'' The Present Influences The Past '', A Quantum Idea Gains Theoretical Support

 

Quantum mechanics is already strange enough, but physicists propose that we could throw in a bit of time shenanigans to resolve a controversial idea that has been argued for almost a century.

 

The idea is called entanglement or, as Einstein mockingly described it, “spooky action at a distance”. This is when particles in a quantum system effect each other, even over ridiculously large distances. This phenomenon has been confirmed by numerous experiments, testing the validity of the Bell test, but the new study argues something different might be at play.

 

They call it “retrocausality”. The set-up of an experiment will affect the particles in the past, so what seems to be an action at a distance is, in reality, something the observer made happen by picking a certain experiment. Two researchers have now put some math behind this theory. Their research is published in Proceedings of The Royal Society A.

 

"There is a small group of researchers and philosophers that think this idea is worth chasing, including Huw Price and Ken Wharton [a physics professor at San José State University]," lead author Matthew Leifer, from Chapman University, told Phys.org. "There is not, to my knowledge, a commonly agreed upon understanding of quantum theory that recovers the entire theory and exploits this idea. It is more of an idea for an interpretation at the moment, so I think that other researchers are rightly uncertain, and the onus is on us to flesh out the idea."

 

This is a good approach to have. Just because the idea is very out there doesn’t mean we won’t learn anythting by exploring it. Since it challenges some solid tenants of quantum physics, the suggested solutions might hint at some unexpected physics even if it's not associated to retrocausality.

 

The theory assumes that quantum theory is perfectly symmetric in time, so that the laws of quantum mechanics need to look the same whether you’re observing them forward or backward. The typical analogy for this is like an egg moving across a kitchen counter. If the egg all of a sudden dropped on the floor and broke, you’d know you were watching it forward. We don’t see eggs jumping back together, do we?

 

But in the quantum world, we don’t have an arrow of time, and if we assume that everything must be symmetric, then retrocausality naturally arises, the physicists argue. That allows you to get rid of entanglement and a lot of limitations placed by the Bell test.

 

While this is early days, it will be exciting to see if this idea can be established in ways that can be tested against the current model.

References:

Phys.org, britannica.com