Fix: Make QuantumCircuitData public.

- `QuantumCircuitData` is an extractor helper built only to extract attributes from a Python-based `Quantumircuit` that are not yet available in rust + the qualities that already are through `CircuitData`.
- Add `Clone` trait `QuantumCircuitData` as all its properties are clonable.
- Make `circuit_to_dag` public in rust in case it needs to be used for a transpiler pass.
- Adapt to renaming of `DAGCircuit::add_from_iter` into `DAGCircuit::extend`.

crates/circuit/src/converters.rs

@@ -18,12 +18,8 @@ use crate::{circuit_data::CircuitData, dag_circuit::DAGCircuit};
 
 /// An extractable representation of a QuantumCircuit reserved only for
 /// conversion purposes.
-///
-/// ## Notes:
-/// This structure does not implement `Clone`, this is the intended behavior as
-/// it contains callbacks to Python and should not be stored anywhere.
-#[derive(Debug)]
-struct QuantumCircuitData<'py> {
+#[derive(Debug, Clone)]
+pub struct QuantumCircuitData<'py> {
     data: CircuitData,
     name: Option<Bound<'py, PyAny>>,
     calibrations: Option<HashMap<String, Py<PyDict>>>,
@@ -63,7 +59,7 @@ impl<'py> FromPyObject<'py> for QuantumCircuitData<'py> {
 }
 
 #[pyfunction(signature = (quantum_circuit, copy_operations = true, qubit_order = None, clbit_order = None))]
-fn circuit_to_dag(
+pub fn circuit_to_dag(
     py: Python,
     quantum_circuit: QuantumCircuitData,
     copy_operations: bool,

crates/circuit/src/dag_circuit.rs

@@ -6638,7 +6638,7 @@ impl DAGCircuit {
             .collect::<PyResult<Vec<_>>>()?;
 
         // Finally add all the instructions back
-        new_dag.add_from_iter(py, instructions)?;
+        new_dag.extend(py, instructions)?;
 
         Ok(new_dag)
     }