Środowiskowe Seminarium z Informacji i Technologii Kwantowych
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2021-03-04 (11:15) 
Geza Toth (University of the Basque Country UPV EHU, Bilbao)
Activating hidden metrological usefulness
Zoom link: https://zoom.us/j/6526721604?pwd=Y0pPdE9vT1hNWWNiZVBMaEVOeHN2dz09
We consider bipartite entangled states that cannot outperformseparable states in any linear interferometer. Then, we show thatthese states can still be more useful metrologically than separablestates if several copies of the state are provided or an ancilla isadded to the quantum system. We present a general method to find thelocal Hamiltonian for which a given quantum state performs the bestcompared to separable states. We obtain analytically the optimalHamiltonian for some quantum states with a high symmetry. We show thatall bipartite entangled pure states outperform separable states inmetrology. Some potential applications of the results are alsosuggested.
[1] G. Toth, T. Vertesi, P. Horodecki, and R. Horodecki, Phys. Rev.Lett. 125, 020402 (2020).
We consider bipartite entangled states that cannot outperformseparable states in any linear interferometer. Then, we show thatthese states can still be more useful metrologically than separablestates if several copies of the state are provided or an ancilla isadded to the quantum system. We present a general method to find thelocal Hamiltonian for which a given quantum state performs the bestcompared to separable states. We obtain analytically the optimalHamiltonian for some quantum states with a high symmetry. We show thatall bipartite entangled pure states outperform separable states inmetrology. Some potential applications of the results are alsosuggested.
[1] G. Toth, T. Vertesi, P. Horodecki, and R. Horodecki, Phys. Rev.Lett. 125, 020402 (2020).