Enhancing the performance of quantum computers (Englisch)

Recent progress in quantum information technology suggests that we will soon be able to carry out computational tasks that are intractable on classical computers. In the common quantum circuit model that divides the underlying quantum algorithms into discrete gates, it is crucial to perform each of these gates with high accuracy. In this thesis we develop an effective model required to precisely describe interactions between superconducting qubits mediated by a resonator. An analytical technique to design optimal control shapes based on derivatives of some base waveform is reviewed, connecting it to related methodology in literature and completing with novel insights. Using this technique, we develop improved pulse sequences to entangle two Rydberg atoms via the Rydberg-blockade interaction and achieve fidelities beyond what previously appeared to be a fundamental limit. A modern optimal control algorithm that combines analytical pulse shapes with numerical optimization is used to study the generation of entanglement between trapped ions. Additionally, we focus on cooling superconducting qubits in adiabatic quantum computation where computational problems are solved by adiabatically changing the Hamiltonian of a quantum system. Errors due to imperfect adiabatic evolution and finite temperatures deteriorate performance in such protocols. We propose a novel approach to reducing these errors efficiently, overcoming limits of previous cooling schemes. ; Aktuelle Entwicklungen im Gebiet Quanteninformationstechnologie lassen erwarten, dass bald erste Rechnungen auf Quantencomputern durchgeführt werden, die auf klassischen Computern nicht ausführbar sind. Unterteilt man die zugrunde liegenden Quantenalgorithmen in individuelle Gatter, ist es nötig, diese Gatter mit hoher Genauigkeit auszuführen. In dieser Arbeit erarbeiten wir ein effektives Modell zur genauen Beschreibung der mittels eines Reso\-nators vermittelten Wechselwirkung zwischen supraleitenden Qubits. Eine analytische Technik zur präzisen Systemkontrolle ...