Bachelor’s Thesis in Physics

Seit der Entdeckung der photokatalytischen Wasserspaltung am Halbleiter TiO₂ im Jahre 1972 versucht sich eine Vielzahl von Wissenschaftlern an der Weiterentwicklung geeigneter Materialien. Das Ziel dieser Arbeit ist die Charakterisierung eines neuen Halbleitermaterials mithilfe verschiedenster optischen Molekülspektroskopiemethoden wie UV/VIS- und Infrarot (FTIR)-Spektroskopie.

The CRESST (Cryogenic Rare-Event Search with Superconducting Thermometers) experiment operated at the Gran Sasso underground laboratory employs highly sensitive cryogenic detectors to the search for signals of the elusive dark matter particles, a main ingredient of the Universe whose nature is still unknown. 

The energy thresholds reached in CRESST-III are the lowest in the field, making CRESST the most sensitive experiment to light dark matter. Optimisation of the tungsten thin-film thermometers and of the techniques for data analysis promise still improvement in energy threshold, which could significantly boost the physics reach of the experiment.

Scientific topics

A student can contribute to:

- design, production and prototyping of new CRESST detectors in Munich 

- development of high purity crystals 

- development of new software tools for data analysis

- dark matter data analysis

and, if interested, can participate in the operation of the main experiment at Gran Sasso. 

Thesis can be carried out at the Chair for astroparticle physics of the Physics Department and/or at the Max-Planck-Institute for Physics (MPP). Supervision at the Physics Deptartment by Prof. Schönert / Dr. Strauss and at the MPP by Prof. Schönert /  Dr. Federica Petricca. Please contact schoenert@ph.tum.de, raimund.strauss@ph.tum.de and petricca@mpp.mpg.de for further information. 

The fabrication of powerful quantum computers is nowadays an accomplishable task. However, many fabrication procedures need to be developed and optimized in order to increase the quality of qubits. To optimize fabrication, a statistically significant amount of data must be obtained, which entails a large number of experiments. However, due to the limited number of devices and the long cooling time of the cryostat, this task becomes quite time-consuming. To increase the number of experiments, it is necessary to learn how to use the same instruments for different samples. For this, we need a microwave switch, to which we will develop a pulsed current source to reduce the heating of the cryostat during switching. During this project you will learn how to work with Arduino and  cryogenic devices and eventually learn how to measure superconducting quantum circuits.

You will develop novel integration algorithms in high-dimensional spaces.  Possibilities include various forms of importance sampling algorithms and the further development of the Adaptive Harmonic Mean Integration algorithm using differently chosen volumes for integration.  Test problems will be chosen from physics projects to validate the algorithm.  Good programming skills and knowledge of linear algebra are a pre-requisite for the project.

Die Detektorentwicklung der nächsten Jahre wird sich auf den 100-TeV-Hadroncollider, das nächste große Zukunftsprojekt in der experimentellen Teilchenphysik konzentrieren. Für das Myonsystem der Detektoren
an diesem Collider werden Myonkammern benötigt, die eine hohe Myonnachweiseffizienz und Ortauflösung selbst bei hohem Gammastrahlungsuntergrund aufweisen. sMDT-Kammern,
das sind Kammern mit zylindrischen Driftrohren mit 15 mm Durchmesser, scheinen hierfür besonders gut geeignet. Allerdings muss ihre bereits gute Hochratenfähigkeit verbessert werden. Zwei sich ergänzende Ansätze werden hierbei verfolgt. Zum einen kann man die Ortsauflösung und Myonnachweiseffizienz bei hohem Raten durch eine hierfür angepasste Elektronik erhöhen. Zum anderen eröffnen neue Zeitdigitalwandler mit Pikosekundenauflösung die Möglichkeit durch die Auslese der Driftrohre an beiden Enden, den Ort des Teilchendurchgangs in allen drei Raumkoordinaten zu messen. Durch geschickte Auslegung der
Ausleseelektronik können diese Myonkammern sogar selbsttriggernd betrieben werden.

