Add mpp_state{_unsigned} methods to stim.Tableau.to_circuit (#690)

Author: Strilanc

doc/python_api_reference_vDev.md

@@ -10366,7 +10366,33 @@ def to_circuit(
                 Note: "graph_state" treats the tableau as a state instead of as a
                 Clifford operation. It will preserve the set of stabilizers, but
                 not the exact choice of generators.
+            "mpp_state": Prepares the tableau's state using MPP and feedback.
+                Gate set: MPP, CX rec, CY rec, CZ rec
+                Circuit qubit count: n
+                Circuit operation count: O(n^2)
+
+                The circuit will be made up of two layers:
+                    1. An MPP layer measuring each of the tableau's stabilizers.
+                    2. A feedback layer using the measurement results to control
+                        whether or not to apply each of the tableau's destabilizers
+                        in order to get the correct sign for each stabilizer.
+
+                Note: "mpp_state" treats the tableau as a state instead of as a
+                Clifford operation. It will preserve the set of stabilizers, but
+                not the exact choice of generators.
+            "mpp_state_unsigned": Prepares the tableau's state up to sign using MPP.
+                Gate set: MPP
+                Circuit qubit count: n
+                Circuit operation count: O(n^2)
 
+                The circuit will contain a series of MPP measurements measuring each
+                of the tableau's stabilizers. The stabilizers are measured in the
+                order used by the tableau (i.e. tableau.z_output(k) is the k'th
+                stabilizer measured).
+
+                Note: "mpp_state_unsigned" treats the tableau as a state instead of
+                as a Clifford operation. It will preserve the set of stabilizers,
+                but not the exact choice of generators.
     Returns:
         The synthesized circuit.
 
