International Conference on Quantum Systems in Extreme Conditions (QSEC2022)

13 Nov 2022, 17:00 → 18 Nov 2022, 18:00 Europe/Berlin

NH Hotel Bingen

Conference photo

Overview

The understanding of quantum systems in extreme conditions requires the resolution of outstanding questions, relevant for a wide range of topical applications from particle and nuclear physics to atomic and condensed matter physics. Many such systems exhibit characteristic common properties despite dramatic differences in key parameters such as temperature, density, field strength and others. The existence of universal regimes, where even quantitative agreements between seemingly disparate physical systems can be observed, drives a remarkable convergence of research activities across traditional lines of specialisation. In turn, the identification and investigation of non-universal properties plays a vital role for an improved under-
standing of fundamental differences between the systems.

The International Conference on Quantum Systems in Extreme Conditions (QSEC2022) brings together experimental and theoretical researchers working on topics that are particularly driven by such cross-disciplinary developments, in particular:

• Far from equilibrium dynamics and thermalisation
• Quantum systems with strong fields
• Phase structure, large fluctuations and quantum critical phenomena

Keynote talks will provide overviews about quantum systems in extreme conditions in heavy ion collisions, precision spectroscopy in highly charged ions, and ultracold quantum gases. Contributed talks are dedicated to recent progress in these systems. Abundant discussion time and two poster sessions are foreseen for the vital interactions between experimental and theoretical physicists working in the different areas.

Keynote Speakers

Laura Fabbietti (Germany)
Thierry Giamarchi (Switzerland)
Gianluca Gregori (United Kingdom)
Rudi Grimm (Austria)
Marianna Safronova (USA)
Dam Thanh Son (USA)

Invited speakers

Jasmine Brewer (Switzerland)
Raphaelle Bailhache (Germany)
David Clément  (France)
Alina Czajka (Poland)
Elina Fuchs (Germany)
Felix Karbstein (Germany)
Esther Menz (Germany)
Julian Schmitt (Germany)
Tapio Simula (Australia)
Federica Surace (USA)
 

Quantum Systems in Extreme Conditions is organized by the DFG funded Collaborative Research Center 1225 ISOQUANT.                       

Preliminary Program QSEC2022.pdf

QSEC2022_poster.pdf

Sunday, 13 November

Welcome reception & registration

Monday, 14 November

1 Opening of the conference

Speaker: Prof. Jürgen Berges (Institut für Theoretische Physik, Universität Heidelberg)

Pretalk

2 Pretalk

Speaker: Prof. Rudolf Grimm (IQOQI)

09:20 Questions

09:30 Break

Keynote talk

3 Ultracold fermions: From polarons to novel superfluids

Speaker: Prof. Rudolf Grimm (IQOQI)

10:25 Questions

10:30 Coffee break

Morning session

4 Observation of Bogoliubov atom pairs: revealing the interplay of quantum fluctuations and interaction in an interacting Bose gas

Speaker: David Clément (Laboratoire Charles Fabry)

11:20 Questions

5 How many particle do make a fluid? Searching for hydrodynamic behavior in mesoscopic ultracold gases

Collective phenomena in quantum many-body systems are often described in terms of hydrodynamics, an appropriate framework when the involved particle numbers are effectively macroscopic. Motivated by the recent observation of collective phenomena in high-energy proton-proton and proton-nucleus collisions, where particle numbers are small and a fluid description is a priori inapplicable, we discuss the possibilities offered by experiments of expanding clouds of ultracold atom gases as a means to study emergent hydrodynamic behavior as a function of particle number. We consider the inversion of the shape of gases prepared in elliptical traps. Shape inversion is a salient signature of an effective pressure-gradient force, ascribable to hydrodynamics. We borrow techniques from the analysis of collective phenomena in the context of high-energy hadron collisions to devise meaningful statistical measures of the cloud shapes and the shape inversion, which allow us to overcome the finiteness of the number of particles. We discuss our qualitative expectations as well as quantitative hydrodynamic predictions for experiments ongoing at Heidelberg University on expanding few-body Fermi gases. We argue, in particular, that genuine collective effects emerging from atom-atom interactions can be easily detected on top of a background of quantum effects induced by the trapping potential that disappear quickly with the atom number.

