Quantum Information Processing

The basic element of quantum information processing is the quantum bit or qubit. In contrast to the classical binary element, a qubit is formed by a quantum mechanical superposition of two states and can take on any value  between 0 and 1. The creation of such qubits, particularly a large number of them, is a major challenge and many concepts and ideas are being developed worldwide in this context.

We focus on the prediction and theoretical design of individual and coupled qubits, based on semiconductor nanostructures and pursue several concepts in close collaboration with several experimental groups:

• Vertically stacked and electronically coupled quantum dots with the qubits being formed by neutral and charged excitons.
• Zeeman splitting and spatially varying g factors of hole states in coupled quantum dots. The qubits are formed by individual hole spins.
• Current carrying electronic states in coupled quantum wires. In this case, the qubits are gate-controlled extended, coherent and stationary modes that exhibit quantum mechanical switching.