Physicists from the University of Queensland in Australia set out to simulate a computer experiment, which could prove the possibility of time travel at the quantum level, predicted in 1991. They managed to simulate the behavior of a single photon passing through a wormhole in space-time in the past and engaging with itself. Such a trajectory of a particle is called a closed timelike curve, i.e. a photon returns to the original space-time point and its worldline closes.
The researchers studied two scenarios. In the first, the particle passes through a wormhole, returning to the past, and interacts with itself. In the second scenario, the photon, forever enclosed in a closed timelike curve interacts with another, ordinary particle.