  In the medium term, quantum computing must tackle two key challenges: fault
tolerance and security. Fault tolerance will be solved with sufficiently high
quality experiments on large numbers of qubits, but the scale and complexity of
these devices means that a cloud-based access model is likely to dominate. How
can we risk evaluating valuable computations on an untrusted server? Here we
detail a verifiable circuit-based model that only requires classical
communication between parties. The server is blind to the details of the
computation, which is computationally secure.
