Well if they tried to travel through time in real space, sure. If you stay in regular space, one can't even travel faster than light. They obviously found a strata of subspace where it's common to reach absolute cold and absolute heat simultaneously... Possibly even "subtime".
Worf does Sliders.
How could you have forgotten Riker's MASSIVE beard?
Quantum Realities are not the same as alternate timelines, since everyone from each quantum reality has different signature that thumb prints them from a specific quantum reality.
The Mirror Universe from TOS and DS9 was possibly a Quantum Reality?