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Format: 2019-12-06
Format: 2019-12-06
Format: 2019-12-06


26th Jul 2016

By mapping the strong interaction between Rydberg excitations in ultra-cold atomic ensembles onto single photons via electromagnetically induced transparency, it is now possible to realize a medium which exhibits a strong optical nonlinearity at the level of individual photons. We review the theoretical concepts and the experimental state-of-the-art of this exciting new field, and discuss first applications in the field of all-optical quantum information processing.


26th Jul 2016

We present a solid-state laser system that generates over 200 mW of continuous-wave, narrowband light, tunable from 316.3 nm – 317.7 nm and 318.0 nm – 319.3 nm.


26th Jul 2016
Optical frequency combs provide the clockwork to relate optical frequencies
to radio frequencies. Hence, combs allow to measure optical frequencies
with respect to a radio frequency where the accuracy is limited
only by the reference signal. In order to provide a stable link between the
radio and optical frequencies, the two parameters of the frequency comb
must be fixed: the carrier envelope offset frequency fceo and the pulse


6th Jul 2016

We study the influence of Rydberg dressed interactions in a one-dimensional (1D) Bose-Einstein Condensate (BEC). We show that 1D is advantageous over 3D for observing BEC Rydberg dressing. The effects of dressing are studied by investigating collective BEC dynamics after a rapid switch-off of the Rydberg dressing interaction. The results can be interpreted as an effective modification of the $s$-wave scattering length.


6th Jul 2016

We present our experimental investigation of an optical Raman transition between the magnetic clock states of $^87$Rb in an atom chip magnetic trap. The transfer of atomic population is induced by a pair of diode lasers which couple the two clock states off-resonantly to an intermediate state manifold.


6th Jul 2016

We present experimental results on the influence of magnetic fields and laser polarization on electromagnetically induced transparency (EIT) using Rydberg levels of $^87$Rb atoms. The measurements are performed in a room temperature vapor cell with two counter-propagating laser beams at 480nm and 780nm in a ladder-type energy level scheme.


20th Jun 2016

Tensor network states and specifically matrix-product states have proven to be a powerful tool for simulating ground states of strongly correlated spin models. Recently, they have also been applied to interacting fermionic problems, specifically in the context of quantum chemistry.


20th Jun 2016

We construct minimax optimal non-asymptotic confidence sets for low rank matrix recovery algorithms such as the Matrix Lasso or Dantzig selector.


20th Jun 2016

In low-rank matrix recovery, one aims to reconstruct a low-rank matrix from a minimal number of linear measurements. Within the paradigm of compressed sensing, this is made computationally efficient by minimizing the nuclear norm as a convex surrogate for rank. In this work, we identify an improved regularizer based on the so-called diamond norm, a concept imported from quantum information theory.


20th Jun 2016

Active error correction of topological quantum codes - in particular the toric code - remains one of the most viable routes to large scale quantum information processing. In this work, we introduce the concept of a dynamical decoder as a promising route for achieving fault-tolerant quantum memories.


20th Jun 2016

Recent years have seen an enormously revived interest in the study of thermodynamic notions in the quantum regime. This applies both to the study of notions of work extraction in thermal machines in the quantum regime, as well as to questions of equilibration and thermalisation of interacting quantum many-body systems as such.


20th Jun 2016

The perspective of probing quantum many-body systems out of equilibrium under well controlled conditions is attracting enormous attention in recent years, a perspective that extends to the study of fermionic systems. In this work, we present an argument that precisely captures the dynamics causing equilibration and Gaussification under quadratic non-interacting fermionic Hamiltonians.


20th Jun 2016

The phenomenon of many-body localised (MBL) systems has attracted significant interest in recent years, for its intriguing implications from a perspective of both condensed-matter and statistical physics: they are insulators even at non-zero temperature and fail to thermalise, violating expectations from quantum statistical mechanics.


20th Jun 2016

One of the main challenges in the field of quantum simulation and computation is to identify ways to certify the correct functioning of a device when a classical efficient simulation is not available. In such a situation one cannot simply classically keep track of the dynamics of the device.


20th Jun 2016

A cornerstone of the theory of phase transitions is the observation that many-body systems exhibiting a spontaneous symmetry breaking in the thermodynamic limit generally show extensive fluctuations of an order parameter in large but finite systems. In this work, we introduce the dynamical analogue of such a theory.

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