Past exam of the computer science course of the University of Oxford / 2023 / Quantum information / 3 / b

An entangling gate is a unitary transformation $U$ on two quantum systems for which at least one pure product input has an entangled output:It need not create quantum entanglement on every product state. For example, the controlled-NOT gate leaves $|00⟩$ a product state but maps $|+⟩|0⟩$ to a Bell state, so it is an entangling gate.