Quantum signature

Multiple realities
(covers information from several alternate timelines)

A quantum signature was the unique signature with which all matter in a universe resonated. It could not be changed by any known process, and was considered to be the basic foundation of existence. However, the quantum signature did differ between different quantum universes, such as between the prime universe and the mirror universe. (TNG: "Parallels"; DIS: "Despite Yourself")

During the first Federation-Klingon War, the USS Discovery found itself transported to the mirror universe due to an incident with its spore drive. It quickly detected that the quantum signature of other ships was inconsistent with its own, helping them determine that they had left their universe. Michael Burnham later used the quantum variance of a Starfleet insignia to prove her origins to Emperor Georgiou. Georgiou confirmed this inference with a scan of the metal insignia. (DIS: "Despite Yourself", "Vaulting Ambition")

In 2370, Lieutenant Worf was thrown into a state of quantum flux as a result of an encounter with a quantum fissure, causing him to shift between different quantum realities. Detecting this flux in Worf's cellular RNA, which extended to the subatomic level, Lieutenant Commander Data was able to determine that Worf's quantum signature was not consistent with the resonance of matter in the rest of the universe, and that he had originated from a different quantum universe. (TNG: "Parallels")

In 2384, Wesley Crusher used a machine created with modified Boreth time crystals and the Orb of Time to read the quantum signatures of the USS Protostar crew and later Maj'el. This allowed Wesley's machine to figure out where they needed to go next in the sequence of events that would allow the crew to save the prime universe from a reality destroying temporal paradox, ultimately leading them through a gateway to Ysida where the Protostar and Captain Chakotay had been marooned for 10 years. (PRO: "The Devourer of All Things, Part II", "Last Flight of the Protostar, Part I")

Later, the crew of the Protostar inadvertently created an interphasic rift that consumed the USS Voyager-A, splitting the ship into dozens of alternate realities which only the Protostar crew was able to pass through and which were examples of things that the crew did or didn't do. Chakotay guessed that since they had created the rift, it was tied to their quantum signatures. (PRO: "Cracked Mirror")

In 2385, Wesley had the Protostar's computer cross-reference all wormholes with the ship's quantum signature and their current space-time coordinates. This helped the crew to find the wormhole that they needed to open in order to send the Protostar back in time and repair the broken timeline. (PRO: "Ouroboros, Part I")

See also