A new protocol for constructing nonlocal n-qubit controlled-U gates

We present a new protocol for constructing a nonlocal n-qubit controlled-U gate. In this protocol, no prior sharing of entanglement is needed and only one ancilla qubit is sent once from one party to another. Thus, the present protocol is very efficient for performing a nonlocal multiqubit controlled-U gate, which is important to network quantum information processing and communication.