Please contact one of the senior members if you are interested in carrying out a Bachelor or a Master degree project in one of the groups of our research division. Below you find suggestions for Bachelor and Master projects in
 Experimental Condensed Matter Physics
 Trapped Ion Quantum Technologies

Quantum Photonics

Theory in quantum optics, quantum information and gravity
Possible Bachelor and Master projects in Experimental Condensed Matter Physics:
 Superconducting quantum electronics. Superconductivity is a fascinating quantum phenomenon that enables macroscopic phase coherence and allows observation of quantummechanical behavior in largescale objects. Therefore, superconductors are widely used for creation of solidstate quantum electronic devices, such as qubits in a quantum computer. The aim of this project is to develop and study experimentally novel superconducting quantum components, based on superconducting tunnel junctions, hybrid superconductor/ferromagnet heterostructures and quantized superconducting vortices.
 Fundamental studies of hightemperature superconductivity. High temperature superconductivity (HTSC) remains one of the most acute unsolved problems of modern physics. Superconductivity is caused by Cooperpairing of electrons. In conventional lowtemperature superconductors it is mediated by phonons, but for HTSC the origin of the “glue” is not confidently known. This project is aiming at fundamental analysis of physical properties of HTSC materials at low temperatures and high magnetic fields using various experimental techniques, including tunneling spectroscopy.
 Nanotechnology and nanofabrication of superconducting devices. The project is aiming at fabrication of nanoscale superconducting devices, which will take place at AlbaNova’s NanoFab clean room. The fabricated devices will then be tested and characterized experimentally
 Development of ultrafast THz electronics. The speed of conventional electronics is limited by the RCtime constant (Rresistance, Ccapacitance) of a metaloxidesemiconductor fieldeffect transistor. Therefore, modern computers have a few GHz operation frequency. Such limitation is lifted for superconductors with R=0. This can allow a radical enhancement of the speed of superconducting electronics, capable of operation at Hz frequencies. The aim of this project is to develop various novel superconducting components, such as ultrafast and ultrasensitive detectors, electromagnetic THz oscillators and digital electronic components with THz operation frequency.
Projects on both Bachelor and Master level can be offered on the abovementioned subjects. It is also possible to combine the subjects. For example, a student can fabricate his/her own device and then study and characterize it experimentally, or perform fundamental studies and research.
For more information, contact prof. Vladimir Krasnov.
Possible experimental Master projects on Trapped Ion Quantum Technologies:
 Ion trap design and setup (for students who like to build the bits and pieces of an experiment). Design and set up of an ion trap for quantum information experiments. Build a vacuum chamber with the ion trap inside, set up the optics for ion trapping, and get everything to run.
 Loading, initialization and quantum control of multiqubit ion strings
Each ion in a larger ion crystal can serve as a quantum bit of a quantum computer. Before starting a quantum calculation, ions first need to be loaded as a isotopepure crystal, cooled by laser light close to the motional ground state and initialized in a welldefined electronic state. Quantum calculations then consist of sequences of addressed and coherent laser pulses. The goal of this Master project is the realization of loading, initialization and quantum control of multiqubit ion strings.
Possible experimental Bachelor projects on Trapped Ion Quantum Technologies:
 Characterization of UV optical fibres. We are using selfmade optical fibres for our UV lasers for Rydberg excitation. The goal of this Bachelor project is to characterize new UV fibres in terms of losses, coupling efficiency and stability.
 Laser intensity stabilisation. Trapped ions are manipulated by laser pulses. Intensity fluctuations of these laser lead to imprecise state manipulation of the ions. The objective of this Bachelor project is to set up an intensity stabilisation for our qubit laser to make the qubit manipulation more precise.
For Trapped Ion Quantum Technology projects, contact Markus Hennrich.
Possible experimental Master projects on Quantum Photonics:
 Quantum light generation in quantum dot systems (60 credits – mostly experimental).
Quantum dots are highly efficient sources of quantum light. They are operated in a cryogenic environment and when excited by laser light they emit light with strong quantum properties. The objective of this thesis is the coherent excitation and characterisation of quantum dots in novel devices for quantum communication and information processing.  Propagation of quantum light in reallife networks (60 credits experiment + theory).
