rzx defined twice in QASM export

[epelofske-LANL]

Environment

• Qiskit Terra version: qiskit-terra==0.19.2
• Python version: 3.9.7
• Operating system: macOS

What is happening?

A Qiskit circuit that contains the ecr two qubit gate exports two definitions of rzx when converting the circuit to a QASM file:

OPENQASM 2.0;
include "qelib1.inc";
gate rzx(param0) q0,q1 { h q1; cx q0,q1; rz(-pi/4) q1; cx q0,q1; h q1; }
gate rzx(param0) q0,q1 { h q1; cx q0,q1; rz(pi/4) q1; cx q0,q1; h q1; }
gate ecr q0,q1 { rzx(pi/4) q0,q1; x q0; rzx(-pi/4) q0,q1; }

How can we reproduce the issue?

Create a Qiskit circuit with an ECR gate, and then export that circuit to QASM.

What should happen?

Upon reading in the QASM file (QuantumCircuit.from_qasm_file) it will throw an error because rzx is defined twice.

Any suggestions?

No response

[jakelishman]

Thanks for the report. In this case, this is a duplicate of issue #7749, which is itself a duplicate in spirit of #7335. There's a bit more information in those issues about why this happens, and how our near-term plans will help fix this.

[jakelishman]

Duplicate of #7749