feat: add parameterized QASM3 exporter

releasenotes/notes/qasm3-parameterized-export-146.yaml

@@ -0,0 +1,14 @@
+---
+features:
+  - |
+    Added the header-only ``Qiskit::qasm3::dumps`` API for exporting quantum
+    circuits as OpenQASM 3. Parameterized circuits can supply their ordered
+    free-parameter names so the exporter emits valid ``input float[64]``
+    declarations. Names must be supplied explicitly because the current
+    Qiskit C API exposes the number of free symbols, but cannot enumerate
+    their names.
+upgrade:
+  - |
+    Removed ``QuantumCircuit::to_qasm3``. Include ``qasm3/exporter.hpp`` and
+    call ``Qiskit::qasm3::dumps(circuit)`` instead. Parameterized circuits must
+    additionally pass the ordered names of their free parameters.

samples/circuit_test.cpp

@@ -19,6 +19,7 @@
 
 #include "circuit/quantumcircuit.hpp"
 #include "circuit/library/quantum_volume.hpp"
+#include "qasm3/exporter.hpp"
 
 using namespace Qiskit::circuit;
 
@@ -71,7 +72,7 @@ int main()
   circ.measure(qr, cr);
 
   circ.draw();
-  std::cout << circ.to_qasm3();
+  std::cout << Qiskit::qasm3::dumps(circ);
 
   return 0;
 }

samples/parameterized_circuit_test.cpp

@@ -21,6 +21,7 @@
 #include <cmath>
 
 #include "circuit/quantumcircuit.hpp"
+#include "qasm3/exporter.hpp"
 
 using namespace Qiskit::circuit;
 
@@ -38,6 +39,8 @@ int main()
 
     circ.measure(qr, cr);
 
+    std::cout << Qiskit::qasm3::dumps(circ, {"t"}) << std::endl;
+
     circ.print();
 
     circ.draw();