CTP PAS Special Seminar – CFT PAN – Centrum Fizyki Teoretycznej Polskiej Akademii Nauk

Tensor Networks for Quantum Many-Body Modelling: Finite temperature, dynamics, and emergent structure in quantum matter

cft — Fri, 20 Mar 2026 08:05:07 +0000

Abstract:
Strongly interacting quantum systems often reveal their essential physics not through uniform order parameters alone, but through fluctuations, clusters, droplets, and other forms of emergent spatial structure. In this talk, I will present selected results from my work on finite-temperature and non-equilibrium quantum lattice models, including finite-temperature precursor phenomena to stripe order, superconductivity, experiment facing emergent spin–charge correlations in the pseudogap regime, and quantized bubble nucleation in false-vacuum decay. Building on these results, I will describe my long-term research vision at CTP PAS: to address a key gap in the literature by developing a unified tensor-network framework for finite-temperature physics, dynamical phase formation, and weakly open many-body systems, together with an open and reusable software platform for modelling problems relevant to quantum technologies.

This special seminar will take place on 24 March, 11AM-noon, in the ground floor Lecture Hall in Al. Lotników, available on Zoom under the following link:

https://us06web.zoom.us/j/89181532906?pwd=9r0Y5hdvcqNwcvVxEppZcgK4hikT6f.1

ID: 891 8153 2906
Passcode: 355220

Quantum Many-Body Dynamics in the Age of Imperfect Simulations

cft — Thu, 19 Mar 2026 14:24:45 +0000

Abstract:

Quantum simulators, despite being still small-scale and noisy, are already challenging our understanding of many-body physics. Frameworks as thermal equilibrium and universality at phase transitions are being replaced by out-of-equilibrium dynamics and a plethora of non-universal, yet generic mechanisms that take place at finite times and system sizes. In this talk, after having introduced some recent developments in the field, I will present two recent results. First, I will show that, in the 2D quantum Ising model, phase-ordering dynamics can be retarded or impeded altogether by interface localization. I will also show how symmetry rebreaking—a dynamical transition that can destroy the order without ever leaving a symmetry-broken phase—can alter quantum phase ordering at intermediate timescales. Second, I will briefly outline how counterdiabatic driving, a method used so far to reduce diabatic excitations in small systems, can be extended to thermodynamically large systems and provide a classification tool for quantum phase transitions.

This special seminar will take place on 25 March, noon-1PM, in the ground floor Lecture Hall in Al. Lotników, available on Zoom under the following link:

https://us06web.zoom.us/j/86976039901?pwd=Nxw4V42bAvQeF5ao88rbQBLTSHBa5n.1

ID: 869 7603 9901
Passcode: 148188

Monitored quantum systems and entanglement transitions

cft — Thu, 19 Mar 2026 14:03:20 +0000

Abstract:

Quantum measurements do not only reveal the state of a quantum system; when applied continuously or repeatedly, they can qualitatively change its many-body dynamics, suppressing thermalisation via the quantum Zeno effect. In this talk, I will discuss how the competition between unitary evolution and monitoring gives rise to a new class of nonequilibrium critical phenomena: measurement-induced entanglement transitions, separating phases with extensive (volume-law) and subextensive (area-law) entanglement scaling. Over the past several years, this phenomenon has opened a broad research direction at the interface of quantum statistical mechanics, quantum information, and open quantum systems.

We will see how monitored systems can be understood intuitively through several pictures: entanglement growth, purification dynamics, and mappings to stat-mech models. Building on this, I will discuss results on the effects of interactions, disorder, symmetries, and dimensionality, highlighting how one can alter the measurement-induced critical behavior and the dynamical phases. I will conclude by describing how controlled monitoring can be harnessed for quantum information processing (state preparation, error mitigation), pointing to future applications in quantum computing architectures.

This special seminar will take place on 25 March, 11AM-12AM, in the ground floor Lecture Hall in Al. Lotników, available on Zoom under the following link:

https://us06web.zoom.us/j/86976039901?pwd=Nxw4V42bAvQeF5ao88rbQBLTSHBa5n.1

ID: 869 7603 9901
Passcode: 148188

Nonequilibrium Quantum Open Systems: from Numerical Methods to Dynamical Phase Diagrams

cft — Thu, 19 Mar 2026 13:41:55 +0000

Abstract:

Simulating the time evolution of many-body quantum systems remains a major challenge in modern theory. In this talk, I will present my work on controlled diagrammatic Monte Carlo approaches to the dynamics of correlated quantum impurity models [1–3], systems where a small interacting region is coupled to large noninteracting baths. While impurity models play a central role in a variety of contexts ranging from nonequilibrium transport to materials science, I will focus on the paradigmatic physics of the sub-Ohmic spin–boson model. There, we recently showed how transient dynamics after a quench reveals signatures of dissipation-driven quantum criticality and a dynamical phase structure that differs from equilibrium expectations [4]. Finally, I will discuss how this work fits into a broader research vision centered on predictive simulation of quantum many-body systems in and out of equilibrium.

[1] G. Cohen, E. Gull, D. R. Reichman, and A. J. Millis, Phys. Rev. Lett. 115, 266802 (2015).

