Support reset operation in QASM importer

[natestemen]

Is your feature request related to a use case or problem? Please describe.

We’ve encountered at least two cases where Mitiq users were unable to apply an error mitigation technique because their Qiskit circuits could not be converted to Cirq. Mitiq internally represents circuits as cirq.Circuit objects and relies on Cirq’s QASM importer for this conversion.

While I recognize that this might not be directly the responsibility of Cirq developers, I wanted to raise this issue for consideration. The QASM importer (#1548) was developed before the reset operation was introduced (#1774), so it’s possible that the reset operation was unintentionally omitted from the importer. It would be helpful to understand whether this is an area Cirq plans to address or if we should explore alternative workarounds.

Describe the solution you’d like

When converting a QASM circuit containing a reset operation, the resulting cirq.Circuit should include an instance of cirq.R to represent the reset operation.

[Optional] Additional context

Here’s a minimal reproducible example:

from cirq.contrib.qasm_import import circuit_from_qasm

circuit_from_qasm("""OPENQASM 2.0;
include "qelib1.inc";

qreg q[1];

reset q[0];
""")

[NoureldinYosri]

@pavoljuhas please take a look

[rscircus]

@natestemen - having interest to support it. Am building the equivalent thing for us planning to cover QASMv3.

[rscircus]

what type of reset do you support? wait, preselection, some dissipative gate? any pointers for a starter?

Given:

Describe the solution you’d like

When converting a QASM circuit containing a reset operation, the resulting cirq.Circuit should include an instance of cirq.R to represent the reset operation.

This should be quick. I add the operation to the QasmParser and document it here.

[rscircus]

To me it looks like that reset is already somewhat prepared in the code. See:

./cirq-core/cirq/ops/common_channels.py -> class ResetChannel ln 704. At least it looks like they can export ResetChannels to QASM.

[rscircus]

@natestemen - I think #6710 should solve your issue. It's been an interesting exercise to get into PLY. Further, so far it has been rather academic. It surely needs some more testing in the wild.