It’s the crucial sticking point in Einstein’s theory that it’s possible to travel back in time – what would happen if you stopped your own grandparents from meeting?
You wouldn’t be born, therefore you couldn’t travel in time, right?
According to scientists at the University of Queensland, maybe not.
Followed up a theory first proposed in 1991 that quantum particles are “fuzzy” and therefore their behaviour in the quantum world is uncertain.
UQ’s study lead author Martin Ringbauer told The Speaker his team had successfully simulated sending a single proton through a wormhole to catch up with its older self.
A wormhole, for the uninitiated and non-sci-fi fans, is a shortcut to the past that can theoretically be built by distorting the fabric of space-time.
Using huge amounts of energy, space-time can be warped and folded back in upon itself. Draw two dots on a sheet of paper and fold it over and you can see how the two points can be brought close together. All that is required is a process by which you can punch a hole from one dot through to the other.
The UQ team researched two scenarios:
- Photon One travels through to the older point and interacts with its older self which is on a linear journey to the as-yet unknown future
- Photon Two travels through to the same point, but instead meets with a version of its older self which is stuck in a Groundhog Day-like loop inside a closed timelike curve
“We used single photons to do this but the time-travel was simulated by using a second photon to play the part of the past incarnation of the time travelling photon,” University of Queensland physics professor Tim Ralph told The Speaker.
In this way, the team say they found a way to bridge the gap between the two theories. And without going into the kind of detail only Hawking-level readers can get excited about, the results were promising.
“We see in our simulation (as was predicted in 1991) how many effects become possible, which are forbidden in standard quantum mechanics,” said Ringbauer. “For example it is possible to perfectly distinguish different states of a quantum system, which are usually only partially distinguishable. This makes quantum cryptography breakable and violates Heisenberg’s uncertainty principle.
“We also show that photons behave differently, depending on how they were created in the first place.”
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