PhD defence by Pooja Chamaparambil Sindhuraj

Abstract

Quantum technologies are advancing rapidly, with single-photon emitters (SPEs) playing a central role in secure communications, quantum computing, and othercutting-edge applications. This research focuses on hexagonal boron nitride (hBN), a promising material capable of hosting quantum emitters even at room temperature, opening up new possibilities for quantum technologies.

This study investigates how strain, low-energy oxygen atom bombardment, and high temperature heat treatments can be used to create localized regions in hBN that emit light. The research aims to develop precise methods for creating and controlling single-photon emitters in specific locations within the material—an essential step toward site-specific emitter fabrication, which is key to developing more reliable and scalable quantum devices.

The findings show that regions under strain in hBN are particularly effective at localizing features that contribute to light emission. These features could be linked to structural defects, but there is also a possibility that molecular accumulation in these regions may play a role.

While the exact origin of these emissions is still under investigation, the results strongly suggest that structural defects in hBN are crucial for emitter formation. However, molecular contributions may also be involved, highlighting the need for further exploration. Understanding these mechanisms will be vital for improving the design of materials used in future quantum technologies.

This research paves the way for deterministic fabrication of quantum emitters in hBN, with potential applications in quantum computing and secure communication systems. The ability to precisely control emitter formation and placement opens up exciting possibilities for developing efficient, customizable quantum devices and advancing the scalability of quantum technologies.

Supervisors

• Principal supervisor: Associate Professor Nicolas Leitherer-Stenger, DTU Electro, Denmark
• Co-supervisor: Professor Martijn Wubs, DTU Electro, DenmarkCo-supervisor: Associate professor Sanshui Xiao, Denmark

Evaluation Board

• Associate Professor Timothy Booth, DTU Physics, Denmark
• Junior Professor Iris Niehues, Institute of Physics, University of Münster, Germany
• Staff Scientist Michael Neumann, Max Planck Institute for Solid State Research, Germany

Master of the Ceremony

• Associate professor Battulga Munkhbat, DTU Electro, Denmark