Public defence in Engineering Physics, M.Sc. Nikita Kirsanov

Title of the doctoral thesis: Thermodynamics and coherence in quantum systems

Doctoral student: Nikita Kirsanov
Opponent: Professor Gerardo Adesso, The University of Nottingham, UK
Custos: Prof. Pertti Hakonen, Aalto University School of Science, Department of Applied Physics

Thesis available for public display 10 days prior to the defence at: https://aaltodoc.aalto.fi/doc_public/eonly/riiputus/

Hot Prospects in Quantum 

The upcoming quantum technology era calls for long-distance quantum-secure communications, robust quantum entanglement generation, and efficient ways of quantum information and heat management at microscales. This thesis seeks solutions to these challenges within the emerging field of quantum thermodynamics. 

In contemplating the quantum foundation of the second law of thermodynamics, this work challenges the conventional quantum communications paradigm and introduces a conceptually new approach to the field. Based on the physical end-to-end line control, this approach enables signal transmission across unprecedented global distances using current technologies and circumventing the need for trusted nodes. This paves the way towards scalable and secure quantum communication networks of tomorrow. 

An important resource for both quantum communications and computing is quantum entanglement, where quantum systems are linked and instantly affect each other no matter how far apart they are. Through rigorous theoretical and experimental research, this thesis shows that entanglement can be harvested by applying heat to specific superconducting structures (normal metal–superconductor–normal metal, or NSN). Such structures can also serve as small multi-functional thermal management devices, crucial for advancements in micro and nanoscale quantum technologies. 

The thesis further explores entropy dynamics within the qubit-based systems—particularly, a qubit-based Maxwell demon. This shows how the quantum version of the fundamental H-theorem, which in classical thermodynamics formalizes the tendency of systems towards maximal entropy, helps to analyze processes particularly occurring in quantum computers.

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Doctoral theses in the School of Science: https://aaltodoc.aalto.fi/handle/123456789/52