Quantum networks require quantum light for secure communication and cryptography. Propagation losses and noise affect the quantum properties and in return also the security of quantum communication protocols. The objective of this thesis is the theoretical and experimental investigation of quantum properties of light, how these properties are preserved during propagation in reallife networks.
For Quantum Photonics projects, contact Ana Predojevic.
Quantum Optics, quantum information and their interface with gravity
Project areas (BA / MA):
 Quantum interferometery in the presence of time dilation: Quantum dynamics with postNewtonian corrections
 Interface between quantum and gravity at low energies: Signatures of quantum gravity models and general relativistic effects in quantum optical systems
 Gravitational waves: Interactions between gravitational waves and matter
 Optomechanics: Nonlinear and nonGaussian features in interaction between light and a macroscopic oscillator
 Open quantum systems: Decoherence in the macroscopic world and in cosmology
 Interstellar flight: Study radiationpressure induced propulsion
For Quantum Optics projects, contact Igor Pikovski
Possible theoretical projects in fundamental quantum mechanics.
Bachelor projects:
 Decay of a 'twolevel atom': In its crudest approximation, an atom can be seen as a system of only two levels (like a spin1/2 particle), one excited and one ground state level. If the atom is initially excited it interacts with its environment and eventually it will spontaneously decay (exponentially) to its ground state. One can affect this decay by monitoring the properties of the environment. In this project we look at how the exponential decay emerges.
 Nonhermitian perturbation theory: A system that is not fully disconnected from its environmeent is called open. The evolution for such an open quantum systems is in a mathematical sense much more complicated than for a closed one since it is no longer unitary. Some of the mathematical intuition is lost and we need to generalize established concepts/methods. Here we focus on how perturbation theory must be modified.
Master projects:
 Subsystem evolution: Quantum mechanics predics unitary timeevolution. However, if one concentrates on only one part of a full system, its timeevolution will not in general be unitary. For example, if the system is chaotic (nonintegrable) such subsystems will thermalize, i.e. in the long run the state of the subsystem will become a thermal one. Can one say something generic about the timeevolution of the subsystem, in other words what happens along the route towards a thermal state?
 Partial Zeno effect: The quantum Zeno effect says that if you repeatedly measure a quantum system it is possible to freeze its evolution (provided the measurement frequency is large enough). Roughly what happens is that the measurement provides information about the system, such that the system state has to be updated (collapsed) to a new state. The new state is such that evolution is hindered. But what happens if we only measure on part of the system? What is the information we need to extract in order to block the full evolution?
 Localization in open quantum systems: We are tought that for bound particles the wave function goes to zero at infinity. Typically such a particle is bounded by some potential such that the particle's energy is lower than the potential at large distances. However, in 1D and for a random potential it turns out that every eigenstate is such that the wave function goes to zero at infinity, something called Anderson localization. This is an inferference phenomenon; destructive interference prohibits the localized wave function to spread. If the system is coupled to some environment, this interference is typically lost and the particle cannot stay localized. The idea of the project is to try to understand this `delocalization' from a somewhat new angle.
If you are interested in any of the above projects contact Jonas Larson, jolarson@fysik.su.se
Possible projects in condensed matter theory
 Spin correlations in frustrated Magnets: study of shortrange vs. longrange correlations in quantum spin liquids
 Entanglement in condensed matter systems: Signatures of entanglement in noninteracting fermionic systems
 Cluster Mott insulators: effective spin interactions via superexchange
For condensed matter theory projects contact "maria.hermanns@fysik.su.se"
Bachelor and master projects on various aspects of 'Topological phases of matter'.
 Models with topological phases: Often in physics, one considers simplified models that can be solved exactly, in order to study a particular phenomenon. There are several interest models for topological phases. The goal of this project is to first study such models, and continue by trying to come up with new/variations on such models, and study their properties.
 Topological phases at finite temperature: One aspect in the study of topological phases that has not received much attention, but is nevertheless very important, is the effect of temperature. The goal of this project is to investigate the socalled Majorana chain model, in the presence of both interactions and finite temperature. This study will involve a combination of analytical and numerical methods.
 Mathematical aspects of anyons: To describe anyons, one can use the mathematical framework of 'modular tensor categories'. In this project, you will use this framework, to study which types of anyons are possible in theory, and of course, what their properties are.
Contact Eddy Ardonne (ardonne@fysik.su.se) if you are interested in doing one of these projects.