Reality operates under very different principles in the enigmatic field of quantum physics than it does in the classical world. Anything from the fanciful to the strangely commonplace can occur in this quantum environment. Recently, while as a completely theoretical experiment, physicists dabbled in the fascinating realm of “time travel” utilizing quantum entanglement.
It is important to note that there has never been any true time travel by any quantum particle. This particular research is known to physicists as a Gedankenexperiment, a word coined by Albert Einstein to refer to theoretical investigations carried out in place of actual experiments.
When investigating the limits of physics, these kinds of thought experiments come in quite handy, particularly when dealing with situations in which particles are traveling at the speed of light.
In this study, the fascinating concept of closed timelike curves (CTCs)—a hypothetical road that travels backward in time—is explored. In spacetime, CTCs basically trace the worldline of a particle’s existence in reverse.
Notably, prominent physicist Stephen Hawking conjectured in his 1992 “Chronology protection conjecture” that time travel is impossible because closed timelike curves cannot exist according to the rules of physics. However, a recent study reveals that quantum-teleportation circuits can be used to imitate CTCs probabilistically.
The Gedankenexperiment conducted by the researchers goes as follows: Researchers apply quantum interactions to photonic probes to obtain quantifiable results. By using these results, they may practically apply hindsight to the experiment and decide what input would have produced an ideal outcome in the past.
But since the outcomes are the product of quantum processes, the researchers can use quantum entanglement to change the quantum probe’s values and improve the result even after the procedure is finished.
The group gave evidence that “probabilistically improving one’s past choice” would be feasible. Though intriguing, this idea hasn’t been implemented yet. According to their research, there would be a 75% failure rate and an apparent time travel effect that happened once every four times. The team suggests sending a lot of entangled photons and employing a filter to make sure that photons with corrected information pass through while eliminating the out-of-date particles in order to address this high failure rate.
Lead author of the study David Arvidsson-Shukur, a quantum physicist at the University of Cambridge, pointed out that the experiment seemed intractable under standard physics, which traces the traditional arrow of time. Still, it appears that quantum entanglement can produce situations that resemble time travel.
Different from macroscopic occurrences, the unusual behaviors of quantum particles offer physicists an invaluable tool for exploring the essence of our existence. One such facet of quantum physics that has fascinated scientists for a long time is quantum entanglement, which defines the interdependence of attributes between two or more quantum particles.
By using quantum entanglement, “effective time travel” has recently been explored as a way to study time-related ideas without going too far outside the bounds of the universe’s laws and restrictions.
Co-author of the paper Nicole Yunger Halpern is a physicist at the University of Maryland in College Park and the National Institute of Standards and Technology. She said, “We don’t know if closed timelike curves exist in reality.” The existence of CTCs is permitted by the known laws of physics, but these laws are not comprehensive; most obviously, we lack a theory of quantum gravity. The work demonstrates how entanglement can mimic real closed timelike curves, providing new insight into the complexities of quantum mechanics even though their existence is still unknown.
Essentially, the goal of this research is to push the frontiers of our knowledge of the universe by using the special qualities of the quantum realm, rather than worrying about whether time travel is feasible.