Fix HERALDED_PAULI_CHANNEL_1 permuting X/Y/Z error argument components

file_lists/test_files

@@ -82,6 +82,7 @@ src/stim/util_bot/twiddle.test.cc
 src/stim/util_top/circuit_flow_generators.test.cc
 src/stim/util_top/circuit_inverse_qec.test.cc
 src/stim/util_top/circuit_inverse_unitary.test.cc
+src/stim/util_top/circuit_to_dem.test.cc
 src/stim/util_top/circuit_to_detecting_regions.test.cc
 src/stim/util_top/circuit_vs_amplitudes.test.cc
 src/stim/util_top/circuit_vs_tableau.test.cc

src/stim.h

@@ -108,6 +108,7 @@
 #include "stim/util_top/circuit_flow_generators.h"
 #include "stim/util_top/circuit_inverse_qec.h"
 #include "stim/util_top/circuit_inverse_unitary.h"
+#include "stim/util_top/circuit_to_dem.h"
 #include "stim/util_top/circuit_to_detecting_regions.h"
 #include "stim/util_top/circuit_vs_amplitudes.h"
 #include "stim/util_top/circuit_vs_tableau.h"

src/stim/cmd/command_diagram.pybind.cc

@@ -268,15 +268,22 @@ DiagramHelper stim_pybind::circuit_diagram(
         type == "timeslice" || type == "time-slice") {
         std::stringstream out;
         DiagramTimelineSvgDrawer::make_diagram_write_to(
-            circuit, out, tick_min, num_ticks, DiagramTimelineSvgDrawerMode::SVG_MODE_TIME_SLICE, filter_coords, num_rows);
+            circuit,
+            out,
+            tick_min,
+            num_ticks,
+            DiagramTimelineSvgDrawerMode::SVG_MODE_TIME_SLICE,
+            filter_coords,
+            num_rows);
         DiagramType d_type =
             type.find("html") != std::string::npos ? DiagramType::DIAGRAM_TYPE_SVG_HTML : DiagramType::DIAGRAM_TYPE_SVG;
         return DiagramHelper{d_type, out.str()};
     } else if (
         type == "detslice-svg" || type == "detslice" || type == "detslice-html" || type == "detslice-svg-html" ||
         type == "detector-slice-svg" || type == "detector-slice") {
         std::stringstream out;
-        DetectorSliceSet::from_circuit_ticks(circuit, tick_min, num_ticks, filter_coords).write_svg_diagram_to(out, num_rows);
+        DetectorSliceSet::from_circuit_ticks(circuit, tick_min, num_ticks, filter_coords)
+            .write_svg_diagram_to(out, num_rows);
         DiagramType d_type =
             type.find("html") != std::string::npos ? DiagramType::DIAGRAM_TYPE_SVG_HTML : DiagramType::DIAGRAM_TYPE_SVG;
         return DiagramHelper{d_type, out.str()};

src/stim/dem/detector_error_model_target.pybind.cc

@@ -28,7 +28,6 @@ pybind11::class_<ExposedDemTarget> stim_pybind::pybind_detector_error_model_targ
 
 void stim_pybind::pybind_detector_error_model_target_methods(
     pybind11::module &m, pybind11::class_<ExposedDemTarget> &c) {
-
     c.def(
         pybind11::init([](const pybind11::object &arg) -> ExposedDemTarget {
             if (pybind11::isinstance<ExposedDemTarget>(arg)) {

src/stim/gates/gates.cc

@@ -47,110 +47,110 @@ GateDataMap::GateDataMap() {
 
 GateType Gate::hadamard_conjugated(bool ignoring_sign) const {
     switch (id) {
-    case GateType::DETECTOR:
-    case GateType::OBSERVABLE_INCLUDE:
-    case GateType::TICK:
-    case GateType::QUBIT_COORDS:
-    case GateType::SHIFT_COORDS:
-    case GateType::MPAD:
-    case GateType::H:
-    case GateType::DEPOLARIZE1:
-    case GateType::DEPOLARIZE2:
-    case GateType::Y_ERROR:
-    case GateType::I:
-    case GateType::Y:
-    case GateType::SQRT_YY:
-    case GateType::SQRT_YY_DAG:
-    case GateType::MYY:
-    case GateType::SWAP:
-        return id;
+        case GateType::DETECTOR:
+        case GateType::OBSERVABLE_INCLUDE:
+        case GateType::TICK:
+        case GateType::QUBIT_COORDS:
+        case GateType::SHIFT_COORDS:
+        case GateType::MPAD:
+        case GateType::H:
+        case GateType::DEPOLARIZE1:
+        case GateType::DEPOLARIZE2:
+        case GateType::Y_ERROR:
+        case GateType::I:
+        case GateType::Y:
+        case GateType::SQRT_YY:
+        case GateType::SQRT_YY_DAG:
+        case GateType::MYY:
+        case GateType::SWAP:
+            return id;
 
