QASM2.0 is not preserved

[pranavm1502]

Pre-Report Checklist

• [Yes] I am running the latest versions of pyQuil and the Forest SDK
• [Yes] I checked to make sure that this bug has not already been reported

Issue Description

Converting a QASM2.0 circuit to native_quil does the not preserve the circuit. There are two obvious errors-

1. It adds extraneous single qubit and multi-qubit gates
2. It removed the Barrier on the three qubits before measuring.

How to Reproduce

If useful, provide a numbered list of the steps that result in the error.

Otherwise, just fill out the "Code Snippet" and "Error Output" sections below.

Code Snippet

new_qasm = """OPENQASM 2.0;
include "qelib1.inc";
qreg q[80];
creg c[2];
cz q[25],q[24];
cz q[23],q[24];
barrier q[25],q[23],q[24];
measure q[25] -> c[0];
measure q[23] -> c[1];
"""
program = pyquil.Program(RawInstr(new_qasm)).wrap_in_numshots_loop(shots)
qc.compiler.quil_to_native_quil(program).instructions

Error Output

[<DECLARE c>,
 <Gate CZ 25 24>,
 <Gate RZ(pi/2) 23>,
 <Gate RZ(pi) 24>,
 <Gate RX(pi/2) 24>,
 <Gate RZ(pi/2) 24>,
 <Gate RX(-pi/2) 24>,
 <Gate RZ(-pi) 24>,
 <Gate XY(pi) 23 24>,
 <Gate RX(pi/2) 23>,
 <Gate RZ(-pi/2) 23>,
 <Gate RX(-pi/2) 23>,
 <Gate XY(pi) 23 24>,
 <Gate RZ(-pi) 24>,
 <Gate RX(pi/2) 24>,
 <Gate RZ(pi/2) 24>,
 <Gate RX(-pi/2) 24>,
 <Gate RZ(-pi/2) 24>,
 <pyquil.quilbase.Measurement at 0x7f3ab82be650>,
 <pyquil.quilbase.Measurement at 0x7f3ab82be770>]

Environment Context

I am running this code on the QCS server.

Operating System:

Python Version (python -V):

Quilc Version (quilc --version):

QVM Version (qvm --version):

Python Environment Details (pip freeze or conda list):

Copy and paste the output of `pip freeze` or `conda list` here.

[dbanty]

Just a note that since the conversion of QASM2.0 to Quil happens in quilc, that any fix is likely to be in quil-lang/quilc#823 . If there is anything specific you end up needing out of pyquil definitely let us know!

[pranavm1502]

Hi @dbanty, the fix won't come from quilc. Looks like we need to modify the ISA in the QuantumComputer object generated by pyquil. qc.to_compiler_isa() gives the backend ISA but there is no method for changing that.