- NumPI - Mailing list — Dipartimento di Matematica, UniPI

Upcoming workshop: NumPI day
by Stefano Massei 18 Sep '24

18 Sep '24

Dear all, I am glad to announce to you that Monday 23rd September we will have a one-day workshop of numerical analysis titled NumPI day. Anyone interested is welcome! The event will take place from 9 a.m. to 16 p.m. in the Aula Magna of the department of Mathematics, see the attached schedule. Best regards, Stefano

1 0

[Indico] Dr Maria Strazzullo, Nonlinear Feedback Control via Dynamical Low-Rank Approximation, 09/09/2024, 15:30 Europe/Rome
by noreply＠cs.dm.unipi.it 09 Sep '24

09 Sep '24

Title: Nonlinear Feedback Control via Dynamical Low-Rank Approximation, Speaker(s): Dr Maria Strazzullo, Politecnico di Torino, Date and time: 9 Sept 2024, 15:30 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento Di Matematica (Sala Riunioni). You can access the full event here: https://events.dm.unipi.it/e/288 Abstract -------- Feedback control plays a crucial role in optimizing the performance of dynamical systems by minimizing a predefined cost functional, to stabilize the system towards a desired state. Despite its undeniable effectiveness, the applicability of feedback control is often limited by the high dimensionality of state spaces, a challenge that is even more pronounced in parametric settings. To overcome these limitations, we employ the Dynamical Low-Rank Approximation (DLRA) methodology, which offers an efficient and accurate solution to high-dimensional feedback control problems. Our approach significantly accelerates the solution of State-Dependent Riccati Equations (SDREs) for infinite horizon optimal control by providing a compact, low-dimensional representation of the system that evolves dynamically with respect to the problem. This not only enhances accuracy but also provides effective real-time control, solving several parametric instances simultaneously. To further accelerate the solution of the SDREs, we propose cascade-control (cc-) algorithms that leverage the Riccati solution from a previous parameter to improve the convergence of Newton-based methods applied to SDREs. The robustness and efficiency of our algorithms are validated through nonlinear test cases. Comparative analysis demonstrates that the proposed ccDLRA outperforms global Proper Orthogonal Decomposition model order reduction (ccPOD), offering superior speed and accuracy when compared to the full-order model (ccFOM) solution. Note ---- Reminder for this afternoon's seminar. -- Indico :: Email Notifier https://events.dm.unipi.it/e/288

1 0

[Indico] Dr Maria Strazzullo, Nonlinear Feedback Control via Dynamical Low-Rank Approximation, 09/09/2024, 15:30 Europe/Rome
by fabio.durastante＠unipi.it 05 Sep '24

05 Sep '24

Title: Nonlinear Feedback Control via Dynamical Low-Rank Approximation, Speaker(s): Dr Maria Strazzullo, Politecnico di Torino, Date and time: 9 Sept 2024, 15:30 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento Di Matematica (Sala Riunioni). You can access the full event here: https://events.dm.unipi.it/e/288 Abstract -------- Feedback control plays a crucial role in optimizing the performance of dynamical systems by minimizing a predefined cost functional, to stabilize the system towards a desired state. Despite its undeniable effectiveness, the applicability of feedback control is often limited by the high dimensionality of state spaces, a challenge that is even more pronounced in parametric settings. To overcome these limitations, we employ the Dynamical Low-Rank Approximation (DLRA) methodology, which offers an efficient and accurate solution to high-dimensional feedback control problems. Our approach significantly accelerates the solution of State-Dependent Riccati Equations (SDREs) for infinite horizon optimal control by providing a compact, low-dimensional representation of the system that evolves dynamically with respect to the problem. This not only enhances accuracy but also provides effective real-time control, solving several parametric instances simultaneously. To further accelerate the solution of the SDREs, we propose cascade-control (cc-) algorithms that leverage the Riccati solution from a previous parameter to improve the convergence of Newton-based methods applied to SDREs. The robustness and efficiency of our algorithms are validated through nonlinear test cases. Comparative analysis demonstrates that the proposed ccDLRA outperforms global Proper Orthogonal Decomposition model order reduction (ccPOD), offering superior speed and accuracy when compared to the full-order model (ccFOM) solution. -- Indico :: Email Notifier https://events.dm.unipi.it/e/288

