Better pyzx visualization

[rafaelha]

Currently, circuits like this

are visualized as the following pyzx diagram

This diagram is technically not correct. What it means to resemble is a version of a "doubled" ZX diagram

where bold vertices imply doubling

and

are measurements and

is the trace.

Detector and observable can be seen to be implemented as the XOR

Unfortunately, pyzx does not support doubled diagrams.

I am not sure what the best way is to go forward. Potentially, one could make a PR into pyzx. I someone has ideas or suggestions, they would be very welcome!

Considerations

• The visualization should use d3, just like pyzx
• I'm somewhat against adding a lot of visualization code to tsim itself, so the ideal would be if pyzx supported doubled diagrams
• There needs to be bold vertices and bold edges
• Currently, the phase of vertices is used to display a label (rec[i]). Maybe there can be a better solution for labeling vertices

[rafaelha]

A draft is implemented here: https://github.com/QuEraComputing/tsim/tree/rafaelha/doubled_diagram_visualization