Image of the Day: quantum entanglement in space and time?

by **Josh "Spikey00" Y.** Mon Jan 31, 2011 1:59 pm

Here's what it looks like when two particles share the same properties — even if they're separated in space and time. Physicists S. Jay Olson and Timothy C. Ralph of Australia's University of Queensland explain further.

Recently, it has been shown that the massless quantum vacuum state contains entanglement between timelike separated regions of spacetime, in addition to the entanglement between the spacelike separated regions usually considered. Here, we show that timelike entanglement can be extracted from the Minkowski vacuum and converted into ordinary entanglement between two inertial, two-state detectors at the same spatial location -- one coupled to the field in the past and the other coupled to the field in the future. The procedure used here demonstrates a clear time correlation as a requirement for extraction, e.g. if the past detector was active at a quarter to 12:00, then the future detector must wait to become active at precisely a quarter past 12:00 in order to achieve entanglement.