Jiří Guth Jarkovský uses state purification to find ground state in complex quantum systems

Jiří Guth Jarkovský, doctoral student in the MPQ Theory group, has finished his PhD. Congratulations! As a next career step, he will start working as a Quantum Application Engineer at a Munich start-up company.

February 09, 2023

His dissertation is located at the interface of two subsectors of quantum physics: quantum many-body physics and quantum information. Via a series of smaller research projects, he succeeded in applying methods from the field of quantum information to find the ground state in complex quantum systems.

Jiří Guth Jarkovský’s thesis is a fusion of two theoretical research papers. While the two articles tackle different problems, they use similar methods from the field of quantum information theory, namely state purification.  According to this concept, you treat a noisy – i.e. mixed or ‘uncertain’ – quantum state as if it were only one half of a larger noiseless quantum state. The other second half is a purely conceptual addition that helps to simplify calculations. Using this concept, Jiří Guth Jarkovský focused particularly on the entanglement in purified states and its implications for the original noisy state.

Consequently, he was able to come up with a trick to find the lowest-energy state in complex symmetric quantum systems; this so-called 'ground state' is essential for understanding the physical properties of the studied systems and their potential real-world uses (such as superconductivity). Instead of looking for the ground state directly, Jiří Guth Jarkovský focused on finding its purification. The clue: Once you have determined the ground state, it is very easy to deduce the original ground state. That’s because state purification always respects the symmetries of the system even when the symmetry in the ground state is broken.

More broadly, Jiří Guth Jarkovský was able to demonstrate the potential of combining methods and approaches from various sub-fields of quantum physics to solve puzzles in adjacent research fields. His thesis also provides formal proofs of statements for phenomena that were previously based on mere assumptions.

“My time at MPQ was great,” Jiří Guth Jarkovský says about his PhD studies, “I was surrounded by a lot of amazing people in the Theory group, as well as other PhD students in the IMPRS-QST programme.”

What’s next?

Jiří Guth Jarkovský has recently taken up a position as a Quantum Application Engineer at the Munich offices of IQM, a quantum start-up. Well done and all the best for your future plans!

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