Speaker: Róbert Trényi (University of the Basque Country, Wigner FK SZFI)
Title: Activation of metrologically useful genuine multipartite entanglement
Date: 2 May 2023, 10:00
Place: Building 1, 2nd floor, conference room
We consider quantum metrology with several copies of bipartite and multipartite quantum states. We characterize the metrological usefulness by determining how much the state outperforms separable states. We identify a large class of entangled states that become maximally useful for metrology in the limit of a large number of copies, even if the state is weakly entangled and not even more useful than separable states. This way, we activate metrologically useful genuine multipartite entanglement. Remarkably, not only that the maximally achievable metrological usefulness is attained exponentially fast in the number of copies, but it can be achieved by the measurement of a few simple correlation observables. We also make general statements about the usefulness of a single copy of pure entangled states. We surprisingly find that the multiqubit states presented in Hyllus et al. [Phys. Rev. A 82, 012337 (2010)], which are not useful, become useful if we embed the qubits locally in qutrits.