The Novikov self-consistency principleis a principle to solve the problem of paradoxes in time travel. The principle asserts that if an event exists that would give rise to a paradox, or to any "change" to the past whatsoever, then the probability of that event is zero. It would thus be impossible to create time paradoxes.
Computer Simulation Confirms the Possibility of Time Travel. Using photons, Australian scientists managed to create a model in which quantum particles can move back in time. As it turned out, the laws of standard quantum mechanics may be violated at the same time. Read more at http://www.learning-mind.com/computer-simulation-confirms-the-possibility-of-time-travel/#tAUpFejDcOglz0eh.99