Support setp and delay pulses

[1tnguyen]

IBM has introduced two new native pulses setp (set phase) and delay (in addition to fc and acquire).

These two instructions can be used inside pulse cmd-def JSON. We need to update IBMAccelerator::contributeInstructions to contribute these new instructions so that the pulse cmd-def Composite can be constructed.

[1tnguyen]

To be able to run a protocol similar to the one described in https://arxiv.org/pdf/2008.04302.pdf,
we need to support a couple of advanced pulse instructions:

• Shift freq. (shiftf)
• Set freq. (setf)

These instructions allow changing LO freq. per pulse (rather than fixed for the whole experiment).
(pulse frequency is an optimization parameter in the protocol)

Note: we may not be able to simulate these two instructions since Aer doesn't support them (see this)

[flatslm]

Topics about pulses are interesting to me. Is this issue still relevant?

[1tnguyen]

Yea, this issue is still relevant. Please feel free to work on this if you're interested.

BTW, we can get around this issue by pre-modulating the pulse signal in the code, but it'd be nice to have these pulse instructions supported in XACC.

[flatslm]

I started implementation (a draft pull request #464 ) and have a few questions:

1. Do I understand correctly that it is necessary to support the processing of 4 new commands: setf / shiftf / setp / shiftp ?
2. What is the best place for testing code? Example program or unit tests (like in xacc/quantum/gate/ir/tests /)?
3. What backend is better for testing? Last version of Aer?

[1tnguyen]

Hi @flatslm,

1. Do I understand correctly that it is necessary to support the processing of 4 new commands: setf / shiftf / setp / shiftp ?

• Yes.

2. What is the best place for testing code? Example program or unit tests (like in xacc/quantum/gate/ir/tests /)?

• I think you can place unit testing code in xacc/quantum/plugins/ibm/tests. There are a few IBM-related tests in there for your reference (including some pulse IR testing).

3. What backend is better for testing? Last version of Aer?

• The 'open' IBMQ provider has the armonk device which can run pulse instructions. You could test by making sure the QObj with those new pulse instructions is accepted.
• I don't think that Aer can handle frequency instructions (setf and shiftf). Looks like it will raise an exception if seeing those frequency instructions (see Aer's digest_pulse_qobj.py).

[flatslm]

Hi @tnguyen-ornl
I added simplest test to pull request #464 .
Check please, is this test correct?
Now I plan send some instructions to armonk ibm device.

[1tnguyen]

Thanks, @flatslm.
This looks good. For the test that you have, you can look at the QObj generated when you execute that cr_comp.
Also, make sure it is validated by the armonk backend :)

[flatslm]

Hi @tnguyen-ornl.
Some code and new test was corrected and I marked PR as "ready for review".
It seems that setf and shiftf works ok, but I did not found backend with support of setp/shiftp operations.