Based on: Floerchinger et al., Phys. Rev. C 105, 044908 (2022), and work in progress

Speaker: Giuliano Giacalone (ITP Heidelberg)

QSEC22_Giacalone.pdf

11:50 Questions

6 A mesoscopic fluid of 10 fermions

A very striking manifestation of collective behaviour of many particles is the emergence of hydrodynamics, the effective description of a system as a fluid. In addition to classical systems, hydrodynamic expansion has also been observed in different many-body quantum systems, ranging from heavy ion collisions (1) to ultracold quantum gases (2). However, the fundamental requirements for hydrodynamic behaviour are, especially in the mesoscopic limit - for example in the case of proton-proton collisions - still unclear (3). Our cold atom experiment opens up new pathways to address these questions starting from the smallest scales with deterministic control over the atom number, interaction strength and initial anisotropy. We observe the inversion of the initial aspect ratio after an interacting expansion – one signature of hydrodynamics - in a system comprised of as little as 10 particles.

For our experiments, we deterministically prepare closed shell configurations of a few fermionic
$^6$Li atoms in two different spin states in the ground state of an elliptical two-dimensional harmonic oscillator. A sudden switch off of the confining potentials in radial direction leads to an expansion in a 2D plane, which we perform at different interaction strengths. Our spin and single atom resolved imaging technique (4) allows us to study single particle resolved correlations of any order between the atoms. Two different matterwave magnification techniques (5,6,7) provide access to momentum or real space at different times during the expansion, such that we can directly observe the inversion of the aspect ratio, as well as the formation of pairs over time. In the near future, this will allow us to study the connection between the formation of pairs and the emergence of hydrodynamics in a few body system.

(1) Braun-Munzinger, P., Stachel, J. “The quest for the quark–gluon plasma ”. Nature 448, 302–309 (2007)
(2) K. M. O’Hara et al. “Observation of a Strongly Interacting Degenerate Fermi Gas of Atoms”. Science 298.5601 (2002)
(3) B. Schenke, “The smallest fluid on Earth”, Rep. Prog. Phys. 84,082301 (2021)
(4) M. Holten et al. “Observation of Cooper pairs in a mesoscopic two-dimensional Fermi gas”. Nature 606, 287–291 (2022)
(5) P. A. Murthy, et al. ‘Matter-wave Fourier optics with a strongly interacting two-dimensional Fermi gas’ Phys. Rev. A 90, 043611 (2014)
(6) P.A Murthy, S. Jochim ‘Direct imaging of the order parameter of an atomic superfluid using matterwave optics’, arXiv:1911.10824 (2019)
(7) L. Asteria, et al. ‘Quantum gas magnifier for sub-lattice-resolved imaging of 3D quantum systems’, Nature 599, 571–575 (2021)

Speaker: Mrs Sandra Brandstetter (Physikalisches Institut, University of Heidelberg)

12:20 Questions

12:30 Lunch

Pretalk

7 Pretalk

Speaker: Prof. Laura Fabbietti (TUM München)

14:50 Questions

15:00 Break

Keynote talk

8 How to employ the LHC to study the many body problem in nuclear physics

Speaker: Prof. Laura Fabbietti (TUM München)

15:55 Questions

16:00 Coffee break

Afternoon session

9 Real and virtual direct photon measurements with ALICE at the LHC

Speaker: Raphaelle Bailhache (TU Darmstadt)

Bailhache_16_45_new.pdf

17:05 Questions

10 Compressibility and the equation of state of an optical quantum gas in a box

Speaker: Julian Schmitt (University of Bonn)

17:35 Questions

11 Universal induced interaction between heavy polarons in superfluids ---Effective field theory approach to polaron physics---

The force between particles is one of the most elementary concepts from condensed-matter physics to high-energy physics. Not only the fundamental interaction mediated by gauge bosons but also the induced interaction between quasiparticles plays an essential role in modern physics.
Recently, impurities in superfluids, called polarons, have been attracting much attention in ultracold atom physics. In particular, thanks to the high experimental controllability of ultracold atoms, induced interactions between two polarons of ultracold atoms are an appealing topic with the potential to be confirmed experimentally.

