Yes, cats can jump over baby gates. In fact, they can jump over just about anything that's in their way. That's one of the things that make them such great climbers.
If you have a baby gate that's low to the ground, your cat will probably be able to jump right over it. If the gate is taller, they may be able to scale it like they would a tree. Either way, it's best to keep an eye on your furry friend if you don't want them going where they're not supposed to.