You will develop novel integration algorithms in high-dimensional spaces.  Possibilities include various forms of importance sampling algorithms and the further development of the Adaptive Harmonic Mean Integration algorithm using differently chosen volumes for integration.  Test problems will be chosen from physics projects to validate the algorithm.  Good programming skills and knowledge of linear algebra are a pre-requisite for the project.

Josephson junctions (JJs) represent a fundamental building block of modern quantum circuits such as superconducting qubits or Josephson parametric amplifiers. The JJs are conventionally fabricated with Al while the surrounding quantum circuits are often made of Nb. Henceforth, there is a need of galvanic connection between them which includes removing Nb oxide via ion milling.  As a consequence, one needs to develop a careful milling and fabrication technique in order to preserve a low-loss microwave environment in the close vicinity of JJs. This task is of paramount importance for achieving high coherence times of the related quantum devices.

The goal of this Master project is to develop a fabrication technique for Al/Nb superconducting circuits which will include Ar/O2 milling. This also includes cryogenic microwave studies of fabricated superconducting circuits (such as Josephson parametric amplifiers and transmon qubits) and participation in experiments towards quantum information processing with superconducting devices.

Neutrinos were discovered in 1956, but only at the turn of the millennium was it experimentally proven that the three known neutrino types can convert into one another. These flavor oscillations are possible only if neutrinos have nonzero mass, which is currently the only established contradiction to the standard model (SM) of particle physics. From tritium beta  decay experiments and cosmological observations, we know that their masses are very small—less than 10^-5  of the electron mass. Neutrinos are the only fundamental spin-1/2 particles (fermions) without electric charge. As a consequence, they might be Majorana fermions, particles identical to their antiparticles. This is a key ingredient of some explanations for why matter is so much more abundant than antimatter in today’s Universe and why neutrinos are so much lighter than the other elementary particles. Majorana neutrinos would lead to nuclear decays that violate lepton number conservation and are therefore forbidden in the Standard Model of particle physics. The so-called neutrinoless double-b (0nbb) decay simultaneously transforms two neutrons inside a nucleus into two protons with the emission of two electrons. The GERDA experiment and future LEGEND-200 experiment are located in the Italian Gran Sasso underground laboratory and are leading experiments in the world-wide competition. 

We offer the opportunity to carry out exciting experimental BSc and MSc theses with a focus on liquid argon detector developments, germanium detector developments, data analysis and/or Monte Carlo simulations. You would be fully integrated into the research team and work closely together with our international partners. 

Der intelligente Schleimpilz Physarum polycephalum ist dafür bekannt, dass er seinen netzförmigen Körper anpasst, um komplexe Probleme zu lösen, wie z.B. den kürzesten Weg durch ein Labyrinth zu finden oder das Problem des Handlungsreisenden zu lösen. Wie kann ein hirnloses Lebewesen solch komplexe Aufgaben bewältigen? Unsere Antwort: mit Hilfe der Physik von Strömungsnetzen. Finde heraus, wie Physarum sein Netzwerk anpasst, indem Du seine Netzwerkarchitektur quantifizierst und nach Skalierungsgesetzen suchst. Vorraussetzung: Statistische Physik. Zu verwendende und zu erlernende Werkzeuge: Matlab-Programmierung, Physik von laminaren Strömungen in Netzwerken, möglicherweise auch Zellkultur- und Hellfeldmikroskopie.

The smart slime mould Physarum polycephalum is renowned for adapting its network-shaped body to solve complex problems like finding the shortest path through a maze or solving the traveling salesman problem. How can a brainless critter accomplish such complex tasks? Our answer: by using the physics of flow networks. Find out how Physarum adapts its network by quantifying its network architecture searching for scaling laws in flow networks. Prerequisite: Statistical Physics. Tools to be used and learned: Matlab programming, physics of laminar flows in networks, potentially also cell culture and brightfieqld microscopy.

