Preliminary support for outputting to OpenQASM 3.0 (quantumlib#6795)

* Preliminary support for outputting to OpenQASM 3.0

- This supports changing the version and the obvious
changes in outputting to OpenQASM 3.0
- This PR does not cover imports from OpenQASM 3.0

cirq-core/cirq/circuits/circuit.py

@@ -1318,14 +1318,19 @@ def _resolve_parameters_(self, resolver: 'cirq.ParamResolver', recursive: bool)
             return self
         return self._from_moments(resolved_moments)
 
-    def _qasm_(self) -> str:
-        return self.to_qasm()
+    def _qasm_(self, args: Optional['cirq.QasmArgs'] = None) -> str:
+        if args is None:
+            output = self._to_qasm_output()
+        else:
+            output = self._to_qasm_output(precision=args.precision, version=args.version)
+        return str(output)
 
     def _to_qasm_output(
         self,
         header: Optional[str] = None,
         precision: int = 10,
         qubit_order: 'cirq.QubitOrderOrList' = ops.QubitOrder.DEFAULT,
+        version: str = '2.0',
     ) -> 'cirq.QasmOutput':
         """Returns a QASM object equivalent to the circuit.
 
@@ -1335,6 +1340,8 @@ def _to_qasm_output(
             precision: Number of digits to use when representing numbers.
             qubit_order: Determines how qubits are ordered in the QASM
                 register.
+            version:  Version of OpenQASM to render as output.  Defaults
+                to OpenQASM 2.0.  For OpenQASM 3.0, set this to '3.0'.
         """
         if header is None:
             header = f'Generated from Cirq v{cirq._version.__version__}'
@@ -1344,14 +1351,15 @@ def _to_qasm_output(
             qubits=qubits,
             header=header,
             precision=precision,
-            version='2.0',
+            version=version,
         )
 
     def to_qasm(
         self,
         header: Optional[str] = None,
         precision: int = 10,
         qubit_order: 'cirq.QubitOrderOrList' = ops.QubitOrder.DEFAULT,
+        version: str = '2.0',
     ) -> str:
         """Returns QASM equivalent to the circuit.
 
@@ -1361,9 +1369,11 @@ def to_qasm(
             precision: Number of digits to use when representing numbers.
             qubit_order: Determines how qubits are ordered in the QASM
                 register.
+            version: Version of OpenQASM to output.  Defaults to OpenQASM 2.0.
+                Specify '3.0' if OpenQASM 3.0 is desired.
         """
 
-        return str(self._to_qasm_output(header, precision, qubit_order))
+        return str(self._to_qasm_output(header, precision, qubit_order, version))
 
     def save_qasm(
         self,

cirq-core/cirq/circuits/circuit_test.py

@@ -3579,7 +3579,7 @@ def test_insert_operations_errors():
 @pytest.mark.parametrize('circuit_cls', [cirq.Circuit, cirq.FrozenCircuit])
 def test_to_qasm(circuit_cls):
     q0 = cirq.NamedQubit('q0')
-    circuit = circuit_cls(cirq.X(q0))
+    circuit = circuit_cls(cirq.X(q0), cirq.measure(q0, key='mmm'))
     assert circuit.to_qasm() == cirq.qasm(circuit)
     assert (
         circuit.to_qasm()
@@ -3591,9 +3591,29 @@ def test_to_qasm(circuit_cls):
 
 // Qubits: [q0]
 qreg q[1];
+creg m_mmm[1];
+
+
+x q[0];
+measure q[0] -> m_mmm[0];
+"""
+    )
+    assert circuit.to_qasm(version="3.0") == cirq.qasm(circuit, args=cirq.QasmArgs(version="3.0"))
+    assert (
+        circuit.to_qasm(version="3.0")
+        == f"""// Generated from Cirq v{cirq.__version__}
+
+OPENQASM 3.0;
+include "stdgates.inc";
+
+
+// Qubits: [q0]
+qubit[1] q;
+bit[1] m_mmm;
 
 
 x q[0];
+m_mmm[0] = measure q[0];
 """
     )
 

cirq-core/cirq/circuits/qasm_output.py

@@ -54,7 +54,7 @@ def _has_unitary_(self):
         return True
 
     def _qasm_(self, qubits: Tuple['cirq.Qid', ...], args: 'cirq.QasmArgs') -> str:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return args.format(
             'u3({0:half_turns},{1:half_turns},{2:half_turns}) {3};\n',
             self.theta,
@@ -246,7 +246,7 @@ def __str__(self) -> str:
         return ''.join(output)
 
     def _write_qasm(self, output_func: Callable[[str], None]) -> None:
-        self.args.validate_version('2.0')
+        self.args.validate_version('2.0', '3.0')
 
