Programmable antimatter

Programmable antimatter was the antimatter counterpart to programmable matter. It repelled negative energy, and thus when applied to shield generators could be used to protect starships traversing the galactic barrier.

Ruon Tarka and Oros, when they were enslaved together by the Emerald Chain, secreted a stash of programmable antimatter in their lab for the interdimensional transporter they were developing, though they ultimately did not have the chance to use it. Years later in 3190, Tarka and Cleveland Booker retrieved the antimatter so that Booker's ship could reach the hyperfield of Species 10-C outside the galaxy.

The USS Discovery crew also used programmable antimatter for their journey to reach the hyperfield. However, they found negative particle density within the barrier to be significantly higher than expected, meaning that their modified shields would not provide sufficient protection. (DIS: "The Galactic Barrier")