Lattice Gauge Theory and Cold Atoms Out of Equilibrium

In this thesis we theoretically investigate the quantum simulation of lattice gauge theories for cold atom experiments. We give an explicit proposal to study a (1+1) - dimensional U(1) lattice gauge theory. Starting with a bosonic and a fermionic atomic gas we tune the geometry and engineer the interactions such that we end up with a one-dimensional system obeying the principle of local gauge invariance. A further important aspect of this proposal is the explicit use of highly occupied bosonic states in order to make the investigation of strong field quantum electrodynamics feasible. In addition, we present an approach based on the functional integral in order to theoretically treat U(1) and SU(N) gauge fields interacting with matter out of equilibrium. We show that under specific conditions the quantum theory can be accurately mapped onto a classical statistical ensemble. Further, exploiting this possibility, we study the prospect to observe intricate high energy phenomena like Schwinger pair-production and string breaking in such future cold atom experiments

Engineering holography with stabilizer graph codes

The discovery of holographic codes established a surprising connection between quantum error correction and the AdS/CFT correspondence. Recent technological progress in artificial quantum systems renders the experimental realisation of such holographic codes now within reach. Formulating the hyperbolic pentagon code in terms of a stabilizer graph code, we propose an experimental implementation that is tailored to systems with long-range interactions. We show how to obtain encoding and decoding circuits for the hyperbolic pentagon code [Pastawski et al., JHEP 2015:149 (2015)], before focusing on a small instance of the holographic code on twelve qubits. Our approach allows to verify holographic properties by partial decoding operations, recovering bulk degrees of freedom from their nearby boundary.Comment: 20 pages, 10 figure

From the Jaynes-Cummings model to non-Abelian gauge theories: a guided tour for the quantum engineer

The design of quantum many body systems, which have to fulfill an extensive number of constraints, appears as a formidable challenge within the field of quantum simulation. Lattice gauge theories are a particular important class of quantum systems with an extensive number of local constraints and play a central role in high energy physics, condensed matter and quantum information. Whereas recent experimental progress points towards the feasibility of large-scale quantum simulation of Abelian gauge theories, the quantum simulation of non-Abelian gauge theories appears still elusive. In this paper we present minimal non-Abelian lattice gauge theories, whereby we introduce the necessary formalism in well-known Abelian gauge theories, such as the Jaynes-Cumming model. In particular, we show that certain minimal non-Abelian lattice gauge theories can be mapped to three or four level systems, for which the design of a quantum simulator is standard with current technologies. Further we give an upper bound for the Hilbert space dimension of a one dimensional SU(2) lattice gauge theory, and argue that the implementation with current digital quantum computer appears feasible

Image quality and high contrast improvements on VLT/NACO

NACO is the famous and versatile diffraction limited NIR imager and spectrograph with which ESO celebrated 10 years of Adaptive Optics at the VLT. Since two years a substantial effort has been put in to understanding and fixing issues that directly affect the image quality and the high contrast performances of the instrument. Experiments to compensate the non-common-path aberrations and recover the highest possible Strehl ratios have been carried out successfully and a plan is hereafter described to perform such measurements regularly. The drift associated to pupil tracking since 2007 was fixed in October 2011. NACO is therefore even better suited for high contrast imaging and can be used with coronagraphic masks in the image plane. Some contrast measurements are shown and discussed. The work accomplished on NACO will serve as reference for the next generation instruments on the VLT, especially those working at the diffraction limit and making use of angular differential imaging (i.e. SPHERE, VISIR, possibly ERIS).Comment: 14 pages, 5 figures, SPIE 2012 Astronomical Instrumentation Proceedin