Measure for Macroscopic Quantumness via Quantum Coherence and Macroscopic Distinction

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Naseri, Moein | 2020

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Type of Document: M.Sc. Thesis
Language: Farsi
Document No: 53498 (04)
University: Sharif University of Technology
Department: Physics
Advisor(s): Raeisi, Sadegh
Abstract:
One of the most elusive problems in quantum mechanics is the transition between classical and quantum physics. This problem can be traced back to the Schrodinger's cat. A key element that lies at the center of this problem is the lack of a clear understanding and characterization of macroscopic quantum states. Our understanding of Macroscopic Quantumness relies on states such as the Greenberger-Horne-Zeilinger(GHZ) or the NOON state. Here we take a first principle approach to this problem. We start from coherence as the key quantity that captures the notion of quantumness and demand the quantumness to be collective and macroscopic. To this end, we introduce macroscopic coherence which is the coherence between macroscopically distinct quantum states. We construct a measure that quantifies how global and collective the coherence of the state is. Our work also provides a first-principle way to derive well-stablished states like the GHZ and the NOON state as the states that maximize our measure. This new approach paves the way towards a better understanding of the Quantum-to-Classical transition
Keywords:
Macroscopic Quantum System ; Quantum Coherence ; Quantum Mechanics ; Quantum Phase Transition ; Greenberger-Horne-Zeilinger (GHZ) ; Macroscopic Coherence