Working at the intersection of light and matter

Raji Bhaskaran Nair was a graduate electronics and communication engineer working with portable spectrometers in her native India when she read a journal article that would change her future career and see her make the move to Sydney. 

That article led Raji to her current role – as a PhD student and SQA PhD Scholarship recipient at Macquarie University researching quantum polaritonics, a hybrid light-matter particle form that emerges when photons (light particles) interact with certain matter. Raji is based at the Low Temperature Cavity QED Lab at CSIRO Lindfield working with her PhD supervisor Professor Thomas Volz of the Macquarie Centre for Quantum Engineering. 

Growing up in a small town on India’s south-western state of Kerala, Raji’s aptitude for mathematics and physics was encouraged by several inspiring female science teachers. She completed a degree in electronics and communication engineering, followed by a Master of Technology Degree in Optoelectronics and Optical Communication.   

“After I finished my bachelor’s degree I initially thought I would work in signal processing – but then I heard about optoelectronics, and thought it would be interesting to find out about how we could in future use light for new electronics applications - so that's why I chose optoelectronics for my master’s.” 

Her master’s thesis looked at the use of Raman spectroscopy and optical coherence tomography to investigate breast tissues. “It was certainly an amazing experience that inspired me a lot, and after completing my master's I joined the National Institute for Interdisciplinary Science and Technology in Kerala,” she says.  

Here, she was working on research and development around the miniaturisation of optoelectronics devices when she first heard about quantum computers. 

“I was fascinated by quantum technology, and started reading articles and viewing a lot of talks about it. I was not from a physics background, so my knowledge of the field was very limited,” she says.  

Raji realised that her own specialisation in opto-electronics and optical communication could have some relevance to work going on in the quantum field after reading an article in Nature Photonics. The article covered attempts to quickly control light with a single light particle (photon), to develop new, more precise quantum devices like single-photon switches or advanced gates. 

She contacted lead author Professor Thomas Volz at Macquarie University, and soon realised that she could potentially contribute to some of the research going on in this field. “Thomas was doing some amazing experimental work in quantum optics,” she says. 

Professor Volz encouraged Raji to apply for a PhD opportunity with Macquarie University through a Sydney Quantum Academy Scholarship, to work with the ARC Centre of Excellence for Engineered Quantum Systems (EQUS) on quantum polaritonics, which she was offered at the beginning of 2020 – but the COVID-19 pandemic delayed her physical arrival in Australia by almost two years.  

Raji was in the very first round of SQA scholarship grants, and began her PhD online in January 2021. 

“Because of Covid, a lot of the SQA events were online, so I was still able to regularly interact with colleagues from Macquarie and SQA’s other partner universities during that time,” she recalls. “It made my eventual arrival in Australia in December 2021 even more exciting because it felt familiar, and I wasn’t anxious about being in a new country.”   

“Being able to access SQA courses from the other partner universities also boosted my confidence level to continue my research,” she says. “At first I was sad because I couldn't start the experimental work, but when I think back now, it was good timing because I could learn a lot of skills such as coding online, and how to research independently.” 

Raji’s work involves exploring single photon sources and while waiting to begin experiments, she was able to apply her newly acquired skills in Python coding to develop various models. 

Her current experiments involve placing semiconductor material (gallium arsenide) inside an optical cavity that can store light, which enables the material to interact strongly with the photons. The ultimate goal is to develop an ultrafast single-photon transistor that could for example find applications in quantum simulations or neuromorphic computing. But as Raji states, “the real-time applications are yet to be uncovered, as we are trying to first understand the non-linear behaviour of applied materials when they are half-electron, half-photon.”

Raji plans to go into industry research and development on completing her PhD. “There is a world of opportunity,” she says.