A type of rumored clarketech device, never actually confirmed.
Some cryptotechologists argue that since time and space are quantized (the Planck distance and Planck time, the smallest unit of either that can be measured) infest a volume of space with Planck machines and than jump it 'out of phase' by one Planck time unit with the rest of the universe around it. The volume then lags by one Planck unit behind everything else. Since nothing can go backwards in time above the quantum level, a barrier would appear to be created where the two regions interfaced. Nothing is able to cross the barrier to enter the volume, although things could leave the barrier since they would be going forward in time in the process. Alternatively the volume in question might just seem to disappear without a trace.