diff --git a/Makefile b/Makefile
index fa0df9102..84ad1fffc 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ TARGETS = qsim
 TESTS = run-cxx-tests
 
 CXX=g++
-CXXFLAGS = -O3 -mavx2 -mfma -fopenmp
+CXXFLAGS = -O3 -march=native -fopenmp
 PYBIND11 = true
 
 export CXX
diff --git a/apps/qsim_amplitudes.cc b/apps/qsim_amplitudes.cc
index a2a7fc907..ae9e11a0e 100644
--- a/apps/qsim_amplitudes.cc
+++ b/apps/qsim_amplitudes.cc
@@ -28,7 +28,7 @@
 #include "../lib/io.h"
 #include "../lib/parfor.h"
 #include "../lib/run_qsim.h"
-#include "../lib/simulator_avx.h"
+#include "../lib/simmux.h"
 #include "../lib/util.h"
 
 constexpr char usage[] = "usage:\n  ./qsim_amplitudes -c circuit_file "
@@ -152,7 +152,7 @@ int main(int argc, char* argv[]) {
     return 1;
   }
 
-  using Simulator = SimulatorAVX<ParallelFor>;
+  using Simulator = qsim::Simulator<ParallelFor>;
   using StateSpace = Simulator::StateSpace;
   using State = StateSpace::State;
 
diff --git a/apps/qsim_base.cc b/apps/qsim_base.cc
index 19b4afe53..73adc5e35 100644
--- a/apps/qsim_base.cc
+++ b/apps/qsim_base.cc
@@ -25,7 +25,7 @@
 #include "../lib/io.h"
 #include "../lib/parfor.h"
 #include "../lib/run_qsim.h"
-#include "../lib/simulator_avx.h"
+#include "../lib/simmux.h"
 
 struct Options {
   std::string circuit_file;
@@ -104,7 +104,7 @@ int main(int argc, char* argv[]) {
     return 1;
   }
 
-  using Simulator = SimulatorAVX<ParallelFor>;
+  using Simulator = qsim::Simulator<ParallelFor>;
   using StateSpace = Simulator::StateSpace;
   using State = StateSpace::State;
   using Runner = QSimRunner<IO, BasicGateFuser<GateQSim<float>>, Simulator>;
diff --git a/apps/qsim_von_neumann.cc b/apps/qsim_von_neumann.cc
index 6262971be..5fcd54de0 100644
--- a/apps/qsim_von_neumann.cc
+++ b/apps/qsim_von_neumann.cc
@@ -27,7 +27,7 @@
 #include "../lib/io.h"
 #include "../lib/parfor.h"
 #include "../lib/run_qsim.h"
-#include "../lib/simulator_avx.h"
+#include "../lib/simmux.h"
 
 struct Options {
   std::string circuit_file;
@@ -89,7 +89,7 @@ int main(int argc, char* argv[]) {
     return 1;
   }
 
-  using Simulator = SimulatorAVX<ParallelFor>;
+  using Simulator = qsim::Simulator<ParallelFor>;
   using StateSpace = Simulator::StateSpace;
   using State = StateSpace::State;
 
diff --git a/apps/qsimh_amplitudes.cc b/apps/qsimh_amplitudes.cc
index c2b42f857..6dc1d1e2f 100644
--- a/apps/qsimh_amplitudes.cc
+++ b/apps/qsimh_amplitudes.cc
@@ -27,7 +27,7 @@
 #include "../lib/io.h"
 #include "../lib/parfor.h"
 #include "../lib/run_qsimh.h"
-#include "../lib/simulator_avx.h"
+#include "../lib/simmux.h"
 #include "../lib/util.h"
 
 constexpr char usage[] = "usage:\n  ./qsimh_amplitudes -c circuit_file "
@@ -184,7 +184,7 @@ int main(int argc, char* argv[]) {
     return 1;
   }
 
