Probing Ultracold Atoms using Faraday Interfaces: new applications in Thermometry and the Measurement of Atomic Probability Distribution Functions

Seminar

In this talk, I will present two new applications of the Faraday spectroscopy to characterize quantum many-body states. In the first part, I will discuss how useful this scheme can be to perform thermometry in ultracold lattice gases. In particular, the XY-model on a chain (which could be realistically implemented in certain regimes using cold atoms) will be used as a prototype model to compare the optimal precision in temperature that can be theoretically attained (given by the quantum Fisher information), and the maximum thermal sensitivity that one could achieve using the Faraday effect [2]. In the second part of my talk, I will focus on the measurement and state characterization using all-order correlations functions. More precisely, the Faraday spectroscopy allows in principle to access any order of the statistical moments of the collective atomic magnetic moment, which contains such correlations, or equivalently, to reconstruct the full probability distribution function. I will show that this function can provide information which is not present in the order parameter or the second order correlation function, and allows for a more complete characterization of certain quantum states and phase transitions. [1] K. Eckert et al., Nature Physics 4, 50-54 (2008); G. De Chiara, O. Romero-Isart, and A. Sanpera; Physical Review A. 83, 021604 (2011). [2] M. Mehboudi, M. Moreno-Cardoner, G. De Chiara, and A. Sanpera; New J. Phys. 17, 055020 (2015).

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