Quantum metrological gain
The quantum metrological gain is defined in the context of carrying out a metrological task using a quantum state of a multiparticle system. It is the improvement in measurement precision achieved by utilizing quantum resources (such as entanglement or state squeezing) compared to the best possible classical methods using separable states, i.e., states without quantum entanglement.
Source: Wikipedia — Quantum metrological gain (CC BY-SA 4.0)