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Q: Fachverband Quantenoptik und Photonik

Q 33: Quantum information: Concepts and methods II

Q 33.8: Vortrag

Dienstag, 19. März 2013, 15:45–16:00, E 214

Directly probing correlatedness in optical lattices — •Janina Gertis, Matthias Ohliger, and Jens Eisert — Freie Universität Berlin, Germany

Full tomography of a quantum state usually requires a large number of measurements. However, often times, one is mostly interested in some characteristics of the quantum state. In this context, we present a method to directly estimate a lower bound on the degree of correlatedness in a system of cold atoms in an optical lattice. We achieve this goal resorting only to minimal a-priori assumptions on the quantum state of the system. By using density distribution data from time of flight measurements, which is available with current technology in this type of systems, we calculate the second and fourth moments of the quantum state. We minimize the relative entropy between an arbitrary quantum state, with the same estimated moments, and an uncorrelated Gaussian reference state. As a result of the minimization, we obtain a lower bound for the actual relative entropy between the state of the system and the closest Gaussian reference state. We can thus detect strong correlations without having to do a full tomographic reconstruction on the quantum state of the system.