State visualization

[anpaz]

Is your feature request related to a problem? Please describe.
Currently, qviz shows only the operations of a quantum program. One key feature is the ability to group operations and expand them to make the program easier to understand.
Another tool that could greatly help developers to visualize a quantum program would be the ability to easily compare the state of the quantum system before and after each operation; this would greatly help in visualizing the effect of each operation.

Describe the solution you'd like
This is a very rough draft of what I have in mind:

Namely, you can select any gate and show the before/after state of the system.

How we represent state is very important: we need to come up with a scalable way to represent a state for many qubits (it's easy when it's 2 but becomes complicated when it's 10+). Ideally, is something that should quickly tell users what's the value we get with the highest probability when measured, and how is the phase affected. In the mock, the top basis state vectors are shown with their size proportional to their probability. It also shows the phase of these top basis state vectors and a histogram with all the probabilities.

[anpaz]

If you are interested on working on this, please contact me (@anpaz) to chat more about it.