Scientists have for some years been able to 'teleport' quantum states from one place to another. Now Seth Lloyd and his MIT team say that, using the same principles and a further strange quantum effect known as 'postselection', it should be possible to do the same backwards in time. Lloyd told the Technology Review: "It is possible for particles (and, in principle, people) to tunnel from the future to the past."
Postselection is a vital part of the nascent science of quantum computing. In traditional computing, if a user needs to determine which set of variables in an equation leads to the answer being true, the computer must try every combination until it hits upon one that works. In quantum computing, due to the weird parallel behaviour of subatomic particles, it seems to be possible to simplify the procedure by running all possible variations simultaneously, and selecting only the combinations that make the answer true.
Professor Lloyd and his team say that, by combining teleportation and postselection, it would be possible to carry out the quantum teleportation effect in reverse; that is, to decide after the teleportation what the quantum state must have been before it. This works as postselection allows you to dictate which quantum states can be teleported, limiting what state it can have been in before the teleportation. The state of the particle post-teleportation has therefore, in effect, travelled back in time.
Read more at The Telegraph
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