Merge pull request #174 from dlyongemallo/support_qasm3_output

Support output to OpenQASM 3 format.

pyzx/circuit/__init__.py

@@ -389,10 +389,15 @@ def to_quipper(self) -> str:
         s += "Outputs: " + ", ".join("{!s}:Qbit".format(i) for i in range(self.qubits))
         return s
 
-    def to_qasm(self) -> str:
+    def to_qasm(self, version: int = 2) -> str:
         """Produces a QASM description of the circuit."""
-        s = """OPENQASM 2.0;\ninclude "qelib1.inc";\n"""
-        s += "qreg q[{!s}];\n".format(self.qubits)
+        assert version in [2, 3]
+        if version == 3:
+            s = """OPENQASM 3;\ninclude "stdgates.inc";\n"""
+            s += "qubit[{!s}] q;\n".format(self.qubits)
+        else:
+            s = """OPENQASM 2.0;\ninclude "qelib1.inc";\n"""
+            s += "qreg q[{!s}];\n".format(self.qubits)
         for g in self.gates:
             s += g.to_qasm() + "\n"
         return s

pyzx/routing/parity_maps.py

@@ -106,8 +106,8 @@ def prepend_gate(self, gate: Union[Gate, str], *args, **kwargs):
             gate = gate_class(*args, **kwargs)
         self.gates.insert(0, gate)
 
-    def to_qasm(self) -> str:
-        qasm = super().to_qasm()
+    def to_qasm(self, version: int = 2) -> str:
+        qasm = super().to_qasm(version)
         initial_perm = "// Initial wiring: " + str(self.row_perm)
         end_perm = "// Resulting wiring: " + str(self.col_perm)
         return "\n".join([initial_perm, end_perm, qasm])

tests/test_qasm.py

@@ -174,6 +174,11 @@ def compare_gate_matrix_with_qiskit(gates, num_qubits: int, num_angles: int, qas
                     self.assertTrue(compare_tensors(pyzx_matrix, qiskit_matrix, False),
                                     f"Gate: {gate}\nqasm:\n{qasm}\npyzx_matrix:\n{pyzx_matrix}\nqiskit_matrix:\n{qiskit_matrix}")
 
+                    s = c.to_qasm(qasm_version)
+                    round_trip = Circuit.from_qasm(s)
+                    self.assertEqual(c.qubits, round_trip.qubits)
+                    self.assertListEqual(c.gates, round_trip.gates)
+
         # Test standard gates common to both OpenQASM 2 and 3.
         compare_gate_matrix_with_qiskit(
             ['x', 'y', 'z', 'h', 's', 'sdg', 't', 'tdg', 'sx'], 1, 0)