         # Generate nice line spacing
         line_gap = [0]
@@ -267,18 +267,26 @@ def output(text):
             output('\n')
 
         # Version
-        output('OPENQASM 2.0;\n')
-        output('include "qelib1.inc";\n')
+        output(f'OPENQASM {self.args.version};\n')
+        if self.args.version == '2.0':
+            output('include "qelib1.inc";\n')
+        else:
+            output('include "stdgates.inc";\n')
+
         output_line_gap(2)
 
         # Function definitions
         # None yet
 
         # Register definitions
         # Qubit registers
+
         output(f"// Qubits: [{', '.join(map(str, self.qubits))}]\n")
         if len(self.qubits) > 0:
-            output(f'qreg q[{len(self.qubits)}];\n')
+            if self.args.version == '2.0':
+                output(f'qreg q[{len(self.qubits)}];\n')
+            else:
+                output(f'qubit[{len(self.qubits)}] q;\n')
         # Classical registers
         # Pick an id for the creg that will store each measurement
         already_output_keys: Set[str] = set()
@@ -288,11 +296,15 @@ def output(text):
                 continue
             already_output_keys.add(key)
             meas_id = self.args.meas_key_id_map[key]
-            comment = self.meas_comments[key]
-            if comment is None:
-                output(f'creg {meas_id}[{len(meas.qubits)}];\n')
+            if self.meas_comments[key] is not None:
+                comment = f'  // Measurement: {self.meas_comments[key]}'
+            else:
+                comment = ''
+
+            if self.args.version == '2.0':
+                output(f'creg {meas_id}[{len(meas.qubits)}];{comment}\n')
             else:
-                output(f'creg {meas_id}[{len(meas.qubits)}];  // Measurement: {comment}\n')
+                output(f'bit[{len(meas.qubits)}] {meas_id};{comment}\n')
         # In OpenQASM 2.0, the transformation of global phase gates is ignored.
         # Therefore, no newline is created when the operations contained in
         # a circuit consist only of global phase gates.

cirq-core/cirq/circuits/qasm_output_test.py

@@ -225,7 +225,7 @@ def test_precision():
 def test_version():
     (q0,) = _make_qubits(1)
     with pytest.raises(ValueError):
-        output = cirq.QasmOutput((), (q0,), version='3.0')
+        output = cirq.QasmOutput((), (q0,), version='4.0')
         _ = str(output)
 
 

cirq-core/cirq/ops/classically_controlled_operation.py

@@ -216,7 +216,7 @@ def _control_keys_(self) -> FrozenSet['cirq.MeasurementKey']:
         return local_keys.union(protocols.control_keys(self._sub_operation))
 
     def _qasm_(self, args: 'cirq.QasmArgs') -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         if len(self._conditions) > 1:
             raise ValueError('QASM does not support multiple conditions.')
         subop_qasm = protocols.qasm(self._sub_operation, args=args)

cirq-core/cirq/ops/common_channels.py

@@ -702,7 +702,7 @@ def _has_stabilizer_effect_(self) -> Optional[bool]:
         return True
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return args.format('reset {0};\n', qubits[0])
 
     def _qid_shape_(self):

cirq-core/cirq/ops/common_gates.py

@@ -272,7 +272,7 @@ def _circuit_diagram_info_(
         )
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         if self._global_shift == 0:
             if self._exponent == 1:
                 return args.format('x {0};\n', qubits[0])
@@ -374,7 +374,7 @@ def __repr__(self) -> str:
         return f'cirq.Rx(rads={proper_repr(self._rads)})'
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return args.format('rx({0:half_turns}) {1};\n', self._exponent, qubits[0])
 
     def _json_dict_(self) -> Dict[str, Any]:
@@ -478,7 +478,7 @@ def _circuit_diagram_info_(
         )
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         if self._exponent == 1 and self.global_shift != -0.5:
             return args.format('y {0};\n', qubits[0])
 