-  using Simulator = SimulatorAVX<ParallelFor>;
+  using Simulator = qsim::Simulator<ParallelFor>;
   using HybridSimulator = HybridSimulator<IO, BasicGateFuser, Simulator,
                                           ParallelFor>;
   using Runner = QSimHRunner<IO, HybridSimulator>;
diff --git a/apps/qsimh_base.cc b/apps/qsimh_base.cc
index 67455cda3..f4f8399e6 100644
--- a/apps/qsimh_base.cc
+++ b/apps/qsimh_base.cc
@@ -27,7 +27,7 @@
 #include "../lib/io.h"
 #include "../lib/parfor.h"
 #include "../lib/run_qsimh.h"
-#include "../lib/simulator_avx.h"
+#include "../lib/simmux.h"
 #include "../lib/util.h"
 
 constexpr char usage[] = "usage:\n  ./qsimh_base -c circuit_file "
@@ -149,7 +149,7 @@ int main(int argc, char* argv[]) {
     bitstrings.push_back(i);
   }
 
-  using Simulator = SimulatorAVX<ParallelFor>;
+  using Simulator = qsim::Simulator<ParallelFor>;
   using HybridSimulator = HybridSimulator<IO, BasicGateFuser, Simulator,
                                           ParallelFor>;
   using Runner = QSimHRunner<IO, HybridSimulator>;
diff --git a/lib/BUILD b/lib/BUILD
index ea372d1c2..3bbfd5588 100644
--- a/lib/BUILD
+++ b/lib/BUILD
@@ -19,6 +19,7 @@ cc_library(
         "run_qsim.h",
         "run_qsimh.h",
         "seqfor.h",
+        "simmux.h",
         "simulator_avx.h",
         "simulator_basic.h",
         "simulator_sse.h",
diff --git a/lib/simmux.h b/lib/simmux.h
new file mode 100644
index 000000000..067ae83ee
--- /dev/null
+++ b/lib/simmux.h
@@ -0,0 +1,38 @@
+// Copyright 2019 Google LLC. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef SIMMUX_H_
+#define SIMMUX_H_
+
+#ifdef __AVX2__
+# include "simulator_avx.h"
+  namespace qsim {
+    template <typename ParallelFor>
+    using Simulator = SimulatorAVX<ParallelFor>;
+  }
+#elif __SSE4_1__
+# include "simulator_sse.h"
+  namespace qsim {
+    template <typename ParallelFor>
+    using Simulator = SimulatorSSE<ParallelFor>;
+  }
+#else
+# include "simulator_basic.h"
+  namespace qsim {
+    template <typename ParallelFor>
+    using Simulator = SimulatorBasic<ParallelFor>;
+  }
+#endif
+
+#endif  // SIMMUX_H_
diff --git a/lib/simulator_basic.h b/lib/simulator_basic.h
index 25d0f4bd9..5b98c9853 100644
--- a/lib/simulator_basic.h
+++ b/lib/simulator_basic.h
@@ -22,7 +22,7 @@
 namespace qsim {
 
 // Quantim circuit simulator without vectorization.
-template <typename ParallelFor, typename FP>
+template <typename ParallelFor, typename FP = float>
 class SimulatorBasic final {
  public:
   using StateSpace = StateSpaceBasic<ParallelFor, FP>;
diff --git a/tests/Makefile b/tests/Makefile
index f4ab39a6f..cc2c8299b 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -6,7 +6,7 @@ GMOCK_DIR = $(CURDIR)/googletest/googlemock
 
 CMAKE=cmake
 
-TESTFLAGS = -I$(GTEST_DIR)/include -L$(GTEST_DIR)/make/lib -mavx2 -mfma -fopenmp -lgtest
+TESTFLAGS = -I$(GTEST_DIR)/include -L$(GTEST_DIR)/make/lib -march=native -fopenmp -lgtest
 
 .PHONY: all
 all: $(TARGETS)