  It was believed until recently that the verification of quantum entanglement
and quantum steering, between two parties, required trust in at least one of
the parties and their devices, in contrast to the verification of Bell
nonseparability. It has since been shown that this is not the case: the need
for trust, in verifying two parties share a given quantum correlation resource,
can be replaced by quantum refereeing, in which the referee sends quantum
signals rather than classical signals to untrusted parties. The existence of
such quantum-refereed games is discussed, with particular emphasis on how they
make it impossible for the parties to cheat. The example of a particular
quantum-refereed steering game is used to show explicitly how
measurement-device independence is achieved via `quantum programming' of
untrusted measurement devices; how cheating is prevented by the steered party
being unable to distinguish sufficiently well between two sets of nonorthogonal
signal states; and that cheating remains impossible when one-way communication
is allowed from the steered party to the unsteered party. This game has been
recently implemented experimentally, and is of particular interest both in
accounting for any imperfections in the referee's preparation of signal states,
and in suggesting the future possibility of secure two-sided quantum key
distribution with Bell-local states.