-    case GateType::MY:
-    case GateType::MRY:
-    case GateType::RY:
-    case GateType::YCY:
-        return ignoring_sign ? id : GateType::NOT_A_GATE;
+        case GateType::MY:
+        case GateType::MRY:
+        case GateType::RY:
+        case GateType::YCY:
+            return ignoring_sign ? id : GateType::NOT_A_GATE;
 
-    case GateType::ISWAP:
-    case GateType::CZSWAP:
-    case GateType::ISWAP_DAG:
-        return GateType::NOT_A_GATE;
+        case GateType::ISWAP:
+        case GateType::CZSWAP:
+        case GateType::ISWAP_DAG:
+            return GateType::NOT_A_GATE;
 
-    case GateType::XCY:
-        return ignoring_sign ? GateType::CY : GateType::NOT_A_GATE;
-    case GateType::CY:
-        return ignoring_sign ? GateType::XCY : GateType::NOT_A_GATE;
-    case GateType::YCX:
-        return ignoring_sign ? GateType::YCZ : GateType::NOT_A_GATE;
-    case GateType::YCZ:
-        return ignoring_sign ? GateType::YCX : GateType::NOT_A_GATE;
-    case GateType::C_XYZ:
-        return ignoring_sign ? GateType::C_ZYX : GateType::NOT_A_GATE;
-    case GateType::C_ZYX:
-        return ignoring_sign ? GateType::C_XYZ : GateType::NOT_A_GATE;
-    case GateType::H_XY:
-        return ignoring_sign ? GateType::H_YZ : GateType::NOT_A_GATE;
-    case GateType::H_YZ:
-        return ignoring_sign ? GateType::H_XY : GateType::NOT_A_GATE;
+        case GateType::XCY:
+            return ignoring_sign ? GateType::CY : GateType::NOT_A_GATE;
+        case GateType::CY:
+            return ignoring_sign ? GateType::XCY : GateType::NOT_A_GATE;
+        case GateType::YCX:
+            return ignoring_sign ? GateType::YCZ : GateType::NOT_A_GATE;
+        case GateType::YCZ:
+            return ignoring_sign ? GateType::YCX : GateType::NOT_A_GATE;
+        case GateType::C_XYZ:
+            return ignoring_sign ? GateType::C_ZYX : GateType::NOT_A_GATE;
+        case GateType::C_ZYX:
+            return ignoring_sign ? GateType::C_XYZ : GateType::NOT_A_GATE;
+        case GateType::H_XY:
+            return ignoring_sign ? GateType::H_YZ : GateType::NOT_A_GATE;
+        case GateType::H_YZ:
+            return ignoring_sign ? GateType::H_XY : GateType::NOT_A_GATE;
 
