Nov. 30, 2020

Class of 2020: Innovation and community define student experience for Governor General’s Gold Medal winner

PhD grad Matthew Mitchell researched novel nanotechnology techniques for telecommunications

The study of quantum science is at once fascinating and intimidating. Terms like “cavity optomechanics,” “transducers,” and “flying qubits” abound along with a number of other words that even other scientists don’t have in their vocabularies.

Matthew Mitchell, who graduated with a PhD in physics Nov. 26, harnessed his curiosity about physics and nanotechnology early. He’d been interested in these areas since high school, and decided to make a career of them by applying for the physics program at UCalgary.

It would turn out that studying physics was the best use of Mitchell’s natural talents; his career as a UCalgary student included completing a Bachelor of Science in physics in 2012. Mitchell was also named this year’s Governor General’s Gold Medal recipient at the PhD level, presented to him in recognition of his academic record, research achievements, and volunteer contributions.

Research project offers a way to connect quantum and fiber optic technologies by using mechanical vibrations

Mitchell’s work is in the field of cavity optomechanics, which focuses on fabricating nanometer-scale devices that could be used to take advantage of interactions between light (photons) and mechanical vibrations (phonons) in order to connect normally incompatible quantum technologies. For reference, one nanometer is one-billionth of a metre!

One of his major projects involved working toward linking artificial atoms in diamonds with telecommunications wavelength photons. This allows for solid-state quantum bits (qubits) to interact with the telecommunications wavelength photons, or “flying qubits,” using the very same fibre optic infrastructure that brings internet service to our homes.

By shrinking the size of these devices to the nano-scale, Mitchell explains, we can also greatly increase the strength of this interaction, which is a big reason why this field has exploded with recent advances in nanofabrication techniques.

One of the most promising applications of Mitchell’s research is creating a transducer able to convert quantum information from solid state qubits to flying qubits.

“By fabricating diamond structures that support optical and mechanical resonances, it is possible to efficiently convert light emitted from a solid-state qubit in the lab, which is at visible wavelengths, to a telecommunication wavelength photon which could travel long distances in existing fibre optic infrastructure,” he explains.

While many different physical implementations of qubits are being studied in the lab such as superconducting qubits, artificial atoms, and quantum dots, photons are currently the best candidate for transferring quantum information from one location to another.

While visible wavelength photons can also be used as flying qubits, they generally suffer from greater loss when transmitted from one place to another. Telecommunications wavelength photons, on the other hand, can travel long distances in existing fibre optic networks with low loss — a key requirement for implementing a “quantum network” or multiple quantum computers connected to each other.

Part of my thesis research demonstrated a diamond microdisk structure capable of converting photons from one wavelength to another by first converting that photon to a phonon, or a mechanical vibration of the device. This conversion process can be extremely efficient, and is scalable.

The techniques Matthew developed have been adopted by researchers internationally and have put Calgary at the forefront of diamond photonics research. He has presented his work at numerous conferences around the world,” says Dr. Paul Barclay, PhD, associate professor in the Department of Physics and Astronomy and member of UCalgary’s Institute for Quantum Science and Technology.

Mitchell worked closely on this project and others with colleague Dr. David Lake, another PhD graduate who is now a postdoc at the California Institute of Technology (Caltech).

fibre optic

Michael Dziedzic on Unsplash

Building community a highlight of UCalgary academic career

Although his research took him on many trips far from home, Mitchell — a native Calgarian — is happy to have gotten an education in his hometown.

“I was also fortunate to work with world-renowned researchers in the Institute for Quantum Science and Technology at UCalgary and learn from dedicated professors and instructors who inspired me with their passion for physics and research,” he says.

"As an undergraduate the highlight for me was working in Pat Irwin’s senior undergraduate physics laboratory. This was my first exposure to a physics laboratory environment and gave me the chance to fall in love with tinkering and trying things out to troubleshoot and problem solve.”

Mitchell was a co-founder of the UofC Nanotechnology group, which provided an opportunity to bring graduate students together from multiple departments to share ideas and network. He also participated in the Alberta Ride to Conquer Cancer as a rider for four seasons prior to graduating, and would fundraise roughly $2,500 per year in order to participate, which he accomplished through volunteering and fundraising events in the community.

Mitchell is now a postdoctoral research fellow at the University of British Columbia, where he is continuing his work in nanophotonics with a shift toward a primary focus on silicon photonics.

“My work at UBC relies heavily on the skills and knowledge I gained during my PhD at UCalgary. I hope to leverage the skills I have developed so far to realize technologies capable of solving some of the challenging problems that society faces today. Currently, I am focused on fabricating prototypes of a mass-producible silicon photonic biosensor capable of detecting SARS-CoV-2 viral particles,” he says.

Mitchell plans to further develop his career in the photonics industry, specifically in the area of nanofabrication and packaging.

However, he says “the work I always found the most rewarding and enjoyable was exploring the tangents that came up during my ‘planned’ research. I would tell my past self to enjoy exploring these and not to be too concerned with sticking to the plan.”