[2] E. Eidelstein, E. Gull, and G. Cohen, Phys. Rev. Lett. 124, 206405 (2020).

[3] A. Erpenbeck, E. Gull, and G. Cohen, Phys. Rev. Lett. 130, 186301 (2023).

[4] O. Goulko, H.-T. Chen, M. Goldstein, and G. Cohen, Phys. Rev. Lett. 134, 056502 (2025).

This special seminar will take place on 24 March, 1PM-2PM, only ONLINE under the following link:

https://us06web.zoom.us/j/87086754153?pwd=5j9rvjOMWbi0rEdU2IUXAi8WFkjHqo.1

ID: 870 8675 4153
Passcode: 516303

Strange metallicity and superconductivity in quantum many-body systems

cft — Tue, 17 Mar 2026 11:03:50 +0000

Abstract:

Strange metal behavior has been observed in most high temperature superconductors, yet its relationship to unconventional superconductivity remains elusive. In the first part of this talk, I will address this problem using the two-dimensional Yukawa-Sachdev-Ye-Kitaev (2D-YSYK) model, which provides a universal theory of strange metals from spatially random interactions [1]. I will present full numerical solutions of a self-consistent disorder averaged analysis of the 2D-YSYK model. The results reproduce key aspects of observations in the cuprates. Motivated by the recent discovery of superconductivity in twisted bilayer WSe₂, I then turn to this highly tunable moiré platform. I will present our recent progress on the underlying correlation physics based on the notion of topology-induced quantum fluctuations in twisted WSe₂ [2,3]. We identify the possible superconducting pairing channels through symmetry-based classification and energetic analysis, which highlight the natural emergence of topological superconductivity in this system.

In the second part of the seminar, I will outline my long-term vision for developing a research group in quantum modeling within the EUCENTRAL framework. The goal is to advance our understanding of non-equilibrium quantum many-body systems with long-ranged interactions through advanced computational tools. My approach to research software development and maintenance will also be discussed.

[1] C. Li et al., “Strange metal and superconductor in the two-dimensional Yukawa-Sachdev-Ye Kitaev model”, Phys. Rev. Lett. 133, 186502 (2024)

[2] F. Xie, C. Li, et al., Kondo-lattice phenomenology of twisted bilayer WSe₂from compact molecular orbitals of topological bands. arXiv:2503.21769.

This special seminar will take place on 19 March, 2PM-3PM, only ONLINE under the following link:

https://us06web.zoom.us/j/83563474461?pwd=bkUYfdnNA2fxkmgqSF3h5QJQS33FDe.1

Meeting ID: 835 6347 4461
Passcode: 546361

Interacting networks of liquid light

cft — Mon, 16 Mar 2026 09:22:32 +0000

Abstract:

Recent years have seen a surge of advancements in optical manipulation over bosonic quasiparticles known as exciton-polaritons that form in semiconductor microcavities in the strong light-matter coupling regime. Their high Coulomb interaction strengths, nonlinearities, picosecond timescales, and optical addressability makes them an excellent testbed to explore physics at the interface of condensed matter and optics, such as nonequilibrium Bose-Einstein condensation, low threshold lasing, driven superfluidity, and much more. Here, I will present some of my recent results based on a reprogrammable optical platform supporting large-scale coherent networks of coupled exciton-polariton condensates. The flexible in-situ optical tuning over many network- and condensate parameters allows us to simulate and explore a variety of physical systems ranging from (i) the spontaneous synchronization of polariton condensates in the form of time-delayed oscillators, (ii) extended Bloch-mode polariton lasing in two-dimensional artificial optical lattices, (iii) geometrically frustrated pumping patterns promoting high-charge quantized vorticity, (iv) simulation of spin Hamiltonians such as the XY and Ising systems, (v) and fractal diffraction patterns in nonlinear polariton Penrose quasicrystals. Many of these achievements were realized in high quality GaAs-based cavities. If time allows, I will explain how my past research ties into a new generation of materials and cavities based on lead-halide-perovskites that open new opportunities to harness and apply polariton physics at ambient conditions for optical neuromorphic computing, and optoelectronic and spinoptronic technologies.

This special seminar will take place on 19 March, 1PM-2PM, only ONLINE under the following link:

https://us06web.zoom.us/j/83304954210?pwd=xu1mEi7ezWBRmmCONbSxQjIjxib0xm.1

Meeting ID: 833 0495 4210
Passcode: 570749

Many-Body Cavity Quantum-Electrodynamics (QED)

cft — Fri, 13 Mar 2026 09:04:43 +0000

Abstract:

Many-body cavity QED is a rapidly growing field known for intriguing correlated emergent phenomena, including „self-ordering” and „superradiance” [1]. Self-ordering – the spontaneous emergence of order out of disorder and chaos under some critical conditions – is a ubiquitous phenomenon not only in physics, but also in chemistry, biology, social sciences, and many other fields. The most well-known example in physics is the crystallization process, while the other commonly known general examples include the collective bird flocking and fish schooling. In this talk, I will first introduce the basic physics of self-ordering in open atom-cavity quantum systems, which is normally accompanied by the superradiance. I will then present in a pedagogical manner some of our works and predictions in many-body cavity QED. At the end, I will briefly discuss my future research plans.