In this work, we investigate the long-range behavior of the induced interaction between two spinless heavy impurities in a superfluid. With the help of an effective field theory, we show that the induced interaction universally exhibits power-law behaviors at both zero and finite temperatures and that the magnitude of the potential depends on the medium properties only through the speed of sound [1]. Our formulation provides a new approach to polaron physics using effective field theory and is valid regardless of the interaction strength between the medium particles. We apply our results to the fermionic superfluid showing the BCS-BEC crossover and evaluate the magnitude of the obtained potential using experimental data of the sound velocity.

Our results, understood as a phonon-mediated Casimir force, provide new insights not only as polaron physics in ultracold atomic systems but also as induced forces in symmetry-breaking phases.

[1] K. Fujii, M. Hongo, and T. Enss, "Universal van der Waals force between heavy polarons in superfluids," arXiv:2206.01048 (2022).

Speaker: Dr Keisuke Fujii (Institute for Theoretical Physics, Heidelberg University)

QSEC2022_Keisuke Fujii.pdf

18:05 Questions

19:00 Dinner

Evening event: SCIENCE PUB QUIZ

Tuesday, 15 November

Pretalk

12 Pretalk

Speaker: Prof. Gianluca Gregori (University of Oxford)

09:20 Questions

09:30 Break

Keynote talk

13 Primordial magnetic fields, Hawking radiation and particles beyond the standard model. What we can learn with high-power lasers

Speaker: Prof. Gianluca Gregori (University of Oxford)

10:25 Questions

10:30 Coffee break

Morning session

14 Characteristics of early time dynamics in relativistic heavy ion collisions

Speaker: Alina Czajka (National Centre for Nuclear Research)

11:20 Questions

15 Gluon, fermion and scalar spectral functions at strong fields

We compute gluon, fermion and scalar spectral functions in highly occupied systems far from equilibrium using classical-statistical lattice simulations. We compare our nonperturbative results for fermion and gluon spectral functions in two and three spatial dimensions with perturbative hard loop calculations, extract the full momentum dependence of the damping rates of quasiparticles and discuss the implications on the quark-gluon plasma at initial stages in heavy-ion collisions, with preliminary results on the Glasma spectral function. Key results are then compared with scalar O(N) models.

Speaker: Dr Kirill Boguslavski (Technische Universität Wien)

11:50 Questions

16 A fluid-dynamic approach to heavy-quark diffusion in the quark-gluon plasma

Heavy quarks (i.e. charm and beauty) are powerful tools to characterize the quark-gluon plasma (QGP) produced in heavy-ion collisions. Although they are initially produced out of kinetic equilibrium via hard partonic scattering processes, recent measurements of anisotropic flow of charmed hadrons [1] pose the question regarding the possible thermalization of heavy quarks in the medium. Our recent work [2] provides new insights on the level of thermalization of charm and bottom quarks in the QGP. In particular, exploiting a mapping between transport theory and fluid-dynamics, we will show how a fluid-dynamic description of the dynamics of charm quarks in the QCD plasma is feasible. Ongoing work concerning the coupling of a heavy-quark conserved current with a hydrodynamic code simulating the QGP phase (FluiduM [3]) to obtain charmed hadron spectra and flow coefficients will be shown.

This work is funded via the DFG ISOQUANT Collaborative Research Center (SFB 1225).

