Merge pull request #481 from tnguyen-ornl/tnguyen/ifstmt-to-extended-…

…qasm2

Support IfStmt to OpenQASM2 generation

quantum/gate/ir/CommonGates.hpp

@@ -76,6 +76,9 @@ class IfStmt : public Circuit {
   std::vector<InstructionParameter> getParameters() override {
     return {bufferName};
   }
+
+  std::vector<std::string> getBufferNames() override { return {bufferName}; }
+
   const int nParameters() override { return 1; }
 
   const int nRequiredBits() const override { return 1; }

quantum/plugins/ibm/aer/accelerator/aer_accelerator.cpp

@@ -832,6 +832,14 @@ IbmqNoiseModel::averageTwoQubitGateFidelity() const {
 
   return result;
 }
+
+std::string
+AerAccelerator::getNativeCode(std::shared_ptr<CompositeInstruction> program,
+                              const HeterogeneousMap &config) {
+  auto qobj_str = xacc_to_qobj->translate(program);
+  nlohmann::json j = nlohmann::json::parse(qobj_str)["qObject"];
+  return j.dump(2);
+}
 } // namespace quantum
 } // namespace xacc
 

quantum/plugins/ibm/aer/accelerator/aer_accelerator.hpp

@@ -60,7 +60,8 @@ class AerAccelerator : public Accelerator {
   void apply(std::shared_ptr<AcceleratorBuffer> buffer,
              std::shared_ptr<Instruction> inst) override;
   bool isInitialized() const { return initialized; }
-
+  std::string getNativeCode(std::shared_ptr<CompositeInstruction> program,
+                            const HeterogeneousMap &config = {}) override;
 private:
   static double calcExpectationValueZ(
       const std::vector<std::pair<double, double>> &in_stateVec,

quantum/plugins/optimizers/simple/CircuitOptimizer.cpp

@@ -678,6 +678,19 @@ bool CircuitOptimizer::tryRotationMergingUsingPhasePolynomials(std::shared_ptr<C
             }
           }
           else if (instruction->bits().size() == 2) {
+            // If this gate not involved the qubits that we are checking
+            if (!container::contains(qubits, instruction->bits()[0]) &&
+                !container::contains(qubits, instruction->bits()[1])) {
+              // Skip
+              continue;
+            }
+
+            // This 2-q gate **involves** at least one qubit:
+            if (instruction->name() != "CNOT") {
+              // Not a CNOT: we need to terminate, hence prune the subcircuit.
+              break;
+            }
+
             assert(instruction->name() == "CNOT");
             // If the control is *outside* the boundary, we need to terminate, hence prune the subcircuit.
             const auto controlIdx = instruction->bits()[0];
@@ -735,6 +748,8 @@ bool CircuitOptimizer::tryRotationMergingUsingPhasePolynomials(std::shared_ptr<C
           }
         }
       }
+      // Move the instruction index
+      ++i;
     }
     else {
       // Not a CNOT gate, continue

quantum/plugins/optimizers/simple/tests/CircuitOptimizerTester.cpp

@@ -818,6 +818,53 @@ measure q[3] -> c[3];
   EXPECT_EQ(truthTableBefore, truthTableAfter);
 }
 
+TEST(CircuitOptimizerTester, checkCZ) {
+  xacc::set_verbose(true);
+  auto compiler = xacc::getService<xacc::Compiler>("xasm");
+  auto program = compiler
+                     ->compile(R"(__qpu__ void testCz(qbit q) {
+        CNOT(q[0], q[1]);
+        CZ(q[0], q[1]);
+        Measure(q[0]);
+        Measure(q[1]);
+    })")
+                     ->getComposites()[0];
+
+  const auto before_xasm_str = program->toString();
+  auto optimizer = xacc::getService<IRTransformation>("circuit-optimizer");
+  optimizer->apply(program, nullptr);
+  std::cout << "FINAL CIRCUIT:\n" << program->toString() << "\n";
+  const auto after_xasm_str = program->toString();
+  EXPECT_EQ(before_xasm_str, after_xasm_str);
+}
+
+// Check circuit with random gates
+TEST(CircuitOptimizerTester, checkComplexCircuit) {
+  xacc::set_verbose(true);
+  auto compiler = xacc::getService<xacc::Compiler>("xasm");
+  auto program = compiler
+                     ->compile(R"(__qpu__ void testRandom(qbit q) {
+    X(q[0]);
+    H(q[1]);
+    CZ(q[0], q[1]);
+    H(q[1]);
+    CNOT(q[1], q[2]);
+    T(q[1]);
+    CZ(q[1], q[0]);
+    Measure(q[0]);
+    Measure(q[1]);
+    Measure(q[2]);
+    })")
+                     ->getComposites()[0];
+
+  const auto before_xasm_str = program->toString();
+  auto optimizer = xacc::getService<IRTransformation>("circuit-optimizer");
+  optimizer->apply(program, nullptr);
+  std::cout << "FINAL CIRCUIT:\n" << program->toString() << "\n";
+  const auto after_xasm_str = program->toString();
+  EXPECT_EQ(before_xasm_str, after_xasm_str);
+}
+
 int main(int argc, char **argv) {
   xacc::Initialize(argc, argv);
   ::testing::InitGoogleTest(&argc, argv);

