Dynamics, thermalization and propagation of quantum systems in complex environments

• Applicant: Ines de Vega, Ph.D.
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas ; Theoretical Condensed Matter Physics
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 329368667

Quantum systems are in general open, i.e. coupled to an environment that induces decoherence and dissipation. The theory of open quantum systems (OQS) is often based on the assumption that there is a large separation of time scales between the system and the environment, which allows one to consider a weak coupling and Markov approximation. In addition, the environment is often modeled as a set of harmonic oscillators, which enables the description of the problem with models such as the Caldeira-Legget or spin-boson Hamiltonians. Finally, when the environment is a solid medium or an ensemble of particles, in most cases it is considered that the particles are not moving but stationary.The purpose of this project is to advance the understanding of OQSs beyond these three situations. In more detail:(a) In a first part, we will analyze the long-time limit dynamics of an open system coupled to a harmonic oscillator environment without considering the Markov and weak coupling approximations. This is relevant to describe OQS in contexts such as solid state physics and quantum control, quantum biology, physical chemistry, and quantum optics in structured environments.(b) In a second part of the project, we model the environment as a set of anharmonic oscillators, rather than harmonic oscillators. This may describe for instance a phononic bath of vibrating molecules which includes phonon-phonon interactions, interacting quantum gases or complex quantum materials.(c) In a third part, and within the context of light-matter interaction, we analyze the properties of a quantum light field propagating in a moving quantum mechanical medium, as it can be encountered in some experimental situations involving atom lasers or in atomic ensembles flying through a cavity. In this case, the atomic medium would play the role of an environment for the quantum light field, which is now considered to be the OQS. The analysis of light interacting with such media may lead to important applications in quantum optics, like the achievement of optical isolation and unidirectional light transport.

• DFG Programme: Research Grants
• Co-Investigators: Dr. Mari Carmen Bañuls; Professor Dr. Ulrich Schollwöck; Professor Dr. Herbert Spohn
• Cooperation Partner: Dr. Jad Halimeh