Final Theses Topics

5th Institute of Physics

Join our team for your Bachelor/Master thesis project!

We are always looking for motivated students to join us for their Bachelor / Master thesis project.

On this page you can find a list of topics currently offered for thesis projects at the 5th Institute of Physics. Information on the research project and team in which each topic is embedded as well as contact persons are provided below.

If you are interested in joining our team for your thesis work please do not hesitate to contact us.

Phatthamon Kongkhambut and Viraatt Anasuri share their experience as students in the Master's program PHYSICS and take us to their labs at the 5th Institute of Physics.

Duration: 2:17 | © University of Stuttgart | Source: YouTube

Bachelor Thesis Topics

In our new project, we aim to realize a quantum computer based on individually controlled Rydberg atoms. The implementation of Rydberg gate operations requires active control of the pulse area for all relevant laser pulses that drive single- and two-qubit operations. In your thesis, you will set up an optical system to realize actively stabilized laser pulses as short as 100ns, making use of an electronic feedback loop that features a so-called sample-and-hold circuit.

Contact: Florian Meinert

In this project, you will realize an active feedback loop to control magnetic fields in a quantum simulator based on individually controlled Rydberg atoms. Magnetic fields are used for many purposes in our experiments, e.g. for cooling and trapping the atoms, for fixing quantization axes, or for controlling energy level shifts via the Zeeman effect. You will realize such time-dependent control using a precise current sensor and a PID controller that closes an active magnetic-field stabilization loop.

Contact: Florian Meinert

Project: Many-body physics with circular Rydberg atom arrays

In our project, we are setting up a quantum simulator based on individually controlled so-called circular Rydberg atoms. The generation of these peculiar Rydberg states requires precise control over magnetic fields. In your thesis, you will simulate and set up electro-magnets which will allow us to control the magnetic field strength and direction our trapped Rydberg atoms experience.

Contact: Florian Meinert

Project: Many-body physics with circular Rydberg atom arrays

Highly engineered hollow core fibres (in cooperation with the Max Planck Institute in Erlangen) allow to guide light over long distances in air beyond the diffraction limit. This allows for ideal atom-light coupling. The spectroscopy of Rubidium filled fibres opens a new pathway to quantum optics.

Contact: Robert Loew, Harald Kübler

Project: Quantum Optics with Hot Atoms

We are currently starting a new experiment to produce ultracold gases of diatomic molecules. To achieve this goal, we will use novel laser cooling techniques. Their implementation requires a number of different laser systems, which will be set up and tested in this thesis.

Contact: Tim Langen

Project: Cold Molecules

The goal of this project will be to integrate 3D-printed optics with ultracold atoms. Over the course of the thesis the student will construct a laser to trap single atoms in a tweezer trap. This tweezer will be formed using lenses that are directly 3D-printed onto the tip of an optical fiber by our collaborators at PI4. The student will then work towards the fluorescence detection of the single atom. Based on this, a single photon source can be realized that will have versatile applications in quantum information processing.

Contact: Tim Langen

Project: Cold Molecules

We are currently setting up a new quantum simulator using ultracold dysprosium atoms. The goal of the experiment is to realize new states of matter with long-range interactions and detect them using quantum gas microscopy.

In this process, there are a large variety of topics available for B.Sc. theses:

  • Setting up a digital mirror device (Programming and optics)
  • Optical transport of ultracold atoms (Lasers and optics)
  • Setup of an accordion lattice (Lasers and optics)
  • Characterization of a magnetic shield (Magnetics & Sensing)
  • Characterization of a high-resolution imaging system (Optics)
  • Designing and building of a wireless low-power sensor for tracking B field, humidity and temperature around the experiment (Electronics & Sensing)
  • Design of an active magnetic field stabilization (Electronics & Sensing)

Please contact Sean Graham & Tim Langen for further details on the individual thesis projects.

Project: Dipolar Quantum Gases

Combining photonic waveguides with the spectroscopy of thermal Rubidium vapours allows for miniaturization of various spectroscopy schemes to the nanometer scale. This is not only interesting for applications but is also of fundamental interest as at such length scale the atom-wall interaction as well the atom-atom interaction become more relevant.