[1] PLB 813 (2021) 136054
[2] e-print [2205.07692]
[3] Phys. Rev. C 100, 014905 (2019)

Speaker: Federica Capellino

QSEC2022_Capellino.pptx

12:20 Questions

12:30 Lunch

Pretalk

17 Pretalk

Speaker: Prof. Thierry Giamarchi (DQMP, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland)

14:50 Questions

15:00 Break

Keynote talk

18 Quantum transport and cold atomic gases

Speaker: Prof. Thierry Giamarchi (DQMP, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland)

15:55 Questions

16:00 Coffee break

Poster Session I

19:00 Dinner

Evening event: INTERNAL SESSION: MEETING OF CRC1225 PRINCIPAL INVESTIGATORS

Wednesday, 16 November

Pretalk

19 Pretalk

Speaker: Prof. Marianna Safronova (University of Delaware)

09:20 Questions

09:30 Break

Keynote talk

20 Quantum sensors in the laboratory and in space for new-physics discoveries

Speaker: Prof. Marianna Safronova (University of Delaware)

10:25 Questions

10:30 Coffee break

Morning session

21 Nuclear parton distribution functions with nCTEQ

Science is entering a new era in the investigation of nuclear matter, driven by a wealth of precision data from the JLab, HERA, RHIC & LHC experiments. The nCTEQ project employs cutting-edge theoretical techniques to analyse these data sets comprehensively. In my talk I will review some of the most recent advances in the nCTEQ approach including 1) the addition of heavy-quark production data from the LHC in order to constrain the nuclear gluon PDF down to very small values of x; 2) the careful reanalysis of neutrino DIS data improving the determination of the strange-quark content and aiding flavour separation; 3) the implications of a new nPDF parametrisation inspired by Short Range Correlations at high x.

Speaker: Tomas Jezo (ITP WWU)

TJezo__.pdf

11:20 Questions

22 Quantum, Gravity and Quantised Vortices

Speaker: Tapio Simula (Swiburne University of Technology)

11:50 Questions

23 Observation of two distinct non-thermal fixed points in spinor condensates

Speaker: Stefan Lanning (KIP, Heidelberg University)

12:30 Lunch

Social program

19:00 CONFERENCE DINNER

Thursday, 17 November

Pretalk

24 Pretalk

Speaker: Prof. Dam Thanh Son (University of Chicago)

09:20 Questions

09:30 Break

Keynote talk

25 Unnuclear physics: conformal symmetry in nuclear reactions

Speaker: Prof. Dam Thanh Son (University of Chicago)

10:25 Questions

10:30 Coffee break

Morning session

26 Rigorous QED for the spectra of heavy muonic atoms

When coming close to an atom, a muon can be captured by the nucleus and form a hydrogen-like muonic ion, which is typically also surrounded by atomic electrons. This atomic system is commonly referred to as a muonic atom. Due to the muon's high mass, it is located much closer to the nucleus; and, especially for heavy nuclei, this results in big nuclear size effects and a strong dependence of the muon bound-state energies on the nuclear charge and current distributions, as well as in large
relativistic effects [1, 2]. A combination of knowledge about the level structure and experiments measuring the transition energies in muonic atoms enabled the determination of nuclear parameters like charge radii, electric quadrupole, and magnetic dipole moments [3].

Theoretical predictions of the fine-, hyperfine structure and dynamical splitting of muonic atoms, based on rigorous QED calculations will be presented. State-of-the-art techniques from both nuclear
and atomic physics are brought together in order to perform the most comprehensive to-date calculations of the quantum-electrodynamics and nuclear contributions. Finally, a long-standing problem of fine-structure anomalies in muonic atoms is revisited in light of the last improvements in nuclear-polarization [4] and self-energy calculations [5].

References
[1] A. Antognini et al., Phys. Rev. C 101, 054313 (2020)
[2] N. Michel, N. S. Oreshkina, and C. H. Keitel, Phys. Rev. A 96, 032510 (2017)
[3] N. Michel and N. S. Oreshkina, Phys. Rev. A 99, 042501 (2019)
[4] I. A. Valuev, G. Colò, X. Roca-Maza, C. H. Keitel, and N. S. Oreshkina, Phys. Rev. Lett. 128, 203001 (2022)
[5] N. S. Oreshkina, https://arxiv.org/abs/2206.01006 (2022)

Speaker: Dr Natalia S. Oreshkina (MPIK)

