PhD defence by Martin Arentoft Jacobsen

Supervisors

• Principal supervisor: Professor Niels Gregersen, DTU Electro, Denmark.
• Co-supervisor: Associate Professor Luca Vannucci, DTU Electro, Denmark.

Assessment committee

• Senior Reseacher Thomas Christensen, DTU Electro, Denmark (chair).
• Associate Professor Thomas Møller Søndergaard, Aalborg University, Denmark.
• Head of the Computational Nano Optics research group, Sven Burger, Zuse Institute Berlin, Germany.

Master of the ceremony

• Senior Researcher Philip Trøst Kristensen, DTU Electro, Denmark

Abstract:
Quantum light sources are one of the candidates for generating quantum bits (qubits), which are the essential part of the quantum computer. Today all computers are based upon the classical bit which is either 0 or 1. Compared to the classical bit, the qubit can be in a superposition of 0 and 1, which is a quantum mechanical property for which there is no classical counterpart. The point is that this property can be exploited using quantum algorithms, and for certain computational tasks, the quantum computer is much more efficient than the classical computer, even with a modest number of qubits. Some examples of areas where the quantum computer can potentially be applied for real-world applications are drug discovery and development, quantum chemistry, protein folding, machine learning, weather forecasting, and finance to name a few.

The quantum light sources considered in this thesis are quantum dot based singlephoton sources. Here the qubits are encoded upon the single photons emitted by the source. The thesis is theoretical, and we have designed, optimized, and performed optical simulations of various quantum dot based single-photon sources. Generally, the ultimate goal of single-photon source engineering is to ensure that the single photons are emitted and collected with 100% probability, such that the qubits can be generated on-demand. Additionally, the emitted photons need to be quantum mechanically indistinguishable. Throughout the thesis, we present different results and design strategies contributing towards these goals and requirements.