Fix more cases of assuming is_unitary == (unitary_matrix is not None)

quantumlib · Oct 28, 2024 · 528dd99 · 528dd99
1 parent 6ab1f13
commit 528dd99
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Showing 5 changed files with 21 additions and 4 deletions.
diff --git a/src/stim/cmd/command_help.cc b/src/stim/cmd/command_help.cc
@@ -290,7 +290,7 @@ void print_stabilizer_generators(Acc &out, const Gate &gate) {
 }
 
 void print_bloch_vector(Acc &out, const Gate &gate) {
-    if (!(gate.flags & GATE_IS_UNITARY) || (gate.flags & GATE_TARGETS_PAIRS)) {
+    if (!(gate.flags & GATE_IS_UNITARY) || !(gate.flags & GATE_IS_SINGLE_QUBIT_GATE)) {
         return;
     }
 
@@ -343,7 +343,7 @@ void print_bloch_vector(Acc &out, const Gate &gate) {
 }
 
 void print_unitary_matrix(Acc &out, const Gate &gate) {
-    if (!(gate.flags & GATE_IS_UNITARY)) {
+    if (!gate.has_known_unitary_matrix()) {
         return;
     }
     auto matrix = gate.unitary();

diff --git a/src/stim/gates/gates.cc b/src/stim/gates/gates.cc
@@ -267,6 +267,10 @@ std::array<float, 4> Gate::to_axis_angle() const {
     return {rx, ry, rz, acosf(rs) * 2};
 }
 
+bool Gate::has_known_unitary_matrix() const {
+    return (flags & GateFlags::GATE_IS_UNITARY) && (flags & (GateFlags::GATE_IS_SINGLE_QUBIT_GATE | GateFlags::GATE_TARGETS_PAIRS));
+}
+
 std::vector<std::vector<std::complex<float>>> Gate::unitary() const {
     if (unitary_data.size() != 2 && unitary_data.size() != 4) {
         throw std::out_of_range(std::string(name) + " doesn't have 1q or 2q unitary data.");

diff --git a/src/stim/gates/gates.h b/src/stim/gates/gates.h
@@ -258,7 +258,7 @@ struct Gate {
 
     template <size_t W>
     std::vector<Flow<W>> flows() const {
-        if (flags & GateFlags::GATE_IS_UNITARY) {
+        if (has_known_unitary_matrix()) {
             auto t = tableau<W>();
             if (flags & GateFlags::GATE_TARGETS_PAIRS) {
                 return {
@@ -285,6 +285,12 @@ struct Gate {
     bool is_symmetric() const;
     GateType hadamard_conjugated(bool ignoring_sign) const;
 
+    /// Determines if the gate has a specified unitary matrix.
+    ///
+    /// Some unitary gates, such as SPP, don't have a specified matrix because the
+    /// matrix depends crucially on the targets.
+    bool has_known_unitary_matrix() const;
+
     /// Converts a single qubit unitary gate into an euler-angles rotation.
     ///
     /// Returns:

diff --git a/src/stim/gates/gates.pybind.cc b/src/stim/gates/gates.pybind.cc
@@ -50,7 +50,7 @@ pybind11::object gate_tableau(const Gate &self) {
     return pybind11::none();
 }
 pybind11::object gate_unitary_matrix(const Gate &self) {
-    if ((self.flags & GateFlags::GATE_IS_UNITARY) && (self.flags & (GateFlags::GATE_IS_SINGLE_QUBIT_GATE | GateFlags::GATE_TARGETS_PAIRS))) {
+    if (self.has_known_unitary_matrix()) {
         auto r = self.unitary();
         auto n = r.size();
         std::complex<float> *buffer = new std::complex<float>[n * n];

diff --git a/src/stim/py/stim_pybind_test.py b/src/stim/py/stim_pybind_test.py
@@ -136,6 +136,13 @@ def test_main_write_to_file():
             assert "Generated repetition_code" in f.read()
 
 
+def test_main_help(capsys):
+    assert stim.main(command_line_args=["help"]) == 0
+    captured = capsys.readouterr()
+    assert captured.err == ""
+    assert 'Available stim commands' in captured.out
+
+
 def test_main_redirects_stdout(capsys):
     assert stim.main(command_line_args=[
         "gen",