High-Performance Phase-Locked Loops for Quantum Computing Applications

Quantum computers have gained widespread interest from both industry and academia in the last decade as they are very promising for solving problems intractable by classical computers. However, there is a limited number of qubits in current quantum processors, which impedes the practical applications of a quantum computer. To increase the number...

Experimental Quantum Simulation with noisy intermediate-scale superconducting processors

Superconducting qubits have seen a tremendous progress in the last two decades, and yet they remain unable to extract quantum advantage for application scenarios. While algorithms like Shor’s demonstrate quantum advantage in theory, they do not seem to fit modern noisy quantum processors. Then, in order to achieve quantum advantage either modern...

Spin Qubits in Silicon and Germanium

Quantum computers based on semiconductor quantum dots are proving promising contenders for large scale quantum information processing. In particular, group IV based semiconductor hosts containing an abundance of nuclear spin-zero isotopes have made considerable headway into fulfilling the requirements of a universal quantum computer. Silicon (Si...

CMOS circuits and systems for cryogenic control of silicon quantum processors

Quantum computers can provide exponential speedup in solving certain computational problems pertaining to drug discovery, cybersecurity, weather forecasting, etc. Although a quantum computer with just 50-qubits has been shown to surpass the computing power of the best supercomputers in specific applications, millions of qubits would be required...

Fault-tolerant quantum computation: Theory and practice

Quantumcomputation is the modern version of Schrödinger’s cat experiment. It is backed up in principle by the theory and thinking about it can make people equally uncomfortable and excited. Besides, its practical realization seems so extremely challenging that some people even doubt it is possible. On the other hand, we are nowadays much closer...

Quantum information in the real world: Diagnosing and correcting errors in practical quantum devices

Quantum computers promise to be a revolutionary new technology. However, in order to realise this promise many hurdles must first be overcome. In this thesis we investigate two such hurdles: the presence of noise in quantum computers and limitations on the connectivity and control in large scale quantum computing architectures.In order to combat...

Scalability and modularity for transmon-based quantum processors

This thesis mainly summarizes two experiments that relate to building a quantum computer out of superconducting transmon qubits. Transmon qubits have emerged as one of the foremost solid state qubits, realizing processors with more than ten qubits and demonstrating small scale quantum algorithms as well as quantum error correction schemes. Right...

Silicon Quantum Electronics

Electrical manipulation and detection of single electron spins in quantum dots

Entanglement in Solid-State Nanostructures

The goal of this thesis is to investigate theoretically the generation and behaviour of multipartite entanglement for solid-state nanosystems, in particular electron spin quantum bits (so-called 'qubits') in quantum dots. A quantum dot is a tiny potential well where a single electron can be trapped. A quantum bit can be implemented in this...

Manipulation and Read-out of Spins in Quantum Dots

Besides an electric charge, electrons also have a tiny magnetic moment, called spin. In a magnetic field, the spin has two possible orientations: 'spin-up' (parallel to the field) and 'spin-down' (anti-parallel to the field) and can therefore be used as a quantum bit, the computational unit of a quantum computer. For quantum computations,...

Fault-tolerant architectures for nanoelectronic and quantum devices

The progress in CMOS technology has entered the sub-micron realm, and the technology will approach its limits within about 15 years. Already various novel information processing devices, based on quantum mechanical effects at the nanometer scale, have been widely investigated and some have been successfully demonstrated at the circuit level....