Posts tagged retrocausality

As with so much else in quantum mechanics, this concept of retrocausality is limited in scope. Only in certain circumstances can we see the future influence the past. Although individual particle processes can move backward or forward in time, the universe as a whole is skewed in the forward direction, because its past endpoint was highly ordered, and its future endpoint is highly disordered. Our mortality is this asymmetry in microcosm.

http://nautil.us/issue/9/time/the-quantum-mechanics-of-fate

Using four photons, we can actively delay the choice of measurement-implemented via a high-speed tunable bipartite state analyzer and a quantum random number generator-on two of the photons into the time-like future of the registration of the other two photons. This effectively projects the two already registered photons onto one definite of two mutually exclusive quantum states in which either the photons are entangled (quantum correlations) or separable (classical correlations). This can also be viewed as “quantum steering into the past”.

http://arxiv.org/abs/1203.4834