@article{2021-winkelmann,
	Abstract = {<div>
	Quantum technology has advanced considerably within the last decades [1, 2]. Quantum simulators are among the primary goals of this ongoing &bdquo;quantum revolution&ldquo; [3]. They promise insight into many-particle phenomena that are too complex to study on classical machines [4].</div>
<div>
	In this thesis, I present my contribution to the discrete-time quantum walk simulator (DQSIM) experiment. We trap neutral cesium atom in a two dimensional state-dependent optical lattice [5], with the goal of realizing two-dimensional discrete-time quantum walks [6] and multi-particle entanglement [7].</div>
<div>
	The atoms are imaged using a high numerical objective lens [8] that allows us to resolve the spatial distribution inside the lattice. An additional retro-reflected beam provides state-independent confinement along the imaging axis. To measure multi-particle interference, we have to confine the atomic ensemble to a single layer along the imaging axis. I propose a novel way of plane selection with neutral cesium atoms in an optical dipole trap utilizing artificial magnetic fields created by a gradient of polarization. The preparation of thin volumes is demonstrated. With further careful adjustment of the experimental parameters, this technique will enable the selection of single planes.</div>
<div>
	We have to apply a magnetic guiding field to enable state-dependent transport of atoms. I designed a current stealing circuit to enable the long coherence times required for quantum simulations. The magnetic guiding field is stabilized to the level of 1 ppm. We measure a coherence time in free fall of T 2 =1.7 (1.4|2.1) ms. Vertical magnetic field gradients appear to be the limiting factor. With plane selection, coherence times of several tens of ms appear possible. This will allow for quantum walks with several hundred steps. The state-dependent potential of the DQSIM experiment can also be used to reconstruct the vibrational state of neutral atoms. I numerically investigate a novel scheme to probe the Wigner function by directly measuring the expectation value of the displaced parity operator. Measuring the parity operator requires us to tune the lattice depth dynamically. Displacing the atoms purely in position space without transferring momentum requires fast modulation of the lattice position. I demonstrate that we can use the processing capabilities of our digital intensity and phase control to achieve this. Stable operation over a large dynamical range is realized by linearizing the system response. Feed-forward control of the lattice position in conjunction with internal model control increases the modulation bandwidth from 230 kHz to 3.3 MHz.</div>
<div>
	Precise control over the vibrational degree of freedom is a prerequisite to preparing arbitrary states of motion, such as Fock states. I demonstrate Raman sideband cooling along the vertical direction using the D1 transition of cesium. This complements the microwave mediated sideband cooling that we use to cool horizontally.</div>
<div>
	Finally, I discuss possible future experiments such as the release-retrap technique to enhance the filling factor in the center of the trap [9, 10], magnetic quantum walks [11], and direct measurement of the exchange phase of indistinguishable particles [12].</div>},
	Author = {Winkelmann, F. G. H.},
	Journal = {},
	Pages = {},
	Title = {{Optical plane selection in a dipole trap}},
	Volume = {},
	Year = {2021}
}