1 0

Seminario a Settembre
by Luca SALUZZI 03 Aug '24

03 Aug '24

Cari tutti, vi mando questa email perche' a Settembre, la settimana del 9-13, verra' in visita Maria Strazzullo dal Politecnico di Torino e vorrei organizzare un suo seminario. Si pensava di farlo o Lunedì 9 o Martedi' 10. Voi avete preferenze su data e orario? Così da permettere di massimizzare il numero di partecipanti. Intanto buone vacanze e ci si vede a Settembre!! Ciao, Luca

2 1

23/07/2024 — R. Van Beeumen — Seminari CN1-SPOKE 10 (Quantum Computing)
by Gianna M. Del Corso 23 Jul '24

23 Jul '24

Dear all, This is a reminder for today’s seminar on quantum computing. Title: Hybrid Quantum-Classical Krylov Methods for Eigenvalue Computation Speaker: Roel Van Beeumen (Lawrence Berkeley National Laboratory) Venue: Sala Gerace, Dipartimento di Informatica Time: Tuesday, 23/07/2024, 14:30 Below the link for the online attendance. https://teams.microsoft.com/l/meetup-join/19%3ameeting_MjliOWRmMDAtMjA4ZC00… Everyone is welcome to attend! Gianna @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

1 0

Seminar on Quantum Computing: Roel Van Beeumen Tuesday 23/7, 14:30
by Gianna M. Del Corso 16 Jul '24

16 Jul '24

Dear All, As part of the CN1-SPOKE 10 on Quantum Computing, we are pleased to announce the last seminar before the summer break. Title: Hybrid Quantum-Classical Krylov Methods for Eigenvalue Computation Speaker: Roel Van Beeumen (Lawrence Berkeley National Laboratory) Venue: Sala Gerace, Dipartimento di Informatica Time: Tuesday, 23/07/2024, 14:30 Abstract: Classical algorithms based on Krylov subspaces are among the most successful tools in the field of numerical linear algebra. More recently, the emergence of quantum subspace methods has resulted in a promising class of hybrid quantum-classical algorithms for eigenvalue approximation, e.g., in the fields of condensed matter physics and electronic structure theory. These quantum Krylov methods harness quantum computers to generate the subspace basis states and retrieve the projected problem through quantum measurement. However, the classical computation of the Ritz values often poses challenges due to the ill-conditioning of the associated generalized eigenvalue problem. In this talk, we present an overview of quantum subspace algorithms from a numerical linear algebra perspective. We discuss strategies to avoid solving an ill-conditioned eigenvalue problem, explain their implementation on quantum computers, and provide numerical and theoretical evidence of their convergence. Furthermore, we present strategies to improve the robustness, especially in the presence of noise. Everyone is welcome to attend! Gianna @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

1 0

[Indico] Dr Jie Meng, Theoretical and computational properties of quasi-Toeplitz M-matrices, 15/07/2024, 15:00 Europe/Rome
by fabio.durastante＠unipi.it 14 Jul '24

14 Jul '24

Title: Theoretical and computational properties of quasi-Toeplitz M-matrices, Speaker(s): Dr Jie Meng, Ocean University of China, Date and time: 15 Jul 2024, 15:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Sala Riunioni). You can access the full event here: https://events.dm.unipi.it/e/287 Abstract -------- A quasi-Toeplitz matrix is a semi-infinite matrix of the form $A=T(a)+E$, where $T(a)$ is a Toeplitz matrix with entries $(T(a))_{i,j}=a_{j-i}$, for $a_{j-i}\in\mathbb C$, $i,j\ge 1$ and $E$ is a compact correction. Quasi-Toeplitz $M$-matrices are encountered in the study of quadratic matrix equations arising in the analysis of a 2-dimensional Quasi-Birth-Death (QBD) stochastic process. We investigate the properties of such matrices and provide conditions under which a quasi-Toeplitz matrix is an $M$-matrix. We show that under a mild and easy-to-check condition, an invertible quasi-Toeplitz $M$-matrix has a unique square root that is an $M$-matrix possessing quasi-Toeplitz structure. Some issues concerning the computation of the square root of quasi-Toeplitz $M$-matrices are discussed and numerical experiments are performed -- Indico :: Email Notifier https://events.dm.unipi.it/e/287

