Decoherence of Spatially Separated Quantum Bits

Substantial technical progress in the last two decades enabled the development and fabrication of nanoscale devices that exhibit explicit quantum mechanical properties on a mesoscopic level. A lot of effort was driven by the emerging discipline of quantum information processing whose basic aim is to understand how quantum mechanical principles can be used for the manipulation, storage, and communication of information. For the implementation of a so-called quantum algorithm it is necessary to ensure and control the unitary evolution of an array of quantum bits (qubits). One of the major challenges is decoherence: The interaction of the qubits with their environment affects the indispensable quantum coherence and entanglement of the quantum states.This work investigates the decoherence of a qubit register caused by spatially correlated quantum noise and develops theoretical tools to describe the associated reduced qubit dynamics. A main focus is put on the short-time dynamics of a single qubit and the consequences of a spatial qubit separation of several qubits for bipartite qubit entanglement and the register fidelity.