Can a wormhole be used for fast interstellar travel?
Even if wormholes exist, we do not know of a way of opening one.
A wormhole, which is also known as an Einstein-Rosen bridge is an opening in spacetime which leads to another place or even another time.
There are solutions to General Relativity which allow for wormholes. It has however been proved that if the two ends are in the same universe it will be so unstable that it will collapse before anything, including light, could pass through it.
There are theories that very small wormholes can briefly come into existence through quantum fluctuations. It may be possible to enlarge and stabilise the opening of such a wormhole but it would require exotic matter which has never been observed.
So, although wormholes are theoretically possible, it is highly unlikely that one could be opened to connect two particular regions of spacetime. New developments in physics could however change this. For now, wormholes for fast interstellar travel are firmly in the realm of science fiction.