# Bell state measurement IBM circuit composer

This is my first post in this forum so it is likely that I'll make some rookie mistakes here. In the simple Bell state circuit in IBM circuit composer

we measure the first qubit and for this seed we get the following statevector

Now if we add a second measurement to the second qubit, we should expect the second qubit to also be in the 0 state with certainty, as decided by the first measurement result with state $$|00\rangle$$. However, instead it seems that the circuit resets somehow. For the same seed the result changes to $$|11\rangle$$ with the addition of the measurement of the second qubit.

Does anyone know why this happens? I'm new to qiskit so any tips and answers will be gladly accepted.

Before any measurement, the state you're creating is: $$\frac{|00\rangle+|11\rangle}{\sqrt{2}}$$ But if you measure one qubit, the state collapses to either $$|00\rangle$$ or $$|11\rangle$$.
In this case, the composer simulates a single shot of your circuit. It just happened that the state collapsed to $$|00\rangle$$ the first time and to $$|11\rangle$$ the second time. If you reload the state vector by adding/removing gates, you should be able to see that it can also collapse to the $$|00\rangle$$ state. Similarly, you can retry the frist experiment to see that you would sometimes get $$1$$.