@@ -10421,6 +10447,19 @@ def to_circuit(
             H 3
             S 3
         ''')
+
+        >>> tableau.to_circuit("mpp_state_unsigned")
+        stim.Circuit('''
+            MPP X0*Z1*Y2*Y3 !X0*Y1*X2 !Z0*X1*X2*Z3 X0*X1*Z2
+        ''')
+
+        >>> tableau.to_circuit("mpp_state")
+        stim.Circuit('''
+            MPP X0*Z1*Y2*Y3 !X0*Y1*X2 !Z0*X1*X2*Z3 X0*X1*Z2
+            CX rec[-3] 2 rec[-1] 2
+            CY rec[-4] 0 rec[-3] 0 rec[-3] 3 rec[-2] 3 rec[-1] 0
+            CZ rec[-4] 1 rec[-1] 1
+        ''')
     """
 ```
 

doc/stim.pyi

@@ -8070,7 +8070,33 @@ class Tableau:
                     Note: "graph_state" treats the tableau as a state instead of as a
                     Clifford operation. It will preserve the set of stabilizers, but
                     not the exact choice of generators.
+                "mpp_state": Prepares the tableau's state using MPP and feedback.
+                    Gate set: MPP, CX rec, CY rec, CZ rec
+                    Circuit qubit count: n
+                    Circuit operation count: O(n^2)
+
+                    The circuit will be made up of two layers:
+                        1. An MPP layer measuring each of the tableau's stabilizers.
+                        2. A feedback layer using the measurement results to control
+                            whether or not to apply each of the tableau's destabilizers
+                            in order to get the correct sign for each stabilizer.
+
+                    Note: "mpp_state" treats the tableau as a state instead of as a
+                    Clifford operation. It will preserve the set of stabilizers, but
+                    not the exact choice of generators.
+                "mpp_state_unsigned": Prepares the tableau's state up to sign using MPP.
+                    Gate set: MPP
+                    Circuit qubit count: n
+                    Circuit operation count: O(n^2)
 
+                    The circuit will contain a series of MPP measurements measuring each
+                    of the tableau's stabilizers. The stabilizers are measured in the
+                    order used by the tableau (i.e. tableau.z_output(k) is the k'th
+                    stabilizer measured).
+
+                    Note: "mpp_state_unsigned" treats the tableau as a state instead of
+                    as a Clifford operation. It will preserve the set of stabilizers,
+                    but not the exact choice of generators.
         Returns:
             The synthesized circuit.
 
@@ -8125,6 +8151,19 @@ class Tableau:
                 H 3
                 S 3
             ''')
+
+            >>> tableau.to_circuit("mpp_state_unsigned")
+            stim.Circuit('''
+                MPP X0*Z1*Y2*Y3 !X0*Y1*X2 !Z0*X1*X2*Z3 X0*X1*Z2
+            ''')
+
+            >>> tableau.to_circuit("mpp_state")
+            stim.Circuit('''
+                MPP X0*Z1*Y2*Y3 !X0*Y1*X2 !Z0*X1*X2*Z3 X0*X1*Z2
+                CX rec[-3] 2 rec[-1] 2
+                CY rec[-4] 0 rec[-3] 0 rec[-3] 3 rec[-2] 3 rec[-1] 0
+                CZ rec[-4] 1 rec[-1] 1
+            ''')
         """
     def to_numpy(
         self,

glue/python/src/stim/__init__.pyi

@@ -8070,7 +8070,33 @@ class Tableau:
                     Note: "graph_state" treats the tableau as a state instead of as a
                     Clifford operation. It will preserve the set of stabilizers, but
                     not the exact choice of generators.
+                "mpp_state": Prepares the tableau's state using MPP and feedback.
+                    Gate set: MPP, CX rec, CY rec, CZ rec
+                    Circuit qubit count: n
+                    Circuit operation count: O(n^2)
+
+                    The circuit will be made up of two layers:
+                        1. An MPP layer measuring each of the tableau's stabilizers.
+                        2. A feedback layer using the measurement results to control
+                            whether or not to apply each of the tableau's destabilizers
+                            in order to get the correct sign for each stabilizer.
+
+                    Note: "mpp_state" treats the tableau as a state instead of as a
+                    Clifford operation. It will preserve the set of stabilizers, but
+                    not the exact choice of generators.
+                "mpp_state_unsigned": Prepares the tableau's state up to sign using MPP.
+                    Gate set: MPP
+                    Circuit qubit count: n
+                    Circuit operation count: O(n^2)
 
+                    The circuit will contain a series of MPP measurements measuring each
+                    of the tableau's stabilizers. The stabilizers are measured in the
+                    order used by the tableau (i.e. tableau.z_output(k) is the k'th
+                    stabilizer measured).
+
+                    Note: "mpp_state_unsigned" treats the tableau as a state instead of
+                    as a Clifford operation. It will preserve the set of stabilizers,
+                    but not the exact choice of generators.
         Returns:
             The synthesized circuit.
 
@@ -8125,6 +8151,19 @@ class Tableau:
                 H 3
                 S 3
             ''')
+
+            >>> tableau.to_circuit("mpp_state_unsigned")
+            stim.Circuit('''
+                MPP X0*Z1*Y2*Y3 !X0*Y1*X2 !Z0*X1*X2*Z3 X0*X1*Z2
+            ''')
+
+            >>> tableau.to_circuit("mpp_state")
+            stim.Circuit('''
+                MPP X0*Z1*Y2*Y3 !X0*Y1*X2 !Z0*X1*X2*Z3 X0*X1*Z2
+                CX rec[-3] 2 rec[-1] 2
+                CY rec[-4] 0 rec[-3] 0 rec[-3] 3 rec[-2] 3 rec[-1] 0
+                CZ rec[-4] 1 rec[-1] 1
+            ''')
         """
     def to_numpy(
         self,

src/stim/circuit/gate_target.cc

@@ -18,6 +18,13 @@
 
 using namespace stim;
 
+GateTarget GateTarget::pauli_xz(uint32_t qubit, bool x, bool z, bool inverted) {
+    if (qubit != (qubit & TARGET_VALUE_MASK)) {
