Curves in spacetime violate Heisenberg's uncertainty principle: "Deutsch's model describes the strange quantum effects that we might see in the presence of CTCs, within a future theory of quantum gravity," Pienaar said. "However, if there are no CTCs in the universe, then we would not expect to see the effects. But since the slowing of time due to gravity looks just like the effect of an OTC from the outside, and since OTCs still lead to strange effects (as we have shown), we suggested that these effects might turn up in strong gravitational fields, even without any closed loops in time. If so, then they would allow us to violate the Heisenberg uncertainty principle and clone coherent states of light without needing a full-blown time machine.
"Of course, the connection between OTCs and gravitational fields is still very speculative and might turn out to be wrong..."