Contact: Robert Loew, Harald Kübler

Project: Quantum Optics with Hot Atoms

The goal of this project will be to calculate the transition frequencies of our molecules by diagonalizing the molecular Hamiltonians. In a second step these calculations will be compared against actual measurements taken by the prospective student using our experimental setup. This spectroscopy has direct applications in precision measurements, where physics that usually require large-scale particle accelerators can be studied on a single optical table.

Contact: Tim Langen

Project: Cold Molecules

When laser cooling diatomic molecules dark states can arise, which do not couple to the cooling lasers anymore. Hence, the cooling stops. A way to mitigate this is to rapidly switch the polarization of the laser light. Such switching can be accomplished using a so-called Pockels cell. The topic of this thesis will be to set up such a Pockels cell, characterize and test it in the lab and apply it to remix dark states in our experiments, e.g. by slowing down a molecular beam. The latter has never been achieved with our molecules before, and would thus be a significant step forward in molecular laser cooling.

Contact: Tim Langen

Project: Cold Molecules

Master Thesis Toptics

We are working on an ion microscope that is designed to spatially resolve ultra-cold Rydberg physics.  Currently we are using rubidium atoms, but for the future, we also want to implement lithium as an additional atomic species, which allows us to study highly correlated fermionic systems. This requites to cool lithium atoms to a temperature of a few Micro-Kelvin such that they can be trapped in a magneto optical trap (MOT).

The first part of this master thesis deals with the construction and characterization of a dual-species atomic source for rubidium and lithium. In the second part the optical setup to slow, cool, trap and manipulate lithium atoms can be designed, setup and tested.  

During this thesis, you can gain experimental experience in working with ultra-high vacuum setups and understand the production of ultra-cold atomic samples. Moreover, you can learn how an optical setup for laser cooling is planned and setup.

Contact: M. Berngruber

Project: Spatially Resolved Ultracold Rydberg Physics

Rydberg atoms have at least one electron excited to a large principal quantum number and show unique and interesting properties. For example, the orbit of the Rydberg electron can be more than thousand times larger compared to the ground state. Moreover, the Rydberg state leads to exotic and interesting interactions with its surroundings.

In our lab, we are working with an Ion microscope to study the interaction of rubidium Rydberg atoms with ions, other Rydberg atoms or an ensemble of ground state atoms. To do this, we prepare an ultra-cold atomic sample in a highly controlled environment in which we can imbed ions and Rydberg atoms by using precise and narrow laser systems. To observe the processes happening in our experiment we use an ion microscope that allows us to study interactions in real space with a resolution of 200nm.

In the future, we want to extend our experimental apparatus to be able to investigate a broader range of interesting physical phenomena. This involves setting up the frequency and intensity stabilization of new laser systems and the optical setup to manipulate ultra-cold atoms.

During this work, you can join a state-of-the-art cold-atom experiment and gain experimental experience in setting up and working with high-precision optical setups. You will also have the opportunity to improve your skills in simulating theoretical models that describe the physics in cold Rydberg systems.

Contact: M. Berngruber

Project: Spatially Resolved Ultracold Rydberg Physics

We seek for controlling individual trapped Rydberg atoms for applications in quantum simulation and quantum computing. To work towards this goal, we offer a master thesis project which will focus on the implementation of narrow-line laser cooling methods. Your task will be to first set up and characterize a narrow-linewidth laser system frequency stabilized to a high-finesse optical resonantor and finally use this system to implement a magneto-optical trap operating on a narrow intercombination line.

Contact: F. Meinert

Project: Many-body physics with circular Rydberg atom arrays

A Rydberg atom provide a single electron in a well defined quantum state that can cover thousands of atoms in a Bose-Einstein Condensate. We are interested to watch this single quantum imersed in a sea of atoms. On the one hand it can bind atoms into molecular states on the other habe it can backact on the collective excitations of a quantum gas. The interaction between the electron and the quantum gas is mediated by low energy scattering. The interaction depends on the electron spin and we have recently studies how this spin dependence can be used to excite very exotic "trilobite" molecules (see figure above) [2]. In this thesis we want to understand the transition from molecular physics to many-body physics [3] including the spin degree of freedom. In addition we want to study the depencence on the orbital angular momentum [4]. The experimenatl tool is high resolution spectroscopy on a BEC sample including single ion detection.