+        throw std::invalid_argument("qubit target larger than " + std::to_string(TARGET_VALUE_MASK));
+    }
+    return {qubit | (TARGET_INVERTED_BIT * inverted) | (TARGET_PAULI_X_BIT * x) | (TARGET_PAULI_Z_BIT * z)};
+}
+
 GateTarget GateTarget::x(uint32_t qubit, bool inverted) {
     if (qubit != (qubit & TARGET_VALUE_MASK)) {
         throw std::invalid_argument("qubit target larger than " + std::to_string(TARGET_VALUE_MASK));

src/stim/circuit/gate_target.h

@@ -39,6 +39,7 @@ struct GateTarget {
     static GateTarget x(uint32_t qubit, bool inverted = false);
     static GateTarget y(uint32_t qubit, bool inverted = false);
     static GateTarget z(uint32_t qubit, bool inverted = false);
+    static GateTarget pauli_xz(uint32_t qubit, bool x, bool z, bool inverted = false);
     static GateTarget qubit(uint32_t qubit, bool inverted = false);
     static GateTarget rec(int32_t lookback);
     static GateTarget sweep_bit(uint32_t index);

src/stim/gates/gates.test.cc

@@ -79,8 +79,8 @@ std::pair<std::vector<PauliString<W>>, std::vector<PauliString<W>>> circuit_outp
     }
     TableauSimulator<W> sim1(INDEPENDENT_TEST_RNG(), circuit.count_qubits(), -1);
     TableauSimulator<W> sim2(INDEPENDENT_TEST_RNG(), circuit.count_qubits(), +1);
-    sim1.expand_do_circuit(circuit);
-    sim2.expand_do_circuit(circuit);
+    sim1.safe_do_circuit(circuit);
+    sim2.safe_do_circuit(circuit);
     return {sim1.canonical_stabilizers(), sim2.canonical_stabilizers()};
 }
 

src/stim/simulators/graph_simulator.test.cc

@@ -16,8 +16,8 @@ void expect_graph_circuit_is_equivalent(const Circuit &circuit) {
     Circuit converted = sim.to_circuit();
     TableauSimulator<64> sim1(std::mt19937_64{}, n);
     TableauSimulator<64> sim2(std::mt19937_64{}, n);
-    sim1.expand_do_circuit(circuit);
-    sim2.expand_do_circuit(converted);
+    sim1.safe_do_circuit(circuit);
+    sim2.safe_do_circuit(converted);
     auto s1 = sim1.canonical_stabilizers();
     auto s2 = sim2.canonical_stabilizers();
     if (s1 != s2) {
@@ -35,9 +35,9 @@ void expect_graph_sim_effect_matches_tableau_sim(const GraphSimulator &state, co
 
     TableauSimulator<64> tableau_sim1(std::mt19937_64{}, n);
     TableauSimulator<64> tableau_sim2(std::mt19937_64{}, n);
-    tableau_sim1.expand_do_circuit(state.to_circuit());
-    tableau_sim1.expand_do_circuit(effect);
-    tableau_sim2.expand_do_circuit(state_after_effect.to_circuit());
+    tableau_sim1.safe_do_circuit(state.to_circuit());
+    tableau_sim1.safe_do_circuit(effect);
+    tableau_sim2.safe_do_circuit(state_after_effect.to_circuit());
     auto s1 = tableau_sim1.canonical_stabilizers();
     auto s2 = tableau_sim2.canonical_stabilizers();
     if (s1 != s2) {
@@ -240,8 +240,8 @@ TEST(graph_simulator, do_complementation) {
 
         TableauSimulator<64> tableau_sim1(std::mt19937_64{}, 8);
         TableauSimulator<64> tableau_sim2(std::mt19937_64{}, 8);
-        tableau_sim1.expand_do_circuit(sim.to_circuit());
-        tableau_sim2.expand_do_circuit(sim2.to_circuit());
+        tableau_sim1.safe_do_circuit(sim.to_circuit());
+        tableau_sim2.safe_do_circuit(sim2.to_circuit());
         auto s1 = tableau_sim1.canonical_stabilizers();
         auto s2 = tableau_sim2.canonical_stabilizers();
         if (s1 != s2) {

src/stim/simulators/tableau_simulator.h

@@ -96,7 +96,7 @@ struct TableauSimulator {
     /// Runs all of the operations in the given circuit.
     ///
     /// Automatically expands the tableau simulator's state, if needed.
-    void expand_do_circuit(const Circuit &circuit, uint64_t reps = 1);
+    void safe_do_circuit(const Circuit &circuit, uint64_t reps = 1);
     void do_operation_ensure_size(const CircuitInstruction &operation);
 
     void apply_tableau(const Tableau<W> &tableau, const std::vector<size_t> &targets);

src/stim/simulators/tableau_simulator.inl

@@ -1107,7 +1107,7 @@ void TableauSimulator<W>::do_Z(const CircuitInstruction &target_data) {
 template <size_t W>
 simd_bits<W> TableauSimulator<W>::sample_circuit(const Circuit &circuit, std::mt19937_64 &rng, int8_t sign_bias) {
     TableauSimulator<W> sim(std::move(rng), circuit.count_qubits(), sign_bias);
-    sim.expand_do_circuit(circuit);
+    sim.safe_do_circuit(circuit);
 
     const std::vector<bool> &v = sim.measurement_record.storage;
     simd_bits<W> result(v.size());
@@ -1347,7 +1347,7 @@ void TableauSimulator<W>::collapse_isolate_qubit_z(size_t target, TableauTranspo
 }
 
 template <size_t W>
-void TableauSimulator<W>::expand_do_circuit(const Circuit &circuit, uint64_t reps) {
+void TableauSimulator<W>::safe_do_circuit(const Circuit &circuit, uint64_t reps) {
     ensure_large_enough_for_qubits(circuit.count_qubits());
     for (uint64_t k = 0; k < reps; k++) {
         circuit.for_each_operation([&](const CircuitInstruction &op) {

src/stim/simulators/tableau_simulator.pybind.cc

@@ -29,10 +29,10 @@ using namespace stim_pybind;
 template <size_t W>
 void do_obj(TableauSimulator<W> &self, const pybind11::object &obj) {
     if (pybind11::isinstance<Circuit>(obj)) {
-        self.expand_do_circuit(pybind11::cast<Circuit>(obj));
+        self.safe_do_circuit(pybind11::cast<Circuit>(obj));
     } else if (pybind11::isinstance<CircuitRepeatBlock>(obj)) {
         const CircuitRepeatBlock &block = pybind11::cast<CircuitRepeatBlock>(obj);
-        self.expand_do_circuit(block.body, block.repeat_count);
+        self.safe_do_circuit(block.body, block.repeat_count);
     } else if (pybind11::isinstance<FlexPauliString>(obj)) {
         const FlexPauliString &pauli_string = pybind11::cast<FlexPauliString>(obj);
         self.ensure_large_enough_for_qubits(pauli_string.value.num_qubits);
@@ -474,7 +474,7 @@ void stim_pybind::pybind_tableau_simulator_methods(
     c.def(
         "do_circuit",
         [](TableauSimulator<MAX_BITWORD_WIDTH> &self, const Circuit &circuit) {
-            self.expand_do_circuit(circuit);
+            self.safe_do_circuit(circuit);
         },
         pybind11::arg("circuit"),
         clean_doc_string(R"DOC(