Category: Seminar PoliMi

Wednesday, June 3, 2026 - 15:00
Sala Consiglio (7th floor) - Bd. 14 "Nave", Via Bonardi 9
Politecnico di Milano

Zoom link on request (contact Alessandro Olgiati by email)

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SPEAKER: Maciej Zworski (University of California, Berkeley)

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Localised Davies generator for pseudodifferential operators

A classical Davies generator provides a Lindbladian for which the Gibbs state is stationary. Its construction involves precise knowledge of the Bohr spectrum or equivalently state evolution for all times. Recently Chen, Kastoryano and Gilyen proposed a construction involving localisation in time and carried it out in the case of finite dimensional Hilbert spaces. The resulting generators are called quantum Gibbs samplers as the corresponding Lindblad is expected to settle to the Gibbs state. In this note, we show that the construction also works for classes of unbounded operators, including pseudodifferential operators used in the study of classical/quantum correspondence in Lindblad evolution. We also show that the resulting jump operators are pseudo local.

Wednesday, June 3, 2026 - 11:00
Sala Consiglio (7th floor) - Bd. 14 "Nave", Via Bonardi 9
Politecnico di Milano

Zoom link on request (contact Alessandro Olgiati by email)

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SPEAKER: Stefan Teufel (University of Tübingen)

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Beyond linear response: an Ohm’s law for quantum Hall currents

I will present a recent result that establishes a form of Ohm’s law for the quantum Hall current in models of interacting fermions on a lattice at zero temperature. I will focus on two novel aspects: defining the Hall current properly in order to go beyond linear response calculations and computing this current to all orders in perturbation theory. These two aspects are both based on the concept of non-equilibrium almost stationary states, a form of ‘many-body resonances’ for infinite-volume quantum systems.

Tuesday, May 26, 2026 - 11:00
Sala Consiglio (7th floor) - Bd. 14 "Nave", Via Bonardi 9
Politecnico di Milano

Zoom link on request (contact Alessandro Olgiati by email)

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SPEAKER: Serena Federico (University of Bologna)

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Weyl calculus on graded Lie groups

In this talk, we shall discuss the existence of a Weyl pseudo-differential calculus on a graded Lie G.
To begin with, we will introduce a family of admissible quantizations on G and develop the corresponding pseudo-differential calculus. Afterwards, following classical criteria, we shall identify the suitable candidate Weyl quantization on G among all the admissible symmetric ones. Finally, we will show that in the case of the Heisenberg group, the Weyl quantization is uniquely determined.
This talk is based on a joint work with D. Rottensteiner and M. Ruzhansky.

Friday, May 8, 2026 - 11:00
Sala Consiglio (7th floor) - Bd. 14 "Nave", Via Bonardi 9
Politecnico di Milano

Zoom link on request (contact Alessandro Olgiati by email)

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SPEAKER: Yelena Guryanova (University of Basel / QuantumBasel)

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Cloning Quantum Channels

For states, the no-cloning theorem is one of the first encounters in quantum information: an arbitrary unknown pure state cannot be perfectly copied onto a waiting register. It’s simple then to infer that cloning N states onto M registers won’t work either, but by relaxing the problem to allow for imperfect (approximate) copying, one can investigate the rate and quality of N-to-M cloning. But what if we go further? Can we imagine cloning the cloner, in other words, cloning devices themselves? Questions around states have constituted decades of investigation and were, most recently, extended to cloning unitary gates. In this work we pose the question comprehensively and study general quantum channel cloning via a framework based on higher-order quantum operations. We establish necessary conditions for a family of channels to exhibit super-replication—those that can be cloned with a quadratic rate at high-quality (bounded error). Noisy phase-gate channels can be super-replicated but the full set of noisy unitaries; classical noise; and amplitude damping channels cannot. We present algorithms that search for channel cloners and study specific cloning strategies. In many cases, estimating and re-preparing is enough: for the unitary gates for which super-replication protocols were known, we construct simpler alternatives and establish a direct connection between channel cloning and Bayesian estimation.

