Research Seminar/Oberseminar "Correlated Quantum Systems"


Mondays 14:15, SR Philosophenweg 19


Program WS 2013/14:


14/10

Tarek Elsayel (Heidelberg University):

Regression relation for pure quantum states and its implications for efficient computing


22/10 (Tuesday - change of date!)

Carlos Viviescas (University of Bogota, Colombia):

Entanglement and conditional quantum evolution

(a stochastic quantum state evolution approach)


Although, at present, we have at our disposal a sophisticated theory on the time evolution of quantum states under environment coupling, a general description of the entanglement dynamics in open quantum systems still remains elusive, with scarce general results stated. In this talk, by switching the focus from the unconditional to the conditional state evolution of the quantum system, I discuss a path to overcome some of the of the hurdles usually encountered in the characterization of the entanglement evolution. A key lesson of the decoherence program is that information flowing out from an open system is stored in the quantum state of the surroundings. Simultaneously, quantum measurement theory shows that the evolution of any open system when its environment is measured is nonlinear and leads to pure states conditioned on the measurement record. We use this conditional evolution to establish a time evolution equations for the average entanglement in the system, avoiding the, up to now, unescapable step of solving first the evolution of the unconditional state. We show how this equations can be use to extract fundamental relations between entanglement and measurement at the level of single trajectories in systems whose environment is being continuously monitored. Moreover, we show how such monitoring can be use to develop general protocols for entanglement protection using local measurements. We conclude with the formulation of a scaling law between the amount of entanglement in the conditional state of the system and the probabilities of the experimental outcomes obtained from measuring the state of the environment.


23/10 SR Philosophenweg 12 11:15 a.m.(Wednesday - change of date and place!)

Ralf Labouvie (TU Kaiserslautern):

Dynamics of Quantum-Systems with Localized Dissipation

In our experiment, we are employing a tightly focussed scanning electron-beam, which ionizes atoms of an atomic cloud by electron-impact ionization. The produced ions are then extracted by means of electrostatic optics and detected. This allows us to probe atomic density distributions with high temporal and spatial resolution. Furthermore, the electron-beam is a versatile tool to manipulate the atomic ensemble e.g. it yields the possibility for localized dissipative defects and therefore to create open quantum-systems. The obtained ion-signal shows the system’s reaction on the defect and allows to measure pair-correlations and Zeno-like behaviour. This method can also be used to engineer non-equilibrium states and investigate their time evolution e.g. tunnel dynamics in a one-dimensional lattice. In addition, subsequently obtained density-profiles allow for a in-vivo investigation of all the samples.