  The ability to perform computations on encrypted data is a powerful tool for
protecting a client's privacy, especially in today's era of cloud and
distributed computing. In terms of privacy, the best solutions that classical
techniques can achieve are unfortunately not unconditionally secure in the
sense that they are dependent on a hacker's computational power. Here we
theoretically investigate, and experimentally demonstrate with Gaussian
displacement and squeezing operations, a quantum solution that achieves the
unconditional security of a user's privacy using the practical technology of
continuous variables. We demonstrate losses of up to 10 km both ways between
the client and the server and show that security can still be achieved. Our
approach offers a number of practical benefits, which can ultimately allow for
the potential widespread adoption of this quantum technology in future
cloud-based computing networks.