Thursday, April 16, 2026 - 15:30
Aula Seminari (3rd floor) - Bd. 14 "Nave", Via Bonardi 9
Politecnico di Milano

Zoom link on request (contact Alessandro Olgiati by email)

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SPEAKER: Hynek Kovařík (Università degli studi di Brescia)

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Cwikel-Lieb-Rozenblum type estimates for magnetic Hamiltonians in dimension two

In this talk I will present Cwikel-Lieb-Rozenblum type inequalities for the number of negative eigenvalues of Pauli and Schroedinger operators in dimension two. The resulting upper bounds are sharp both in the weak as well as the strong coupling limit. In both cases, the nature of the inequality depends on whether the flux of the magnetic field is integer or not. The talk is based on a joint work with Matthias Baur.

Schedule:   Monday, April 28th, 14.00 - 16.00
            Tuesday, April 29th, 10:00 - 12:00
            Wednesday, April 30, 14:00 - 16:00
            Monday, May 5th, 14:00 - 16:00
            Wednesday, May 7th, 14:00 - 16:00


Aula Seminari (3rd floor)
Bd. 14 "Nave", Via Bonardi 9,
D-Mat Mathematics Department of PoliMi, Politecnico di Milano.

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SPEAKER: Douglas Lundholm (Uppsala Universitet)

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Mathematics of the 2D anyon gas

In the theory of quantum statistics, if one follows mathematical logic to its conclusion, one reaches the possibility of intermediate exchange statistics and “anyons”, i.e. identical particles different from bosons and fermions. Over the course of about 50 years this topic has evolved from merely an exotic possibility to an almost inevitability when orientation symmetry is broken, such as in effectively two-dimensional systems subject to rotation or an external magnetic field. The signature example is the fractional quantum Hall effect, and in just the last few years very strong signatures of individual anyons have finally arrived from experiments. However, the many-body theory necessary to study precise collective properties of anyons has remained rather undeveloped until relatively recently. This mini course will focus on the mathematics of the many-anyon gas, introduce some of the main concepts involved, and thus provide a foundation for further exploration of the topic, starting from the toy model of ideal anyons, to more realistic emergent models, and also promising applications to quantum computing.

Lecture plan:

I. Quantum statistics & transmutation

II. Local exclusion & stability

III. The almost-bosonic interacting anyon gas

IV. Emergent models: FQHE & polarons

V. Non-abelian anyons & topological quantum computing

Further information: https://sites.google.com/view/qmp25-intensiveperiod/courses

Tuesday, December 17, 2024 - 11:30

Aula Seminari MOX (6th floor), D-Mat
Mathematics Department of PoliMi
Campus Leonardo, bd.14 "Nave".

Superfluidity and the spectrum of polaron Hamiltonians

I will discuss how superfluidity manifests itself in the spectrum of the Hamiltonian for a test particle travelling through a Bose Einstein condensate.

In the Bogoliubov-Fröhlich polaron model, a stable polaron with momentum P corresponds to a ground state of the Hamiltonian at fixed total momentum. I will explain a recent result in collaboration with Benjamin Hinrichs, which shows that a ground state exists if the momentum is less than mc, where m is the particle mass and c is the slope at zero momentum of the dispersion relation of the Bogoliubov phonons.

Wednesday, November 27, 2024 - 9:00 - 12:30

Sala Consiglio (7th floor), D-Mat
Mathematics Department of PoliMi
Campus Leonardo, bd.14 "Nave".

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Program:

9:00 Karim Thebault (Bristol): “The Universe as an Open Quantum System”

9:45 Mike Cuffaro (Munich): “The Open Systems View (and Algebraic Quantum Field Theory)”

Coffee break

11:00 Sebastien Rivat (Munich): “The Open Systems View in Field Theory”

11:45 Michele Correggi (PoliMi): Quasi-classical Limit of a Spin Coupled to a Reservoir

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Description

The existence of open systems in physics poses outstanding philosophical issues. Indeed, while closed systems can be studied in isolation from the rest of the universe, open systems interact with the environment by exchanging heat and work, information, or matter. As such, open systems are subjected to changes due to uncontrollable external influences, which makes it challenging to precisely determine their properties. Since typical systems in the physical universe are not isolated, providing an adequate description of open systems lies at the heart of contemporary physics. In quantum theory, this issue is further complicated by the presence of entanglement between distant systems. Even more puzzling, at a cosmological scale, it is still a controversial matter whether the whole universe should be considered a closed or open system. The present workshop brings together philosophers and mathematical physicists to discuss the foundations of open systems both from a formal and a conceptual point of view. The invited speakers are Mike Cuffaro (Munich), Michele Correggi (PoliMi), Karim Thebault (Bristol) and Sebastien Rivat (Munich).

