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Clément Sayrin @clementsayrin.eurosky.social · 30/09/2026

To do so, we use circular Rydberg atoms which we laser trap in optical tweezers specially tailored for Rydberg atom: optical bottle beams (or BoBs as we call them, but not the sponge).

A blue torus (representing a circular Rydberg atom) is in the middle a blue shaded area, elongated along the vertical axis, which represents a light beam with a local minimum of intensity, where the atom sits.

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Clément Sayrin @clementsayrin.eurosky.social · 30/09/2026

We observe the interaction between two Rydberg atoms, namely a spin-exchange oscillation or flip-flop, akin to the interaction between spin 1/2s. Importantly, we observe these oscillations over more than 60µs and 40 oscillation periods, an order of magnitude longer than the state-of-the-art.

The picture has one main panel and three smaller panels which are zooms into the bigger one. Data points indicate an oscillation of the measured quantity (M on the vertical axis), plotted as a function of a time delta t in micro seconds. A continuous line represents a damped sinusoidal fit the data points and reproduces well the data. The time intervals which correspond to the three smaller panels are indicated by three coloured areas (green, violet, yellow, from left to right).

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Clément Sayrin @clementsayrin.eurosky.social · 07/07/2026

And thanks to all the participants to have come and visit us in @normalesup.bsky.social, @psl-univ.bsky.social and @sorbonne-universite.fr. It was great to welcome you and to organize the school for you together with Tarik Yefsah.

(Almost) All the participants and mentors stand on the scene for a final goodbye picture.

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Clément Sayrin @clementsayrin.eurosky.social · 07/07/2026

Thanks to our 6 great mentors, Thomas Copie, Óscar Mañas Chambert, Ekaterina Gradova, Antoine Lefebvre, Pedro Minarelli Gaspar and Iliana Tsoni, from @lkblab.bsky.social, @lpens-phys.bsky.social or LPL, to have led their students along a quantum path and for all their help in organising the school!

The students of group 5 conclude their presentations with a slide showing a selfie of the group in the scene in front of all the participants with a thanks to the organizers, mentors and all students. The fire extinguisher applauds.

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Clément Sayrin @clementsayrin.eurosky.social · 07/07/2026

The students themselves then took on the stage to present to their fellows the results of their works with their mentors.

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Clément Sayrin @clementsayrin.eurosky.social · 07/07/2026

Thursday was our fourth and last day of the DigiQ Paris Summer School. Antoine Browaeys opened the day with in-depth lecture about #Quantum Simulation with individual Rydberg atoms.

Antoine Browaeys stands in front of our students and concludes his lectures on quantum simulations with individual Rydberg atoms with a slide questioning "How large can a controlled quantum system be?" with a picture of Schrödinger and his cats, a frontier between quantum and classical worlds, and a picture of thousand of individual laser-trapped atoms

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Clément Sayrin @clementsayrin.eurosky.social · 01/07/2026

After a relaxing trip along the Seine river, to discover the beauties of Paris, the students could enjoy a nice diner in Le Procope, walking along the path of Voltaire, Diderot and d'Alembert.

Our students and mentors have a nice diner together in Le Procope, enjoying French cuisine together. The fire extinguisher was not hungry, it seems.

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Clément Sayrin @clementsayrin.eurosky.social · 01/07/2026

Our third day of the DigiQ Paris Summer School starts with a Bavarian morning. We had the chance to welcome Immanuel Bloch (@lmu.de, MPQ) for his 2nd lecture on Quantum Simulation with Ultracold Atoms and Barbara Kraus @tum.de, teaching our students about Quantum Information and Entanglement Theory.

Immanuel Bloch stands in front of a whiteboard and writes on it to answer questions form our students, while a beautiful picture of Munich is displayed on screen.

Barbara Kraus stands in front of our young audience to teach them everything to know about Quantum Information and Entanglement Theory. A slide "LOCC-transformations among bipartite pure states" is displayed on screen. The fire extinguisher attends all the lectures, it will soon become a quantum specialist!

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Clément Sayrin @clementsayrin.eurosky.social · 30/06/2026

This afternoon, Immanuel Bloch, from @lmu.de and MPQ, teaches his first lecture on Quantum Simulation with Ultracold Atoms, guiding the students in understanding cold atom physics and their use in quantum simulators.

Immanuel Bloch stands in front of the students, with the screen on his back showing a nice green picture of atoms organized in a crystal. He also uses a white board to give insights in atom trapping with light, while challenging the students in their physics understanding. The fire extinguisher, on the left, did not know the answer to Immanuel's question, but it is learning.

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Clément Sayrin @clementsayrin.eurosky.social · 30/06/2026

On our second day of the DigiQ Paris Summer School, Saïda Guellati-Khelifa from @lkblab.bsky.social has introduced our students to the fascinating realm of #quantum sensing and presented her experimental activities in LKB. @normalesup.bsky.social @psl-univ.bsky.social @sorbonne-universite.fr

Saïda Guellati stand in front of our wonderful students, and explains them everything about quantum sensing and her experiments in LKB. The screen shows one of her slides giving details about the Zeeman effect. Even the fire extinguisher on the left seems fascinated and understands everything.

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Clément Sayrin @clementsayrin.eurosky.social · 29/06/2026

Zaki Leghtas from @lpens-phys.bsky.social @minesparis-psl.bsky.social now teaches everything to know about quantum computing with superconducting circuits.

