Well, the Alcubierre drive [1] uses negative energy, but at this point it is not clear whether this type of propulsion is just a mathematical gimmick.
[1] https://en.wikipedia.org/wiki/Alcubierre_drive
Not only negative energy but insane amounts of it as well. Originally required converting more mass than the entire observable universe. That was lowered in later works. A recent work moreover made a drive using only positive energy.
We do not know if and I bet plenty of people do not believe such negative energy really exists.
Besides, all warp bubble metrics so far are inertial; meaning the ship is unable to accelerate, so they're a gimmick nowadays. I have hopes we find something workable though.
>We do not know if and I bet plenty of people do not believe such negative energy really exists.
Plenty of people believe that mental problems are all caused by disembodied souls unleashed by Xenu of the Galactic Confederation when he blew them up with A-bombs in Hawaii, back when Earth was called Teegeeack.