Use correct port when rewiring in DelayMeasures pass (#2230)

Author: cqc-alec

TKET_VERSION

@@ -1 +1 @@
-2.1.97
+2.1.98

pytket/docs/changelog.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## Unreleased
+
+Fixes:
+- Fix bug in `DelayMeasures` when multi-qubit gate follows final measurement.
+
 ## 2.18.1 (July 2026)
 
 ## 2.18.0 (May 2026)

tket/src/Transformations/MeasurePass.cpp

@@ -257,6 +257,7 @@ std::pair<bool, bool> run_delay_measures(
     Vertex v = p.first;
     Edge current_edge = p.second;
     Vertex current_vertex = circ.target(current_edge);
+    port_t current_port = circ.get_target_port(current_edge);
 
     Edge in_edge = circ.get_nth_in_edge(v, 0);
     Edge out_edge = circ.get_nth_out_edge(v, 0);
@@ -270,7 +271,7 @@ std::pair<bool, bool> run_delay_measures(
     circ.add_edge(
         {circ.source(current_edge), circ.get_source_port(current_edge)}, {v, 0},
         EdgeType::Quantum);
-    circ.add_edge({v, 0}, {current_vertex, 0}, EdgeType::Quantum);
+    circ.add_edge({v, 0}, {current_vertex, current_port}, EdgeType::Quantum);
     circ.remove_edge(current_edge);
   }
   return {true, true};

tket/test/src/test_CompilerPass.cpp

@@ -1476,6 +1476,16 @@ SCENARIO("Commute measurements to the end of a circuit") {
     CompilationUnit cu(c);
     CHECK_FALSE(try_delay_pass->apply(cu));
   }
+  GIVEN("Reuse of measured qubit") {
+    // https://github.com/Quantinuum/tket/issues/2229
+    Circuit c(2, 1);
+    c.add_measure(0, 0);
+    c.add_op<unsigned>(OpType::T, {0});
+    c.add_op<unsigned>(OpType::CX, {1, 0});
+    CompilationUnit cu(c);
+    REQUIRE(try_delay_pass->apply(cu));
+    Circuit c1 = cu.get_circ_ref();
+  }
 }
 
 SCENARIO("RemoveRedundancies and phase") {