Sign in

Mattia Walschaers

@walschaers.eu
839 followers 1.2K following 154 posts

CNRS researcher @lkblab.bsky.social in Paris. Theoretical quantum physicist, working on quantum optics, and continuous-variable systems. (Pour-over) coffee nerd ☕️ He/him

PostsRepliesMedia
Mattia Walschaers @walschaers.eu · 10/01/2026
A late Christmas gift by me to me 😅 It did not disappoint ☕️ #coffee #specialtycoffee
A box that reads "Geisha collection" and "terres de café".
030
Reposted by Mattia Walschaers
Physics World @physicsworld.bsky.social · 07/10/2025
🚨The 2025 #NobelPrize for Physics goes to John Clark, Michel Devoret & John Martinis “for the discovery of macroscopic quantum mechanical tunnelling and energy quantization in an electric circuit”. More details soon... ⚛️🧪 physicsworld.com/a/john-clark...
physicsworld.com
John Clarke, Michel Devoret and John Martinis win the 2025 Nobel Prize for Physics – Physics World
Trio honoured for their work on quantum tunnelling
07424
Reposted by Mattia Walschaers
John Preskill @preskill.bsky.social · 07/10/2025
The pioneering work of Clarke, Devoret, and Martinis showed that very cold electrical circuits behave in ways that exhibit fundamental principles of quantum physics. www.nobelprize.org/prizes/physi...
nobelprize.org
Nobel Prize in Physics 2025
The Nobel Prize in Physics 2025 was awarded jointly to John Clarke, Michel H. Devoret and John M. Martinis "for the discovery of macroscopic quantum mechanical tunnelling and energy quantisation in an...
2597
Mattia Walschaers @walschaers.eu · 18/09/2025
Both relative to V60 and French press, but before I mainly used a V60.
010
Mattia Walschaers @walschaers.eu · 18/09/2025
Not sure if there are any #coffee lovers out there among my followers? If so, this one's for you. ☕ I just got a Hario Switch after a lot of hesitation, thinking that it would not make much of a difference. After brewing a few cups with it, I am genuinely amazed by the result. Strongly recommended!
380
Mattia Walschaers @walschaers.eu · 15/09/2025
This one just dropped! Using parameter estimation techniques to efficiently characterise Gaussian states of light. journals.aps.org/prl/abstract...
journals.aps.org
Optimal Moment-Based Characterization of a Gaussian State
Fast and precise characterization of Gaussian states is crucial for their effective use in quantum technologies. In this work, we apply a multiparameter moment-based estimation method that enables rap...
020
Mattia Walschaers @walschaers.eu · 05/09/2025
It's a bit haunting to be alone in a room with Van Gogh... I recommend everyone who likes art to get a carte blanche at @museeorsay.bsky.social, which gives you entry 30 minutes before the museum opens to the crowds!
Van Gogh paintings on a wall in an empty roomVan Gogh autoportrait.
060
Mattia Walschaers @walschaers.eu · 28/07/2025
Probably should have put a #quantum.. Also, shout out to my postdoc Massimo Frigerio who did an excellent job conceiving and supervising the project!
040
Mattia Walschaers @walschaers.eu · 28/07/2025
What happens when you put a bunch of highly talented first-year master students together with a brilliant post-doc? First, there is a lot of magic involving algebraic geometry and then you have a protocol for generating arbitrary multimode multi-photon states! 💪 arxiv.org/abs/2507.19397
An image of a photonic circuit. Starting from vacuum states, photon creation operators and interferometers (denoted U) are applied in an alternating fashion. At the end, the top mode is measured with a photon-number resolving detector, and upon the second mode one applies a displacement operator and then postselects on a zero-photon count. The remaining modes are indicated to be in a state denoted as psi.
160
Reposted by Mattia Walschaers
Sauvons le Palais de la Découverte ! @sauvonslepdld.bsky.social · 20/06/2025
📣 Le Palais de la Découverte a besoin de vous ! Musée de sciences installé à proximité des Champs-Élysées, il attire les curieux et férus de science depuis son ouverture en 1937. Fermé depuis 2020 pour rénovation, sa réouverture est aujourd'hui menacée.
