Program on Quantum Many-Body Dynamics: Thermalization and its Violations

September 8 – 19, 2025

ICTP-SAIFR, São Paulo, Brazil
Venue: Principia Institute

Zoom ID: 863 0592 5650
Password: quantum

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How isolated quantum systems thermalize and reach equilibrium constitutes a long-standing question, dating back to the early days of quantum mechanics. During the last 20 years, the celebrated Eigenstate Thermalization Hypothesis has shed light on the mechanism of thermalization, and its predictions have been massively tested, at the theoretical, numerical, and experimental level. Simultaneously, huge efforts have been devoted to find robust mechanisms that quantum systems can exploit to escape thermalization and retain information in their local degrees of freedom. With the advent of the second quantum revolution and quantum technologies, these mechanisms are of uttermost importance, since they can be used to build quantum memory devices. At the same time, recent quantum simulators allow the study of these phenomena at the experimental level, with high precision and in almost perfect isolation.

This program will bring together international experts on these topics, to provide an overview of the most recent results and techniques, spanning the theoretical, computational, and experimental aspects. A lightweight talk schedule will create the perfect atmosphere for discussions and will foster new collaborations among participants. In parallel, there will be pedagogical activities specifically tailored to young scientists, to offer them the possibility of including these developments in their research horizons.

There is no registration fee.

Organizers:

  • Eduardo Miranda (Unicamp, Brazil)
  • Zlatko Papic (University of Leeds. England)
  • Dario Rosa (ICTP-SAIFR/IFT-UNESP, Brazil)
  • Lev Vidmar (Jozef Stefan Institute and University of Ljubljana, Slovenia)

 

Participants list here.

 

Announcement:

Click HERE for online registration
Registration deadline: July 19, 2025

 

Invited Speakers

Invited speakers

First Week

  • Ceren Dag (Harvard University, USA)
  • Anatoli Polkovnikov (Boston University, USA)
  • Tobias Micklitz (CBPF, Brazil)
  • Thomas Iadecola (Iowa State University, USA)
  • Natalia Chepiga (Delft University of Technology, Netherlands)
  • Pedram Roushan (Google, USA)
  • Antonello Scardicchio (ICTP, Italy)
  • Dries Sels (New York University, USA)
  • David Logan (Oxford, England)
  • Ivan Khaymovich (Nordita, Sweden)
  • Soumya Bera (Indian Institute of Technology Bombay, India)
  • Yevgeny Bar Lev (Ben Gurion University of the Negev, Israel)
  • Jean-Yves Desaules (Institute of Science and Technology Austria, Austria)
  • Piotr Sierant (Barcelona Supercomputing Center, Spain)

Second Week

  • Lea Santos (University of Connecticut, USA)
  • Pieter Claeys (Max Planck Institute for the Physics of Complex Systems, Germany)
  • Nicolas Regnault (Ecole Normale Superieure Paris, France)
  • Marcos Rigol (Penn State University, USA)
  • Thomas Iadecola (Iowa State University, USA)
  • Natalia Chepiga (Delft University of Technology, Netherlands) TBC
  • Antonello Scardicchio (ICTP, Italy)
  • Dries Sels (New York University, USA)
  • David Logan (Oxford, England)
  • Ivan Khaymovich (Nordita, Sweden)
  • Piotr Sierant (Barcelona Supercomputing Center, Spain)
  • Soumya Bera (Indian Institute of Technology Bombay, India)
  • Fabian Heidrich-Meisner (Georg-August-Universität Göttingen, Germany)
  • Yevgeny Bar Lev (Ben Gurion University of the Negev, Israel)
  • David Weiss (Penn State University, USA)
  • Ulrich Schneider (Cambridge, England)
  • Sona Najafi (IBM TJ Watson Research Center, USA)
  • Jean-Yves Desaules (Institute of Science and Technology Austria, Austria)
  • Eduardo Jonathan Torres Herrera (Instituto de Fisica, BUAP, Puebla, Mexico)

Posters

  • Maykon Araújo (University of São Paulo (USP), Brazil): The Hubbard Model on Anisotropic Triangular Lattice

A great deal of interest has been given to low-dimensional frustrated systems over the past decades, in particular because of the occurence of exotic phases like charge order, superconductivity and spin liquid states. When such systems are combined with disorder or anisotropy, the degree of complexity is further increased, and the nature of their ground state is less clear. This situation, together with the experimental results of optical lattices, increase the interest on the Hubbard model, once cold atoms experiments offer excelent routes to verify and expand on the theoretical results for this model. Within this context, here we investigate the thermodynam- ical properties of the Hubbard model on the triangular lattice with hopping anisotropy. Our theoretical analises are performed through unbiased Quantum Monte Carlo simulations close to the half-filling regime, where Mott insulating phases are expected. By performing electronic compressibility calculations for different temperatures and interaction strengths, we have obtained the phase diagram that characterizes the metal-insulator transition of the system, at half-filling, through the calculation of the critical interaction values (U/t) as a function of the hopping anisotropy (t’/t). Furthermore, in orther to gain insight about the nature of the phases involved, we calculated the nearest neighbors and the next-nearest neighbors spin correlation functions, as well as the charge-charge correlation functions. These results may shed light on the complex physics of such a frustrated system.