The Belle II experiment, situated in Tsukuba, Japan, performs precision measurements of parameters of the Standard Model using decays of B mesons. The MPI Belle II group is very involved in measurements that depend on the decay time of the B mesons. This type of measurements can provide very strong constraints on the Standard Model, and they require a precise knowledge of the position of the B meson decay, the so called B vertex. It is therefore primordial to have an excellent knowledge of the B vertex resolution, and to be able to calibrate it using control channels. The project proposed here will be the development of a calibration method using  the decay of D0 mesons to four charged tracks as a control channel. Measuring the resolution on the distance between two pairs of tracks in the D0 decay provides a very useful way to control the vertex resolution using real data. The student will develop the selection and full analysis of this control channel, and his or her results will be an important input for all forthcoming time-dependent analyses at Belle II.

Wie entstehen Organe? Welches physikalischen Konzepte beschreiben die Zellbewegungen, die ultimativ zu der Formierung von verschiedensten Geometrien führen?

Es ist seit Neuestem möglich, Mini-Organe im Labor wachsen zu lassen. Einzelne Zellen werden in ein 3D Zellkultur eingebettet, und aus dieser entstehet dann ganz von selber ein kleiner Pankreas oder Brustdrüsen. Diese Systeme eröffnen die einzigartige Möglichkeit den Wachstumsprozess direkt zu beobachte, aber auch gleichzeitig fehlgeleitete Prozesse in Krankheiten zu untersuchen. Ultimativ dienen diese Organoidsysteme für die Entwicklung von personlasieriten Medikamenten. 

Im Rahmen der Arbeit soll die Zellbewegung in den Epithelzelllagen bestimmt werden. KI Technoligien werden dabei eingesetzt, um die komplexen 3D Bewegungen zu analysieren. Es soll herausgefunden werden, ob die kollektive Bewegungen der Zellen  anhand von einer Navier-Stokes Gleichung für aktive Fluide beschrieben werden kann. 

Realization of quantum computers consisting of a few tens of qubits has become a possibility in recent years. In order to do computations, quantum gates must be applied onto qubits and qubit states must be readout. In the Q-Computing lab, qubits are realized using superconducting circuits and quantum gates are applied using microwave pulses. Moreover, the qubits can be readout(measured) using microwave pulses. To generate microwave pulses we use In-phase and Quadrature (IQ) modulation where we use an IQ mixer to mix a continuous microwave tone generated by a microwave signal generator called Local Oscillator (LO) and external IQ signals generated by Arbitrary Waveform Generators(AWGs). This is called up-conversion of a microwave tone. These pulses are then sent to the device situated in a dilution refrigerator. In order to complete the readout process we need to demodulate the readout signal which reflects from the device. For this we use down-conversion of reflected microwave pulse with the help of IQ mixers and LO, and extract IQ signals, which encode the information about qubit state. In this project you will implement both upconversion and downconversion using different IQ mixers and perform calibration of this process. You will learn about microwave pulse generation, IQ modulation, non-idealities in IQ mixers, signal detection and analysis. Therefore, you will gain a practical perspective on the challenges in operating a quantum computer.

Durch die Integration von molekularen Photoschaltern lassen sich DNA-Origamistrukturen mittels Lichteinwirkung gezielt beeinflussen. Die Kombination verschiedener Mechanismen erlaubt es letztlich „molekulare Maschinen“ zu bauen, die auf mikroskopischer Ebene ihre Arbeit verrichten.

Der UV-induzierte reversible Umschaltprozess zwischen den unterschiedlichen Isomeren des Photoschalters lässt sich mit Hilfe von UVVis-Absorptionsspektroskopie beobachten. In einem Kooperationsprojekt zwischen den Arbeitsgruppen von Prof. Kienberger (Lehrstuhl für Laser- und Röntgenphysik) und Prof. Dietz (Lehrstuhl für Biomolekulare Nanotechnologie) soll die Schaltdynamik solcher DNA-Photoschalterstrukturen, in diesem Fall basierend auf Azobenzol, ausführlich charakterisiert werden.

