# New Study Says Quantum Particles Can Travel Through Time

Physicists from the University of Queenland assert that quantum particles may be able to become "unstuck in time," after simulating time travel using photons.

At the heart of their study is the apparent incompatibility between the two prevailing theories of physics: quantum mechanics and Einstein's theory of relativity. Where general relativity satisfactorily explains the behavior of larger, readily observable objects, quantum mechanics explains the differing behaviors of extremely small particles, such as photons and electrons.

Relativity predicts the ability to travel back in time using a timelike spacetime curve. In order to travel back in time, one would travel along a curve of spacetime that would return to the same point in space, but at a different time. Intuitively, this concept leads to paradoxes such as the "grandparent paradox." If a person were to travel back in time and prevent his or her grandparents from ever meeting, then he or she would never be born. Paradoxically, he or she would never have the opportunity to travel back in time and make these changes.

One of the co-authors of the paper, physics professor Tim Ralph, explained that it was first postulated in 1991 that using quantum particles could circumvent such paradoxes: "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."

By simulating time travel using photons, the researchers were able to demonstrate the particular behaviors of particles in a closed timelike curve, and thus the potential for the resolution of these paradoxes when using quantum particles.

Ralph et al wrote in the paper, "In the quantum regime these paradoxes can be resolved, leaving closed timelike curves consistent with relativity. The study of these systems therefore provides valuable insight into nonlinearities and the emergence of causal structures in quantum mechanics-essential for any formulation of a quantum theory of gravity."

The existence of closed timelike curves could open up a multitude of possibilities for theoretical physicists. In addition to time travel, it could lead to the discovery of parts of the universe in which the uncertainty principle does not hold, as well as perfecting the process of cloning quantum states.