  The quality of high-end videoconferencing systems has improved significantly
over the last few years enabling a class of applications known as
"telepresence" wherein the users engaged in a communication session experience
a feeling of mutual presence in a shared virtual space. Telepresence systems
have reached a maturity level that seriously challenges the old familiar truism
that a face-to-face meeting is always better than a technology-mediated
alternative. To explore the state of the art in telepresence technology and
outline future opportunities, this paper proposes an optimality condition,
expressed as a "Turing Test," whereby the subjective experience of using a
telepresence system is compared to the corresponding face-to-face situation.
The requirements and challenges of designing a system passing such a Turing
Test for telepresence are analyzed with respect to the limits of human
perception, and the feasibility of achieving this goal with currently available
or near future technology is discussed.
