  Blindness is a desirable feature in delegated computation. In the classical
setting, blind computations protect the data or even the program run by a
server. In the quantum regime, blind computing may also enable testing
computational or other quantum properties of the server system. Here we propose
a scheme for universal blind quantum computation using a quantum simulator
capable of emulating Heisenberg-like Hamiltonians. Our scheme is inspired by
the central spin Hamiltonian in which a single spin controls dynamics of a
number of bath spins. We show how, by manipulating this spin, a client that
only accesses the central spin can effectively perform blind computation on the
bath spins. Remarkably, two-way quantum communication mediated by the central
spin is sufficient to ensure security in the scheme. Finally, we provide
explicit examples of how our universal blind quantum computation enables
verification of the power of the server from classical to stabilizer to full
BQP computation.
