Qiskit-terra: Show pi in the text drawer as π

[enavarro51]

What is the expected enhancement?

Based on a discussion in #4931, there's interest in displaying pi in the text drawer as πinstead of pi.

                   ┌─────────┐               ┌─────────┐
Change from   q_0: ┤ RX(pij) ├     to   q_0: ┤ RX(πj)  ├
                   └─────────┘               └─────────┘

To do this on all platforms requires completion of #4900 and modifying pi_check and 24 tests.

[PaulMcElligott]

Can I be assigned this issue please? I'd like to give it a shot, I actually think it might be a good first issue.

[enavarro51]

It's ok by me. @1ucian0 Ok by you?

[1ucian0]

Sure

[1ucian0]

ping @PaulMcElligott ! Any news?

[PaulMcElligott]

Still working on it.
Have been busy. I'll have more time tomorrow morning.

[1ucian0]

another ping @PaulMcElligott?

[PaulMcElligott]

Hi @1ucian0. I have managed to recreate the issue, but I'm having difficulty recreating it in a new environment. I have been following @aasfaw's episode closely. I am new to using git & anaconda.

Method to reproduce

from qiskit import *
import numpy as np
import sympy
from sympy.abc import pi
pi = np.pi
qr = QuantumRegister(1)
circuit_all = QuantumCircuit(qr)
circuit_all.rx(pi,0)
circuit_all.draw()
       ┌────────┐
q10_0: ┤ RX(pi) ├
       └────────┘
circuit_all.draw(output='mpl')

mpl (below) subtext uses the greek letter 'π' instead of the latinized 'pi'

Action plan

1. Attempt pass in a greek letter π using sympy in the notebook.
2. Inspect visualization.matplotlib.py to see what the mpl uses for greek letters and try to insert it in the code in visualiztions.txt.py

[1ucian0]

You might be overthinking this one.

Either inpt in pi_check can take the self.encoding as input, or you replace pi by π after that (if the encoding allows it).

[alejomonbar]

@PaulMcElligott are you still in it? can I try this one? @1ucian0

[1ucian0]

Sure! Go ahead @alejomonbar