Basically, it is saying that if you want to go back in time through a wormhole to kill your own grandfather, that quantum interference effects caused by the inc

Basically, it is saying that if you want to go back in time through a wormhole to kill your own grandfather, that quantum interference effects caused by the inconsistency in time which that would cause would make you reflect off the wormhole and not be able to enter it. This provides a protection mechanism which would prevent the typical type of time-travel paradox.