The Quantum Vortex is powerful weapon that is first used by the Taelons where its destructive effects were used secretly on Earth during the time of the SI War. After being launched, it led to the death of 100,000 Humans and led to a quick end to the conflict as the various sides believed the other was responsible for its deployment.
Following the Taelons arrival on Earth, SI War veteran Colonel Dennis Robillard came to believe that these alien visitors had been observing the planet in secret and were responsible for the deployment of the weapon. Thus, he began attempts at recreating it in secret and used it against the Taelon Embassy. A forensic unit managd to uncover the link to the Quantum Vortex which shocked Ronald Sandoval.
Afterwards, Robillard attempted to use the Vortex against the Taelon Mothership in order to destroy it. However, the resultant act would have destroyed the entire eastern seaboard of the United States of America. Liam Kincaid and Renee Palmer managed to reverse the weapon to cause it to feed back on itself which destroyed the installation holding it. (Episode: Scorched Earth)