  Quantum computers, besides offering substantial computational speedups, are
also expected to provide the possibility of preserving the privacy of a
computation. Here we show the first such experimental demonstration of blind
quantum computation where the input, computation, and output all remain unknown
to the computer. We exploit the conceptual framework of measurement-based
quantum computation that enables a client to delegate a computation to a
quantum server. We demonstrate various blind delegated computations, including
one- and two-qubit gates and the Deutsch and Grover algorithms. Remarkably, the
client only needs to be able to prepare and transmit individual photonic
qubits. Our demonstration is crucial for future unconditionally secure quantum
cloud computing and might become a key ingredient for real-life applications,
especially when considering the challenges of making powerful quantum computers
widely available.
