Add verifiers to quantum.paulirot op

doc/releases/changelog-dev.md

@@ -13,6 +13,10 @@
   program outputs are typically probabilistic and statistics produced by measurement processes are
   conditional on the selected decision tree path.
 
+* Two new verifiers were added to the `quantum.paulirot` operation. They verify that the Pauli word
+  length and the number of qubit operands are the same, and that all of the Pauli words are legal.
+  [(#2405)](https://github.com/PennyLaneAI/catalyst/pull/2405)
+
 <h3>Breaking changes 💔</h3>
 
 <h3>Deprecations 👋</h3>
@@ -47,7 +51,8 @@
 <h3>Contributors ✍️</h3>
 
 This release contains contributions from (in alphabetical order):
-Ali Asadi
+Ali Asadi,
 Sengthai Heng,
 Jeffrey Kam,
-Mudit Pandey.
+Mudit Pandey,
+Paul Haochen Wang.

mlir/include/Quantum/IR/QuantumAttrDefs.td

@@ -38,5 +38,6 @@ def NamedObservable : I32EnumAttr<"NamedObservable",
 
 def NamedObservableAttr : EnumAttr<QuantumDialect, NamedObservable, "named_observable">;
 
+def PauliWord : TypedArrayAttrBase<StrAttr, "A product of Pauli operators, aka a Pauli word.">;
 
 #endif // QUANTUM_ATTR_DEFS

mlir/include/Quantum/IR/QuantumOps.td

@@ -534,8 +534,6 @@ def CustomOp : UnitaryGate_Op<"custom", [DifferentiableGate, NoMemoryEffect,
     let hasVerifier = 1;
 }
 
-def PauliWord : TypedArrayAttrBase<StrAttr, "A product of Pauli operators, aka a Pauli word.">;
-
 def PauliRotOp : UnitaryGate_Op<"paulirot", [DifferentiableGate, NoMemoryEffect,
                                          AttrSizedOperandSegments, AttrSizedResultSegments]> {
     let summary = "Apply a Pauli Product Rotation";
@@ -571,6 +569,8 @@ def PauliRotOp : UnitaryGate_Op<"paulirot", [DifferentiableGate, NoMemoryEffect,
             return getODSOperands(getParamOperandIdx());
         }
     }];
+
+    let hasVerifier = 1;
 }
 
 def GlobalPhaseOp : UnitaryGate_Op<"gphase", [DifferentiableGate, AttrSizedOperandSegments]> {

mlir/lib/Quantum/IR/QuantumOps.cpp

@@ -262,6 +262,27 @@ static LogicalResult verifyTensorResult(Type ty, int64_t length0, int64_t length
 
 // ----- gates
 
+static const mlir::StringSet<> validPauliWords = {"X", "Y", "Z", "I"};
+
+LogicalResult PauliRotOp::verify()
+{
+    size_t pauliWordLength = getPauliProduct().size();
+    size_t numQubits = getInQubits().size();
+    if (pauliWordLength != numQubits) {
+        return emitOpError() << "length of Pauli word (" << pauliWordLength
+                             << ") and number of qubits (" << numQubits << ") must be the same";
+    }
+
+    if (!llvm::all_of(getPauliProduct(), [](mlir::Attribute attr) {
+            auto pauliStr = llvm::cast<mlir::StringAttr>(attr);
+            return validPauliWords.contains(pauliStr.getValue());
+        })) {
+        return emitOpError() << "Only \"X\", \"Y\", \"Z\", and \"I\" are valid Pauli words.";
+    }
+
+    return success();
+}
+
 LogicalResult QubitUnitaryOp::verify()
 {
     size_t dim = std::pow(2, getInQubits().size());

mlir/test/Quantum/VerifierTest.mlir

@@ -127,6 +127,23 @@ func.func @controlled2(%1 : !quantum.bit, %2 : !quantum.bit, %3 : !quantum.bit)
     return
 }
 
+// -----
+
+func.func @test_paulirot_length_mismatch(%1 : !quantum.bit, %angle: f64) {
+    // expected-error@+1 {{length of Pauli word (2) and number of qubits (1) must be the same}}
+    %q = quantum.paulirot ["Z", "X"](%angle) %1 : !quantum.bit
+    return
+}
+
+// -----
+
+func.func @test_paulirot_bad_pauli_word(%1 : !quantum.bit, %angle: f64) {
+    // expected-error@+1 {{Only "X", "Y", "Z", and "I" are valid Pauli words.}}
+    %q = quantum.paulirot ["bad"](%angle) %1 : !quantum.bit
+    return
+}
+
+// -----
 
 //////////////////
 // Measurements //