1 0

Difesa dottorato
by Angelo Alberto CASULLI 12 Jul '24

12 Jul '24

Cari tutti, Lunedì 22 luglio alle 14.30 discuterò la mia tesi di dottorato dal titolo "Block rational Krylov methods for matrix equations and matrix functions" presso la Scuola Normale. Chiunque abbia piacere di partecipare è il benvenuto! Seguirà un piccolo rinfresco nel chiostro della Scuola. A presto, Angelo Casulli

1 0

[Indico] Dr Jie Meng, Theoretical and computational properties of quasi-Toeplitz M-matrices, 7/15/24, 3:00 PM Europe/Rome
by fabio.durastante＠unipi.it 04 Jul '24

04 Jul '24

Title: Theoretical and computational properties of quasi-Toeplitz M-matrices, Speaker(s): Dr Jie Meng, Ocean University of China, Date and time: Jul 15, 2024, 3:00 PM (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Sala Riunioni). You can access the full event here: https://events.dm.unipi.it/e/287 Abstract -------- A quasi-Toeplitz matrix is a semi-infinite matrix of the form $A=T(a)+E$, where $T(a)$ is a Toeplitz matrix with entries $(T(a))_{i,j}=a_{j-i}$, for $a_{j-i}\in\mathbb C$, $i,j\ge 1$ and $E$ is a compact correction. Quasi-Toeplitz $M$-matrices are encountered in the study of quadratic matrix equations arising in the analysis of a 2-dimensional Quasi-Birth-Death (QBD) stochastic process. We investigate the properties of such matrices and provide conditions under which a quasi-Toeplitz matrix is an $M$-matrix. We show that under a mild and easy-to-check condition, an invertible quasi-Toeplitz $M$-matrix has a unique square root that is an $M$-matrix possessing quasi-Toeplitz structure. Some issues concerning the computation of the square root of quasi-Toeplitz $M$-matrices are discussed and numerical experiments are performed -- Indico :: Email Notifier https://events.dm.unipi.it/e/287

1 0

[Indico] Taejun Park, A low-rank approximation of parameter-dependent matrices via CUR decomposition, 13/06/2024, 11:00 Europe/Rome
by leonardo.robol＠unipi.it 11 Jun '24

11 Jun '24

Title: A low-rank approximation of parameter-dependent matrices via CUR decomposition, Speaker(s): Taejun Park, University of Oxford, Date and time: 13 Jun 2024, 11:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Sala Riunioni). You can access the full event here: https://events.dm.unipi.it/e/285 Abstract -------- Finding a low-rank approximation for parameter-dependent matrices $A(t)$ is an important task appearing in dynamical systems and image series compression. In this talk, we present an efficient randomized algorithm that computes a low-rank approximation of $A(t)$ at finite specified parameter values using the CUR decomposition. The key idea lies in reusing the same or a similar set of column and row indices for the CUR decomposition at nearby parameter values. The resulting algorithm is rank-adaptive, certifiable and has complexity that compares favorably to existing methods. This is joint work with Yuji Nakatsukasa. -- Indico :: Email Notifier https://events.dm.unipi.it/e/285

