Beschreibung
Quantum communication and quantum information processing has the potential to revolutionize how information is shared and processed by offering a very high level of security. One of the key building blocks of a quantum communication network are reliable quantum nodes, where quantum information can be stored, processed and distributed. Nowadays, quantum technology in general is a heavily investigated area of research. Some quantum computation devices were already presented in scientific journals as well as to the public. In these devices a small number of qubits is used. However, these systems have the disadvantage, that they are not easily scalable to larger numbers of qubits. One promising platform to address this issue sre systems based on molecules, as all molecules of a type will exhibit identical level schemes. These molecules need to be coupled to optical resonators, in order to influence and engineer their photon emission properties. In this thesis, these systems will be simulated and studied using numerical methods. Initially, suitable resonators are designed and optimized. A difficult task is the positioning of a molecule in the resonator. Therefore, there is an emphasis on the coupling properties based on the position of the molecule with respect to the resonator. Resonators based on cavities in photonic crystals have been shown to achieve very high Q-factors. Since this is achieved despite their small size, high Purcell factors and strong coupling are enabled. Here, this platform is investigated for a semiconductor material with phosphorous, which is a less well studied material for photonic crystals. The phosphorous content is needed to enable a connection to the molecule complex. Moreover, a nano pit is introduced to the cavity and analyzed, which can be shown to improve the Purcell-effect for surface emitters (such as molecule complexes). Furthermore, distribution and read-out of the quantum information in such a system is studied. As photonic crystals are polarization sensitive, time bin encoding (encoding in time intervals of the photon emission) appears to be the most promising approach. For a single molecule-cavity system suitable electromagnetic pulses and additional system parameters will be calculated and presented. To study a larger network, two such systems are considered in a next step, where the transfer of information from one molecule-cavity system to the next one is simulated. There, parameters for a high transfer probability are found, where the intricate spectrum of the coupled system is taken into account as well. Once such a system is operated at high temperatures (e.g. above 4K or 50K) additional effects need to be considered. To do so, a phonon model is derived to study temperature influences on the system. On the one hand, phonons have an effect on the decay rate, as they introduce an additional loss path, while on the other hand they enable faster operating speeds and less strict conditions on the tunings of the subsystems (e.g. molecules and cavities). The results of this thesis show, that a molecular complex coupled to a photonic crystal cavity is a feasible and promising approach for a scalable quantum network. Parts of this thesis have already been published in peer-reviewed journals or at conferences: • P. Mertin, F. Romer, and B.Witzigmann, “Numerical analysis of subwavelength field effects in photonic crystal slab cavities,” Journal of Physics: Photonics, vol. 2, p. 015001, Jan. 2020. • P. Mertin and B. Witzigmann, “Quantum information interface on a photonic crystal chip,” in 2021 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD), IEEE, Sept. 2021.
