16 December 2021 Stéphanie Dubreuil

PhD Portrait: Jessica Lemieux

Photo : Fournie

Jessica concludes her university studies at the Université de Sherbrooke, where she completed her master’s and PhD in accelerated studies, assisted by professors David Sénéchal and Guillaume Duclos-Cianci.


After high school in her hometown of Rouyn-Noranda, Abitibi, Jessica went straight to university at the University of Ottawa. With the intention of going into medicine, she enrolls in biochemistry. However, after one year in this field, she decides to reorient herself in physics, at that time guided by her fascination for Einstein and the theory of relativity.

During her bachelor’s degree in physics and mathematics, Jessica experiments thanks to a few internships, which allow her to discover an interest in programming, theory and quantum mechanics.

After completing her bachelor’s degree, she took a study break, during which she applied for graduate school scholarships. Among the professors she contacted for the master’s degree, David Poulin was the one who caught her attention and with whom she decided to work. She began her master’s degree in 2016 and entered the doctoral program on an accelerated basis in 2018. She will complete her course with the help of David Sénéchal and Guillaume Duclos-Cianci.

“In addition to her obvious talent, Jessica demonstrated exceptional organizational skills and professionalism for a graduate student. This has allowed her to further distinguish herself. I am grateful for the opportunity to work with her over the past few years and wish her all the best as she continues her career.” – Guillaume Duclos-Cianci, associate professor of theoretical quantum computing


During her master’s and doctoral studies, Jessica worked mainly on three research projects. All related to discrete adiabatic evolution, her projects aim at preparing states on the quantum computer allowing, among others, to solve optimization problems or to study the phases of matter at low temperature.

The first project focuses on a state preparation algorithm for N-body systems by adiabatic evolution, via the Zeno effect. The second project focuses on a quantum version of random walk and simulated annealing algorithms that can, for example, prepare a stationary state. The last one describes a new algorithm: an adiabatic evolution based on reflection.

“What I was doing is I was simulating a discrete adiabatic evolution algorithm to prepare the ground state of the Hubbard model. The goal of the exercise is to calculate the number of resources, in terms of quantum gates, operations to be done, how long it will take to get to prepare our ground state, to give an idea of how many qubits will be needed, how fault-tolerant the computer needs to be, etc.,” Jessica explains. All of this is to determine if there is indeed a quantum advantage.

“The results demonstrate the high cost associated with fault-tolerant algorithms. Although one expects to have an acceleration compared to the classical computer, when one considers the number of physical qubits, the number of physical operations and the time of each of these operations, including error correction in particular, the size of the instances offering a real advantage is far from being achievable for quantum processors in the short term. However, by combining clever methods and using different optimization processes, it is possible to significantly reduce the cost of quantum algorithms, and thus reduce the time to achieve quantum supremacy.”

“Jessica’s thesis is marked by unity in diversity. Diversity of environments, because the three projects she led were carried out respectively at Microsoft, at UdeS and at 1Qubit. Unity of objectives, because in all three cases, she seeks to reduce and evaluate the cost of quantum algorithms, by adopting a very practical attitude. Thanks to this practicality, Jessica has become a ‘quantum engineer’, an ‘emerging species’.” – David Sénéchal, professor in physics


Jessica does not regret choosing to pursue her university studies in Sherbrooke. On the opposite, she is very grateful for the internship opportunities, summer schools and other doors that were opened to her at UdeS. “It’s crazy how well-known Sherbrooke is in the quantum computing world internationally. I think it’s a really nice university that offers plenty of opportunities to showcase yourself.”


Jessica now holds a full-time position at 1QBit, a company for which she had already had the chance to work as an intern. She plans to move to Sherbrooke.

Congratulations Jessica!


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