1 0

Fwd: seminario Pearson: 6 giugno alle 14:30
by Fabio Durastante 31 May '24

31 May '24

Buonasera, Inoltro il seguente annuncio di seminario. Saluti, Fabio -------- Messaggio Inoltrato -------- Oggetto: seminario Pearson: 6 giugno alle 14:30 Data: Wed, 29 May 2024 12:12:19 +0200 Mittente: Mariarosa Mazza <mariarosa.mazza(a)uniroma2.it> A: mariarosa.mazza(a)uniroma2.it Car* tutt*, giovedi 6 giugno alle 14.30 in aula Dal Passo, Dipartimento di Matematica, Roma Tor Vergata, il Prof. John Pearson (University of Edinburgh) terrà un seminario dal titolo: "Recent Developments in the Numerical Solution of PDE-Constrained Optimization Problems". Il seminario può essere seguito online usando il link: https://teams.microsoft.com/l/meetup-join/19%3ad48916dee7364e0bbb08216ea621… Vi prego di diffondere l'annuncio fra i possibili interessati. Grazie, Mariarosa ----------------------------------------------- ABSTRACT: Optimization problems subject to PDE constraints form a mathematical tool that can be applied to a wide range of scientific processes, including fluid flow control, medical imaging, option pricing, biological and chemical processes, and electromagnetic inverse problems, to name a few. These problems involve minimizing some function arising from a particular physical objective, while at the same time obeying a system of PDEs which describe the process. It is necessary to obtain accurate solutions to such problems within a reasonable CPU time, in particular for time-dependent problems, for which the “all-at-once” solution can lead to extremely large linear systems. In this talk we consider iterative methods, in particular Krylov subspace methods, to solve such systems, accelerated by fast and robust preconditioning strategies. In particular, we will survey several new developments, including block preconditioners for fluid flow control problems, a circulant preconditioning framework for solving certain optimization problems constrained by fractional differential equations, and multiple saddle-point preconditioners for block tridiagonal linear systems. We will illustrate the benefit of using these new approaches through a range of numerical experiments. This talk is based on work with Santolo Leveque (Scuola Normale Superiore, Pisa), Spyros Pougkakiotis (Yale University), Jacek Gondzio (University of Edinburgh), and Andreas Potschka (TU Clausthal). This talk is part of the activity of the MUR Excellence Department Project MatMod@TOV (CUP E83C23000330006). -- ------------------------------------- Dr. Mariarosa Mazza University of Rome Tor Vergata Via della Ricerca Scientifica, 1 00133, Rome, Italy Email:mariarosa.mazza@uniroma2.it Tel: 0039 06-7259-4636 Url:https://sites.google.com/site/mariarosamazza1/ ---------------------------------

1 0

Due Giorni di Algebra Lineare Numerica e Applicazioni @ UNIPI 20/21 January 2025
by Fabio Durastante 31 May '24

31 May '24

We are pleased to announce the next edition of the Due Giorni di Algebra Lineare Numerica e Applicazioni @ UNIPI 20/21 January 2025 This is the 20th workshop in a series dedicated to Numerical Linear Algebra and Applications. It aims at gathering the Italian Numerical Linear Algebra scientific community to discuss recent advances in this area and to promote the exchange of novel ideas and collaboration among researchers. We strongly encourage contributions by junior scholars on theoretical and computational topics, as well as on applications. Contributions covering other areas requiring tools from Numerical Linear Algebra are very welcome. Topics of interest include (but are not limited to): iterative methods for large-scale linear systems, preconditioning, eigen and singular values, numerical optimization, numerical dynamical systems, mathematics of machine learning, structured matrices, tensors, matrix functions, Krylov methods, randomized linear algebra algorithms, and high-performance computing for matrix computations. Applications include optimization and control, image processing and inverse problems, networks and graphs, machine learning and artificial neural networks, uncertainty quantification, finance, material sciences, life sciences, and industrial processes. Steering committee: M. Benzi, M. Donatelli, N. Guglielmi, B. Meini, V. Simoncini Important dates: - Registration is open with Deadline 30 Nov 2024 - Call for Abstracts is open with Deadline 30 Nov 2024 Location: - Area Bruno Pontecorvo of the University of Pisa The conference is without registration fee, but registration is mandatory. There is a limited amount of support for PhD students who want to attend the event, application can be done through the registration form. Full information are available at the web-page: https://events.dm.unipi.it/event/280/ The organizing committee, P. Boito, G.M. Del Corso, F. Durastante, S. Gazzola, L. Heltai, S. Massei, C. Pagliantini, F. Poloni, L. Robol.

1 0

[Indico] Taejun Park, A low-rank approximation of parameter-dependent matrices via CUR decomposition, 13/06/2024, 11:00 Europe/Rome
by leonardo.robol＠unipi.it 31 May '24

31 May '24

Title: A low-rank approximation of parameter-dependent matrices via CUR decomposition, Speaker(s): Taejun Park, University of Oxford, Date and time: 13 Jun 2024, 11:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Sala Riunioni). You can access the full event here: https://events.dm.unipi.it/e/285 Abstract -------- Finding a low-rank approximation for parameter-dependent matrices $A(t)$ is an important task appearing in dynamical systems and image series compression. In this talk, we present an efficient randomized algorithm that computes a low-rank approximation of $A(t)$ at finite specified parameter values using the CUR decomposition. The key idea lies in reusing the same or a similar set of column and row indices for the CUR decomposition at nearby parameter values. The resulting algorithm is rank-adaptive, certifiable and has complexity that compares favorably to existing methods. This is joint work with Yuji Nakatsukasa. -- Indico :: Email Notifier https://events.dm.unipi.it/e/285

