Australian scientists created a computer simulation in which quantum particles can move back in time. This might confirm the possibility of time travel on a quantum level, suggested in 1991. At the same time, the study revealed a number of effects which are considered impossible according to the standard quantum mechanics.
Using photons, physicists from the University of Queensland in Australia simulated time-traveling quantum particles. In particular, they studied the behavior of a single photon traveling back in time through a wormhole in space-time and interacting with itself. This time-traveling loop is called a closed timelike curve, i.e. a path followed by a particle which returns to its initial space-time point.
The physicists studied two possible scenarios for a time-traveling photon. In the first, the particle passes through a wormhole, moving back in time, and interacts with its older self. In the second scenario, the photon passes through normal space-time and interacts with another photon which is stuck in a closed timelike curve.
According to the researchers, their study will help to find a link between two great theories in physics: the Einstein’s general theory of relativity and quantum mechanics.
“The question of time travel features at the interface between two of our most successful yet incompatible physical theories – Einstein’s general relativity and quantum mechanics,” said Martin Ringbauer of the University of Queensland who led the study. “Einstein’s theory describes the world at the very large scale of stars and galaxies, while quantum mechanics is an excellent description of the world at the very small scale of atoms and molecules.”
Einstein’s General Relativity suggests the possibility of moving back in time if the time-traveling object is stuck in a closed timelike curve. Yet, this possibility is known to cause a number of paradoxes, such as the famous “grandfather paradox”, in which a time traveler prevents his own existence by preventing his grandparents from meeting each other.
In 1991, the concept of time travel in the quantum world was suggested. It was said that traveling through time on a quantum level can prevent such paradoxes, since the properties of quantum particles are not precisely defined, in accordance with Heisenberg’s uncertainty principle.
“The properties of quantum particles are “fuzzy” or uncertain to start with, so this gives them enough wiggle room to avoid inconsistent time travel situations,” said professor Timothy Ralph who participated in the study.
Thus, the experiment conducted by the Australian scientists shows that such kind of time travel might be possible.
At the same time, some new bizarre effects were discovered, which are forbidden by standard quantum mechanics. For instance, it appears that it is possible to accurately distinguish various states of a quantum system, despite the fact that it violates Heisenberg’s uncertainty principle.