Fix stim.TableauSimulator.cnot and friends crashing on target_rec t…

…argets (#37)
quantumlib · Apr 16, 2021 · 5933aef · 5933aef
1 parent 0b2b430
commit 5933aef
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Showing 2 changed files with 17 additions and 1 deletion.
diff --git a/src/simulators/tableau_simulator.pybind.cc b/src/simulators/tableau_simulator.pybind.cc
@@ -38,7 +38,7 @@ TempViewableData args_to_targets(TableauSimulator &self, const pybind11::args &a
     try {
         for (const auto &e : args) {
             size_t q = e.cast<uint32_t>();
-            max_q = std::max(max_q, q);
+            max_q = std::max(max_q, q & TARGET_VALUE_MASK);
             arguments.push_back(q);
         }
     } catch (const pybind11::cast_error &) {

diff --git a/src/simulators/tableau_simulator_pybind_test.py b/src/simulators/tableau_simulator_pybind_test.py
@@ -265,3 +265,19 @@ def test_canonical_stabilizers():
         stim.PauliString("-ZXY"),
         stim.PauliString("+_ZX"),
     ]
+
+
+def test_classical_control_cnot():
+    s = stim.TableauSimulator()
+
+    with pytest.raises(IndexError, match="beginning of time"):
+        s.cnot(stim.target_rec(-1), 0)
+
+    assert not s.measure(1)
+    s.cnot(stim.target_rec(-1), 0)
+    assert not s.measure(0)
+
+    s.x(1)
+    assert s.measure(1)
+    s.cnot(stim.target_rec(-1), 0)
+    assert s.measure(0)