Abhiroop Chellu: Semiconductor Light Sources For Quantum Communication And Computing Applications

Quantum technology is set to transform many aspects of our lives. One particular class of quantum technology is photonic quantum information processing, which operates by manipulating single quanta of light, called photons. This approach is proving to be an attractive option for the efficient and scalable implementation of next-generation applications such as quantum computing, quantum key distribution, and quantum metrology. In his doctoral dissertation, Abhiroop Chellu reports on the development of semiconductor light sources that could be used for practical photonic quantum technologies in the future.

The Nobel prize for physics in 2022 was awarded for groundbreaking experiments carried out in the field of quantum information science. These experiments essentially highlight the advantage of using certain unique aspects of quantum mechanics, such as entanglement and superposition, for unlocking exponentially faster information-processing capabilities of devices. There has since been significant effort, largely under the umbrella of activities related to the second quantum revolution, focused on utilizing fundamental mechanical principles in practical technologies. For instance, the most popular effort in this direction in the recent past has been towards the development of a practical quantum computer.

More recently, there has been increasing interest in functionalizing photons for implementing various quantum technologies. Photonic quantum technologies essentially rely on the controlled generation, transmission, manipulation, and detection of photons. The task of generating single photon states is particularly challenging and is currently a widely pursued topic of research.

“In the quest to identify suitable sources, semiconductor quantum dots (QDs) have emerged as a promising candidate for generating high-quality single photons states,” says Chellu.

In fact, the relevance of QDs as a practical quantum light source has recently been highlighted by the 2023 Nobel Prize in Chemistry awarded for their discovery.

Semiconductor QDs, also known as artificial atoms due to their atom-like nature, are optically active nanostructures that can be triggered to generate photons on demand. Just like in atoms, the physical and electronic properties of QDs play a key role in determining their optical properties. State-of-the-art QDs used in quantum technologies are generally fabricated on semiconductor chips using wafer-scale growth processes that offer nanoscale accuracy.

“The most important aspect here is the possibility to tailor the dimensions and material composition of QDs with atomic-level precision which in turn allows for an unprecedented level of control over their optical properties. All these attractive features make QDs the ideal choice as a quantum light source, especially in applications that make use of chip-based light sources,” he adds.

In his doctoral research, Abhiroop has worked on addressing two key aspects of QDs, namely their emission rate and wavelength. The insights presented in his dissertation are believed to be crucial for bringing semiconductor QDs closer to adoption in practical photonic quantum technologies.

Abhiroop Chellu is originally from the bustling, seaside metropolitan city of Chennai located in southern India. He now lives in Tampere where he has been working as a doctoral researcher in the Optoelectronics Research Centre group at Tampere University since 2019.

Public defence on Friday 16 May 2025
The doctoral dissertation of M.Sc. (Tech.) Abhiroop Chellu in the field of quantum photonics titled Semiconductor Quantum Dots for Quantum Information Processing: Addressing Key Bottlenecks Related to Emission Rate and Wavelength will be publicly examined at the Faculty of Engineering and Natural Sciences of Tampere University at 12:00 on Friday, the 16th of May, 2025, on Hervanta campus, Tietotalo building, auditorium TB109 (Korkeakoulunkatu 1, Tampere).

The Opponent will be Professor Armando Rastelli from Johannes Kepler University in Linz, Austria. The Custos will be Senior Research Fellow Teemu Hakkarainen from the Faculty of Engineering and Natural Sciences of Tampere University in Tampere, Finland.