-    case GateType::X:
-        return GateType::Z;
-    case GateType::Z:
-        return GateType::X;
-    case GateType::SQRT_Y:
-        return GateType::SQRT_Y_DAG;
-    case GateType::SQRT_Y_DAG:
-        return GateType::SQRT_Y;
-    case GateType::MX:
-        return GateType::M;
-    case GateType::M:
-        return GateType::MX;
-    case GateType::MRX:
-        return GateType::MR;
-    case GateType::MR:
-        return GateType::MRX;
-    case GateType::RX:
-        return GateType::R;
-    case GateType::R:
-        return GateType::RX;
-    case GateType::XCX:
-        return GateType::CZ;
-    case GateType::XCZ:
-        return GateType::CX;
-    case GateType::CX:
-        return GateType::XCZ;
-    case GateType::CZ:
-        return GateType::XCX;
-    case GateType::X_ERROR:
-        return GateType::Z_ERROR;
-    case GateType::Z_ERROR:
-        return GateType::X_ERROR;
-    case GateType::SQRT_X:
-        return GateType::S;
-    case GateType::SQRT_X_DAG:
-        return GateType::S_DAG;
-    case GateType::S:
-        return GateType::SQRT_X;
-    case GateType::S_DAG:
-        return GateType::SQRT_X_DAG;
-    case GateType::SQRT_XX:
-        return GateType::SQRT_ZZ;
-    case GateType::SQRT_XX_DAG:
-        return GateType::SQRT_ZZ_DAG;
-    case GateType::SQRT_ZZ:
-        return GateType::SQRT_XX;
-    case GateType::SQRT_ZZ_DAG:
-        return GateType::SQRT_XX_DAG;
-    case GateType::CXSWAP:
-        return GateType::SWAPCX;
-    case GateType::SWAPCX:
-        return GateType::CXSWAP;
-    case GateType::MXX:
-        return GateType::MZZ;
-    case GateType::MZZ:
-        return GateType::MXX;
-    default:
-        return GateType::NOT_A_GATE;
+        case GateType::X:
+            return GateType::Z;
+        case GateType::Z:
+            return GateType::X;
+        case GateType::SQRT_Y:
+            return GateType::SQRT_Y_DAG;
+        case GateType::SQRT_Y_DAG:
+            return GateType::SQRT_Y;
+        case GateType::MX:
+            return GateType::M;
+        case GateType::M:
+            return GateType::MX;
+        case GateType::MRX:
+            return GateType::MR;
+        case GateType::MR:
+            return GateType::MRX;
+        case GateType::RX:
+            return GateType::R;
+        case GateType::R:
+            return GateType::RX;
+        case GateType::XCX:
+            return GateType::CZ;
+        case GateType::XCZ:
+            return GateType::CX;
+        case GateType::CX:
+            return GateType::XCZ;
+        case GateType::CZ:
+            return GateType::XCX;
+        case GateType::X_ERROR:
+            return GateType::Z_ERROR;
+        case GateType::Z_ERROR:
+            return GateType::X_ERROR;
+        case GateType::SQRT_X:
+            return GateType::S;
+        case GateType::SQRT_X_DAG:
+            return GateType::S_DAG;
+        case GateType::S:
+            return GateType::SQRT_X;
+        case GateType::S_DAG:
+            return GateType::SQRT_X_DAG;
+        case GateType::SQRT_XX:
+            return GateType::SQRT_ZZ;
+        case GateType::SQRT_XX_DAG:
+            return GateType::SQRT_ZZ_DAG;
+        case GateType::SQRT_ZZ:
+            return GateType::SQRT_XX;
+        case GateType::SQRT_ZZ_DAG:
+            return GateType::SQRT_XX_DAG;
+        case GateType::CXSWAP:
+            return GateType::SWAPCX;
+        case GateType::SWAPCX:
+            return GateType::CXSWAP;
+        case GateType::MXX:
+            return GateType::MZZ;
+        case GateType::MZZ:
+            return GateType::MXX;
+        default:
+            return GateType::NOT_A_GATE;
     }
 }
 

src/stim/gates/gates.test.cc

@@ -22,8 +22,8 @@
 #include "stim/simulators/tableau_simulator.h"
 #include "stim/util_bot/str_util.h"
 #include "stim/util_bot/test_util.test.h"
-#include "stim/util_top/has_flow.h"
 #include "stim/util_top/circuit_flow_generators.h"
+#include "stim/util_top/has_flow.h"
 
 using namespace stim;
 
@@ -375,8 +375,10 @@ TEST(gate_data, hadamard_conjugated_vs_flow_generators_of_two_qubit_gates) {
             GateType actual_s = g.hadamard_conjugated(false);
             GateType actual_u = g.hadamard_conjugated(true);
             bool found = std::find(other_us.begin(), other_us.end(), actual_u) != other_us.end();
-            EXPECT_EQ(actual_s, expected_s) << "signed " << g.name << " -> " << GATE_DATA[actual_s].name << " != " << GATE_DATA[expected_s].name;
-            EXPECT_TRUE(found) << "unsigned " << g.name << " -> " << GATE_DATA[actual_u].name << " not in " << GATE_DATA[other_us[0]].name;
+            EXPECT_EQ(actual_s, expected_s)
+                << "signed " << g.name << " -> " << GATE_DATA[actual_s].name << " != " << GATE_DATA[expected_s].name;
+            EXPECT_TRUE(found) << "unsigned " << g.name << " -> " << GATE_DATA[actual_u].name << " not in "
+                               << GATE_DATA[other_us[0]].name;
         }
     }
 }

src/stim/simulators/error_analyzer.cc

@@ -307,7 +307,7 @@ void ErrorAnalyzer::undo_MZ_with_context(const CircuitInstruction &dat, const ch
 }
 
 void ErrorAnalyzer::undo_HERALDED_ERASE(const CircuitInstruction &dat) {
-    check_can_approximate_disjoint("HERALDED_ERASE", dat.args);
+    check_can_approximate_disjoint("HERALDED_ERASE", dat.args, false);
     double p = dat.args[0] * 0.25;
     double i = std::max(0.0, 1.0 - 4 * p);
 
