Added a more complex test for circuit optimizer

Testing non-conventional gate set.
Signed-off-by: Thien Nguyen <nguyentm@ornl.gov>

quantum/plugins/optimizers/simple/CircuitOptimizer.cpp

@@ -688,8 +688,6 @@ bool CircuitOptimizer::tryRotationMergingUsingPhasePolynomials(std::shared_ptr<C
             // This 2-q gate **involves** at least one qubit:
             if (instruction->name() != "CNOT") {
               // Not a CNOT: we need to terminate, hence prune the subcircuit.
-              // Move the outer loop index to after this gate.
-              i = idx + 1;
               break;
             }
 
@@ -750,6 +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

@@ -838,6 +838,33 @@ TEST(CircuitOptimizerTester, checkCZ) {
   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);