Future influences past
Quantum physics has spawned a number of strange ideas.
Einstein called it as spooky action.
Recent research in quantum physics introduces another strange idea, called retro-causality.
This basically proposes that the future can influence the past.
The effect, in essence happens before the cause.
It does not mean that we can send signals from the future to the past.
It means that a experimenter's measurement of a particle can influence properties of the particle in the past,
even before making their choice.
The researchers propose that retro-causality could be a part of quantum theory.
They say that, if the accepted concept of time symmetry is true, retro-causality should also be true.
Time symmetry says that physical processes can run forward and backwards in time,
while being subject to the same physical laws.
Scientists describe an experiment where time symmetry would require processes to have the same probabilities,
whether they go backwards or forward in time.
This would cause a contradiction if there was no retro-causality,
as it requires these processes to have different probabilities.
They point out that you can't have both concepts to be true at the same time.
Eliminating time symmetry would also would also get rid of other sticky problems of quantum physics.
Einstein was uncomfortable with entanglement, which he described as 'spooky action at a distance'.
He saw challenges to quantum theory in the idea that entangled or connected particles could instantly affect each other, even at large distances.
In fact, accepting retro-causality could allow for the reinterpretation of Bell test,Â
that were used to show evidence of spooky action at a distance.
Instead the tests could be supporting retro-causality.
They say that any interpretation that fits into the standard framework of realistic interpretations,
must have features that would be regarded as undesirable.
Therefore the only option seems to be to abandon realism, or the breakout of the standard realist framework.
Are we going to have time travel as a result of this?
In one proposed idea, existence of retro-causality could mean that positrons, anti matter counterparts of electrons,
would move backwards in time so that they could have a positive charge.
If this was proven to be true, time travel could involve simply changing the direction of moving particles,
in the single dimension of time.
Scientists speculate that if retro-causality does exists in the universe, there could be evidence in cosmological data.
There are certain eras, perhaps near the big bang, in which there is not a definitive arrow of causality.
As of now, the idea of retro-causality is an interpretation.
There are no experiments being done by scientists to test the theory.
They hope that their ideas will question the assumption of quantum physics, and lead to new discoveries.