1 0

Reminder: seminar of the quantum series. Taday at 15:00 G. De Palma
by Gianna M. Del Corso 27 May '24

27 May '24

This is a reminder for today’s seminar: Title: Quantum neural networks are Gaussian processes Speaker: Giacomo De Palma (University of Bologna) Venue: sala Galilei, room 131, Ed. C, Polo Fibonacci Time: Monday, 27/05/2024, 15:00 Here the link for attending online https://teams.microsoft.com/l/meetup-join/19%3ameeting_YWY5ZTRjN2MtOWI5OC00… <https://teams.microsoft.com/l/meetup-join/19:meeting_YWY5ZTRjN2MtOWI5OC00OD…> Gianna @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

1 0

[Indico] Dierk Schleicher, The Weierstrass and Ehrlich-Aberth root finders as dynamical systems, 24/05/2024, 16:00 Europe/Rome
by leonardo.robol＠unipi.it 23 May '24

23 May '24

Title: The Weierstrass and Ehrlich-Aberth root finders as dynamical systems, Speaker(s): Dierk Schleicher, Aix-Marseille Université, Date and time: 24 May 2024, 16:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Aula Seminari). You can access the full event here: https://events.dm.unipi.it/e/282 Abstract -------- Finding roots of complex polynomials in one variable is a fundamental challenge at the interface of theoretical and applied mathematics, as well as in many applications. Many methods have been proposed; the best known is Newton’s method that tries to find a single root at a time. There are several methods that try to approximate all roots at the same time. The best known are the Weierstrass—Durand—Kerner and Ehrlich—Aberth methods. These are known to work very well in practice, but little is known about their properties as global dynamical systems. We discuss various global dynamical properties, especially the search for attracting periodic orbits (which rule out general convergence) and orbits that diverge to infinity. This reports on joint work, partially still in progress, with Bernhard Reinke, Michael Stoll, and others. -- Indico :: Email Notifier https://events.dm.unipi.it/e/282

1 0

[Indico] Dierk Schleicher, The Weierstrass and Ehrlich-Aberth root finders as dynamical systems, 24/05/2024, 16:00 Europe/Rome
by leonardo.robol＠unipi.it 20 May '24

20 May '24

Title: The Weierstrass and Ehrlich-Aberth root finders as dynamical systems, Speaker(s): Dierk Schleicher, Aix-Marseille Université, Date and time: 24 May 2024, 16:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Aula Seminari). You can access the full event here: https://events.dm.unipi.it/e/282 Abstract -------- Finding roots of complex polynomials in one variable is a fundamental challenge at the interface of theoretical and applied mathematics, as well as in many applications. Many methods have been proposed; the best known is Newton’s method that tries to find a single root at a time. There are several methods that try to approximate all roots at the same time. The best known are the Weierstrass—Durand—Kerner and Ehrlich—Aberth methods. These are known to work very well in practice, but little is known about their properties as global dynamical systems. We discuss various global dynamical properties, especially the search for attracting periodic orbits (which rule out general convergence) and orbits that diverge to infinity. This reports on joint work, partially still in progress, with Bernhard Reinke, Michael Stoll, and others. -- Indico :: Email Notifier https://events.dm.unipi.it/e/282

1 0

Next week's seminar on quantum Computing : Monday 20 at 17:00 Oliver Morsch
by Gianna M. Del Corso 16 May '24

16 May '24

Dear All, As part of the CN1-SPOKE 10 on Quantum Computing, we are organizing a weekly seminar series. Next week's there will be: Title: Rydberg qubits for simulation and sensing Speaker: Oliver Morsch (CNR-INO and University of Pisa) Venue: Seminar room of Math department (1st floor on the left) Time: Monday, 20/05/2024, 17:00 Abstract: In recent years, Rydberg atoms have been increasingly used in several quantum technologies. In this talk I will give a brief introduction to Rydberg qubits and their applications in quantum simulation and quantum sensing. I will then give some examples of our recent work on these two technologies: the simulation of open quantum systems (phase transitions in driven quantum systems with controlled dissipation) and spatially resolved temperature measurements in a cold atomic gas using Rydberg- Doppler broadening thermometry. Everyone is welcome! GIanna @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