  • Thiago Rodrigues De Oliveira (Universidade Federal Fluminense, Brazil): Quantum equilibration under extended experimentally realistic conditions

Understanding how macroscopic systems exhibit irreversible thermal behavior has been a longstanding challenge, first brought to prominence by Boltzmann. Recent advances have established rigorous conditions for isolated quantum systems to equilibrate to a maximum entropy state, contingent upon weak assumptions. These theorems, while powerful, applied for a sudden quench. However, natural processes involve finite-time perturbations or quenches, which raises a crucial question: Can these systems still equilibrate under more realistic, finite-time dynamics? In this work, we extend the established results to account for finite-time quenches, demonstrating that, even under finite-time perturbations, the system will equilibrate provided it populates many significant energy levels. While the mathematical proof is more intricate than in the instantaneous case, the physical conclusion remains the same: sufficient perturbation leads to equilibration. Our results provide a broader and more physically realistic framework for understanding thermalization in isolated quantum systems.

  • Gabriel Oliveira Alves (Max Planck Institute for the Physics of Complex Systems, Germany): Probes of Full Eigenstate Thermalization in Ergodicity-Breaking Quantum Circuits

The eigenstate thermalization hypothesis (ETH) is the leading interpretation in our current understanding of quantum thermalization. Recent results uncovered strong connections between quantum correlations in thermalizing systems and the structure of free probability theory, leading to the notion of full ETH. However, most studies have been performed for ergodic systems and it is still unclear whether or how full ETH manifests in ergodicity-breaking models. We fill this gap by studying standard probes of full ETH in ergodicity-breaking quantum circuits, presenting numerical and analytical results for interacting integrable systems. These probes can display distinct behavior and undergo a different scaling than the ones observed in ergodic systems. For the analytical results we consider an interacting integrable dual-unitary model and present the exact eigenstates, allowing us to analytically express common probes for full ETH. We discuss the underlying mechanisms responsible for these differences and show how the presence of solitons dictates the behavior of ETH-related quantities in the dual-unitary model. We show numerical evidence that this behavior is sufficiently generic away from dual-unitarity when restricted to the appropriate symmetry sectors.

  • Debarghya Chakraborty (ICTP-SAIFR, Brazil): Scars and Phases in Coupled SYK Models

I will talk about the different dynamical regimes that arise in two copies of SYK model coupled with a bilinear interaction. This is a variant of the model studied by Maldacena and Qi. By changing correlations between the copies, we find novel transitions between ergodic to non-ergodic behavior of the correlation functions for different parameters. This model has a scar sector which is spanned by states which have a well-defined fermion “size”.

  • Konrad Pawlik (Jagiellonian University, Poland): Tracking the ergodic instabilities in the Anderson-quantum sun model

The study of many-body localized (MBL) phases inseparably links properties of spectra and eigenstates: localized systems exhibit Poisson level statistics and area-law of entanglement entropy, while the ergodic systems are faithful to random matrix ensemble predictions, implying level repulsion and volume-law entanglement. We introduce an interacting spin-1/2 model, Anderson-quantum sun model (AQSM), inspired by the quantum sun model (QSM), which significantly deviates from these expectations. In addition to conventional localized and ergodic phases, we identify a phase with volume-law entanglement and intermediate spectral properties. We also find a regime with Poisson level statistics, subvolume (power-law) entanglement scaling, and correlation functions that begin to display ergodic features. These findings extend the known landscape of ergodicity-breaking beyond the traditional MBL phenomenology.

  • Pedro Ruyter Nicácio Falcão (Institute of Theoretical Physics, Jagiellonian University in Krakow, Poland, Poland): Magic dynamics in many-body localized systems

Nonstabilizerness, also known as quantum magic, characterizes the beyond-Clifford operations needed to prepare a quantum state and constitutes an essential resource, alongside entanglement, for achieving quantum advantage. This work investigates how nonstabilizerness spreads under the dynamics of disordered quantum many-body systems. Using the l-bit model, a phenomenological model of many-body localization (MBL), we present an analytical description of the nonstabilizerness growth in MBL systems. We demonstrate that our formulas describe the nonstabilizerness growth in strongly disordered quantum spin chains. Our findings establish a new facet of MBL phenomenology and identify the vital role of the disorder in slowing down the growth of the complexity of quantum states, important for our understanding of quantum advantage.