[1] F. Mivehvar, F. Piazza, T. Donner, H. Ritsch,”Cavity QED with quantum gases: New paradigms in many-body physics”, Advances in Physics 70 (1), 1-153 (2021).

The seminar will take place on Friday 2026-03-19 at 11:00 CET

in the seminar room D, Al. Lotników 32/46, 02-668 Warszawa and under the following link:

https://us06web.zoom.us/j/88435224609?pwd=3rLXEzW6oJCB1r0BH2AQ3wZghTHA1D.1
Meeting ID: 884 3522 4609
Passcode: 174077

Dynamical spatial curvature replaces dark energy: exploding the Hubble tension

dev — Fri, 27 Dec 2024 12:19:37 +0000

The timescape cosmology returns to first principles, with quasilocal gravitational energy replacing dark energy, to explain apparent cosmic acceleration. As inhomogeneities grow, they back react on average cosmic expansion, which differs from conventional FLRW models. Crucially, dynamical spatial curvature arises as time-varying gradients of the kinetic spatial curvature, and depends directly on the void volume fraction. The first investigation of void statistics in cosmological simulations in full general relativity, without Λ, now supports this.

The timescape expansion history is close to ΛCDM, but with differences at a precision which we are now finally probing. Whereas ΛCDM is increasingly challenged -independent observational tests now favour timescape – some with strong Bayesian evidence. I will survey these results, open questions, current limitations, and possible future tests.

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This is a hybrid event:
Room D, the Institute of Physics PAS, Al. Lotników 32/46

Online: Zoom Link, (Passcode: 134595, Meeting ID: 823 8038 0442)

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Engineering topological phases in lattices with ultracold atoms carrying orbital angular momentum

dev — Fri, 27 Dec 2024 12:19:37 +0000

Tunnelling is one of the paradigms of quantum mechanics and its control in the context of ultracold neutral atoms has been, recently, a topic of intense research. In this seminar, we will show that in systems of ultracold atoms carrying orbital angular momentum loaded in certain lattice geometries complex tunnelling amplitudes appear naturally and allow to engineer topological phases. First, we will introduce the single-particle problem in two and three rings coupled side by side [1], which gives us a foundation to describe arbitrary coplanar lattices of identical rings. Then, after introducing some basic concepts about topology, we will sketch two examples of the engineering of topological phases in different systems [2]. Namely, we will introduce a diamond lattice, both in the single-particle limit and in the presence of interactions for the two-body case and a one-dimensional staggered lattice of rings.

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[1] J. Polo, J. Mompart and V. Ahufinger, Geometrically induced complex tunnelings for ultracold atoms carrying orbital angular momentum. Phys. Rev. A 93, 033613 (2016).

[2] E.Nicolau, G. Pelegrı́, J. Polo, A. M. Marques, A. Daley, J. Mompart, R. G. Dias and V. Ahufinger, Ultracold atoms carrying orbital angular momentum: engineering topological phases in lattices. Europhysics Letters (invited perspective article) 145, 35001 (2024).

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This is a hybrid event:
Room D, the Institute of Physics PAS, Al. Lotników 32/46

Online: Zoom Link, (Passcode: 134595, Meeting ID: 823 8038 0442)

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Novel Non-equilibrium Phenomena in Quantum Fluids of Light

dev — Fri, 27 Dec 2024 12:19:37 +0000

Driven-dissipative quantum fluids of light, realised in semiconductor microcavities, circuit or cavity QED systems, provide a unique testbed to explore non-equilibrium quantum phenomena. I will review recent progress in this field. We show [1] that photonic quantum fluid exhibits a non-equilibrium order, where superfluidity is accompanied by stretched exponential decay of correlations — the celebrated Kardar-Parisi-Zhang (KPZ) phase, as well as other unconventional orders [2] and display flow properties connected but distinct from conventional superfluidity [3]. When placed in strained honeycomb lattice, polaritons condense into a rotating state, the lowest Landau level, breaking time reversal symmetry [4]. Describing quantum correlations in open systems in 2D is a numerical challenge. I will present our attempts at developing methods, based on stochastic and tensor network approaches [5].

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[1] A. Zamora et al, PRX 7, 041006 (2017); PRL 125, 265701 (2020); A. Ferrier et al, PRB 105, 205301 (2022).

[2] G. Dagvadorj et al, PRL 130, 136001 (2023); PRB 104, 165301 (2021).

[3] R. T. Juggins et al, Nature Comms. 9, 4062 (2018); I. Timofeev et al, PRB 108, 214513 (2023).

[4] C. Lledo et al, SciPost 12, 068 (2022).

[5] C. Mc Keever et al, PRX 11, 021035 (2021); P. Deuar et al, PRX Quantum, 2, 010319 (2021).

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This is a hybrid event:
Room D, the Institute of Physics PAS, Al. Lotników 32/46

Online: Zoom Link, (Passcode: 134595, Meeting ID: 823 8038 0442)

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