A quantum reaction was the physical effect caused by a stimuli at the quantum level. In 2371, the USS Olympia was investigating an exogenic field surrounding the fourth planet of a star system in the Rutharian sector. When the Olympia scanned the energy barrier, it triggered quantum reaction that sent a surge of metreon radiation that destroyed the Olympia's engines, causing it to crash on the planet's surface. (DS9: "The Sound of Her Voice")