A circuit plotting routine using SymPy

[BoxiLi]

The current circuit plotting in qutip-qip uses LaTeX, which is powerful but requires dependencies that are hard to control as a Python package. The installation for users who do not already have a working tex environment is very clumsy.

As shown in this notebook. Sympy might have a way to do this already (see here). It is much easier to make SymPy an optional package than asking the user to install a full Tex distribution, which could be several Gigabytes large.
As Sympy uses a class for each gate, we could leave a method in our gate class that initialize this SymPy class, e.g:

class XGate(SingleQubitGate):
    ...
    def get_sympy_object(self):
        return sympy.physics.quantum.gate.X(self.targets[0])

And even better, SymPy seems to support QASM 2.0 gates! If that is true, we can first export our circuit to QASM then use SymPy to plot them. I haven't explored this yet.

[TheCharmingSociopath]

Hi,

If this enhancement is still relevant (which I think it is, installing a Tex distribution is heavy and painful) can I take this issue up?

The approach you mentioned in the example seems easy to implement, push all the returned sympy gate objects into a list and write a function to plot them using sympy.physics.quantum.circuitplot, passing the said list as a parameter.

[BoxiLi]

Hi @TheCharmingSociopath, yes, this enhancement is still relevant. You are very welcome to take this issue up.

The only thing is that right now our own gate classes have not yet been merged (#96). So you probably need to define get_sympy_object under the class Gate and add lots of if branches to check the name of the gate. Nonetheless, it should work, I think.

You probably also need to add another function that draws the sympy circuit. It would be nice to first have this in a separate file and then try to merge it with other workflows later when it is complete.