Illustration faite à la main représentant le Grand Palais en noir, et le Palais d'Antin qui lui est rattaché, en rouge. Le fond est blanc.
Le Palais d'Antin est le lieu de résidence du Palais de la Découverte depuis 1937.
8169128
Mattia Walschaers @walschaers.eu · 16/06/2025
Dear friends and colleagues from the physics community, be sure not to forget that you can nominate young researchers for the early career prize of New Journal of Physics! 🏆 iopscience.iop.org/journal/1367...
iopscience.iop.org
Early Career Award - New Journal of Physics - IOPscienceSearch
067
Mattia Walschaers @walschaers.eu · 13/06/2025
Hello #quantum community! Just a little heads up that there is still some time to apply !
061
Reposted by Mattia Walschaers
Emmanuel Flurin @manuflurin.bsky.social · 28/05/2025
New paper out! We resonantly couple a superconducting heavy-fluxonium qubit ⚛️ to a macroscopic membrane 🥁 oscillating at a few MHz. ~300 repeated interactions let us track its quantum motion, observe back-action & probe non-commuting operators. Diósi–Penrose next? (1/8) arxiv.org/abs/2505.21481
arxiv.org
Probing the quantum motion of a macroscopic mechanical oscillator with a radio-frequency superconducting qubit
Long-lived mechanical resonators like drums oscillating at MHz frequencies and operating in the quantum regime offer a powerful platform for quantum technologies and tests of fundamental physics. Yet,...
1204
Mattia Walschaers @walschaers.eu · 19/05/2025
🌟 Post-Doc Opportunity in Quantum Computing! 🌟 Join us at @lkblab.bsky.social in Paris to explore photonic quantum computing. Apply by June 15th, 2025. 🔗 Job Announcement: www.lkb.fr/multimodequa... #QuantumComputing #PostDoc #JobOpportunity
084
Reposted by Mattia Walschaers
Multimode Quantum Optics - LKB @mqo-lkb.bsky.social · 16/05/2025
Being a quantum optics group in the city of lights, we love light! Happy international day of light, everyone! #dayoflight
The Eiffel tower is seen in the dark. The light reflects from the Seine.
031
Mattia Walschaers @walschaers.eu · 12/05/2025
I'm at the perfect place for a workshop on #quantum correlations 😎
090
Mattia Walschaers @walschaers.eu · 07/05/2025
Hopefully, this should make it clearer why some works get a desk rejection. However, it should also help authors avoid them by writing better 100-word justifications. These 100 words are a chance for authors to explain why submitted work is exceptional.
110
Mattia Walschaers @walschaers.eu · 07/05/2025
It's really meantime as a clarification. The way editors and editorial board members judge papers does not change, but we hope that with these reformulated criteria, it's clearer why certain are the way they are.
110
Mattia Walschaers @walschaers.eu · 07/05/2025
Our paper "Purification of Gaussian states by photon subtraction or addition" is now published in PRA! 🎉 We explore how, surprisingly, photon subtraction and addition can enhance Gaussian state purity, revealing new potential in quantum optics. journals.aps.org/pra/abstract... #QuantumOptics
journals.aps.org
Purification of Gaussian states by photon subtraction or addition
Photon subtraction (PS) can enhance entanglement, which, for pure states, induces a decrease in the purity of reduced states. In contrast, by analyzing the purities of Gaussian states before and after...
060
Mattia Walschaers @walschaers.eu · 06/05/2025
I think I completed the next level of "being french".
030
Mattia Walschaers @walschaers.eu · 06/05/2025
Don't forget to focus on these criteria in de 100-word justification. That's your chance to explain the editorial team why your work is exceptional!
011
Mattia Walschaers @walschaers.eu · 06/05/2025
📢 Service announcement for the #quantum crowd : PRX Quantum just updated its acceptance criteria. This update is a clarification and does not change editorial practices. However, it should make it easier for you to choose what to submit to the journal. journals.aps.org/prxquantum/a...
journals.aps.org
Editorial: Clarifying PRX Quantum's Acceptance Criteria
PRX Quantum 6, 020001 (2025)
251
Mattia Walschaers @walschaers.eu · 04/05/2025
Finally, a holiday I celebrate. Happy 4th of May from behind my mug of tea, everyone!
