Add translation to RX(X) basis to equivalence library

[Cryoris]

What is the expected enhancement?

Allow using RX and RXX as basis gates by adding appropriate entries to the equivalence library:

• RZ = H RX H (and RZZ = HH RXX HH)
• RY = Sdg RX S (and equivalently for 2 qubits)

Currently this translation is not supported:

>>> from qiskit import QuantumCircuit, transpile
>>> qc = QuantumCircuit(1)
>>> qc.ry(0.1, 0);
>>> transpile(qc, basis_gates=["rx", "h", "s", "sdg"])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/jul/Qiskit/qiskit-terra/qiskit/compiler/transpiler.py", line 319, in transpile
    circuits = parallel_map(_transpile_circuit, list(zip(circuits, transpile_args)))
  File "/Users/jul/Qiskit/qiskit-terra/qiskit/tools/parallel.py", line 132, in parallel_map
    return [task(values[0], *task_args, **task_kwargs)]
  File "/Users/jul/Qiskit/qiskit-terra/qiskit/compiler/transpiler.py", line 407, in _transpile_circuit
    circuit, callback=transpile_config["callback"], output_name=transpile_config["output_name"]
  File "/Users/jul/Qiskit/qiskit-terra/qiskit/transpiler/passmanager.py", line 216, in run
    return self._run_single_circuit(circuits, output_name, callback)
  File "/Users/jul/Qiskit/qiskit-terra/qiskit/transpiler/passmanager.py", line 272, in _run_single_circuit
    result = running_passmanager.run(circuit, output_name=output_name, callback=callback)
  File "/Users/jul/Qiskit/qiskit-terra/qiskit/transpiler/runningpassmanager.py", line 123, in run
    dag = self._do_pass(pass_, dag, passset.options)
  File "/Users/jul/Qiskit/qiskit-terra/qiskit/transpiler/runningpassmanager.py", line 154, in _do_pass
    dag = self._run_this_pass(pass_, dag)
  File "/Users/jul/Qiskit/qiskit-terra/qiskit/transpiler/runningpassmanager.py", line 166, in _run_this_pass
    new_dag = pass_.run(dag)
  File "/Users/jul/Qiskit/qiskit-terra/qiskit/transpiler/passes/basis/basis_translator.py", line 114, in run
    "over library {}.".format(source_basis, target_basis, self._equiv_lib)
qiskit.transpiler.exceptions.TranspilerError: "Unable to map source basis {('ry', 1)} to target basis {'reset', 'snapshot', 's', 'delay', 'barrier', 'h', 'measure', 'sdg', 'rx'} over library <qiskit.circuit.equivalence.EquivalenceLibrary object at 0x7f9058c20a90>."

[ajavadia]

basis_gates=["rx", "rz"] works.

So I agree that it should be enough to add the equivalence relations you have highlighted.

[Osmanilge]

Hello I want to assigned for this issue. I am new in qiskit but I am interested in Qiskit so may you inform me about issue? I hope this issue is suitable for me.

[Cryoris]

Currently, @tyrolize is already working on this issue with their PR #7407 🙂