Konstantin Nestmann

PhD candidate in Physics

RWTH Aachen

I am currently completing my PhD in theoretical physics at RWTH Aachen University. My research focuses on various aspects of open quantum systems from both a quantum information and a statistical physics perspective.

Interests

• Non-perturbative quantum master equations
• Quantum non-Markovianity
• Quantum Thermodynamics

Education

• PhD in Physics (with Prof. M. R. Wegewijs), 2018 - present

  RWTH Aachen University

• MSc in Physics (with Prof. C. Timm), 2018

  Dresden University of Technology

• BSc in Physics (with Prof. C. Timm), 2015

  Dresden University of Technology

Highlights

K. Nestmann, M. R. Wegewijs

April 2022 SciPost Phys. 12, 121

Renormalization group for open quantum systems using environment temperature as flow parameter

We develop the $T$-flow renormalization group scheme to access the low-temperature many-body physics of open quantum systems by literally lowering the temperature of the environment.

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Publications

Renormalization group for open quantum systems using environment temperature as flow parameter

We develop the $T$-flow renormalization group scheme to access the low-temperature many-body physics of open quantum systems by literally lowering the temperature of the environment.

K. Nestmann, M. R. Wegewijs Apr 2022 SciPost Phys. 12, 121

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General connection between time-local and time-nonlocal perturbation expansions

We show how to translate a perturbation expansion for the easier to compute time-nonlocal memory kernel $\mathcal{K}$ into a corresponding expansion for the more complicated time-local generator $\mathcal{G}$.

K. Nestmann, M. R. Wegewijs Oct 2021 Phys. Rev. B 104, 155407  ·  Editor’s Suggestion

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Fermionic duality: General symmetry of open systems with strong dissipation and memory

We present intriguing exact relations between quantities that describe the time-evolution of quite generic open quantum systems. Combined with our fixed-point equation this leads to powerful insights into various approximation strategies.

V. Bruch, K. Nestmann, J. Schulenborg, M. R. Wegewijs Sep 2021 SciPost Phys. 11, 053

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How quantum evolution with memory is generated in a time-local way

We establish that the general connection between time-local and non-local quantum master equations is a simple yet general fixed-point equation with far reaching applications.
→ See press releases by RWTH Aachen, FZ Jülich and JARA

K. Nestmann, V. Bruch, M. R. Wegewijs May 2021 Phys. Rev. X 11, 021041

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Five approaches to exact open-system dynamics: Complete positivity, divisibility, and time-dependent observables

We show that the “trivial” resonant level model actually provides a rich source of examples for interesting dynamics by solving it in 5 different ways.

V. Reimer, M. R. Wegewijs, K. Nestmann, M. Pletyukhov Jul 2019 J. Chem. Phys. 151, 044101

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Teaching

Lead teaching assistant (creating exercise sheets, organizing sections):

• Quantum Information (Prof. David DiVincenzo and Prof. Maarten Wegewijs)
• Introduction to Theoretical Physics (Prof. Dante Kennes)

Teaching assistant:

• Statistical Physics (Prof. Volker Meden)
• Quantum Mechanics (Prof. Volker Meden; Prof. Fabian Hassler)

Contact

• nestmann@physik.rwth-aachen.de