Zaki Leghtas standing in front of the students, all looking forward to learning everything to know about quantum computing and its superconducting architecture. On the screen, an example of a quantum circuit.

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Clément Sayrin @clementsayrin.eurosky.social · 29/06/2026

Julien Laurat from @quantumnet-lkb.bsky.social @lkblab.bsky.social opens the school with a lecture on quantum memories.

Julien Laurat, standing in front of fascinated students, begins is lecture on Quantum Memories. The title slide is projected on the screen.

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Clément Sayrin @clementsayrin.eurosky.social · 29/06/2026

Today we launch the DigiQ Paris Summer School, co-organized by @normalesup.bsky.social @psl-univ.bsky.social and @sorbonne-universite.fr. We are happy to welcome in ENS 55 students from 14 different European universities for a series of lectures on quantum technologies. www.lkb.fr/en/evenement...

DigiQ Paris Summer School 2026, 29/06-02/07.
Below, the logos of DigiQ, Sorbonne Université and ENS-PSL Université. On the right, a picture of the Eiffel Tower.

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Clément Sayrin @clementsayrin.eurosky.social · 30/09/2025

In this picture, the ancilla circular atoms stay in n=52 (small blue torus) if a nearby ancilla is in 45S (large green sphere) but it is excited to n=54 (large red torus) if the ancillae are in their ground state (small red sphere). (13/14)

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Clément Sayrin @clementsayrin.eurosky.social · 30/09/2025

If we try and optically excite the ancilla to 45S, the process is impervious to the presence of a circular atom with n=52. However, if the circular atom is in n=54, the strong interaction splits the excitation line and blocks the excitation, in a usual Rydberg blockade mechanism. (10/14)

Population in the ground state after the optical excitation of the ancilla to 45S, as a function of the frequency of the excitation laser. The blue squares are measured with a circular atom in n=52, the red spheres with n=54. A low probability indicates a successful excitation

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Clément Sayrin @clementsayrin.eurosky.social · 30/09/2025

In this work, we make circular Rydberg atoms (blue torus in the picture) interact with other atoms initially in their ground state (red spheres) and excited to low-angular-momentum Rydberg levels. All atoms are laser trapped in the experiment. (8/14)

Three atoms on a line: a red sphere (ground state), a blue torus (circular Rydberg state), and another red sphere. The ground state atoms are trapped in focused Gaussian beam (red beam) and and the circular atom in a bottle beam (blue beam).

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Clément Sayrin @clementsayrin.eurosky.social · 30/09/2025

They can also be laser trapped in so-called optical bottle beams, that present a local minimum of intensity. (5/14)

A circular Rydberg atom (blue torus) inside an optical bottle beam (blue beam with an intensity minimum at the place of the atom).

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Clément Sayrin @clementsayrin.eurosky.social · 30/09/2025

I am quite happy to share our latest work from the #Rydberg Atoms team of @lkblab.bsky.social, that just appeared on arXiv, by Yohann Machu and all the Rb team @college-de-france.fr @psl-univ.bsky.social @normalesup.bsky.social @cnrs.fr @sorbonne-universite.fr (1/14) arxiv.org/abs/2509.24691

Four ensembles of atoms arranged on a square. Within every ensemble, there are three atoms. On the two left ensembles, the central atom is depicted with a yellow torus (circular Rydberg level) and the two outer ones with a red sphere (ground state). In the two left ensembles, the central atom is depicted by a small blue torus (circular level), the left atom as a large green sphere (other Rydberg level) and the right atom as a red sphere. All red-sphere atoms are illuminated by a red beam that represents a laser trap.

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Clément Sayrin @clementsayrin.eurosky.social · 09/04/2025

Vous pourrez y croiser des objets ou des instantanés échappés de nos laboratoires et même une revisite de réseaux d’atomes piégés en pinces optiques.

Une vue artistique d’un réseau d’atomes observés par fluorescence, représentés par une mosaïque de photographies d’une femme. Certaines des photos s’allument transitoirement.

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Clément Sayrin @clementsayrin.eurosky.social · 28/03/2025

Dites @francetv.bsky.social #france2, on essaie d’apprendre à nos étudiants le concept de « nombre de chiffres significatifs ». C’est bien de fournir des exemples de ce qu’il ne faut pas faire mais quand même… une hausse de température estimée à 10 nano degrés près, vraiment ?

Extrait du journal météo climat de France2. Le présentateur montre la hausse de température annoncée due à l’influence humaine, de 1,35808944°C.

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Clément Sayrin @clementsayrin.eurosky.social · 15/11/2024

Twenty years after my master internship (ouch, I feel old… 👨‍🦳), it was great to be back in Harvard and @mitofficial.bsky.social to visit the wonderful labs of the CUA and talk there about our circular #Rydberg atoms!

Night view from building in Harvard university.

Photo of Ray and Maria Stat center in MIT, Boston

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Clément Sayrin @clementsayrin.eurosky.social · 08/07/2024

News from Kastler Brossel Laboratory! We have measured the dipole-dipole interaction between two circular #Rydberg atoms trapped in optical bottle beams. Check out our now work on the arXiv: arxiv.org/abs/2407.04109 @collegedefrance.bsky.social @cnrs.bsky.social ENS-PSL Univ. Sorbonne Univ.

Two circular Rydberg atoms are trapped in a pair of optical bottle beams. They interact through dipole-dipole interaction. The distance d between the atoms and the angle theta between the interatomic axis and the quantization axis are represented.

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