010
Mattia Walschaers @walschaers.eu · 30/04/2025
C'est trop bien !
010
Mattia Walschaers @walschaers.eu · 23/04/2025
Enjoy your stay!
020
Mattia Walschaers @walschaers.eu · 16/04/2025
🌟 Quantum Community, Help Needed! 🌟 My tutorial "Non-Gaussian States and Where to Find Them" needs a few updates. If you've spotted errors, please share! Let's improve it together. journals.aps.org/prxquantum/a... #QuantumOptics #Feedback
journals.aps.org
Non-Gaussian Quantum States and Where to Find Them
A phase-space exploration of continuous-variable systems is presented, guiding newcomers through the methodology needed for investigating non-Gaussian states.
091
Reposted by Mattia Walschaers
Lab. Kastler Brossel @lkblab.bsky.social · 10/04/2025
🎨The Sensation Quantique exhibition, blending art and science, opens today at the Institut Henri Poincaré and runs until July 25. Go check it out! 🔗 More info here: lnkd.in/dnp6C9Rw @sorbonne-universite.fr @normalesup.bsky.social @collegedefrance.bsky.social
093
Mattia Walschaers @walschaers.eu · 07/04/2025
One of the surprising joys of parenthood is waking up at 5.30 am and listening to the imperial march together with your baby. The force is strong in this one...
media.tenor.com
darth vader holding a red light saber in a dark room
Alt: darth vader holding a red light saber in a dark room
070
Mattia Walschaers @walschaers.eu · 04/04/2025
Ah yes, a fun final observation: the optimal states at fixed energy are Fock states. This is perhaps surprisingly unexotic compared to grid states and compass states that have been proposed for this task in the past.
020
Mattia Walschaers @walschaers.eu · 04/04/2025
Once you start mixing, it's more subtle. Non-Gaussian mixtures of Gaussian states can be resourceful, but on the other hand, we even found some Wigner negative states that are worse than some Gaussian states. It's a really fun problem, and we really learned new things about non-Gaussian states.
100
Mattia Walschaers @walschaers.eu · 04/04/2025
There has been much work about this in the past. People knew this was possible. However, I think we are the first to really formalise the importance of non-Gaussianity. For example, we show that *every* pure non-Gaussian state outperforms all Gaussian states for this task!
110
Mattia Walschaers @walschaers.eu · 04/04/2025
The answer we give in this paper is beautifully fundamental, at the heart of quantum physics: Joint stimation of position and momentum beyond the limits of the uncertainty relation. 🤩
130
Mattia Walschaers @walschaers.eu · 04/04/2025
Remember: Gaussian states are *much* easier to produce experimentally, so going non-Gaussian must really be worth it. The question then transformed into: What metrological task can we only do with non-Gaussian states? We ultimately realised we had to think of multiparameter estimation.
110
Mattia Walschaers @walschaers.eu · 04/04/2025
Naively, the answer is yes, because for quite a few parameters, you can reach high quantum Fisher information with non-Gaussian states. However, in every case we could think of, you could reach the same values by cleverly displacing and/or squeezing a Gaussian state.
110
Mattia Walschaers @walschaers.eu · 04/04/2025
Now that I have some time. Here are a few more words on this work. At its root, this work started from a simple question: is non-Gaussianity fundamentally useful in quantum metrology?
170
Mattia Walschaers @walschaers.eu · 03/04/2025
This fun result is mainly a "tour de force" of our postdoc Massimo Frigerio 💪
000
Mattia Walschaers @walschaers.eu · 03/04/2025
📃 Heisenberg put limits on how well we can jointly *measure* position and momentum. However, these limits do not apply in the framework of estimation theory. In our new work, we show that non-Gaussianity is a crucial resource to increase precision in such estimation. arxiv.org/abs/2504.01910
arxiv.org
Joint estimation of position and momentum with arbitrarily high precision using non-Gaussian states
We address the joint estimation of changes in the position and linear momentum of a quantum particle or, equivalently, changes in the complex field of a bosonic mode. Although these changes are genera...