@@ -327,7 +327,7 @@ void ErrorAnalyzer::undo_HERALDED_ERASE(const CircuitInstruction &dat) {
 }
 
 void ErrorAnalyzer::undo_HERALDED_PAULI_CHANNEL_1(const CircuitInstruction &dat) {
-    check_can_approximate_disjoint("HERALDED_PAULI_CHANNEL_1", dat.args);
+    check_can_approximate_disjoint("HERALDED_PAULI_CHANNEL_1", dat.args, true);
     double hi = dat.args[0];
     double hx = dat.args[1];
     double hy = dat.args[2];
@@ -341,7 +341,7 @@ void ErrorAnalyzer::undo_HERALDED_PAULI_CHANNEL_1(const CircuitInstruction &dat)
         SparseXorVec<DemTarget> &herald_symptoms = tracker.rec_bits[tracker.num_measurements_in_past];
         if (accumulate_errors) {
             add_error_combinations<3>(
-                {i, 0, 0, 0, hi, hx, hy, hz},
+                {i, 0, 0, 0, hi, hz, hx, hy},
                 {tracker.xs[q].range(), tracker.zs[q].range(), herald_symptoms.range()},
                 true);
         }
@@ -750,7 +750,7 @@ void ErrorAnalyzer::correlated_error_block(const std::vector<CircuitInstruction>
         add_composite_error(dats[0].args[0], dats[0].targets);
         return;
     }
-    check_can_approximate_disjoint("ELSE_CORRELATED_ERROR", {});
+    check_can_approximate_disjoint("ELSE_CORRELATED_ERROR", {}, false);
 
     double remaining_p = 1;
     for (size_t k = dats.size(); k--;) {
@@ -820,7 +820,18 @@ void ErrorAnalyzer::undo_ELSE_CORRELATED_ERROR(const CircuitInstruction &dat) {
     }
 }
 
-void ErrorAnalyzer::check_can_approximate_disjoint(const char *op_name, SpanRef<const double> probabilities) const {
+void ErrorAnalyzer::check_can_approximate_disjoint(
+    const char *op_name, SpanRef<const double> probabilities, bool allow_single_component) const {
+    if (allow_single_component) {
+        size_t num_specified = 0;
+        for (double p : probabilities) {
+            num_specified += p > 0;
+        }
+        if (num_specified <= 1) {
+            return;
+        }
+    }
+
     if (approximate_disjoint_errors_threshold == 0) {
         std::stringstream msg;
         msg << "Encountered the operation " << op_name
@@ -854,7 +865,7 @@ void ErrorAnalyzer::undo_PAULI_CHANNEL_1(const CircuitInstruction &dat) {
     double iz;
     bool is_independent = try_disjoint_to_independent_xyz_errors_approx(dx, dy, dz, &ix, &iy, &iz);
     if (!is_independent) {
-        check_can_approximate_disjoint("PAULI_CHANNEL_1", dat.args);
+        check_can_approximate_disjoint("PAULI_CHANNEL_1", dat.args, true);
         ix = dx;
         iy = dy;
         iz = dz;
@@ -875,7 +886,7 @@ void ErrorAnalyzer::undo_PAULI_CHANNEL_1(const CircuitInstruction &dat) {
 }
 
 void ErrorAnalyzer::undo_PAULI_CHANNEL_2(const CircuitInstruction &dat) {
-    check_can_approximate_disjoint("PAULI_CHANNEL_2", dat.args);
+    check_can_approximate_disjoint("PAULI_CHANNEL_2", dat.args, true);
 
     std::array<double, 16> probabilities;
     for (size_t k = 0; k < 15; k++) {

src/stim/simulators/error_analyzer.h

@@ -329,7 +329,8 @@ struct ErrorAnalyzer {
     void undo_MXX_disjoint_controls_segment(const CircuitInstruction &inst);
     void undo_MYY_disjoint_controls_segment(const CircuitInstruction &inst);
     void undo_MZZ_disjoint_controls_segment(const CircuitInstruction &inst);
-    void check_can_approximate_disjoint(const char *op_name, SpanRef<const double> probabilities) const;
+    void check_can_approximate_disjoint(
+        const char *op_name, SpanRef<const double> probabilities, bool allow_single_component) const;
     void add_composite_error(double probability, SpanRef<const GateTarget> targets);
     void correlated_error_block(const std::vector<CircuitInstruction> &dats);
 };