# Could someone give an example of this pic?

This is a picture from Wiki(https://en.wikipedia.org/wiki/Quantum_logic_gate). Can someone give me a simple example by using two qubits?

• If you apply a unitary $F$ to the first qubit (q[0]), then your state would be the same as if you applied the conjugate transpose $F^\dagger$ to the second qubit (q[1]). Can you be more specific? – Mark S Apr 12 at 2:05
• could you please edit the title to something that reflects what is being asked? – glS Apr 13 at 8:01

First circuit (Fourier transform applied on qubit $$q_0$$)
First circuit (inverse Fourier transform applied on qubit $$q_1$$)
$$|\psi\rangle = \frac{1}{2}(|00\rangle + |01\rangle + |10\rangle - |11\rangle).$$
EDIT: I have just realized that the gate $$F$$ is general unitary transformation and not the QFT (I was missleaded by F = Fourier). However, my example is also valid. It is a particular case for two qubits asked for in the question.