Quantentechnologie

This thesis describes the development of an optical phase lock loop on a digital platform, in order to realize state-dependent transport on a two-dimensional optical lattice. The digital platform consists of a field programmable gate array in combination of a vector generator module, which is used to steer the amplitude and phase of the optical lattice deterministically. The digital system enables the implementation of a feedforward control scheme based on internal model control, which overcomes the bandwidth limitations of feedback systems. The control bandwidth is shown to be increased by more than an order of magnitude, directly improving the number of coherent operations that can be executed with the atoms in the optical lattice. The system is implemented into the optical setup of the experimental apparatus, and the first signatures of state-dependent transport of atoms in the two-dimensional optical lattice is observed and presented.

The content of this thesis is divided into four parts: In chapter one I will describe the experimental techniques and scientific principles used to realize transport in state-dependent optical lattices in two dimensions. The second chapter is dedicated to introducing the digital device platform and a characterization of its basic properties. In the third chapter I will give an overview of control theory with a focus on the fundamentals of feedback control. In addition, I will explain the implementation of the control loops on the digital system in the second part of the chapter. At the end of this chapter, I will present how an internal model control of the lattice can be implemented on the digital platform. The experimental results on state-dependent transport are presented in the last chapter. Furthermore, I will give an outlook of future milestones of the two-dimensional quantum walk experiment.