Quantum resonance signature

A quantum resonance signature is a signature that all matter features.

In 2370, Worf travelled through alternate realities, where the Data of one of them discovered Worf's quantum resonance signature was different to their own and thus he was not from their reality. 

Data's discovery would later enable Starfleet to differentiate people from the mirror universe. In 2377, when Julian Bashir ran the alternate $𝜇$'s signature through a database, the only match was that of the alternate $𝜇$.