
            # Also double any controlled lines off these wires
            for i,g in enumerate(self._gates()):
                if isinstance(g, CGate) or isinstance(g, CGateS):
                    wires = g.controls + g.targets
                    for wire in wires:
                        if wire in ismeasured and \
                               self._gate_grid[i] > self._gate_grid[ismeasured[wire]]:
                            ydata = min(wires), max(wires)
                            xdata = self._gate_grid[i]-dy, self._gate_grid[i]-dy
                            line = Line2D(
                                xdata, ydata,
                                color='k',
                                lw=self.linewidth
                                )
                            self._axes.add_line(line)
        def _gates(self):
            """Create a list of all gates in the circuit plot."""
            gates = []
            if isinstance(self.circuit, Mul):
                for g in reversed(self.circuit.args):
                    if isinstance(g, Gate):
                        gates.append(g)
            elif isinstance(self.circuit, Gate):
                gates.append(self.circuit)
            return gates

        def _plot_gates(self):
            """Iterate through the gates and plot each of them."""
            for i, gate in enumerate(self._gates()):
                gate.plot_gate(self, i)

        def _measurements(self):
            """Return a dict {i:j} where i is the index of the wire that has
            been measured, and j is the gate where the wire is measured.
            """
            ismeasured = {}
            for i,g in enumerate(self._gates()):
                if getattr(g,'measurement',False):
                    for target in g.targets:
                        if target in ismeasured:
                            if ismeasured[target] > i:
                                ismeasured[target] = i
                        else:
                            ismeasured[target] = i
            return ismeasured

        def _finish(self):
            # Disable clipping to make panning work well for large circuits.
            for o in self._figure.findobj():
                o.set_clip_on(False)

        def one_qubit_box(self, t, gate_idx, wire_idx):
            """Draw a box for a single qubit gate."""
            x = self._gate_grid[gate_idx]
            y = self._wire_grid[wire_idx]
            self._axes.text(
                x, y, t,
                color='k',
                ha='center',
                va='center',
                bbox=dict(ec='k', fc='w', fill=True, lw=self.linewidth),
                size=self.fontsize
            )

        def two_qubit_box(self, t, gate_idx, wire_idx):
            """Draw a box for a two qubit gate. Doesn't work yet.
            """
            x = self._gate_grid[gate_idx]
            y = self._wire_grid[wire_idx]+0.5
            print(self._gate_grid)
            print(self._wire_grid)
            obj = self._axes.text(
                x, y, t,
                color='k',
                ha='center',
                va='center',
                bbox=dict(ec='k', fc='w', fill=True, lw=self.linewidth),
                size=self.fontsize
            )

        def control_line(self, gate_idx, min_wire, max_wire):
            """Draw a vertical control line."""
            xdata = (self._gate_grid[gate_idx], self._gate_grid[gate_idx])
            ydata = (self._wire_grid[min_wire], self._wire_grid[max_wire])
            line = Line2D(
                xdata, ydata,
                color='k',
                lw=self.linewidth
            )
            self._axes.add_line(line)

        def control_point(self, gate_idx, wire_idx):
            """Draw a control point."""
            x = self._gate_grid[gate_idx]
            y = self._wire_grid[wire_idx]
            radius = self.control_radius
            c = Circle(
                (x, y),
                radius*self.scale,
                ec='k',
                fc='k',
                fill=True,
                lw=self.linewidth
            )
            self._axes.add_patch(c)

        def not_point(self, gate_idx, wire_idx):
            """Draw a NOT gates as the circle with plus in the middle."""
            x = self._gate_grid[gate_idx]
            y = self._wire_grid[wire_idx]
            radius = self.not_radius
            c = Circle(
                (x, y),
                radius,
                ec='k',
                fc='w',
                fill=False,
                lw=self.linewidth
            )
            self._axes.add_patch(c)
            l = Line2D(
                (x, x), (y - radius, y + radius),
                color='k',
                lw=self.linewidth
            )
            self._axes.add_line(l)

        def swap_point(self, gate_idx, wire_idx):
            """Draw a swap point as a cross."""
            x = self._gate_grid[gate_idx]
            y = self._wire_grid[wire_idx]
            d = self.swap_delta
            l1 = Line2D(
                (x - d, x + d),
                (y - d, y + d),
                color='k',
                lw=self.linewidth
            )
            l2 = Line2D(
                (x - d, x + d),
                (y + d, y - d),
                color='k',
                lw=self.linewidth
            )
            self._axes.add_line(l1)
            self._axes.add_line(l2)

    def circuit_plot(c, nqubits, **kwargs):
        """Draw the circuit diagram for the circuit with nqubits.

        Parameters
        ==========

        c : circuit
            The circuit to plot. Should be a product of Gate instances.
        nqubits : int
            The number of qubits to include in the circuit. Must be at least
            as big as the largest `min_qubits`` of the gates.
        """
        return CircuitPlot(c, nqubits, **kwargs)

def render_label(label, inits={}):
    """Slightly more flexible way to render labels.

    >>> from sympy.physics.quantum.circuitplot import render_label
    >>> render_label('q0')
    '$|q0\\\\rangle$'
    >>> render_label('q0', {'q0':'0'})
    '$|q0\\\\rangle=|0\\\\rangle$'
    """
    init = inits.get(label)
    if init:
        return r'$|%s\rangle=|%s\rangle$' % (label, init)
    return r'$|%s\rangle$' % label

[docs]def labeller(n, symbol='q'): """Autogenerate labels for wires of quantum circuits. Parameters ========== n : int number of qubits in the circuit symbol : string A character string to precede all gate labels. E.g. 'q_0', 'q_1', etc. >>> from sympy.physics.quantum.circuitplot import labeller >>> labeller(2) ['q_1', 'q_0'] >>> labeller(3,'j') ['j_2', 'j_1', 'j_0'] """ return ['%s_%d' % (symbol,n-i-1) for i in range(n)]
[docs]class Mz(OneQubitGate): """Mock-up of a z measurement gate. This is in circuitplot rather than gate.py because it's not a real gate, it just draws one. """ measurement = True gate_name='Mz' gate_name_latex=u('M_z')
[docs]class Mx(OneQubitGate): """Mock-up of an x measurement gate. This is in circuitplot rather than gate.py because it's not a real gate, it just draws one. """ measurement = True gate_name='Mx' gate_name_latex=u('M_x')
class CreateOneQubitGate(ManagedProperties): def __new__(mcl, name, latexname=None): if not latexname: latexname = name return BasicMeta.__new__(mcl, name + "Gate", (OneQubitGate,), {'gate_name': name, 'gate_name_latex': latexname})
[docs]def CreateCGate(name, latexname=None): """Use a lexical closure to make a controlled gate. """ if not latexname: latexname = name onequbitgate = CreateOneQubitGate(name, latexname) def ControlledGate(ctrls,target): return CGate(tuple(ctrls),onequbitgate(target)) return ControlledGate