diff --git a/nuTens/propagator/CMakeLists.txt b/nuTens/propagator/CMakeLists.txt
index 8b13789..aff6add 100644
--- a/nuTens/propagator/CMakeLists.txt
+++ b/nuTens/propagator/CMakeLists.txt
@@ -1 +1,7 @@
 
+
+add_library(propagator STATIC vacuum-propagator.hpp vacuum-propagator.cpp)
+target_link_libraries(propagator PUBLIC tensor)
+
+target_include_directories(propagator PUBLIC "${CMAKE_SOURCE_DIR}")
+set_target_properties(propagator PROPERTIES LINKER_LANGUAGE CXX)
diff --git a/nuTens/propagator/vacuum-propagator.cpp b/nuTens/propagator/vacuum-propagator.cpp
new file mode 100644
index 0000000..3dca301
--- /dev/null
+++ b/nuTens/propagator/vacuum-propagator.cpp
@@ -0,0 +1,17 @@
+#include <nuTens/propagator/vacuum-propagator.hpp>
+
+
+Tensor VacuumPropagator::calculateProbs(){
+    Tensor weightMatrix;
+    weightMatrix.ones({1,nGenerations, nGenerations}, NTdtypes::kComplexFloat).requiresGrad(false);
+    
+    for(int i = 0; i < nGenerations; i++){
+        weightMatrix.setValue({0, i, "..."}, Tensor::exp(Tensor::div(Tensor::scale(Tensor::mul(masses, masses), -1.0j * baseline), Tensor::scale(energies, 2.0))));
+    }
+    weightMatrix.requiresGrad(true);
+
+    Tensor sqrtProbabilities = Tensor::matmul(PMNSmatrix.conj(), Tensor::transpose(Tensor::mul(PMNSmatrix, weightMatrix), 1, 2));
+    Tensor probabilities = Tensor::mul(sqrtProbabilities.abs(), sqrtProbabilities.abs());
+
+    return probabilities;
+}
diff --git a/nuTens/propagator/vacuum-propagator.hpp b/nuTens/propagator/vacuum-propagator.hpp
new file mode 100644
index 0000000..bf2eab8
--- /dev/null
+++ b/nuTens/propagator/vacuum-propagator.hpp
@@ -0,0 +1,37 @@
+#pragma once
+
+#include <nuTens/tensors/tensor.hpp>
+#include <vector>
+
+class VacuumPropagator{
+
+    public:
+
+        VacuumPropagator(int nGenerations, float baseline)
+            :
+            baseline(baseline),
+            nGenerations(nGenerations)
+            {};
+
+        Tensor calculateProbs();
+
+        /// @name Setters
+        /// @{
+        void setEnergies(Tensor newEnergies){ energies = newEnergies; }
+        
+        void setMasses(Tensor newMasses){ masses = newMasses; }
+
+        inline void setPMNS(Tensor newPMNS){ PMNSmatrix = newPMNS; }
+
+        inline void setPMNS(const std::vector<int> &indices, float value){ PMNSmatrix.setValue(indices, value); }
+
+        inline void setPMNS(const std::vector<int> &indices, std::complex<float> value){ PMNSmatrix.setValue(indices, value); }
+        /// @}
+
+    private:
+        Tensor PMNSmatrix;
+        Tensor masses;
+        Tensor energies;
+        int nGenerations;
+        float baseline;
+};
\ No newline at end of file