ESR-Untersuchungen an molekularen Ein- und Zwei-Quantenbit-Systemen [article]

Dominik Dengler, Universität Stuttgart, Universität Stuttgart
2016
This work deals with the investigation of potential quantum bits (qubits), which are important building blocks for the development of quantum computers. The here studied molecular qubits are based on paramagnetic transition metal complexes. Here, the energy states of the electron spins are used for the realization of the qubits and the molecular systems are of advantage because of their well defined structure. This leads to a simple scalability and the properties of the qubits can be tailored
more » ... s can be tailored by the choice of the metals and ligands. To implement more complex quantum algorithms, apart from individual qubits also so called 2-qubit systems are required. These are characterized by a weak magnetic interaction between the two qubits. A particularly important criterion for qubits is called the coherence time. This time describes the period in which the superposition states are stable and therefore corresponds to the time available for quantum calculations. In chapter 4 an antiferromagnetically coupled trinuclear Cu(II) complex was examined, which can be considered as a qubit with spin S=1/2. The magnetic properties of the approximately in an equilateral triangle arranged Cu(II) ions were satisfactory described with the model of the antisymmetric exchange (ASE). The influence of the ASE could further be observed both in cw X-band ESR and high-field ESR measurements (HFESR) by the presence of a for Cu(II) ions atypical g-value. By pulsed ESR measurements at Q-band quantum coherence in solution was detected. Measurements of the phase memory time were carried out both with the simple Hahn echo sequence and the Carr-Purcell-Meiboom-Gill (CPMG) sequence and showed the fundamental suitability of such systems as qubits. The transition from a simple qubit to a 2-qubit system was investigated in chapter 5. Here, a vanadyl complex was characterized, which showed features of a S=1/2 qubit, but the complex could also be extended to an oxo-bridged VO(IV)-Cu(II)-dimer, which is formally composed of two S=1/2 qubits. Here quantum coher [...]
doi:10.18419/opus-8733 fatcat:lk6tpbbjlvdojhelkqatzlk6ke