quantum/plugins/staq/compiler/staq_compiler.cpp

@@ -428,27 +428,56 @@ std::shared_ptr<IR> StaqCompiler::compile(const std::string &src) {
 const std::string
 StaqCompiler::translate(std::shared_ptr<xacc::CompositeInstruction> function) {
   std::map<std::string, int> bufNamesToSize;
+  std::map<std::string, int> cRegNamesToSize;
   InstructionIterator iter(function);
   // First search buffer names and see if we have
   while (iter.hasNext()) {
     auto &next = *iter.next();
-    if (next.isEnabled()) {
-      for (int i = 0; i < next.nRequiredBits(); i++) {
-        auto bufName = next.getBufferName(i);
-        int size = next.bits()[i] + 1;
-        if (bufNamesToSize.count(bufName)) {
-          if (bufNamesToSize[bufName] < size) {
-            bufNamesToSize[bufName] = size;
+    if (!next.isComposite() && next.isEnabled()) {
+      if (next.name() == "Measure") {
+        xacc::quantum::Measure &m = (xacc::quantum::Measure &)next;
+        if (m.hasClassicalRegAssignment()) {
+          auto cregName = next.getBufferName(1);
+          int size = m.getClassicalBitIndex() + 1;
+          if (cRegNamesToSize.count(cregName)) {
+            if (cRegNamesToSize[cregName] < size) {
+              cRegNamesToSize[cregName] = size;
+            }
+          } else {
+            cRegNamesToSize.insert({cregName, size});
           }
         } else {
-          bufNamesToSize.insert({bufName, size});
+          auto bufName = next.getBufferName(0);
+          int size = next.bits()[0] + 1;
+          if (bufNamesToSize.count(bufName)) {
+            if (bufNamesToSize[bufName] < size) {
+              bufNamesToSize[bufName] = size;
+            }
+          } else {
+            bufNamesToSize.insert({bufName, size});
+          }
+        }
+      } else {
+        for (int i = 0; i < next.nRequiredBits(); i++) {
+          auto bufName = next.getBufferName(i);
+          int size = next.bits()[i] + 1;
+          if (bufNamesToSize.count(bufName)) {
+            if (bufNamesToSize[bufName] < size) {
+              bufNamesToSize[bufName] = size;
+            }
+          } else {
+            bufNamesToSize.insert({bufName, size});
+          }
         }
       }
     }
   }
 
   auto translate =
-      std::make_shared<internal_staq::XACCToStaqOpenQasm>(bufNamesToSize);
+      cRegNamesToSize.empty()
+          ? std::make_shared<internal_staq::XACCToStaqOpenQasm>(bufNamesToSize)
+          : std::make_shared<internal_staq::XACCToStaqOpenQasm>(
+                bufNamesToSize, cRegNamesToSize);
   InstructionIterator iter2(function);
   while (iter2.hasNext()) {
     auto &next = *iter2.next();

quantum/plugins/staq/compiler/tests/StaqCompilerTester.in.cpp

@@ -246,6 +246,31 @@ TEST(StaqCompilerTester, checkFloatingPointFormat) {
   EXPECT_NEAR(rxInst->getParameter(0).as<double>(), 2.5e-07, 1e-12);
 }
 
+TEST(StaqCompilerTester, checkIfStatementTranslate) {
+  auto xasmCompiler = xacc::getCompiler("xasm");
+  auto ir = xasmCompiler->compile(R"(__qpu__ void test(qbit q) {
+    Measure(q[0], c[0]);
+    if(c[0]) {
+      Rz(q[0], -pi/2);
+    }
+    H(q[0]);
+    Measure(q[0], c[1]);
+    CPhase(q[0], q[1], -5*pi/8);
+    if(c[0]) {
+        Rz(q[0], -pi/4);
+    }
+    if(c[1]) {
+        Rz(q[0], -pi/2);
+    }
+  })", nullptr);
+  auto staq_compiler = xacc::getCompiler("staq");
+  auto qasm = staq_compiler->translate(ir->getComposites()[0]);
+  std::cout << "HOWDY:\n" << qasm << "\n";
+  // Check that If statements are translated.
+  EXPECT_TRUE(qasm.find("if (c[0] == 1) rz") != std::string::npos);
+  EXPECT_TRUE(qasm.find("if (c[1] == 1) rz") != std::string::npos);
+}
+
 int main(int argc, char **argv) {
   xacc::Initialize(argc, argv);
   xacc::set_verbose(true);

quantum/plugins/staq/utils/staq_visitors.cpp

@@ -24,6 +24,18 @@ XACCToStaqOpenQasm::XACCToStaqOpenQasm(std::map<std::string, int> bufNamesToSize
   }
 }
 
