I'm new to qiskit and I want to know how do I define a projector operator in qiskit? Specifically, I have prepared a 3 qubit system, and after applying a whole lot of gates and measuring it in a state vector simulator, I have to apply the projector operator $|0\rangle_{1}|0\rangle_{2} \langle0|_{1}\langle0|_{2}$ on the state that I get after I measured all the qubits in the circuit. I do know the physics and math behind it, and the tensor product it represents but I'm unable to code this successfully. I was thinking maybe a 4x4 matrix representation of this operator might help but I'm not sure about it.
So I'm asking 2 questions here-
- How do I define a projector operator like this in qiskit
- How do I apply that operator to a state that I have measured with a state vector simulator?
Thanks in advance