Solid-State Qubits


Principal Investigators: David DiVincenzo, Fabian Hassler


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.



GaAs-AlGaAs heterostructure Copyright: Pascal 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. Recently, we have been investigating the prospects of realizing all electrical control of a qubit formed in a triple quantum dot system.


Superconducting Qubits and Cavities

Electrial circuit Copyright: David DiVincenzo

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.


Majorana Qubits and Non-Abelian Anyons

T-junction made from superconducting islands used for braiding Majorana fermions Copyright: Fabian Hassler

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.