Theme and goal

We do theoretical research on solid-state quantum devices, including semiconductor spin qubits, certain types of superconducting qubits, topologically protected qubits, gate-tunable Josephson junctions, and superconducting diodes. The long-term goal in this field is the realization of disruptive quantum technologies such as fault-tolerant quantum computing and more accurate quantum sensing.

In many solid-state quantum devices, an important role is played by semiconducting components. The precise control over the carrier density that most semiconductors offer, combined with the often strong and tunable spin-orbit coupling they induce, makes them versatile building blocks for a plethora of applications: In the ultra-low-density regime, single electrons or holes can be isolated for the purpose of using their spins as qubits; in this context the presence of strong spin-orbit coupling provides efficient ways of electrical qubit control. In combination with superconducting elements, semiconductors can be used to create highly tunable Josephson junctions, where the spin-orbit coupling can yield an unconventional current-phase relationship (potentially useful for creating protected superconducting qubits and superconducting diodes), or to realize effective topological superconductivity, which should host non- Abelian anyonic excitations that could be used to encode topologically protected quantum information.

Our goal is to understand the complex dynamics of cutting-edge semiconductor-based quantum devices, often in collaboration with world-leading experimental groups, and try to use that understanding to predict, design, and develop new functionalities in the next generation of devices. In parallel, we started investigating machine-learning techniques for tuning and control of more complex quantum devices as well as for quantum
sensing applications.

Key questions 

The questions my group is currently working on are quite diverse, a few examples are the following: How can we improve quantum coherence properties of spin qubits or superconducting qubits, by smart choice of material platform, advanced device design, or machine-learning- assisted operation methods? How could we scale up so-called “artificial Kitaev chains” to a size that yields topologically protected zero-energy end modes? What kind of new quantum-device functionalities could result from using hybrid structures including superconductors and lower-dimensional hole gases?

For current activities, see QuSpin Annual Report 2025.

Theme and goal

Our group’s research centers around lattice models of quantum antiferromagnets, especially models with competing (aka “frustrated”) interactions. In combination with strong quantum fluctuations, frustration may prevent magnetic order and instead lead to other, magnetically disordered phases that possess more exotic types of order that are of great fundamental interest

Of particular interest are phases known as quantum spin liquids, whose order is not described by broken symmetries but may instead be of a topological nature. In recent years new materials have been discovered which exhibit evidence of unconventional behaviour pointing towards spin-liquid physics.In recent years it has also been realized that various concepts and quantities originating in quantum information theory, like entanglement entropy and fidelity, may be very useful for characterizing quantum many-body phases and the quantum phase transitions between them. Different types of order may give rise to characteristic “signatures” in such quantities and their behaviour as a function of various parameters.

The overall goal is to get a better understanding of the “zoo of phases” that may arise in frustrated quantum anti- ferromagnets, and contribute towards their description and classification.

Key questions 

Key questions include whether/where quantum spin liquids arise the phase diagram of various lattice quantum spin models, what types of quantum spin liquids can arise, and how various types of order can manifest themselves through signatures in quantities like entanglement entropy (including both orders that are and are not described by broken symmetries).

For current activities, see QuSpin Annual Report 2025. 

Theme and goal

Our primary theme is to probe and understand excitations in the charge, spin and lattice, and their interactions at the atomic scale. Our primary method is through developing excitation spectroscopy techniques, primarily scanning-based probe techniques and other experiments that provide insights into the fate of charge and spin in materials.

Our short-term goal is to explore the magnetoelectronics and magnonics of oxide ferromagnets and antiferro-magnets. In a more applied context, the long-term goal is to understand and control coupling in the thermal energy scale in order to contribute to the use of thermal energy to communicate information. The long-term goal on the method side is to develop STM-based point-contact techniques to explore mesoscopic and magnetodynamic
physics at a very local scale.

Key questions

We primarily study the excitations and coupling between magnons, phonons and charge carriers at an energy scale that ranges from sub-thermal energies to electron volts. In the spin domain, the prime motive is to understand magnons, and the expression in the form of propagating magnons and their interaction with charge and phonons. In the phonon regime, we are interested in understanding size and material control and tunability in coupling to the charge and spin excitations. We are primarily investigating model systems in oxide materials, developing an understanding of perovskite- type ferromagnets and antiferromagnets, mainly seeking collaboration with groups on the material synthesis side to address our key questions.

For current activities, see QuSpin Annual Report 2025. 

Theme and goal

Topological spin textures, such as domain walls, magnetic dislocations and skyrmions, exhibit emergent physical phenomena and hold great
promise as functional nanoscale systems for low-energy information processing and data storage. Application opportunities range from logic gates and memory devices to innovative concepts for unconventional computing. Our research studies the fundamental physics that give rise to the unique properties and dynamical responses of topological spin textures in ferroic materials. We are particularly interested in the unusual local responses of these special magnetic entities, and how they can be utilized in future devices.

Key questions

Many developments in the field have occurred only recently, and it has become clear they only scratched the surface regarding topological textures that form in magnetically ordered materials. Specifically, controlling such textures remains a major challenge. We investigate new magnetic materials that host topological spin textures at the nanoscale, with a focus on spin-spiral systems. For this purpose, we apply micromagnetic simulations in combination with different microscopy and nanostructuring methods, such as magnetic force microscopy (MFM) and focused ion beam (FIB), working towards first proof-of-concept devices. For example, we use FIB to shape materials of interest into device- relevant structures. Based on these structures, we study, e.g., the impact of reduced physical dimensions on the magnetic order and how electrical currents and magnetic
fields control the position and movement of individual spin textures. Ultimately, we want to understand the new degrees of flexibility topological spin textures can offer and demonstrate new opportunities that arise for future applications, including Green-IT (i.e. low-power technologies) and modern concepts for unconventional computing.

For current activities, see QuSpin Annual Report 2025.