Organizing Committee: Antoine Brandelet, Massimo Moscolari and Giovanni Valente – Department of Mathematics, Politecnico di Milano

Participation is free of charge.

Funding: The conference is funded by Line 3 of the “Dipartimento di Eccellenza 2023-2027” on Mathematical features of quantum mechanics (Principal Investigator: Prof. Correggi), and by the Italian Ministry of University and Research within the PRIN 2022 project Analogical Reasoning in Contemporary Physical Theories (ID: 2022F4Z8YH, Principal Investigator: Giovanni Valente).

Wednesday, October 30, 2024 - 14:00

Sala Consiglio (7th floor), D-Mat
Mathematics Department of PoliMi
Campus Leonardo, bd.14 "Nave".

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Semi-classical measures, two scale semi-classical measures and applications

In this lecture, we will present semi-classical measures and show how they  describe the obstructions to strong convergence of bounded families of square integrable functions. We will also describe applications for families of solutions to PDEs, in particular to wave equations.

This initiative is part of the “PhD Lectures” activity of the project “Departments of Excellence 2023-2027” of the Department of Mathematics of Politecnico di Milano. This activity consists of seminars open to PhD students, followed by meetings with the speaker to discuss and go into detail on the topics presented at the talk.

Wednesday, October 9, 2024 - 15:00
Thursday, October 10, 2024 - 11:30

Sala Consiglio (7th floor), D-Mat
Mathematics Department of PoliMi
Campus Leonardo, bd.14 "Nave".

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A quantitative approach to entanglement theory via hypothesis testing (Oct. 9)

I will start by presenting the notion of entanglement as studied in quantum information theory. According to this definition, originally proposed by Werner in 1989, a density operator on a bipartite quantum system is declared to be entangled if it cannot be written as a convex combination of tensor products of single-system density operators, and separable (or unentangled) otherwise. I will then discuss the basics of quantum hypothesis testing and introduce the task of “entanglement testing”, which consists in discriminating a given entangled state from the set of all separable states. This task is a fundamental quantum information primitive, with applications ranging from device certification to gravitational entanglement detection. I will finish by discussing the statement of the “generalised quantum Stein’s lemma”, which connects the ultimate efficiency of entanglement testing with a key entanglement measure known as “relative entropy of entanglement”.

A solution of the generalised quantum Stein’s lemma (Oct. 10)

I will discuss the solution of the generalised quantum Stein’s lemma presented in [Lami, arXiv:2408.06410] (see also [Hayashi/Yamasaki, arXiv:2408.02722] forrelated work), which establishes that the Stein exponent associated with entanglement testing, namely, the quantum hypothesis testing task of distinguishing between n copies of an entangled state and a generic separable state, equals the regularised relative entropy of entanglement. To solve the problem I will briefly introduce two techniques. The first is a procedure called “blurring”, which, informally, transforms a permutationally symmetric state by making it more evenly spread across nearby type classes. I will discuss this technique extensively in the classical case, where it already suffices to prove the generalised Stein’s lemma. Depending on time, I will then present a second technical innovation, which is needed to prove the quantum version of the statement. This consists in a second quantisation step, which lifts the problem from a finite-dimensional system to an infinite-dimensionalbosonic quantum system, where it can then be solved with techniques from continuous-variable quantum information. Rather remarkably, the second-quantised action of the blurring map corresponds to a pure loss channel.


This initiative is part of the “PhD Lectures” activity of the project “Departments of Excellence 2023-2027” of the Department of Mathematics of Politecnico di Milano. This activity consists of seminars open to PhD students, followed by meetings with the speaker to discuss and go into detail on the topics presented at the talk.