11:20 Questions

27 Atomic precision spectroscopy for New Physics searches

Speaker: Elina Fuchs (Leibniz Universität Hannover)

11:50 Questions

28 Engineering interactions in an isolated many-body spin system

Controlling interactions is a key to experimentally study far-from-equilibrium dynamics in isolated quantum systems. Here we present two methods of changing the symmetry properties of Heisenberg spin systems implemented with Rydberg atoms. By using time-periodic driving, a naturally given many-body Hamiltonian of a closed quantum system can be
transformed into an effective target Hamiltonian. Such Floquet engineering allows for a stroboscopic observation of vastly different many-body dynamics. For contineous probing we choosing appropriate Rydberg state combinations with which we can directly realize a large range of spin Hamiltonians. We measure the relaxation dynamics of the magnetization of disordered Heisenberg XX-, XXZ- and Ising Hamiltonians. By rescaling time of the individual dynamics, we find a collapse of the magnetization data onto a single curve. Remarkably, the observed dynamics can be captured by theoretical models that only consider localized ensembles of spins down to single pairs. Since the dynamics of pairs are independent of the type of Hamiltonian up to a scaling factor, this simplified model provides an effective integrable Hamiltonian that directly explains the emergence of the scaling behavior.

Speaker: Dr Gerhard Zürn (Heidelberg University)

12:20 Questions

12:30 Lunch break

Afternoon session

29 Quantum vacuum effects in strong electromagnetic fields

Speaker: Felix Karbstein (Helmholtz Instiute Jena)

14:50 Questions

30 Scaling and adiabaticity in a rapidly expanding gluon plasma

Speaker: Jasmine Brewer (CERN)

15:20 Questions

31 Stable and unstable perturbations in universal scaling phenomena far from equilibrium

We study the dynamics of perturbations around nonthermal fixed points associated to universal scaling phenomena in quantum many-body systems far from equilibrium. For an N -component scalar quantum field theory in 3+1 space-time dimensions, we determine the stability scaling exponents using a self-consistent large-N expansion to next-to-leading order. Our analysis reveals the presence of both stable and unstable perturbations, the latter leading to quasi-exponential deviations from the fixed point in the infrared. We identify a tower of far-from-equilibrium quasi-particle states and their dispersion relations by computing the spectral function. With the help of linear response theory, we demonstrate that unstable dynamics arises from a competition between elastic scattering processes among the quasi-particle states. What ultimately renders the fixed point dynamically attractive is the phenomenon of a scaling instability, which is the universal scaling of the unstable regime towards the infrared due to a self-similar quasi-particle cascade. Our results provide ab initio understanding of emergent stability properties in self-organized scaling phenomena.

Speaker: Mr Thimo Preis (Heidelberg University )

QSEC2022_ThimoPreis.pdf

15:50 Questions

16:00 Coffee break

Poster Session II

19:00 Dinner

Friday, 18 November

Afternoon session

32 High-Resolution DR Spectroscopy of Ne^{2+} at CRYRING@ESR

Speaker: Esther Menz (Helmholtz Institute Jena)

09:20 Questions

33 Extending the fluid dynamic description of heavy-ions collisions to times before the collision

It is well established that the late states of a high energy nuclear collision can be described in terms of relativistic fluid dynamics. An open problem in this context is how the actual collision and the early time dynamics directly after it can be described. Phenomenological models are currently employed here and they have several parameters that need to be fitted to experimental data.
Using relativistic fluid dynamics of second order we develop a new approach which addresses the entire collision event, and which gets initialized in fact already before the collision. This is based on the droplet model for the incoming nuclei and a state-the-art equation of state including the first-order liquid-gas phase transition. The physics picture we propose assumes that the soft features of a high energy nuclear collision can be fully described through the dynamics of the energy-momentum tensor and other conserved currents.

This work is part of and supported by the DFG Collaborative Research Centre "SFB 1225 (ISOQUANT)".