170
Mattia Walschaers @walschaers.eu · 02/04/2025
Very impressive work!
000
Reposted by Mattia Walschaers
Lab. Kastler Brossel @lkblab.bsky.social · 31/03/2025
🔬 @cnrs.fr  is recruiting a Junior Professor Chair in Fundamental Physics! Join Laboratoire Kastler Brossel, LAC, or LPL for an experimental research project in quantum physics. 📌 Duration: 6 years | 📍 Location: Paris 📢 More information:
lkb.fr
Jobs - Laboratoire Kastler Brossel
021
Reposted by Mattia Walschaers
Lab. Kastler Brossel @lkblab.bsky.social · 02/04/2025
🔬 Junior Professor Chair – Quantum Science and Technology The Kastler Brossel Laboratory and @sorbonne-universite.frare hiring a Junior Professor. 📌 Duration: 3 to 6 years | 📍 Location: Paris 📢 More information: www.lkb.fr/jobs/?type_poste=chaire-… #QuantumPhysics
lkb.fr
Jobs - Laboratoire Kastler Brossel
044
Mattia Walschaers @walschaers.eu · 01/04/2025
What saddens me about public debate France today is that there seems to be more outrage about someone being excluded from an election rather than about that someone stealing over 4 million euros of our money...
021
Mattia Walschaers @walschaers.eu · 27/03/2025
Want to be sure not to add the wrong person to your group chat? Perhaps quantum communication might be a thing for you! Here we investigate under which conditions providers can safely establish entanglement links between two end-users : arxiv.org/abs/2503.20547
arxiv.org
Entanglement routing via passive optics in CV-networks
Large-scale operations in quantum networks require efficient sorting of desired paths between nodes. In this article, we consider entanglement routing, which involves establishing an entanglement link...
0120
Mattia Walschaers @walschaers.eu · 26/03/2025
We're opening a few postdoc positions in our group. The first one is about experimental multi parameter estimation in imaging problems using Spatial Mode Demultiplexing (SPADE). Contact @nicolastreps.bsky.social if you're interested! www.lkb.fr/multimodequa...
032
Mattia Walschaers @walschaers.eu · 19/03/2025
Our theoretician Ilya Karuseichyk and experimentalist Niels Tripier-Mondancin put their heads together and developed a new, and provably optimal, method to characterise Gaussian states! 😎 arxiv.org/abs/2503.14188
arxiv.org
Optimal Moment-based Characterization of a Gaussian State
Fast and precise characterization of Gaussian states is crucial for their effective use in quantum technologies. In this work, we apply a multi-parameter moment-based estimation method that enables ra...
011
Reposted by Mattia Walschaers
Quantum Networks Team at LKB Paris @quantumnet-lkb.bsky.social · 17/03/2025
Julien Laurat is at the APS Global Physics Summit. He will give a talk at the Kimble Memorial Session, "20 Years of Quantum Memories". 20 years ago Julien moved to Caltech and started his journey in memories and networks with Jeff. Jeff was a giant in Physics and a friend to many of us. #APSSummit25
141
Mattia Walschaers @walschaers.eu · 15/03/2025
It depends. They seem to claim that, now that everything is developed, it should be easy to scale and treat the other cases. It might go fast. But yes, it might be longer. I have no idea, I just base myself on what they say...
110
Mattia Walschaers @walschaers.eu · 14/03/2025
I would say that's actually not a lot of time, given that you have to read the paper, find a student/postdoc to work on the problem, design a simulation strategy, write and debug the code, run the simulation, and write the paper.
110
Mattia Walschaers @walschaers.eu · 14/03/2025
I'm not sure it's a dead end, but it seems quite clear to me that these claims will be taken less and less seriously over time as they keep on being refuted. Things might change once the community can attack problems that people have seriously tried to tackle with classical methods in the past.
000
Mattia Walschaers @walschaers.eu · 14/03/2025
It's actually on Wikipedia, so reasonably well-know I would say.
160
Mattia Walschaers @walschaers.eu · 14/03/2025
But isn't the take-home here that classical methods tend to catch up with quantum advantage claims quite quickly. Couldn't we just ommit these "it would take classical computers X centuries to simulate this"-type claims?
110