1 0

Next week's seminars on quantum Computing : Monday 6 and Friday 10
by Gianna M. Del Corso 02 May '24

02 May '24

Dear All, As part of the CN1-SPOKE 10 on Quantum Computing, we are organizing a weekly seminar series. This week, exceptionally we will have two seminars: Title: The effect of phase noise in superconducting qubit control Speaker: Agata Barsotti (Università di Pisa) Venue: room 250, first floor Ed. C, Polo Fibonacci (Physics Dept.) Time: Monday, 06/05/2024, 17:00 At the end of the same week there is: Title: Certified randomness from single-particle entanglement Speaker: Sonia Mazzucchi (Università di Trento) Venue: Sala Gerace, Ed. C Polo Fibonacci (Computer Science Dept.) Time: Friday, 10/05/2024, 16:00 The abstracts of both the seminars are attached. Everyone is welcome! Gianna Del Corso @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

1 0

Next week's seminar on quantum Computing : Today at 14:00 Lindsay Bassman Oftelie
by Gianna M. Del Corso 22 Apr '24

22 Apr '24

Dear all, this message is a reminder for today's quantum series seminar. Title: Dynamic Cooling of Qubits on Contemporary Quantum Computers Speaker: Lindsay Bassman Oftelie (NEST-CNR) Venue: Sala Polifunzionale, Ed. C, Polo Fibonacci (Dip. Informatica) Time: Monday, 22/04/2024, 14:00 Abstract: Quantum computers require qubits to be initialized in a pure (i.e., cold) state for successful computation. Dynamic cooling offers a route to effectively lower qubit temperatures beyond what is possible with direct, physical cooling techniques. It works by cooling a subset of qubits, at the expense of heating others, by applying certain logic gates to the entire system. While it was initially dismissed as impractical for the high-temperature NMR-based quantum computers available at the time of its inception, we show how dynamic cooling is substantially more effective and efficient on the low-temperature quantum computers available today. In this talk, we will examine how optimal dynamic cooling scales with total system size, in terms of the minimal achievable final temperature, the work cost, and the complexity of the associated quantum circuits. We will observe the effect of hardware noise on cooling and we will propose a sub-optimal dynamic cooling scheme with fixed (low) complexity to improve the feasibility of implementation on noisy quantum hardware. Here the link for the online attendance https://teams.microsoft.com/l/meetup-join/19%3ameeting_YzgwYmY4NDMtZWUwZi00… <https://teams.microsoft.com/l/meetup-join/19:meeting_YzgwYmY4NDMtZWUwZi00Mz…> See you there. Gianna Del Corso @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

1 0

Next week's seminar on quantum Computing : Lindasy Bassman Oftelie
by Gianna M. Del Corso 16 Apr '24

16 Apr '24

Dear all, As part of the CN1-SPOKE 10 on Quantum Computing, we are organizing a weekly seminar series. Next week’s seminar is: Title: Dynamic Cooling of Qubits on Contemporary Quantum Computers Speaker: Lindsay Bassman Oftelie (NEST-CNR) Venue: Sala Polifunzionale, Ed. C, Polo Fibonacci (Dip. Informatica) Time: Monday, 22/04/2024, 14:00 Abstract: Quantum computers require qubits to be initialized in a pure (i.e., cold) state for successful computation. Dynamic cooling offers a route to effectively lower qubit temperatures beyond what is possible with direct, physical cooling techniques. It works by cooling a subset of qubits, at the expense of heating others, by applying certain logic gates to the entire system. While it was initially dismissed as impractical for the high-temperature NMR-based quantum computers available at the time of its inception, we show how dynamic cooling is substantially more effective and efficient on the low-temperature quantum computers available today. In this talk, we will examine how optimal dynamic cooling scales with total system size, in terms of the minimal achievable final temperature, the work cost, and the complexity of the associated quantum circuits. We will observe the effect of hardware noise on cooling and we will propose a sub-optimal dynamic cooling scheme with fixed (low) complexity to improve the feasibility of implementation on noisy quantum hardware. Everyone is welcome! Please, note the change of venue and time. ======================================================================= @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

