diff --git a/SS2026/Quantum Computing/4. Observing and measuring/Observing probabilistic and measuring quantum systems.md b/SS2026/Quantum Computing/4. Observing and measuring/Observing probabilistic and measuring quantum systems.md
index b5f5994..a2b23a0 100644
--- a/SS2026/Quantum Computing/4. Observing and measuring/Observing probabilistic and measuring quantum systems.md	
+++ b/SS2026/Quantum Computing/4. Observing and measuring/Observing probabilistic and measuring quantum systems.md	
@@ -49,5 +49,6 @@ The bomb tester now looks like this:
 
 ![[Pasted image 20260729101220.png]]
 
-
+A photon in the up state $\begin{pmatrix} 1 \\ 0 \end{pmatrix}$ is sent through the first beam splitter.
+Afterwards the photon is in the state $\begin{pmatrix} \frac{1}{\sqrt{2}} \\ \frac{1}{\sqrt{2}} \end{pmatrix}$