  Here we extend the concept of blind client-server quantum computation, in
which a client with limited quantum power controls the execution of a quantum
computation on a powerful server, without revealing any details of the
computation. Our extension is to introduce a three-node setting in which an
oracular quantum computation can be executed blindly. In this Blind Oracular
Quantum Computation (BOQC), the oracle (Oscar) is another node, with limited
power, who acts in cooperation with the client (Alice) to supply quantum
information to the server so that the oracle part of the quantum computation
can also be executed blindly. We develop tests of this protocol using two- and
three-qubit versions of the exact Grover algorithm (i.e., with database sizes
$4\leq N\leq 8$), obtaining optimal implementations of these algorithms within
a gate array scheme and the blinded cluster-state scheme. We discuss the
feasibility of executing these protocols in state-of-the-art three-node
experiments using NV-diamond electronic and nuclear qubits.

Quantum Physics