Already Received - Tuned to a Future Signal

A paper just accepted at Physical Review Letters - from researchers at Cornell and MIT - formally calculates the capacity of a quantum channel to transmit information backward in time. The mechanism relies on what physicists call closed timelike curves, paths permitted by general relativity where something could loop back to its own past. At the quantum scale, entanglement can simulate these curves. And the paper's central finding is strange: backward-time communication through a noisy channel can be more efficient than forward-time communication, because the sender already carries memory of how the message was decoded.

 The future informs t...