Diese Untersuchungen bilden die Grundlage für spätere zeitaufgelöste Messungen in denen der Schaltprozess auf ultrakurzen Zeitskalen direkt verfolgt werden soll. Als Teil der Bachelorarbeit wird eine Probenküvette für diese Messungen konstruiert.

New theoretical studies indicate an up to 5% difference of the calculated cross section from final state radiation on the measurement of the B0 -> K+pi- cross section.  The student will implement  the new calculations in a Monte Carlo simulation program. The impact will be studies and included in the systematic error and verified in the data.

Um die Raumabdeckung und die Effizienz des Myontriggers des ATLAS-Experiments am HL-LHC zu maximieren, werden ab 2027 etwa 300 RPCs in der innersten Lage des ATLAS-Myonspektrometers eingebaut werden. Die Entwicklung dieser Kammern ist weit vorangeschritten. Für die Serienfertigung muss das Herstellungsverfahren auf eine Massenfertigung ausgerichtet werden; für den kritischen Herstellungs-
schritt der Lackierung der Innenflächen der RPCs zur Gewährleistung deren Hochspannungsfestigkeit haben wir am MPI ein neues Verfahren entwickelt. RPCs, bei denen dieses Verfahren eingesetzt wird, müssen nun hergestellt und sowohl am MPI als auch am CERN auf ihre volle Funktionsfähigkeit untersucht werden.

Disorder has a drastic influence on transport properties. In the presence of a random potential, a system of electrons can become insulating; a phenomenon known as many-body localization (MBL) that has been envisioned by the Nobel laureate Phil Anderson. However, even beyond the vanishing transport such systems have very intriguing properties. For example, many-body localization describes an exotic state of matter, in which fundamental concepts of statistical mechanics break down. In this project we will explore these exciting aspects of many-body localization.

Gamma-ray bursts (GRBs) are flashes of gamma-rays resulting from the death of massive stars or the merger of neutron stars. The latter also produce gravitational waves. The presently most prolific GRB detector is the "Gamma-Ray Burst Monitor" (GBM) on the Fermi satellite, containing 12 NaI scintillation detectors. The position is derived by comparing the relative count rates in the differently oriented scintillator planes.

This thesis shall use existing flight data of the brightest gamma-ray source on the sky (the Crab nebula) and improve the spatial resolution of the response matrix of selected detectors. The result shall be tested by localizing selected GRBs with GBM, and comparison against known positions of these GRBs from other satellites (e.g. Swift).

Technically, this thesis involves learning of (i) learning the basics of GRBs, (ii) data analysis of non-imaging gamma-ray detectors, (iii) understanding and correcting detector effects, (iv) fitting light curves with different count statistics, and (v) analyzing and combining large amounts of individual constraints into a coherent picture.

Some background in astrophysics is advantegeous. Python knowledge is required, and good programming skills. Joy in data analysis is required.

    Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847

The combination of quantum mechanical calculations and machine-learning techniques has led to massive advances in the high-throughput computational screening of materials and molecules. Here, it is frequently stated that training data obtained from quantum mechanical simulations (e.g. using density functional theory) is 'noise-free', because the calculations can be numerically converged to very high precision. However, this assumes that the self-consistent algorithm used to calculate the Kohn-Sham determinant always converges to the correct ground-state solution, which is by no means guaranteed. The goal of this project is to quantify the noise introduced into DFT data by different choices of intital guess and convergence acceleration. To this end, the true ground-state solutions for a representative set of molecules will be determined using wavefunction stability analysis. This benchmark will allow the development of an effective 'black-box' method for obtaining well-converged training data. Furthermore, the effect of noise on quantum mechanical machine-learning applications will be studied.

The candidate should be interested learning the fundamentals of density functional theory and supervised machine learning. The project will require the development of automated workflows for high-throughput electronic structure calculations and data analysis. Experience with a scripting language (e.g. Python) and UNIX operating systems is advantageous but not mandatory.

Questions about the project can be directed to johannes.margraf@ch.tum.de.