[CircuitSeq] Add a linear function to translate CCZ gates into CX and…

… RZ gates (#170) * [CircuitSeq] Add a linear function to translate Rz gates into T gates * [CircuitSeq] Add a linear function to translate CCZ gates into CX and RZ gates * code format
quantum-compiler · Mar 5, 2024 · 2dce4f8 · 2dce4f8
1 parent fefbff2
commit 2dce4f8
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Showing 2 changed files with 60 additions and 3 deletions.
diff --git a/src/quartz/circuitseq/circuitseq.cpp b/src/quartz/circuitseq/circuitseq.cpp
@@ -1551,7 +1551,7 @@ void CircuitSeq::clone_from(const CircuitSeq &other,
   }
 }
 
-std::unique_ptr<CircuitSeq> CircuitSeq::get_rz_to_t_gates(Context *ctx) const {
+std::unique_ptr<CircuitSeq> CircuitSeq::get_rz_to_t(Context *ctx) const {
   auto result = std::make_unique<CircuitSeq>(num_qubits, num_input_parameters);
   for (auto &gate : gates) {
     if (gate->gate->tp == GateType::rz) {
@@ -1591,6 +1591,54 @@ std::unique_ptr<CircuitSeq> CircuitSeq::get_rz_to_t_gates(Context *ctx) const {
   return std::move(result);
 }
 
+std::unique_ptr<CircuitSeq> CircuitSeq::get_ccz_to_cx_rz(Context *ctx) const {
+  auto t = ctx->get_new_param_id(/*is_symbolic=*/false);
+  ctx->set_param_value(t, 0.25 * PI);
+  auto tdg = ctx->get_new_param_id(/*is_symbolic=*/false);
+  ctx->set_param_value(tdg, -0.25 * PI);
+  auto result =
+      std::make_unique<CircuitSeq>(num_qubits, ctx->get_num_parameters());
+  for (auto &gate : gates) {
+    if (gate->gate->tp == GateType::ccz) {
+      auto qubit_indices = gate->get_qubit_indices();
+      auto q0 = qubit_indices[0];
+      auto q1 = qubit_indices[1];
+      auto q2 = qubit_indices[2];
+      bool ok;
+      ok = result->add_gate({q1, q2}, {}, ctx->get_gate(GateType::cx), nullptr);
+      assert(ok);
+      ok = result->add_gate({q2}, {tdg}, ctx->get_gate(GateType::rz), nullptr);
+      assert(ok);
+      ok = result->add_gate({q0, q2}, {}, ctx->get_gate(GateType::cx), nullptr);
+      assert(ok);
+      ok = result->add_gate({q2}, {t}, ctx->get_gate(GateType::rz), nullptr);
+      assert(ok);
+      ok = result->add_gate({q1, q2}, {}, ctx->get_gate(GateType::cx), nullptr);
+      assert(ok);
+      ok = result->add_gate({q2}, {tdg}, ctx->get_gate(GateType::rz), nullptr);
+      assert(ok);
+      ok = result->add_gate({q0, q2}, {}, ctx->get_gate(GateType::cx), nullptr);
+      assert(ok);
+      ok = result->add_gate({q0, q1}, {}, ctx->get_gate(GateType::cx), nullptr);
+      assert(ok);
+      ok = result->add_gate({q1}, {tdg}, ctx->get_gate(GateType::rz), nullptr);
+      assert(ok);
+      ok = result->add_gate({q0, q1}, {}, ctx->get_gate(GateType::cx), nullptr);
+      assert(ok);
+      ok = result->add_gate({q0}, {t}, ctx->get_gate(GateType::rz), nullptr);
+      assert(ok);
+      ok = result->add_gate({q1}, {t}, ctx->get_gate(GateType::rz), nullptr);
+      assert(ok);
+      ok = result->add_gate({q2}, {t}, ctx->get_gate(GateType::rz), nullptr);
+    } else {
+      bool ok;
+      ok = result->add_gate(gate.get());
+      assert(ok);
+    }
+  }
+  return std::move(result);
+}
+
 void CircuitSeq::remove_quantum_gate_from_graph(
     CircuitGate *circuit_gate, bool assert_no_logical_qubit_permutation,
     std::unordered_set<CircuitWire *> *output_wires_to_be_removed) {

diff --git a/src/quartz/circuitseq/circuitseq.h b/src/quartz/circuitseq/circuitseq.h
@@ -206,10 +206,19 @@ class CircuitSeq {
                    const std::vector<int> &param_permutation) const;
 
   /**
-   * Get a circuit which replaces Rz gates with T, Tdg, S, Sdg, and Z gates.
+   * Get a circuit which replaces RZ gates with T, Tdg, S, Sdg, and Z gates.
    * Requires all Rz gates to have parameters that are multiples of Pi/4.
    */
-  std::unique_ptr<CircuitSeq> get_rz_to_t_gates(Context *ctx) const;
+  std::unique_ptr<CircuitSeq> get_rz_to_t(Context *ctx) const;
+
+  /**
+   * Get a circuit which replaces CCZ gates with CX and RZ gates.
+   * Use only one decomposition:
+   * ccz q0 q1 q2 = cx q1 q2; rz q2 -0.25pi; cx q0 q2; rz q2 0.25pi; cx q1 q2;
+   * rz q2 -0.25pi; cx q0 q2; cx q0 q1; rz q1 -0.25pi; cx q0 q1; rz q0 0.25pi;
+   * rz q1 0.25pi; rz q2 0.25pi;
+   */
+  std::unique_ptr<CircuitSeq> get_ccz_to_cx_rz(Context *ctx) const;
 
   // Returns quantum gates which do not topologically depend on any other
   // quantum gates.