  • Guilherme Antônio De Souza (Universidade Estadual de Campinas – UNICAMP, Brazil): Excess work in quantum Hamiltonian impurity models

In this work, we numerically investigate the dynamics of excess work in quantum systems described by the XX Hamiltonian, subjected to linear control protocols executed in finite times. Initially, we analyze a spin chain with an impurity at the first site, subjected to a locally applied transverse linear magnetic field protocol, varying as h(t)=h(0)+δh t/τ, t∈[0,τ], considering that the remainder of the system constitutes a fermionic reservoir after a Jordan-Wigner transformation. We numerically evaluate the excess work behavior as a function of the protocol duration (τ). Subsequently, we study a closed XX spin chain system, where one site acts as an impurity and the remaining spins form a quantum reservoir. For this case, we also numerically investigate how the excess work evolves with respect to the duration of the transverse linear magnetic field protocol applied to the impurity. This investigation enhances the fundamental understanding of excitation dynamics in complex quantum systems, thereby opening prospects for practical applications in quantum information processing and efficient control of these systems.

  • Vitória Freitas De Souza (Universidade Federal Fluminense, Brazil): Scrambling of Information and Complexity in Floquet time crystals: An Analysis through the Lipkin-Meshkov-Glick model

We study the breakdown of thermalization and the emergence of long-lived non-ergodic phases in periodically driven quantum many-body systems. Focusing on the Lipkin-Meshkov-Glick (LMG) model under Floquet dynamics, we investigate how time-translation symmetry breaking is connected to information scrambling and quantum complexity. By working in the Dicke basis, we efficiently simulate large system sizes and compute dynamical observables such as spin magnetizations, Loschmidt echoes, and out-of-time-ordered correlators (OTOCs). These quantities allow us to characterize the persistence of coherence, the buildup of complexity, and the non-thermal nature of the discrete time-crystalline phase. Our results contribute to understanding how collective dynamics and long-range interactions can stabilize non-thermal behavior in the absence of disorder.

  • Carlos Adolfo Diaz Mejia (Instituto de Ciencias Nucleares, Mexico): Thermalization of Bosons in Disordered Systems: The Role of Broken Symmetries

The interplay between disorder, interactions, and symmetries in quantum systems can dramatically alter thermalization dynamics. In this work, we study chaos and thermalization in a disordered bosonic chain specifically, the interacting Aubry-André model—where Fock states (experimentally accessible in optical lattices) serve as initial conditions. By analyzing the system’s spectral statistics and subsystem dynamics, we identify a chaotic regime where most states thermalize, albeit with striking exceptions: certain Fock states exhibit delayed thermalization, contingent on the underlying symmetries of the chain. We focus on parity and translation symmetries, demonstrating how their breaking or preservation selectively enhances or suppresses thermalization even in the chaotic phase. Our results bridge theoretical predictions with experimental observables, offering insights into the control of thermalization in engineered quantum systems.

  • Tiago Pernambuco Toledo De Macedo (Universidade Federal do Rio Grande do Norte, Brazil): Efficient detection of localization transitions using observable predictability

Identifying phase transition points is a fundamental challenge in condensed matter physics, par- ticularly for transitions driven by quantum interference effects, such as Anderson and many-body localization. Recent studies have demonstrated that quantum coherence provides an effective means of detecting localization transitions, offering a practical alternative to full quantum state tomogra- phy required for entanglement quantification. Building on this approach, we investigate localization transitions through complementarity relations that connect local predictability, local coherence, and entanglement in bipartite pure states. Our results show that observable predictability serves as a robust and efficient marker for localization transitions. Crucially, its experimental determination requires exponentially fewer measurements than coherence or entanglement, making it a powerful tool for probing quantum phase transitions.

  • Jakub Novotný (Institute of Particle and Nuclear Physics, Charles University, Czechia): Zeros of the Complexified Survival Amplitude

Motivated by recent interest in dynamical quantum phase transitions (DQPTs), we study the distribution of zeros of the complexified survival amplitude for an arbitrary quantum state in the complex-time plane. The survival amplitude is the overlap between the initial state and its time-evolved counterpart. As a holomorphic function, it is completely determined by its zeros up to a normalization function. We demonstrate that these zeros “move” as the coherence of the initial state decays, and that their positions at later times can be accurately captured by a few-level (or even two-level) approximation. We illustrate this on a spin chain model with tunable interaction and show how the interaction range influences the distribution of zeros. Finally, we discuss the stability of these zeros and illustrate how critical phenomena—both ground-state quantum phase transitions (QPTs) and excited-state quantum phase transitions (ESQPTs)—modify their distribution and characteristic timescales.