Speaker: Mr Andreas Kirchner (ITP Heidelberg)

QSEC_Landau.pdf

09:50 Questions

34 Theory of the magnetic moments and hyperfine splitting of ³He+

In an external magnetic field, the ground state of the $^3$He$^+$ ion is split into into four sublevels due to the combined hyperfine splitting and Zeeman effect. By measuring transition frequencies between these sublevels, it is possible to determine the $g$-factor of the bound electron, the ground-state hyperfine splitting as well as the shielded magnetic moment of the nucleus [1].
In this work, we present the theoretical calculations of the nuclear shielding constant, the ground-state hyperfine splitting and the bound-electron $g$-factor [2]. The theoretical uncertainty of the bound-electron $g$-factor is dominated by the uncertainty of the fine-structure constant $\alpha$. This would allow an independent determination of $\alpha$ in future, provided that the experimental precision can be improved accordingly [3]. Combining the experimental value for the shielded nuclear magnetic moment and the theoretical value for the nuclear shielding constant, we extracted the magnetic moment of the bare nucleus with unprecedented precision, enabling new applications in magnetometry. Furthermore, we extracted the nuclear Zemach radius from the experimental hyperfine splitting value, in tension with the established literature value [4].

[1] A. Mooser, A. Rischka, A. Schneider, et al., J. Phys. Conf. Ser. 1138, 012004 (2018).
[2] A. Schneider, B. Sikora, S. Dickopf, et al., Nature 606, 878 (2022).
[3] J. Zatorski, B. Sikora, S. G. Karshenboim, et al., Phys. Rev. A 96, 012502 (2017).
[4] I. Sick, Phys. Rev. C 90, 064002 (2014).

Speaker: Bastian Sikora (Max Planck Institute for Nuclear Physics)

10:20 Questions

35 Poster prize awards

10:40 Coffee break

Morning session

36 Quantum simulation of particle collisions

Speaker: Federica Surace (IQIM at Caltech)

11:20 Questions

37 Towards real-time simulation of false vacuum decay in quantum field theory

Tabletop experiments with ultracold atoms provide the opportunity to simulate non-perturbative phenomena in quantum field theory. In the proposed experiment, we consider two weakly coupled, one-dimensional Bose-Einstein condensates. The evolution of the population imbalance, in the mean field approximation, is described by a scalar field moving in an effective potential. We discuss in detail the rich nonlinear dynamics in this system for the Josephson and macroscopic quantum self-trapped regimes. We study the effect of quantum fluctuations through numerical simulations using the Truncated Wigner approximation. The primary and secondary instabilities consist in resonant excitations of characteristic modes with spinodal and parametric instabilities that cause bands of fluctuation modes to grow exponentially in time. We perform the analytical study of the excited modes and their respective growth rates and compare with the numerical results. The excitation of fluctuations acts as an effective dissipation term in the equation of motion of the condensate. This causes the damping of the imbalance oscillations and final thermalization of the system in the two regimes. Our study provides the basis for comparison with existing experimental measurements and suggestions for future experimental implementations.

Speaker: Mrs Laura Batini (Institut für Theoretische Physik, Universität Heidelberg)

11:50 Questions

38 What are the time-scales of particle formation in the Schwinger effect?

Lasers providing ultra-strong fields might allow for the first time a verification of electron-positron pair production via the Schwinger effect. Recent theoretical investigations have elucidated many aspects of this essentially non-perturbative effect. However, there is, at least, one fundamental question which has remained elusive: What is the formation time of the electron (or, equivalently, of the positron) in this process? We will discuss whether and how this question can be formulated as a well-posed problem and point out the advantages of the adiabatic particle number as a pseudo-observable in this process. Furthermore, we will analyze the numerical results obtained in Dirac-Heisenberg-Wigner formalism for time-dependent and inhomogeneous electric fields in 1+1- dimensional QED to extract at least three different time-scales which are relevant for particle formation. Hereby, the time evolution of late-time-observable quantities such as the charge density and the particle number density are studied with respect to the influence of spatial and temporal field variations. An outlook for a corresponding investigation in 3+1-dimensional QED will be given.

Speaker: Mr Matthias Diez (University of Graz)

12:20 Questions

12:30 Lunch