Contact: Florian Meinert

Project: Giant Rydberg Atoms in Ultracold Quantum Gases

[1] Kathrin S. Kleinbach, Florian Meinert, Felix Engel, Woo Jin Kwon, Robert Löw, Tilman Pfau, Georg Raithel
"Photo-association of trilobite Rydberg molecules via resonant spin-orbit coupling"
Phys. Rev. Lett. 118, 223001 (2017)

[2] A. Gaj, A. T. Krupp, J. B. Balewski, R. Löw, S. Hofferberth, and T. Pfau
"From molecular spectra to a density shift in dense Rydberg gases"
Nature Comm. 5, 4546 (2014)

[3] A.T. Krupp, A. Gaj, J.B. Balewski, P. Ilzhöfer, S. Hofferberth, R. Löw, T. Pfau, M. Kurz, and P. Schmelcher,
"Alignment of D-state Rydberg molecules"
Phys. Rev. Lett. 112, 143008 (2014)

If you are interested in a cutting-edge interdisciplinary research on the interface of atomic physics, quantum optics, and Nano-photonics this is a proper project for you. Within the scope of this Master’s thesis, you will develop good theoretical understanding and experimental skills by working on an efficient integrated optical cavity embedded in an atomic vapor cell.

For further details please refer to this pdf file.

Contact: Tilman Pfau

Project: Quantum Optics with Hot Atoms

In our experiment we excite nitric oxide to Rydberg states by a three-photon excitation scheme. Due to subsequent collisions the molecules are ionized. The generated charges can be measured via electrodes in the cell. This thesis will focus on the measurement of these currents and the corresponding spectroscopy cells. This comprises testing and characterisation of the fabricated cells, optimisation of the cell geometry via computer simulation and investigation of the ionisation mechanism of the Rydberg molecules. Tackling questions like the influence of space charges on the detection and checking if the generation of a pre-plasma is possible in our cell.
You will learn something about sensing technology and the detection of very small currents in the nA to pA range. Furthermore you will use modern thin film technology directly bonding microelectronics on glass surfaces involving use of the clean room facilities of the Institute for Large Area Microelectronics. Measurements in the lab will be performed with a state of the art laser system involving a UV laser, a visible and a near infrared laser.

Contact: Harald Kübler, Fabian Munkes

Project: Trace Gas Sensing

To investigate a new kind of gas sensor, we have to excite nitric oxide molecules to a Rydberg state with a three-photon excitation scheme. It was already shown that our excitation path works. However, to be as sensitive as possible with the investigated sensing principle we need to excite as many molecules to Rydberg states as possible. Therefore, this thesis will aim at the optimisation of the excitation path. This includes measurements of different molecular transitions with well controlled parameters to find the strongest transition lines as well as the investigation of predissociation of the molecules. Furthermore the signal-to-noise-ratio will be optimised by setting up frequency modulation devices and the corresponding electronics.
In the scope of this thesis you will work with a modern laser system and learn how to maintain it.  The system comprises a state of the art UV laser, a self build frequency doubled high power green laser and a near infrared tapered amplifier system. In addition you will work with an in house developed gas mixing unit and pump system to control pressure and nitric oxide flow inside the measurement setup. You will also learn to work with optical components like acousto-optic modulators, electronics like lock-in amplifiers and modern industrial technology like mass flow controllers.

Contact: Harald Kübler, Patrick Kaspar

Project: Trace Gas Sensing

In collaboration with ITO a high-numeric aperture solid-immersion lenses will be placed on a glass cell. Different lens geometries will be explored and characterized. This topic is in context of the room-temperature single-photon emitter project.

Contact: Harald Kübler

Project: Quantum Optics with Hot Atoms

This project is a collaboration with the IHFG. We plan to develop a blue laser source in a compact package based on the VECSEL-technology developed at the IHFG. This light source will be integrated in our trace gas sensor project.