@@ -560,7 +560,7 @@ def __repr__(self) -> str:
         return f'cirq.Ry(rads={proper_repr(self._rads)})'
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return args.format('ry({0:half_turns}) {1};\n', self._exponent, qubits[0])
 
     def _json_dict_(self) -> Dict[str, Any]:
@@ -791,7 +791,7 @@ def _circuit_diagram_info_(
         return protocols.CircuitDiagramInfo(wire_symbols=('Z',), exponent=e)
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
 
         if self.global_shift == 0:
             if self._exponent == 1:
@@ -910,7 +910,7 @@ def __repr__(self) -> str:
         return f'cirq.Rz(rads={proper_repr(self._rads)})'
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return args.format('rz({0:half_turns}) {1};\n', self._exponent, qubits[0])
 
     def _json_dict_(self) -> Dict[str, Any]:
@@ -1016,7 +1016,7 @@ def _circuit_diagram_info_(
         )
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         if self._exponent == 0:
             return args.format('id {0};\n', qubits[0])
         elif self._exponent == 1 and self._global_shift == 0:
@@ -1204,7 +1204,7 @@ def _circuit_diagram_info_(
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
         if self._exponent != 1:
             return None  # Don't have an equivalent gate in QASM
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return args.format('cz {0},{1};\n', qubits[0], qubits[1])
 
     def _has_stabilizer_effect_(self) -> Optional[bool]:
@@ -1405,7 +1405,7 @@ def controlled(
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
         if self._exponent != 1:
             return None  # Don't have an equivalent gate in QASM
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return args.format('cx {0},{1};\n', qubits[0], qubits[1])
 
     def _has_stabilizer_effect_(self) -> Optional[bool]:

cirq-core/cirq/ops/identity.py

@@ -138,7 +138,7 @@ def _circuit_diagram_info_(self, args) -> Tuple[str, ...]:
         return ('I',) * self.num_qubits()
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return ''.join([args.format('id {0};\n', qubit) for qubit in qubits])
 
     @classmethod

cirq-core/cirq/ops/matrix_gates.py

@@ -181,7 +181,7 @@ def _circuit_diagram_info_(
         return protocols.CircuitDiagramInfo(wire_symbols=[main, *rest])
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         if self._qid_shape == (2,):
             return protocols.qasm(
                 phased_x_z_gate.PhasedXZGate.from_matrix(self._matrix), args=args, qubits=qubits

cirq-core/cirq/ops/measurement_gate.py

@@ -227,15 +227,18 @@ def _circuit_diagram_info_(
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
         if self.confusion_map or not all(d == 2 for d in self._qid_shape):
             return NotImplemented
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         invert_mask = self.invert_mask
         if len(invert_mask) < len(qubits):
             invert_mask = invert_mask + (False,) * (len(qubits) - len(invert_mask))
         lines = []
         for i, (qubit, inv) in enumerate(zip(qubits, invert_mask)):
             if inv:
                 lines.append(args.format('x {0};  // Invert the following measurement\n', qubit))
-            lines.append(args.format('measure {0} -> {1:meas}[{2}];\n', qubit, self.key, i))
+            if args.version == '2.0':
+                lines.append(args.format('measure {0} -> {1:meas}[{2}];\n', qubit, self.key, i))
+            else:
+                lines.append(args.format('{1:meas}[{2}] = measure {0};\n', qubit, self.key, i))
             if inv:
                 lines.append(args.format('x {0};  // Undo the inversion\n', qubit))
         return ''.join(lines)

cirq-core/cirq/ops/phased_x_gate.py

@@ -69,7 +69,7 @@ def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optio
         if cirq.is_parameterized(self):
             return None
 
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
 
         e = cast(float, value.canonicalize_half_turns(self._exponent))
         p = cast(float, self.phase_exponent)

cirq-core/cirq/ops/swap_gates.py

@@ -148,7 +148,7 @@ def _circuit_diagram_info_(
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
         if self._exponent != 1:
             return None  # Don't have an equivalent gate in QASM
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return args.format('swap {0},{1};\n', qubits[0], qubits[1])
 
     def __str__(self) -> str:

cirq-core/cirq/ops/three_qubit_gates.py

@@ -164,7 +164,7 @@ def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optio
         if self._exponent != 1:
             return None
 
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         lines = [
             args.format('h {0};\n', qubits[2]),
             args.format('ccx {0},{1},{2};\n', qubits[0], qubits[1], qubits[2]),
@@ -483,7 +483,7 @@ def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optio
         if self._exponent != 1:
             return None
 
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return args.format('ccx {0},{1},{2};\n', qubits[0], qubits[1], qubits[2])
 
     def __repr__(self) -> str:
@@ -661,7 +661,7 @@ def _circuit_diagram_info_(
         return protocols.CircuitDiagramInfo(('@', '×', '×'))
 
     def _qasm_(self, args: 'cirq.QasmArgs', qubits: Tuple['cirq.Qid', ...]) -> Optional[str]:
-        args.validate_version('2.0')
+        args.validate_version('2.0', '3.0')
         return args.format('cswap {0},{1},{2};\n', qubits[0], qubits[1], qubits[2])
 
     def _value_equality_values_(self):