Unset noise after noise tests (NVIDIA#635)

This helps fix issue NVIDIA#609 by unsetting noise models at the end of noise tests. Without this change, the prior test's noise model could be used in subsequent tests, which is undesirable.
fermioniq · Sep 12, 2023 · add6d36 · add6d36
1 parent f9a591f
commit add6d36
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diff --git a/.github/workflows/config/spelling_allowlist.txt b/.github/workflows/config/spelling_allowlist.txt
@@ -5,6 +5,7 @@ BFGS
 CLA
 CMake
 COBYLA
+CPTP
 CPU
 CPUs
 CUDA
@@ -25,6 +26,7 @@ JIT
 JSON
 Kraus
 LLVM
+LSB
 MLIR
 MPI
 Max-Cut
@@ -107,6 +109,7 @@ instantiations
 namespace
 namespaces
 natively
+nullary
 optimizer
 optimizers
 parallelization

diff --git a/docs/sphinx/examples/cpp/basics/noise_modeling.cpp b/docs/sphinx/examples/cpp/basics/noise_modeling.cpp
@@ -49,4 +49,8 @@ int main() {
   // Run the noisy simulation
   counts = cudaq::sample(xgate);
   counts.dump();
+
+  // Unset the noise model when done. This is not necessary in this case but is
+  // good practice in order to not interfere with future simulations.
+  cudaq::unset_noise();
 }
diff --git a/docs/sphinx/using/advanced/_noise.rst b/docs/sphinx/using/advanced/_noise.rst
@@ -47,7 +47,10 @@ apply to the simulated state via a :code:`noise_model::get_channel(...)` call.
 Noise models can be constructed via the :code:`cudaq::noise_model` and specified for 
 execution via a public :code:`cudaq::set_noise(cudaq::noise_model&)` function. This function 
 should forward the :code:`noise_model` to the current :code:`quantum_platform` which can attach it 
-to the current :code:`ExecutionContext` and retrieved by backend simulators. 
+to the current :code:`ExecutionContext` and retrieved by backend simulators. The
+:code:`noise_model` must stay in scope in order to be successfully used by the
+backend simulators, and you must call :code:`cudaq::unset_noise()` when you are
+done with the noise model.
 
 The :code:`kraus_op` matrix data assumes a LSB qubit ordering. 
 

diff --git a/runtime/cudaq.h b/runtime/cudaq.h
@@ -182,7 +182,8 @@ void set_target_backend(const char *backend);
 /// @brief Utility function for setting the shots on the platform
 void set_shots(const std::size_t nShots);
 
-/// @brief Set a custom noise model for simulation
+/// @brief Set a custom noise model for simulation. The caller must also call
+/// `cudaq::unset_noise` before `model` gets deallocated or goes out of scope.
 void set_noise(cudaq::noise_model &model);
 
 /// @brief Remove an existing noise model from simulation.

diff --git a/unittests/integration/noise_tester.cpp b/unittests/integration/noise_tester.cpp
@@ -78,6 +78,7 @@ CUDAQ_TEST(NoiseTest, checkAmplitudeDamping) {
 
   EXPECT_NEAR(counts.probability("0"), .25, .1);
   EXPECT_NEAR(counts.probability("1"), .75, .1);
+  cudaq::unset_noise(); // clear for subsequent tests
 }
 
 CUDAQ_TEST(NoiseTest, checkCNOT) {
@@ -154,6 +155,7 @@ CUDAQ_TEST(NoiseTest, checkCNOT) {
   auto counts = cudaq::sample(10000, bell{});
   counts.dump();
   EXPECT_TRUE(counts.size() > 2);
+  cudaq::unset_noise(); // clear for subsequent tests
 }
 
 CUDAQ_TEST(NoiseTest, checkExceptions) {
@@ -174,6 +176,7 @@ CUDAQ_TEST(NoiseTest, checkDepolType) {
   auto counts = cudaq::sample(xOp{});
   counts.dump();
   EXPECT_EQ(2, counts.size());
+  cudaq::unset_noise(); // clear for subsequent tests
 }
 
 CUDAQ_TEST(NoiseTest, checkDepolTypeSimple) {
@@ -187,6 +190,7 @@ CUDAQ_TEST(NoiseTest, checkDepolTypeSimple) {
   EXPECT_EQ(2, counts.size());
   EXPECT_NEAR(counts.probability("0"), .50, .2);
   EXPECT_NEAR(counts.probability("1"), .50, .2);
+  cudaq::unset_noise(); // clear for subsequent tests
 }
 
 CUDAQ_TEST(NoiseTest, checkAmpDampType) {
@@ -199,6 +203,7 @@ CUDAQ_TEST(NoiseTest, checkAmpDampType) {
   EXPECT_EQ(2, counts.size());
   EXPECT_NEAR(counts.probability("0"), .25, .1);
   EXPECT_NEAR(counts.probability("1"), .75, .1);
+  cudaq::unset_noise(); // clear for subsequent tests
 }
 
 CUDAQ_TEST(NoiseTest, checkAmpDampTypeSimple) {
@@ -210,6 +215,7 @@ CUDAQ_TEST(NoiseTest, checkAmpDampTypeSimple) {
   counts.dump();
   EXPECT_EQ(1, counts.size());
   EXPECT_NEAR(counts.probability("0"), 1., .1);
+  cudaq::unset_noise(); // clear for subsequent tests
 }
 
 CUDAQ_TEST(NoiseTest, checkBitFlipType) {
@@ -222,6 +228,7 @@ CUDAQ_TEST(NoiseTest, checkBitFlipType) {
   EXPECT_EQ(2, counts.size());
   EXPECT_NEAR(counts.probability("0"), .1, .1);
   EXPECT_NEAR(counts.probability("1"), .9, .1);
+  cudaq::unset_noise(); // clear for subsequent tests
 }
 
 CUDAQ_TEST(NoiseTest, checkBitFlipTypeSimple) {
@@ -233,6 +240,7 @@ CUDAQ_TEST(NoiseTest, checkBitFlipTypeSimple) {
   counts.dump();
   EXPECT_EQ(1, counts.size());
   EXPECT_NEAR(counts.probability("0"), 1., .1);
+  cudaq::unset_noise(); // clear for subsequent tests
 }
 
 CUDAQ_TEST(NoiseTest, checkPhaseFlipType) {
@@ -253,6 +261,7 @@ CUDAQ_TEST(NoiseTest, checkPhaseFlipType) {
   counts.dump();
   EXPECT_EQ(1, counts.size());
   EXPECT_NEAR(counts.probability("0"), 1., .1);
+  cudaq::unset_noise(); // clear for subsequent tests
 }
 
 #endif