The new laser source will be compared to an existing commercial laser source at the PI5.

Contact: Robert Löw, Harald Kübler

Project: Quantum Optics with Hot Atoms

The current state-of-the-art theoretical model to describe strongly dipolar Bose-Eintein condensates of Dysprosium is the so-called extended Gross-Pitaevskii equation. This equation is based on the mean-field Gross-Pitaevskii equation including the long-range anisotropic dipole-dipole interaction, to which an effective term is added to take into account the effect of beyond-mean-field corrections. These correction arise from quantum fluctuations in the fluid and act as an effective extra non-linearity. The goal of this project is to perform simulations of this equation to compare to experiments in order to test the thepry at the current level and make useful predictions for our experiments on Dysprosium. These numerical simultions are developped in our group, and they allow to implement the exact experimental conditions.

Contact:Tilman Pfau

Project: Dipolar Quantum Gases

We are currently setting up a new quantum simulator using ultracold dysprosium atoms. The goal of the experiment is to realize new states of matter with long-range interactions and detect them using quantum gas microscopy.

In this process, there are a large variety of topics available for and B.Sc and M.Sc. theses:

  • Setting up a digital mirror device (Programming and optics)
  • Optical transport of ultracold atoms (Lasers and optics)
  • Setup of an accordion lattice (Lasers and optics)
  • Characterization of a magnetic shield (Magnetics & Sensing)
  • Characterization of a high-resolution imaging system (Optics)
  • Designing and building of a wireless low-power sensor for tracking B field, humidity and temperature around the experiment (Electronics & Sensing)
  • Design of an active magnetic field stabilization (Electronics & Sensing)

Please contact Sean Graham & Tim Langen for further details on the individual thesis projects.

Project: Dipolar Quantum Gases

Laser light at 421nm created by second harmonic generation in our current setup.

Quantum gas experiments rely on high power, narrow-line laser sources at element-specific wavelengths. In our lab, we use blue light at 421nm in order to cool down a hot atomic beam of dysprosium atoms to temperatures near absolute zero. Subsequently the atoms are captured in a magneto-optical trap where they are cooled further for our experiments on exotic phases in dipolar quantum gases. The amount of atoms that we can cool down and subsequently capture is directly related to the available laser power.

Currently two different projects are available, both aiming at the setup and characterization of a new laser light source.

Injection-locked 421nm diode laser [1]:
The goal of this project is to build and characterize an injection-locked diode laser at a wavelength of 421nm using seed light from an existing setup. We will start by setting up an extended-cavity diode laser using a blue laser diode. We will then use existing light from one of our narrow 421nm lasers in order to injection lock the diode laser. This technique ensures that the diode laser inherits many of the optical properties of the narrow laser including the narrow linewidth and frequency stability while providing additional laser power. The project also includes techniques to scale from one to many injection-locked diode lasers.

Cavity enhanced second-harmonic generation [2]:
The goal of this approach is to generate up to 1.5W of light at 421nm by means of cavity enhanced second-harmonic generation. We will start by setting up a tapered amplifier that can deliver light in excess of 2W at a wavelength of 842nm. A bow-tie cavity with a non-linear crystal is then used in order to generate light at the desired wavelength of 421nm by means of second-harmonic generation. In order to reduce the size of the system we want to integrate both the tapered amplifier and the bow-tie cavity in one compact monolithic design. 

Both projects provide excellent training in modern optical technologies and combine optics, electronics, mechanical design and will be implemented directly in our new state of the art quantum gas experiment.

