25 March 2021 Jessica Blakeney
Now an expert in spin qubits in silicon

Chloé Bureau-Oxton obtains her PhD

To complete her studies in physics at the Université de Sherbrooke, including an international internship and a doctorate in New Mexico, Chloé Bureau-Oxton will defend her thesis on March 25th virtually from the Netherlands, in Europe. Focusing on quantum computing, Chloé investigated singlet-triplet qubits in silicon, a posture with several advantages in quantum systems.

A Noticeable Interest for Physics

Having always had an interest in science, Chloé hesitated between medicine and physics when she enrolled in university: “I did the Sciences, lettres et arts program at the Cégep de Sherbrooke, since my interests revolved around mathematics, physics and visual arts. When it came time to choose a university program, I preferred to continue in science, so I chose physics. The Université de Sherbrooke was an obvious choice, firstly since it was near my home, but especially since UdeS is renowned in physics.”

From the start of her undergraduate degree, which began in the fall of 2007, Chloé was exposed to quantum computing, thus developing a particular interest: “During my undergrad, I did a four-month internship in Sweden at Chalmers University of Technology where I worked with superconducting transmon-type qubits. I had been involved in making samples in their clean rooms. Since I had greatly enjoyed my internship, I decided to continue my research in the quantum field.”

Chloé later completed her master’s degree in Professor Michel Pioro-Ladrière’s group, during which she worked with spin qubits in gallium arsenide, while manufacturing and measuring quantum devices. The young physicist’s academic career then continued at the PhD level as Chloé directed her research towards another type of qubit : qubits in silicon.

Her Research Topic

In 2013, Chloé began her doctorate in experimental physics at Sandia National Laboratories in the city of Albuquerque, New Mexico, still in Prof. Pioro-Ladrière’s group, but also having Dr. Dwight Luhman as research co-director, while working with Dr. Malcom Carol. “I found my experience particularly pleasant since it wasn’t a university laboratory, but a national one. I was surrounded by professionals, doctoral students, and researchers. Sandia has its own silicon foundry and ultra-specialized machinery, so obtaining samples was quick and efficient,” shares the doctoral student.

Her research subject concerns singlet-triplet qubits in silicon in the field of quantum computing: “As part of my experiments, I made measurements on systems composed of a quantum dot and a phosphorus atom, and on systems composed of two quantum dots. With double quantum dots, I experimented with singlet-triplet qubits (two electrons in the double dot) driven by the spin-orbit. Generally, spin qubits in semiconductors require micro magnets or resonators to generate the difference in a magnetic field that controls the qubit. Using the spin-orbit is advantageous since quantum qubit operations can be performed without these components, which simplifies the device manufacturing process. I have studied two distinct ways of performing universal quantum gates with these qubits, a pulsed method, and a resonant method. Finally, I used the ‘gate set tomography’ to measure the fidelity of these quantum gates and to determine what is the best method to perform this type of qubit.”

The idea of ​​using qubits in silicon is that they can be integrated into other quantum systems, such as superconducting resonant cavities. Another advantage of silicon is that it has an isotope without nuclear spin, which avoids disturbing the quantum bit. Bit fidelity is therefore better compared to gallium and arsenic, both of which have nuclear spin.

Prof. Michel Pioro-Ladrière testifies to her success: “Through her doctorate, Chloé has become an expert in spin qubits in silicon. A seasoned experimenter, she pushed the frontiers of knowledge by testing the most sophisticated method of investigating qubit performance in the laboratory.”

“Chloe took every opportunity to work directly with leading experts in the field of silicon quantum computing during her time at Sandia National Laboratories. Her clear communication style, combined with her systematic and tireless approach to experiments, fostered fruitful collaborations that led to new and interesting results across a breadth of topics,” adds Dr. Dwight Luhman.

During her PhD, Chloé’s name appeared in two articles, one on cryogenic amplifiers, and the other on the spin-orbit effect in silicon qubits.

The Next Step

For the moment, Chloé is concentrating her efforts on completing her thesis and her defence, which will take place on March 25th. “As for what’s next, I don’t have a fixed plan, but I would like to find myself a research job in the industry,” she concludes.

The IQ wishes Chloé a good thesis defence, and good luck for the future!

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