Erlangen 2018 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 51: Poster: Quantum Optics and Photonics IV
Q 51.55: Poster
Mittwoch, 7. März 2018, 16:15–18:15, Redoutensaal
Topological order in finite-temperature and driven dissipative systems — •Lukas Wawer1, Michael Fleischhauer1, Charles Bardyn2, Sebastian Diehl3, and Alexander Altland3 — 1University of Kaiserslautern, Kaiserslautern, Germany — 2Department of Quantum Matter Physics, University of Geneva — 3University of Cologne, Cologne, Germany
There are many exciting topological properties of topological systems in pure states. Although mixed quantum states can be understood as a generalization of pure states their topological properties are not investigated so far. For example, quantization of charge transport in a so-called Thouless adiabatic pump is lifted at any finite temperature in topological insulators. Here we show, that many body correlations preserve the integrity of topological invariants for mixed Gaussian states in one dimension. In our approach we show that the expectation value of the many body momentum-shift operator leads to a definition of a physical observable called the "ensemble geometric phase" (EGP). It turns out that in analogy to the Zak phase of pure states this phase is a general representation of a geometric phase for mixed Gaussian quantum states in the thermodynamic limit. Additionally the EGP provides a topologically quantized observable which detects encircled spectral singularities of density matrices. [1] Bardyn et. al., arXiv:1706.02741v2