QUROPE Quantum Information Processing and Communication in Europe

Bad Honnef, 17.11. - 20.11.2015

Andrea Alberti (UBONN) Talk: Control of atomic motion in state-dependent optical lattices

http://www.we-heraeus-stiftung.de/index.php?option=com_icagenda&view=lis...

Hannover, 29.02. - 04.03.2016

Lothar Ratschbacher (UBONN) Talk: High finesse Fabry-Perot fiber resonators for efficient photonic interfacing: optimal mode-matching and stabilization

http://hannover16.dpg-tagungen.de/

Brussels, 04.04.2016 - 07.04.2016

Lothar Ratschbacher (UBONN) Talk: High finesse optical fiber cavities - optimal alignment and robust stabilization

https://spie.org/conferences-and-exhibitions/photonics-europe

https://spie.org/EPE/conferencedetails/quantum-technologies

Discrete-time quantum walks allow Floquet topological insulator materials to be explored using controllable systems such as ultracold atoms in optical lattices. By numerical simulations, we study the robustness of topologically protected edge states in the presence of temporal disorder in one- and two-dimensional discrete-time quantum walks. We also develop a simple analytical model to gain further insight into the robustness of these edge states against either spin or spatial dephasing.

We report on image processing techniques and experimental procedures to determine the lattice-site positions of single atoms in an optical lattice with high reliability, even for limited acquisition time or optical resolution. Determining the positions of atoms beyond the diffraction limit relies on parametric deconvolution in close analogy to methods employed in super-resolution microscopy. We develop a deconvolution method that makes effective use of the prior knowledge of the optical transfer function, noise properties, and discreteness of the optical lattice.

The coherence power of a quantum channel, that is, its ability to increase the coherence of input states, is a fundamental concept within the framework of the resource theory of coherence. In this note we discuss various possible definitions of coherence power. Then we prove that the coherence power of a unitary operator acting on a qubit, computed with respect to the l1-coherence measure, can be calculated by maximizing its coherence gain over pure incoherent states.

The use of the von Neumann entropy in formulating the laws of thermodynamics has recently been challenged. It is associated with the average work whereas the work guaranteed to be extracted in any single run of an experiment is the more interesting quantity in general. We show that an expression that quantifies majorization determines the optimal guaranteed work. We argue it should therefore be the central quantity of statistical mechanics, rather than the von Neumann entropy.

The accumulation of quantum phase in response to a signal is the central mechanism of quantum sensing, as such, loss of phase information presents a fundamental limitation. For this reason approaches to extend quantum coherence in the presence of noise are actively being explored. Here we experimentally protect a room-temperature hybrid spin register against environmental decoherence by performing repeated quantum error correction whilst maintaining sensitivity to signal fields.

Analyzing the physical and chemical properties of single DNA based molecular machines such as polymerases and helicases often necessitates to track stepping motion on the length scale of base pairs. Although high resolution instruments have been developed that are capable of reaching that limit, individual steps are oftentimes hidden by experimental noise which complicates data processing. Here, we present an effective two-step algorithm which detects steps in a high bandwidth signal by minimizing an energy based model (Energy based step-finder, EBS).

Precision sensing, and in particular high precision magnetometry, is a central goal of research into quantum technologies. For magnetometers often trade-offs exist between sensitivity, spatial resolution, and frequency range. The precision, and thus the sensitivity of magnetometry scales as 1/(T2)1/2 with the phase coherence time, T2, of the sensing system playing the role of a key determinant.