+XACCToStaqOpenQasm::XACCToStaqOpenQasm(
+    std::map<std::string, int> bufNamesToSize,
+    std::map<std::string, int> cRegNameToSize) {
+  ss << "OPENQASM 2.0;\ninclude \"qelib1.inc\";\n";
+  for (auto &kv : bufNamesToSize) {
+    ss << "qreg " << kv.first << "[" << kv.second << "];\n";
+  }
+  for (auto &kv : cRegNameToSize) {
+    ss << "creg " << kv.first << "[" << kv.second << "];\n";
+  }
+}
+
 void XACCToStaqOpenQasm::visit(Hadamard &h) {
   ss << "h " << (h.getBufferNames().empty() ? "q" : h.getBufferName(0))
      << h.bits() << ";\n";
@@ -97,12 +109,38 @@ void XACCToStaqOpenQasm::visit(CPhase &cphase) {
      << "[" << cphase.bits()[0] << "], " << (cphase.getBufferNames().empty() ? "q" : cphase.getBufferName(1)) << "[" << cphase.bits()[1] << "];\n";
 }
 void XACCToStaqOpenQasm::visit(Measure &m) {
-    ss << "measure " << (m.getBufferNames().empty() ? "q" : m.getBufferName(0)) << m.bits() << " -> " << cregNames[m.getBufferName(0)] << m.bits() << ";\n";
+  if (m.hasClassicalRegAssignment()) {
+    ss << "measure " << (m.getBufferNames().empty() ? "q" : m.getBufferName(0))
+       << m.bits() << " -> " << m.getBufferName(1) << "["
+       << m.getClassicalBitIndex() << "]"
+       << ";\n";
+  } else {
+    ss << "measure " << (m.getBufferNames().empty() ? "q" : m.getBufferName(0))
+       << m.bits() << " -> " << cregNames[m.getBufferName(0)] << m.bits()
+       << ";\n";
+  }
 }
 void XACCToStaqOpenQasm::visit(Identity &i) {}
 void XACCToStaqOpenQasm::visit(U &u) {
     ss << "u3(" << std::fixed << std::setprecision(16) << xacc::InstructionParameterToDouble(u.getParameter(0)) << "," << xacc::InstructionParameterToDouble(u.getParameter(1)) << "," <<xacc::InstructionParameterToDouble(u.getParameter(2)) << ") " << (u.getBufferNames().empty() ? "q" : u.getBufferName(0)) << u.bits() << ";\n";
 }
-void XACCToStaqOpenQasm::visit(IfStmt &ifStmt) {}
+void XACCToStaqOpenQasm::visit(IfStmt &ifStmt) {
+  // Note: QASM2 'if' must be inline (no braces)
+  // Note: this extended syntax: if (creg[k] == 1) is not supported by IBM.
+  // (IBM requires comparison to the full register value, not a bit check)
+  for (auto i : ifStmt.getInstructions()) {
+    // If statement was specified by the qreg name -> find the associated cReg
+    if (cregNames.find(ifStmt.getBufferNames()[0]) != cregNames.end()) {
+      ss << "if (" << cregNames[ifStmt.getBufferNames()[0]] << "["
+         << ifStmt.bits()[0] << "] == 1) ";
+    } else {
+      // Explicit creg was used:
+      ss << "if (" << ifStmt.getBufferNames()[0] << "[" << ifStmt.bits()[0]
+         << "] == 1) ";
+    }
+
+    i->accept(this);
+  }
+}
 } // namespace internal_staq
 } // namespace xacc

quantum/plugins/staq/utils/staq_visitors.hpp

@@ -266,8 +266,13 @@ class XACCToStaqOpenQasm : public AllGateVisitor {
 public:
   std::stringstream ss;
   std::map<std::string, std::string> cregNames;
-
+  // Default: assume each qreg is accompanied by a creg of the same size
   XACCToStaqOpenQasm(std::map<std::string, int> bufNamesToSize);
+  // Explicit list of creg:
+  // e.g., IQPE algo: we requires a much larger creg than qreg to store all
+  // measurements.
+  XACCToStaqOpenQasm(std::map<std::string, int> bufNamesToSize,
+                     std::map<std::string, int> cRegNameToSize);
   void visit(Hadamard &h) override;
   void visit(CNOT &cnot) override;
   void visit(Rz &rz) override;