I am currently trying to implement circuit (in Qiskit if that is relevant) to approximate a state of a qubit without measuring it (basically I want to "attach it" to a qubit and have some approximate idea about it's state while not collapsing it's quantum state and not changing it)
I have noticed that this does seem to change the state of the input qubit (I had an input state of |1> but some of the post measurements returned 0 in a simulator).
is anyone aware of an approach that allows to approximate state of a qubit without changing it? (is that even possible under no cloning theorem or any other restrictions coming from quantum mechanics?)
I would be very grateful for any pointers