[BUG] `Circuit.draw()` returns an error when gate parameter is a string

[ValentinS4t1qbit]

Issue: Bug Report

We wanted to provide a default draw method on the Circuit class in Tangelo for convenience, and decided that cirq 's would do: when we call draw() we implicitly ask cirq to draw it for us (Thanks cirq ❤️ )

Tangelo circuits can take almost anything as a value for gate.parameter, including a string. cirq is however not happy with that:

circuit = Circuit([Gate('H', 0), Gate('CNOT', 1, 0), Gate('RY', 1, parameter='theta')])
circuit.draw()

Can you help us ensure draw() works for strings as parameters ?

How to win

It turns out cirq is happy if we define a sympy symbol. Then we observe that both draw and print in Tangelo work just fine:

Which means one could ask draw to make a copy of the circuit on-the-fly (we don't want the method to modify the object itself) that replaces string values for parameters by equivalent sympy symbols.

• Try with an arbitrary circuit of 100 gates with parameters: if this takes less than 2-3 seconds, then your solution is performant enough.
• If not, compare the time of your new draw function and and show us the difference in performance with the old one (which you can keep around and rename: we'll only push the new one into the PR).

Validation

• Verify that draw and print give satisfying results on the circuit above
• give valentin.senicourt@sandboxquantum.com access to a Google Colab notebook whose first cell installs Tangelo from your branch and then runs those draw / print cells with a few clicks and if it looks good, we're good !

[anushkrishnav]

Hey, I saw this issue on Unitary hacks , I think I can get it done, I will take this issue , Thanks for the how to win seems like a straight forward task if I have more questions will reach out

[alexfleury-sb]

Thank you for looking into this! We will look forward updates, and provide additional info if needed.

[anushkrishnav]

Hopefully, with my PR, This issue has been completed. !! Kindly assign me the issue

[ValentinS4t1qbit]

Solved by @anushkrishnav in #391