Measure using StabilizerStateChForm

[smitsanghavi]

Going through the paper, there is a way to simulate measurements without using the tableau.

Previous discussion at #2423 (comment).

[smitsanghavi]

The CliffordTableau is still not being removed from the CliffordSimulator because direct_fidelity_estimation still relies on the availability of stabilizers from CliffordState. We can move that to use the tableau directly

[tonybruguier]

Hi,
I opened:
#3567

[balopat]

Looks simple enough - I do have to dig in myself and understand it before I can approve it.
In the meantime, do you mind adding a test for this?

[smitsanghavi]

Looks simple enough - I do have to dig in myself and understand it before I can approve it.
In the meantime, do you mind adding a test for this?

I have added a test (not really a unit test since it's pretty error prone to initialize the detailed internal state before measurement by hand). Let me know if it looks good. My plan after this PR:

• Add measurement support to ActOnStabilizerChFormArgs and update MeasurementGate to use this _measure method for that case
• Update the test added here to use act_on instead of going through CliffordSimulator
• Resume Perform CliffordState measurements via method dispatch #3503 but this time with StabilizerStateChForm instead of CliffordTableau
• Remove CliffordTableau from CliffordSimulator