Le Centre de Physique Théorique (CPHT) réunit des chercheurs dont les activités couvrent un large spectre de la Physique, tant dans ses aspects fondamentaux qu'appliqués.
Le CPHT est une unité mixte de recherche (UMR 7644) du Centre National de la Recherche Scientifique (CNRS) et de l’Ecole polytechnique. Au niveau du CNRS, il est rattaché à l’Institut de physique. Il est dirigé par Jean-René Chazottes, directeur de Recherche au CNRS.
Le CPHT est implanté sur le site de l’Ecole Polytechnique à Palaiseau, dans le bâtiment 6 et dans l'aile 0 du bâtiment 5. Le secrétariat se situe dans le Bâtiment 6, bureaux 06.1046 et 06.1045. 
 

Adresse postale : 
CPHT 
Ecole Polytechnique 
91128 Palaiseau cedex 
France

Tél. Secrétariat : 01 69 33 42 01

Pour écrire un email à un membre du laboratoire : prenom.nom@polytechnique.edu

 

 

The Summer School will take place from July 7 to July 17 2020 at the Institut d'Etudes Scientifiques de Cargèse, located on the west cost of the beautiful Corsica island, nearby the city of Ajaccio.

The purpose of this Summer School is to train the next generation of young researchers in the field of quantum simulation and, more generally, quantum technologies. Grouping together a diverse community as well as young and leading senior researchers, we expect a stimulating cross-fertilization of ideas, methods, and approaches, able to further develop this fields beyond the present frontiers.

Information about the Summer School, including a list of speakers and application forms can be found on the website: 
https://quantsim2020.sciencesconf.org

Important dates
Opening of applications: Mon, 24 Feb 2020
Deadline for application: Fri, 20 March 2020
Notification of acceptance: Mid-April
Deadline for registration: Mon, 15 May 2020

Organizers 
Thierry Giamarchi, Giacomo Roati, and Laurent Sanchez-Palencia

 

 

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Silke Biermann, Présidente du Département de Physique à l'Ecole Polytechnique, Professeur à l'Ecole Polytechnique et chercheuse au Centre de Physique Théorique, s'est vue décerner la médaille d'argent du CNRS pour ses travaux développant des approches de calculs de structures électroniques pour les matériaux corrélés à partir de premiers principes.

La médaille d'argent distingue des chercheurs et des chercheuses pour l'originalité, la qualité et l'importance de leurs travaux, reconnus sur le plan national et international.

Français

 

JEUDI 13 FEVRIER 14h  SALLE LOUIS MICHEL

BALT VAN REES

QANTUM FIELD THEORY in ANTI-DE SITTER and the S-MATRIX

Abstract:
We discuss results obtained by considering gapped QFTs in a fixed Anti-de Sitter background. Much like in the AdS/CFT correspondence, we can naturally define
'boundary' observables that exhibit conformal invariance in one dimension less. These observables can be analyzed using conformal bootstrap techniques which results in new non-perturbative bounds on the strength of the coupling constants in a general QFT. When we send the AdS curvature to zero the boundary observables should morph into the S-matrix of the flat-space QFT. We will discuss the different ways in which this connection can be made explicit, and how it might end up teaching us new lessons about the non-perturbative structure of scattering amplitudes.

JEUDI 13 FEVRIER  15h15   SALLE LOUIS MICHEL

JÜRG FRÖHLICH

THE FOURTH PILLAR which QUANTUM MECHANICS RESTS UPON

Abstract:
Traditionally, the three concepts of states, observables and unitary evolution form the pillars Quantum Mechanics is built upon. It is well known that they do not suffice to solve, for example, the so-called measurement problem.
In this talk I will describe a fourth fundamental concept, proposed only recently, namely the "Principle of Diminishing Potentialities". I will then show how it enables one to come up with a precise notion of "events" in Quantum Mechanics and with a new understanding of the time evolution of states of isolated systems.
 As results, the "measurement problem" and the unitarity- or information paradox disappear, and a "Quantum Mechanics without Observers" emerges. 

 

Français

 

Le prochain colloquium du CPHT aura lieu jeudi 6 février à 14h en salle Louis Michel.

Il sera donné par Zaki Leghtas, qui nous parlera d'information quantique. 

"Quantum computing with Schrödinger cat states"

Superconducting qubits are one of the most promising platforms to implement quantum technologies. Quantum processors of tens of qubits are now available, and exciting applications with these intermediate size systems are in perspective. However, many algorithms, including all those with a proved quantum speed-up, require extremely low error rates. This will most likely require quantum error correction (QEC). Unfortunately, current QEC architectures require daunting overheads in physical qubits and control electronics. The goal of this research is to reduce this overhead, and our approach is based on two key ideas. First, we redundantly encode quantum information in Schrödinger cat states embedded in superconducting resonators. Second, we engineer non-linear dissipation to protect and manipulate this information.

Français

 

Le processus de définition de la stratégie européenne en physique des particules est en son cours. Après la réunion de Grenade, le « Physics Briefing Book » a été publié en septembre, et depuis le groupe restreint sur la stratégie prépare la session de rédaction de Bad Honnef (20-24 janvier 2020) qui doit déboucher sur des recommandations qui seront données au Conseil du CERN.

Plusieurs scénarios de futurs collisionneurs sont discutés dans ce cadre-là. Nous vous proposons d'échanger ensemble à ce sujet, le lundi 13 janvier de 14h à 17h dans l'amphi Charpak du LPNHE. Il s'agira notamment de présenter les scénarios considérés et de discuter d'une position commune française à défendre à Bad Honnef.

