We investigate many different varieties of solid state qubits. Our research ranges from well-estabilshed devices like spin-qubits in semicondutor 2DEGs and superconducting qubits such as the transmon qubits, to novel ideas of incoding quantum information in topological properties of solid state devices like Majorana fermions or non-Abelian anyons.Copyright: P. Cerfontaine
The investigation of spin-qubit in semiconductors profits from strong collaboration with the experimental groups implementing spin-qubits in GaAs and SiGe heterostructures. Our interest ranges from understanding the decoherence in these systems to proposing novel ways to encode or couple qubits.Copyright: D. DiVincenzo
Superconducting Qubits and Cavities
Our main interest lies in the study of transmon qubits coupled to microwave cavities as they are realized in the experimental group at IBM with whom we enjoy an active collaboration. We study how to realistically model the complicated electromagnetic system by a Hamilitonian involving only a few effective degrees of freedom. Moreover, we investigate how cavities can be used to implement single and multi-qubit measurements and gates. An additional line of research is focused on developing pulse schemes for high precision control of the qubits.Copyright: F. Hassler
Majorana Qubits and Non-Abelian Anyons
We are interested in understanding how to encode quantum information in topological properties of solid state systems. Such encodings offer the advantage the information is (partially) protected against unwanted influence of the environment. A promising route is to use Majorana fermions which are special quasiparticles which appear in some superconducting systems. These particles are non-Abelian anyons which implies that the quantum information can be manipulated, e.g., gates can be performed, by braiding the quasiparticles around each other. Recently, we have also been interested in ways to "simulate" non-Abelian by conventional quantum circuits.Copyright: D. DiVincenzo
Quantum Fault-Tolerance and Error Correction
Defeating the effects of decoherence by means of effective error correction schemes is one of the essential notions of quantum computation. We investigate different aspects of quantum error correction, going from the theoretical analysis of different class of codes and models for quantum computing, to their possible physical implementations, in particular in the paradigm of circuit QED.