1 0

[Indico] Ivan Bioli, Preconditioned Low-Rank Riemannian Optimization for Multiterm Linear Matrix Equations, 11/04/2024, 16:00 Europe/Rome
by fabio.durastante＠unipi.it 10 Apr '24

10 Apr '24

Title: Preconditioned Low-Rank Riemannian Optimization for Multiterm Linear Matrix Equations, Speaker(s): Ivan Bioli, Università degli Studi di Pavia, Date and time: 11 Apr 2024, 16:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Aula Seminari). You can access the full event here: https://events.dm.unipi.it/e/268 Abstract -------- We focus on the development and analysis of Riemannian optimization methods for solving multiterm linear matrix equations, when the associated linear operator is symmetric positive definite. Assuming low-rank approximability of the solution, we employ first- and second-order Riemannian optimization algorithms on low-rank matrix manifolds. To enhance competitiveness with existing solvers on realistic problems, significant efforts are dedicated to developing efficient Riemannian preconditioners, which are interpreted as changing the Riemannian metric. By alternating between fixed-rank Riemannian optimization and rank updates, we devise a rank-adaptive algorithm that does not require fixing the rank a priori. In numerical experiments, we illustrate the effectiveness of the developed Riemannian preconditioners, comparing our approach with established solvers such as Conjugate Gradient with truncation. Results indicate that the Riemannian optimization approach, in both its fixed-rank and rank-adaptive variants, is competitive with other solvers and can avoid excessive growth of ranks in intermediate iterations. References [Bou23] Nicolas Boumal. An Introduction to Optimization on Smooth Manifolds. 1st ed. Cambridge University Press, Mar. 16, 2023. [KSV16] Daniel Kressner, Michael Steinlechner, and Bart Vandereycken. “Preconditioned Low-rank Riemannian Optimization for Linear Systems with Tensor Product Structure”. In: SIAM Journal on Scientific Computing 38.4 (Jan. 2016), A2018–A2044. [VV10] Bart Vandereycken and Stefan Vandewalle. “A Riemannian Optimization Ap proach for Computing Low-Rank Solutions of Lyapunov Equations”. In: SIAM Journal on Matrix Analysis and Applications 31.5 (Jan. 2010), pp. 2553–2579. -- Indico :: Email Notifier https://events.dm.unipi.it/e/268

1 0

Next week's seminar on quantum Computing : Leonardo Banchi
by Gianna M. Del Corso 05 Apr '24

05 Apr '24

Dear all, As part of the CN1-SPOKE 10 on Quantum Computing, we are organizing a weekly seminar series. Next week’s seminar is: Title: Statistical Complexity of Quantum Learning Speaker: Leonardo Banchi (Università degli Studi di Firenze) Venue: Room 250, Ed. C, Polo Fibonacci (Physics Department, first floor) Time: Monday, 08/04/2024, 17:00 Abstract: Recent years have seen significant activity on the problem of using data for the purpose of learning properties of quantum systems or of processing classical or quantum data via quantum computing. As in classical learning, quantum learning problems involve settings in which the mechanism generating the data is unknown, and the main goal of a learning algorithm is to ensure satisfactory accuracy levels when only given access to data and, possibly, side information such as expert knowledge. I will introduce the complexity of quantum learning using information-theoretic techniques by focusing on data complexity, copy complexity, and model complexity. Copy complexity arises from the destructive nature of quantum measurements, which irreversibly alter the state to be processed, limiting the information that can be extracted about quantum data. For example, in a quantum system, unlike in classical machine learning, it is generally not possible to evaluate the training loss simultaneously on multiple hypotheses using the same quantum data. To make the seminar approachable by different research communities, I will provide extensive background material on classical results from statistical learning theory, as well as on the distinguishability of quantum states. Throughout, we highlight the differences between quantum and classical learning by addressing both supervised and unsupervised learning, and discuss potential advantages. Reference: arXiv:2309.11617 - Adv. Quant. Tech 2024 - in press Everyone is welcome! @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

1 0

[Indico] Ivan Bioli, Preconditioned Low-Rank Riemannian Optimization for Multiterm Linear Matrix Equations, 11/04/2024, 16:00 Europe/Rome
by fabio.durastante＠unipi.it 04 Apr '24

