Quantum slipstream drive

The quantum slipstream drive was an advanced form of interstellar propulsion which was able to allow starships to break through the warp speed barrier. The technology was acquired from an unknown species by the crew of the USS Voyager in 2374. A later test of the drive in 2375 nearly led to the destruction of Voyager, and it was decided to put the use of the device on hold. (VOY episodes: "Hope and Fear" & "Timeless")

In 2380 the Vesta class Federation starship USS Aventine was among the first Starfleet vessels to be fitted with a quantum slipstream drive. 

In 2381 following the defeat of the Borg,Starfleet was beginning to install quantum slipstream drives on its vessels. However due to the nature of the technology, not all ships were compatible with the upgrade. (A Singular Destiny) Later, a small contingent of Starfleet vessels, including Voyager, were outfitted with the drives in order to explore the Delta Quadrant in greater detail, and to learn any information available of the Borg. (Full Circle (novel))

Unknown to Starfleet, at the same time in 2381, B'Elanna Torres had managed to recreate the technology from memory and outfitted a small vessel with the drive, for the purpose of evading groups persuing her daughter.(Full Circle (novel))