Added some missing header include clauses

Signed-off-by: Thien Nguyen <nguyentm@ornl.gov>

quantum/plugins/algorithms/gradient_strategies/QuantumNaturalGradient.cpp

@@ -15,7 +15,7 @@
 #include "xacc.hpp"
 #include "xacc_service.hpp"
 #include <cassert>
-
+#include <optional>
 using namespace xacc;
 
 namespace {

quantum/plugins/ibm/accelerator/json/PulseQObject.hpp

@@ -16,6 +16,7 @@
 
 #include <stdexcept>
 #include <regex>
+#include <optional>
 
 namespace xacc {
 namespace ibm_pulse {

quantum/plugins/ibm/accelerator/json/QObject.hpp

@@ -20,6 +20,7 @@
 #include <stdexcept>
 #include <regex>
 #include <unordered_map>
+#include <optional>
 #ifndef NLOHMANN_OPT_HELPER
 #define NLOHMANN_OPT_HELPER
 namespace nlohmann {

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

@@ -29,6 +29,7 @@
 #include "xacc_service.hpp"
 
 #include <bitset>
+#include <optional>
 #include "QObjGenerator.hpp"
 #include "py-aer/aer_python_adapter.hpp"
 

quantum/plugins/optimizers/gate_merge/GateMergeOptimizer.cpp

@@ -2,7 +2,7 @@
 #include "GateMergeOptimizer.hpp"
 #include "GateFusion.hpp"
 #include "xacc_service.hpp"
-
+#include <optional>
 namespace {
 bool compareMatIgnoreGlobalPhase(const Eigen::Matrix4cd& in_a, const Eigen::Matrix4cd& in_b)
 {

quantum/plugins/qsim/accelerator/QsimAccelerator.cpp

@@ -14,7 +14,7 @@
 #include "xacc_plugin.hpp"
 #include "IRUtils.hpp"
 #include <cassert>
-
+#include <optional>
 namespace {
 inline bool isMeasureGate(const xacc::InstPtr &in_instr) {
   return (in_instr->name() == "Measure");

xacc/ir/Instruction.hpp

@@ -17,6 +17,7 @@
 #include "Cloneable.hpp"
 #include "InstructionVisitor.hpp"
 #include "heterogeneous.hpp"
+#include <limits>
 
 namespace xacc {
 using InstructionParameter = Variant<int, double, std::string>;