Inscription (gratuite mais indispensable) sur https://indico.in2p3.fr/event/20221/

Divers documents d’information sont disponibles aux liens suivants:

http://arxiv.org/abs/1912.11871

https://arxiv.org/abs/1912.13466

http://cds.cern.ch/record/2705370

 

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Soutenance de thèse au CPHT  le mardi 17 décembre 2019, 14h00 au Centre de Physique Théorique

Julien Despres
(Groupe Matière condensée)

"Correlation spreading in quantum lattice models with variable-range interactions"

Salle de conférence Louis Michel, CPHT, Bâtiment 6

 

In this thesis, we have investigated the spreading of quantum correlations in isolated lattice models with short- or long-range interactions driven far from equilibrium via sudden global quenches. A main motivation for this research topic was to shed new light on the conflicting results in the literature concerning the scaling law of the correlation edge, its lack of universality and the incompleteness of the existing physical pictures to fully characterize the propagation of quantum correlations. To do so, we have presented a general theoretical approach relying on a quasiparticle theory. The latter has permitted to unveil a generic expression for the equal-time connected correlation functions valid both for short-range and long-range interacting particle and spin lattice models on a hypercubic lattice. Relying on stationary phase arguments, we have shown that its causality cone displays a universal twofold structure consisting of a correlation edge and a series of local extrema defining the outer and inner structure of the space-time correlations. For short-range interactions, the motion of each structure is ballistic and the associated spreading velocities are related to the group and phase velocites of the quasiparticle dispersion relation of the post-quench Hamiltonian. For long-range interactions of the form 1/|R|^{\alpha}, the correlation spreading is substantially different due to a possible divergence of group velocity when tuning the power-law exponent \alpha. For a divergent group velocity, ie. the quasi-local regime, we have presented evidence of a universal algebraic structure for the causality cone. While, the correlation edge motion has been found to be always slower than ballistic, the local extrema propagate faster than ballistically and ballistically for gapless and gapped quantum systems respectively. For the local regime implying a well-defined group velocity, we have recovered similar scaling laws and spreading velocities than the short-range case for the causality cone of correlations. The previous theoretical predictions have been verified numerically using tensor network techniques within the case study of the short-range Bose-Hubbard chain and the long-range s=1/2 XY and transverse Ising chains.

Français

 

Le premier colloquium du CPHT de cette nouvelle série aura lieu mardi 19 novembre à 11h en salle des conférences Louis Michel

Mette Gaarde, Professeure à l'Université d'État de la Louisiane

"Making movies of ultrafast dynamics: tracking and controlling femtosecond absorption and emission processes"

Immense progress in the development of femtosecond and attosecond light sources means that scientists are now routinely directing movies of ultrafast electron and molecular dynamics as it is unfolding on its natural time scale. For example, intense femtosecond X-ray pulses from free-electron lasers can directly take pictures of molecular structural changes, and attosecond extreme ultraviolet (XUV) pulses have been used to time the photoelectric effect. I will start this talk with a brief overview of different types of dynamics that are of interest to the ultrafast community and how to probe them. Then I will discuss an example of opto-optical modulation: how to manipulate the femtosecond time-dependence of absorption and emission processes in gases, with an optical laser pulse, in order to control the temporal and spatial properties of an XUV pulse.

 

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La Journée des Thèses a eu lieu au CPHT le vendredi 22 novembre 2019  dans la salle de conférence Louis Michel.

Format : 10 minutes/exposé + 5 minutes pour les questions

10h00 - 11h15

• [10h00 - 10h15] Nicolas DELPORTE Quantum field theory on random geometries

• [10h15 - 10h30] Jordan MOLES Concentration inequalities

• [10h30 - 10h45] James BOUST Rare-Earth-based hard magnetic materials

• [10h45 - 11h00] Thibaut COUDARCHET Vacuum stability in string theory

• [11h00 - 11h15] Alice MOUTENET Developing diagrammatic algorithms to tackle the quantum many-body problem in and out of equilibrium

11h15 - 11h30 : pause café

11h30 - 12h45

• [11h30 - 11h45] Julian LEGENDRE Topology in magnetically ordered Kagome systems

• [11h45 - 12h00] Jan SCHNEIDER Correlation spreading in long-range systems

• [12h00 - 12h15] David RIVERA Topological regularization of gravity

• [12h15 - 12h30] Nahuel BARRIOS Perturbative study of long-distance non-abelian gauge theories

• [12h30 - 12h45] Hepeng YAO One-dimesional ultracold bosons in quasiperiodic potential: localization and fractality

12h45 - 14h00 : pause déjeûner

14h00 -15h00

• [14h00 - 14h15] Sabine HARRIBEY Renormalization in tensor field theory and the melonic fixed point

• [14h15 - 14h30] Benjamin BACQ-LABREUIL Study of an unconventional phase in Na-doped Ca2CuO2Cl using Dynamical Mean Field Theory

• [14h30 - 14h45] Louis VILLA Correlation spreading and excitation spectra of quantum systems out-of-equilibrium

• [14h45 - 15h00] Grégoire VARILLON Non-modal hydrodynamic stability analysis of ablation flows relative to inertial confinement fusion

15h00 - 15h15 : pause café

15h15 - 15h30

Aurélien Canou : Soutien au calcul numérique au CPHT

15h30 - 16h30

• [15h30 - 15h45] Mufei LUO The role of laser bandwidth and random phase effects on the coupling in stimulated scattering instabilities in inhomogeneous plasma

• [15h45 - 16h00] William FOCILLON Structure du spin du proton et théorie de jauge

• [16h00 - 16h15] Balthazar DE VAULCHIER Induced gravity through compactification

• [16h15 - 16h30] Dung LE Light-cone wave function of onium in onium-nucleus scattering in different frames

16h30 : goûter et présentation des nouveaux membres du CPHT

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