New research supports retrocausality, where the effect comes before the cause.
One of the most incredible aspects of quantum mechanics can be explained by the equally incredible idea that causality can go both forward in time and backward. Einstein's "creepy" action at a distance could theoretically be proof of retroactivity: as if you had a stomach ache today because of tomorrow's bad lunch.
Two physicists from the USA and Canada took a closer look at some of the basic assumptions in quantum theory and came to the conclusion: if we did not discover that time necessarily moves in the same direction, then measurements carried out on a particle can equally affect both the past and the future.
Everyone knows that there are a lot of oddities in quantum mechanics. This is partly due to the fact that at a fundamental level, particles do not behave like billiard balls rolling on a table, but rather like a murky "cloud of probability" moving around the room. This cloudy cloud takes on sharpness when we try to measure particles. That is, in principle, we can only see how one white ball drives black into the corner pocket, but not the countless number of white balls that drive black into each pocket.
Physicists debate whether this probability cloud is something - or just a convenient representation. In 2012, scientist Hugh Price argued that if strange probabilities behind quantum states reflect something real, and time does not tie anything to one direction, then a black ball in a cloud of probabilities could theoretically roll out of the pocket and hit the white one.
“Critics argue that there is complete temporal symmetry in classical physics, but there is no apparent retrocausality. Why should the quantum world be different? - wrote Price, paraphrasing the thoughts of most physicists.
Matthew S. Leifer of Chapman University in California and Matthew F. Pusey of the Perimeter Institute for Theoretical Physics in Ontario also wondered if the quantum world could be different with respect to time. They replaced some of Price's assumptions and applied their new model to Bell's theorem, which is of great importance today in matters of "spooky" action at a distance.
John Stuart Bell said that the strange things that happen in quantum mechanics cannot be explained by nearby actions: as if nothing had caused many billiard balls to choose such different paths. On a fundamental level, everything in the universe is random.
Promotional video:
Influence diagram representing possible causal influences in a non-retrocausal model. The square represents the variable under the direct control of the experimenter, and the circle represents the uncontrolled variable. The arrow between the two nodes u and v in the diagram represents the possibility that u may be a direct cause of v / Matthew S. Leifer / Matthew F. Pusey.
But what about actions taking place elsewhere … or time? Could something from afar affect this cloud without touching it? This is what Einstein called "creepy."
If two particles are connected at some point in space, measuring the properties of one of them instantly sets the parameters of the other, regardless of where in the Universe it has moved.
This entanglement has been repeatedly tested in light of Bell's theorem, trying to figure out if particles interact with each other in any way locally, despite what appears to be a distance.
But if the causality can be reversed, it would mean that the particle is able to transfer the action of its dimensions back in time - to the moment of entanglement - acting on its "partner". And no messages faster than the speed of light are needed. This hypothesis was put forward by Leifer and Pusey.
"There is a small group of physicists and philosophers who think this idea is worth pursuing," Leifer told Phys.org in an interview.
By reformulating several basic assumptions, the researchers developed a model based on Bell's theorem, where space and time were reversed. According to their calculations, if we cannot show why time must always go forward, then we are faced with some contradictions.
Influence diagram for an ontological model, which is an ontic extension satisfying the conditions λ and the absence of retrocausality / Matthew S. Leifer / Matthew F. Pusey.
“As far as I know, there is no generally accepted interpretation of quantum theory that reconstructs it in its entirety and uses this idea. This is more of an interpretation idea at the moment, so I think other physicists are quite rightly skeptical about it and our duty is to concretize it,”says Leifer.
It is worth noting that such a "travel" in time does not mean that a person will go back and consciously change the present. And scientists of the future will also not be able to encode lottery ticket numbers into entangled electrons and send them back in time.
In any case, the idea of something traveling back in time is unlikely to sound appealing. But let's be frank: when it comes to such a phenomenon as quantum entanglement, almost any explanation is insane.
Vladimir Mirny