04 Apr '24

Title: Preconditioned Low-Rank Riemannian Optimization for Multiterm Linear Matrix Equations, Speaker(s): Ivan Bioli, École Polytechnique Fédérale de Lausanne, Date and time: 11 Apr 2024, 16:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Aula Seminari). You can access the full event here: https://events.dm.unipi.it/e/268 Abstract -------- We focus on the development and analysis of Riemannian optimization methods for solving multiterm linear matrix equations, when the associated linear operator is symmetric positive definite. Assuming low-rank approximability of the solution, we employ first- and second-order Riemannian optimization algorithms on low-rank matrix manifolds. To enhance competitiveness with existing solvers on realistic problems, significant efforts are dedicated to developing efficient Riemannian preconditioners, which are interpreted as changing the Riemannian metric. By alternating between fixed-rank Riemannian optimization and rank updates, we devise a rank-adaptive algorithm that does not require fixing the rank a priori. In numerical experiments, we illustrate the effectiveness of the developed Riemannian preconditioners, comparing our approach with established solvers such as Conjugate Gradient with truncation. Results indicate that the Riemannian optimization approach, in both its fixed-rank and rank-adaptive variants, is competitive with other solvers and can avoid excessive growth of ranks in intermediate iterations. References [Bou23] Nicolas Boumal. An Introduction to Optimization on Smooth Manifolds. 1st ed. Cambridge University Press, Mar. 16, 2023. [KSV16] Daniel Kressner, Michael Steinlechner, and Bart Vandereycken. “Preconditioned Low-rank Riemannian Optimization for Linear Systems with Tensor Product Structure”. In: SIAM Journal on Scientific Computing 38.4 (Jan. 2016), A2018–A2044. [VV10] Bart Vandereycken and Stefan Vandewalle. “A Riemannian Optimization Ap proach for Computing Low-Rank Solutions of Lyapunov Equations”. In: SIAM Journal on Matrix Analysis and Applications 31.5 (Jan. 2010), pp. 2553–2579. -- Indico :: Email Notifier https://events.dm.unipi.it/e/268

1 0

Next seminar on Quantum Computing : Simone Montangero Monday 25 h.16:00
by Gianna M. Del Corso 21 Mar '24

21 Mar '24

Dear All, As part of the CN1-SPOKE 10 on Quantum Computing, we are organizing a weekly seminar series. Next week’s seminar is: Title: Platforms and methods for quantum computing Speaker: Simone Montangero (University of Padova) Venue: Sala Gerace, Dipartimento di Informatica Time: Monday, 25/03/2024, 16:00 Abstract: We present an overview of the current status of the quantum computing landscape, presenting some fo the most developed hardware platforms together with a selection of recent results and methods currently driving the technological development of this potentially disruptive technology. Everyone is welcome! PS. Note that the seminar is at 4:00PM and not at 5Pm as usual ============================================================================== @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

1 0

Seminario CN1-SPOKE 10 (Quantum Computing) today
by Gianna M. Del Corso 11 Mar '24

11 Mar '24

Dear All, As part of the CN1-SPOKE 10 on Quantum Computing, we are organizing a weekly seminar series. This week’s seminar is: Title: Hybrid Variational Algorithms for Classical and Quantum Complex Systems Speaker: Elisa Ercolessi (University of Bologna) Venue: Sala Galilei, room 131 ground floor, Bldg C (Dipartimento di Fisica) Time: Monday, 11/03/2024, 17:00 Abstract: Quantum Computing is seen as a potential breakthrough for the study of hard classical problems as well as for quantum many body systems. However, we are in the era of NISQ devices and still far away from fault-tolerant machines. This leads us to consider the possibility of hybrid classical-quantum protocols of variational type: they exploit quantum resources to efficiently prepare states that depend on a suitable chosen set of variational parameters, which can then be determined by means of optimization algorithms to be run on a classical computer. The choice of such classical optimizer schemes is to be guided by compatibility requirements with respect to current available quantum platforms. To evaluate the feasibility of such an approach, we present different applications of the Quantum Approximate Optimization Algorithm to both classical and quantum systems implemented by means of emulations of the full protocol on a classical hardware as well as a case study that has been run on a real Rydberg atom quantum machine. Everyone is welcome! Gianna @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

1 0

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

NumPI