PhD defence by Dayang Li

Abstract

Quantum computers and quantum networks are envisioned to help tackle some of the most fundamental challenges of our time, such as climate change, drug development, communication security and many more. To highlight its potential, researchers from quantum information science and quantum dots have received Nobel Prizes in Physics 2022 and Chemistry 2023. My research is closely related to both fields.

Quantum dots are "artificial atoms" designed and fabricated in research labs. They behave similarly to natural atoms with discrete and well-defined energy levels, emitting light at specific wavelengths. Being "artificial", their energy levels can be controlled by tuning their sizes. However, quantum dots with the best optical properties thus far lack precise size control, and scientists are limited to working with single or double quantum dots.

My research aims to develop a novel multi-quantum-dot system with precise control of quantum dot sizes and positioning. I have been working on theoretical study and optical characterization of nanowire crystal-phase quantum dots - made of one crystal structure embedded in another. By controlling the crystal structure during growth down to a single atomic layer, we can precisely control both size (energy levels) and positioning. This allows us to deterministically fabricate arrays of quantum dots on a single nanowire, making them suitable for versatile multi-qubit quantum photonic devices. My research extends to proposals for a new type of qubit native to crystal-phase quantum dots, the location qubits, and its quantum control techniques, while also providing insights into fundamental physical principles like extended Pauli constraints.

Supervisors

• Main Supervisor: Associate Professor Nika Akopian, DTU Electro.
• Co-supervisor: Professor Søren Stobbe, DTU Electro.

Assessment committee

• Associate Professor Sanshui Xiao, DTU Electro.
• Professor Dr. Gabriel Bester, University of Hamburg, Institute of Physical Chemistry, Germany.
• Professor David Gershoni, Technion – Israel Institute of Technology, Physics Department, Israel.

Master of the Ceremony

• TBA