From 3850cecce5d6cd384b781e40c7d1e23b1da76a18 Mon Sep 17 00:00:00 2001
From: paul0403 <paulhaochen.wang@gmail.com>
Date: Fri, 16 Jan 2026 14:38:17 -0500
Subject: [PATCH 1/3] Add verifiers to quantum.paulirot op

---
 mlir/include/Quantum/IR/QuantumAttrDefs.td |  1 +
 mlir/include/Quantum/IR/QuantumOps.td      |  4 ++--
 mlir/lib/Quantum/IR/QuantumOps.cpp         | 21 +++++++++++++++++++++
 mlir/test/Quantum/VerifierTest.mlir        | 17 +++++++++++++++++
 4 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/mlir/include/Quantum/IR/QuantumAttrDefs.td b/mlir/include/Quantum/IR/QuantumAttrDefs.td
index 133462bae1..716c60b2aa 100644
--- a/mlir/include/Quantum/IR/QuantumAttrDefs.td
+++ b/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
diff --git a/mlir/include/Quantum/IR/QuantumOps.td b/mlir/include/Quantum/IR/QuantumOps.td
index 165aa880d1..8e3e4a9ad7 100644
--- a/mlir/include/Quantum/IR/QuantumOps.td
+++ b/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]> {
diff --git a/mlir/lib/Quantum/IR/QuantumOps.cpp b/mlir/lib/Quantum/IR/QuantumOps.cpp
index 47686d99e2..13dacb38c2 100644
--- a/mlir/lib/Quantum/IR/QuantumOps.cpp
+++ b/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());
diff --git a/mlir/test/Quantum/VerifierTest.mlir b/mlir/test/Quantum/VerifierTest.mlir
index f6fbb90ac1..31686aa350 100644
--- a/mlir/test/Quantum/VerifierTest.mlir
+++ b/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 //

From b7a355f9438b59c1cdf1adbb3071b3dc8ab5f6c4 Mon Sep 17 00:00:00 2001
From: paul0403 <paulhaochen.wang@gmail.com>
Date: Fri, 16 Jan 2026 15:36:56 -0500
Subject: [PATCH 2/3] changelog

---
 doc/releases/changelog-dev.md | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/doc/releases/changelog-dev.md b/doc/releases/changelog-dev.md
index b082fef31f..f4254cb39a 100644
--- a/doc/releases/changelog-dev.md
+++ b/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>
@@ -44,6 +48,7 @@
 <h3>Contributors ✍️</h3>
 
 This release contains contributions from (in alphabetical order):
-Ali Asadi
+Ali Asadi,
 Sengthai Heng,
-Jeffrey Kam.
+Jeffrey Kam,
+Paul Haochen Wang.

From 53e49f0d6f6342da7cf9f507291677bb56d024c4 Mon Sep 17 00:00:00 2001
From: paul0403 <paulhaochen.wang@gmail.com>
Date: Mon, 19 Jan 2026 13:13:02 -0500
Subject: [PATCH 3/3] CI