We know that the noise of the $\text{CNOT}$ gate varies depending on the input state before it.
What are the gates that I can put in the place of the 4 identity gates above to change the input state that goes to $\text{CNOT}$?
For example, if I just place a Hadamard gate then $|+\rangle$ state is the input to $\text{CNOT}$ and this might be noisier than other states. What are the possible gates that I can put before $\text{CNOT}$ to vary the input state?
I know that $S$, $T$, $S^\dagger$, $T^\dagger$, $X$, $Y$, and $Z$ gates do not change the $|+\rangle$ state if I put them. and if I use a general
u3
gate then Qiskit divides it into multiple gate operations and that can be even noisier to start with.
Qiskit Ignis
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