History of Mathematical Aspects of Quantum Theory Seminar
Friday, April 24, 2020, 14:00
Jan Tuziemski (Stockholm University)
Out-of-time-ordered correlation functions in open systems
Abstract: Recent theoretical and experimental studies have shown significance of quantum information scrambling for problems encountered in high-energy physics, quantum information, and condensed matter. Due to complexity of quantum many-body systems it is plausible that new developments in this field will be achieved by experimental explorations. Therefore, a better theoretical understanding of quantum information scrambling in systems affected by noise is needed. To address this problem I will discuss indicators of quantum scrambling - out-of-time-ordered correlation functions (OTOCs) in open quantum systems. As most experimental protocols for measuring OTOCs are based on backward time evolution, two possible scenarios of joint system-environment dynamics reversal will be considered. Derivation of general formulas for OTOCs in those cases as well as a study of the spin chain model coupled to the environment of harmonic oscillators will be presented.
Based on Phys. Rev. A 100, 062106 (2019), arXiv:1903.05025.
Friday, April 3, 2020, at 12:15
Katarzyna Roszak (Wrocław University of Science and Technology)
How to detect qubit-environment entanglement in pure dephasing evolutions
Friday, March 27, 2020, at 12:00
Steven Bass (Kitzbühel & UJ)
The Cosmological Constant Puzzle - Symmetries of Quantum Fluctuations
Abstract: The cosmological constant in Einstein's equations of General Relativity is a prime candidate to describe the dark energy that drives the accelerating expansion of the Universe and which contributes 69% of its energy budget. The cosmological constant measures the energy density of the vacuum perceived by gravitation. Experimentally, it is characterised by a tiny energy scale 0.002 eV. How should we understand this ? The quantum vacuum is described by particle physics where the mass scales that enter are very much larger. If one naively sums the zero-point energies of quantum fluctuations up to the energies where we do collider experiments at CERN then the cosmological constant comes out 10^60 times too large. Here we argue that the tiny value of the cosmological constant may be telling us something deep about the origin of symmetry in the subatomic world. The gauge symmetries which describe particle interactions may be emergent. The presentation will be given at Colloquium level and suitable for good Masters students.
Tuesday, March 3, 2020, at 10:15
Erik Aurell, KTH Royal Institute of Technology (Stockholm), Jagiellonian University (Kraków)
Quantum black holes as solvent
Abstract: Most of the entropy in the current universe is believed to be in the form of Bekenstein-Hawking (BH) entropy of super-massive black holes. This entropy is proportional to the area of the horizon in units of Planck area, or, alternatively, proportional to the square of the mass of the black hole in units of Planck mass. In the "strong interpretation" BH entropy is assumed to satisfy Boltzmann's formula S = log N. The question then arises what is the huge phase space volume N available to the universe after a gravitational collapse, but not before. Inspired by recent proposals for table-top experiments to show (or disprove) that gravity acts quantum-mechanically, I will discuss the possibility that N can be a massive entanglement of the matter in black hole with its own gravitational field, and some consequences of such an idea. This is joint work Michal Eckstein and Pawel Horodecki, available as [arXiv:1912.08607].