  • Orion De Macedo Xavier Villanueva Filho (Institute of Physics of São Carlos at the University of São Paulo (IFSC/USP), Brazil): Approximations for the quantum work extracted from a correlated fermionic system

The present project is inspired by the idea of approximating the work extracted in a quantum interacting system using Density Functional Theory (DFT). One of the key elements in DFT is the Kohn-Sham formulation, which converts the many-body problem in an effective non-interacting one by means of the so-called exchange-correlation functional. It has been shown that dealing with systems at finite temperature by means of DFT approximations built at previous works could produce accurate results up to a characteristic temperature. While in the previous studies for the quantum thermodynamics of the Hubbard model aforementioned the DFT approximations considered the exchange-correlation potential static and as that for the ground-state, an interesting route to improve their accuracy would be employing approximations constructed in the thermal DFT and Time-Dependent (TDDFT) framework. In this project, we propose to study the extracted quantum work in the driven Hubbard model using density functional approximations. Our goal is to identify strategies for designing reliable approximations for quantities of interest of Quantum Thermodynamics in various correlation regimes and thermal ranges.

  • Edgard Macena Cabral (Instituto de Física de São Carlos -USP, Brazil): Usage of quantum information mesures to classify phases in machine learning models.

Identifying quantum phases of matter is a central challenge in condensed matter physics. Building on recent work showing that quantum information measures can serve as probes for phase transitions, this work explores their use as features in machine learning algorithms. We investigate how (i) short and long-range correlators, (ii) Von Neumann Entropy, (iii) and Quantum Fisher Information can distinguish phases across three distinct spin-1 chains: the XXZ chain with uniaxial anisotropy, the bond-alternating XXZ chain, and the bilinear-biquadratic chain. Our initial results, relying exclusively on (i), show that a simple K-Nearest Neighbors (KNN) model trained on two of the systems can predict the common phases of the previously unseen model with over 70% accuracy. This demonstrates the potential for machine learning models to identify universal phase characteristics and generalizes across different physical Hamiltonians.

 

Registration

Announcement:

Click HERE for online registration
Registration deadline: July 19, 2025

Program

 

Videos and Files


2025-09-08 2025-09-09 2025-09-10 2025-09-11 2025-09-12 2025-09-15 2025-09-16 2025-09-17
  • 11:00 - David Weiss (Penn State University, USA): Hydrodynamization and Local Prethermalization
  • 14:00 - Thomas Iadecola (Iowa State University): Hilbert space fragmentation and many-body scars - 2
  • 16:30 - Ulrich Schneider (Cambridge, England): Ultracold atoms in optical quasicrystals
2025-09-18
  • 11:00 - Marcos Rigol (Penn State University, USA): Onset of Quantum Chaos and Ergoditicy in Spin Systems with Highly Degenerate Hilbert Spaces
  • 14:00 - Antonello Scardicchio (ICTP, Italy): Disorder in quantum systems: Anderson Localization and Many-Body Localization
  • 16:30 - Pieter Claeys (Max Planck Institute for the Physics of Complex Systems, Germany): Free Probability in Quantum Circuits
2025-09-19
  • 11:00 - Antonello Scardicchio (ICTP, Italy): TBA
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Additional Information

Attention! Some participants in ICTP-SAIFR activities have received email from fake travel agencies asking for credit card information. All communication with participants will be made by ICTP-SAIFR staff using an e-mail “@ictp-saifr.org”. We will not send any mailings about accommodation that require a credit card number or any sort of deposit. Also, if you are staying at Hotel Intercity the Universe Paulista, please confirm with the Uber/Taxi driver that the hotel is located at Rua Pamplona 83 in Bela Vista (and not in Jardim Etelvina).

BOARDING PASS: All participants, whose travel has been provided or will be reimbursed by ICTP-SAIFR, should bring the boarding pass  upon registration. The return boarding pass (PDF, if online check-in, scan or picture, if physical) should be sent to secretary@ictp-saifr.org by e-mail.

Visa information: Nationals from several countries in Latin America and Europe are exempt from tourist visa. Nationals from Australia, Canada and USA are exempt from tourist visa until April 10, 2025, but it is unclear if the exemption will be extended after this date.

Accommodation: Participants whose accommodations are provided by ICTP-SAIFR will stay at Hotel Intercity the Universe Paulista. Other hotel recommendations are available here.

Poster presentation: Participants who are presenting a poster MUST BRING A PRINTED BANNER . The banner size should be at most 1 m (width) x 1,5 m (length). We do not accept A4 or A3 paper.