Contact: Sean Graham

Project: Dipolar Quantum Gases

  1. Chen, X., Xu, Y., Tsai, C.-C., Chen, Y.-H., Chen, N.-K., Chui, H.-C.. An injection-locked green InGaN diode laser. Microw Opt Technol Lett. 2021; 1– 5. https://doi.org/10.1002/mop.33094
  2. Hannig, S., Mielke, J., Fenske, J. A., Misera, M., Beev, N., Ospelkaus, C., & Schmidt, P. O. (2018). A highly stable monolithic enhancement cavity for second harmonic generation in the ultraviolet. Review of Scientific Instruments, 89(1). https://doi.org/10.1063/1.5005515
DMD projecting an image with 1920 x 1080 micromirrors

A digital micromirror device (DMD) chip is a two-dimensional array of (up to) millions of individually controllable microscopic mirrors. While the DMD is an industry standard in technical applications such as the projector, its utility for fundamental research in quantum gas experiments has become increasingly clear over the last years [1,2].

Combined with a controller the DMD chip allows for the generation of arbitrary and dynamically adaptable light distributions. In our lab, we study exotic phases of matter in ultracold dipolar quantum gases trapped in various optical potentials. For such experiments, the DMD provides a versatile tool enabling the projection of arbitrary potentials such as box traps, the correction or introduction of defects in preexisting potentials, and the injection of angular momentum into the quantum gas cloud.

The goal of this project is to program an interface between the DMD controller and our experimental control software as well as building and characterizing an optical setup with the DMD in place.

This project combines programming and optics to provide a microoptoelectromechanical system crucial for the flexibility of our new state of the art experiment.

Contact: Ralf Klemt

Project: Dipolar Quantum Gases

  1. Navon, N., Smith, R. P., & Hadzibabic, Z. (2021). Quantum gases in optical boxes. Nature Physics, 17(12), 1334–1341. https://doi.org/10.1038/s41567-021-01403-z 
  2. Gauthier, G., Lenton, I., McKay Parry, N., Baker, M., Davis, M. J., Rubinsztein-Dunlop, H., & Neely, T. W. (2016). Direct imaging of a digital-micromirror device for configurable microscopic optical potentials. Optica, 3(10), 1136. https://doi.org/10.1364/optica.3.001136

The focus of the thesis can be both theoretical or experimental. The goal of this project will be the characterization and optimization of a cold beam of dipolar molecules using laser ablation in a cryogenic cell. This is the starting point for a large number of applications of these molecules, e.g. in precision spectroscopy or quantum simulation.

In the cell, collisions with a cold Helium buffer gas thermalize the molecules to 4 K. The molecular beam is formed using an exit aperture in the cell, and provides very good starting conditions for subsequent laser cooling.

For a more theory focussed thesis, extensive computer simulations can be used to model and optimize the molecular beam and the dynamics inside the buffer gas cell. This will increase the available number of molecules, which will have direct applications in precision measurements.

For an experimentally focussed thesis, your goal will be to plan and setup a new cryostat, implement the buffer gas cell and characterize the resulting molecular beam. In this process, you will learn about cryogenics, lasers, optics and electronics.

Contact: T. Langen

Project: Cold Molecules

The goal of this project will be to integrate 3D-printed optics with ultracold atoms. The atoms will first be cooled to microkelvin temperatures in a magneto-optical trap and then transfered into an optical tweezer. This tweezer will be formed using lenses that are directly 3D-printed onto the tip of an optical fiber by our collaborators at PI4. Their unique properties should make it possible to both trap single atoms in the tweezers and collect the fluorescence of these atoms with high efficiency. Based on this, a single photon source can be realized that will have versatile applications in quantum information processing.

Contact: Tim Langen

Project: Cold Molecules

The usual laser cooling in atoms relies on the spontaneous force, which arises from many individual photon absorption and emission cycles. Molecules can typically only scatter a much smaller number of photons. Moreover, they feature many internal states. Taken together, this significantly reduces the magnitude and versatility of the spontaneous force for molecules. An promising alternative are stimulated forces, where instead of spontaneously decaying back into the ground state, the molecules return to the ground state by stimulated emission. The goal of this Master's thesis will be to calculate the forces in these processes, which can be orders of magnitude higher than spontaneous forces. Once understood, we will apply them to the molecules in our experiment for the first time.

Contact: T. Langen

Project: Cold Molecules

Teacher Candidate (Lehramt) Thesis Topics

The group "Physics Didactics Research" is constantly offering various topics for your final thesis projects. To find out more on current offerings please contact:

Ronny Nawrodt

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