The center for Theoretical Physics (CPHT) at Ecole Polytechnique gathers research scientists working in diverse domains of fundamental and applied Physics. The overall coherence is assured by the corpus of common, transposable, mathematical and numerical methods.
CPHT is a joint research unit of CNRS and Ecole Polytechnique, and has a partnership with the Collège de France. His director is Jean-René Chazottes, Senior Researcher at CNRS.
CPHT is on the campus of Ecole Polytechnique, buildings 5 and 6. The reception offices are located in building 6 , offices 06.1046 and 06.1045.

Postal Address :
Ecole Polytechnique 
91128 Palaiseau cedex 

Secretary phone number : 01 69 33 42 01 (from abroad: +33 169 334 201)

Write an email to someone at CPHT :  :


La Journée des Thèses du CPHT a lieu à l'amphi Cauchy  le vendredi 17 novembre 2021.

9am: Introduction by the director of CPHT, Jean-René Chazottes
9.15am —> 10.30am: First session
1. Victor Tomas Mari Surkau
2. Matthieu Vilatte                           
3. Fanny Eustachon
4. Sariah AlSaati
5. Jean-Gabriel Thiriet
6. Félix Fossati                      
11am —> 12.15am: Second session
7. Victor Franken
8. Frederick del Pozo            
9. Dylan Bansard-Tresse
10. Adrien Kahn
11. Pierre Wang
12. Godefroy Meynard           
1.45pm —> 3.30pm: Third session
13. Hoyeon Won
14. Adrien Loty
15. Anustrup Mukherjee
16. Victor Dubois
17. Liam Rampon
18. Ahmedeo Shokri
19. Tristan Gamot
4pm —> 5.30pm: Fourth session
20. Jie Xiong
21. Vincent Wawrzyniak
22. Shengjie Yu
23. Yorgo Pano                     
24. Théophile Truchis
25. Zhaoxuan Zhu                


The 16th CPHT Young Researchers Seminar will be held Monday 13th November at 15h00 in Jean Lascoux conference room.

Our two speakers are coming from out side our lab this time !!

Ismael Ahlouche (Mons University, Belgium): A geometric point of view on Wigner's classification

Nehal Mittal (Collège de France): Identifying topological phases: verification of bulk-edge correspondence

The seminar will be followed by a high tea.



The 15th CPHT Young Researchers Seminar will be held on November 9th, 2023 at 3:00 p.m. in the Louis Michel Conference Room with two presentations :

Pierre Wang: Analysis of the $\varphi^4_4$-theory with N components using the flow equations

Victor Dubois: Producing energy with nuclear reactions : focus on the fusion-fission hybrid reactor

The seminar will be followed by a high tea.



Tuesday, March 12 at 14:30

at CPHT, Conference room Louis Michel

Eleanor Crane (MIT, USA)

Advantages of Digital Qubit-Boson Hardware for Quantum Simulation

Abstract: Finding a straightforward, scalable and universal framework for quantum simulation of strongly correlated fermions and bosons is important from material science to high-energy physics. Here, we develop hybrid qubit-oscillator operations for microwave cavities coupled to transmon qubits required for implementing dynamics of bosonic matter, fermionic matter, and Abelian gauge fields in (2+1)D. We then expand the method to ground state preparation and propose measurement of various long-range correlation functions required for the study of phase transitions. We implement numerical proof of principle experiments for a (1+1)D Z2 Bose Hubbard (BH) gauge theory and the U(1) Schwinger model. We include the main sources of hardware noise, which we mitigate through post-selection based on Gauss' law. This new approach motivates us to uncover the phase diagram of the Z2 BH model, relevant to the Higgs sector. We discover a new phase of matter which exhibits strong density fluctuations which we dub the `clump' phase. Finally, we perform a complexity analysis and find that for one Trotter step of these example models, qubit systems require higher gate counts than our proposal by three orders of magnitude. Our correspondingly higher circuit fidelities may help us to successfully capture the essential physics of these theories in the near-term.



Le CMAP, le CMLS et le CPHT organisent des journées thématiques dont l'audience visée est un large public de mathématicien-ne-s et de physicien-ne-s. La prochaine journée aura pour thème l'écologie, thème qui sera abordé sous différents points de vue par :

Ada Altieri (Laboratoire Matière et Systèmes Complexes, Université Paris Cité)
Guy Bunin (Physics departement, Technion)
Olivier Hénard (LMO, université Paris-Saclay)
Gaël Raoul (CMAP, CNRS, école polytechnique)

Cette journée aura lieu le 15 novembre 2023 de 10h30 à 16h15.

Plus d'informations sont disponibles à l'adresse suivante :

Pour des raisons logistiques, l'inscription est gratuite mais obligatoire. Elle s'effectue à l'adresse suivante :

En espérant vous y voir nombreux et nombreuses,
Pour l'organisation, Anne-Sophie de Suzzoni Jean-René Chazottes Anne de Bouard Cécile Huneau


Conférence grand public à l'occasion de la fête de la science

Samedi 14 octobre 2023 à 15h15 

Amphithéâtre Becquerel 

Tout est quantique !
par Laurent Sanchez-Palencia

La physique quantique a révolutionné notre compréhension du monde à l’échelle atomique et au-delà. Venez en découvrir les mystères, mais également comment elle a envahi les technologies du quotidien et ses promesses pour une nouvelle révolution technologique.

Plaquette de la fête de la science



Tuesday, October 17 at 14:00

at CPHT, Conference room Louis Michel

Ilya Kull (University of Vienna)

Lower bounds on ground-state energies of local Hamiltonians through the renormalization group

Abstract: "Quantum many-body systems present us with intractable optimization problems, e.g. finding the ground state of a many-body system. This problem is most often addressed through the variational ansatz approach, where physical insight can guide us in constructing the correct ansatz for a given system. Yet, variational methods can only provide us with a one sided estimate---an upper bound on the ground state energy. To certify a variational solution a lower bound is also required. Lower bounds can be obtained through relaxation methods, in which the optimization problem is simplified by relaxing some of the constraints that define the set of admissible optimization variables. Relaxation methods have been applied to many-body systems since the 50s and have also proven to be an essential tool in tackling various problems in quantum information theory and conformal field theory (the numerical bootstrap). Such methods, however, suffer from the drawback of exponential scaling of their complexity with the accuracy of the solution. In contrast, variational algorithms such as the density matrix renormalization group (DMRG), and other tensor-network algorithms which are based on the renormalization group idea, exhibit polynomial scaling.
In this talk I will describe how one can incorporate the power of the renormalization group approach into the relaxation framework to efficiently compute lower bounds. I will present the results we obtained with this method for translation-invariant spin chains where we observe a polynomial scaling of the complexity with the accuracy.