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31 August (2024)
A bit of off-the-beaten-track history of science. Who understood the continuous spectra from planetary nebulae? laussy.org/wiki/Blog:Scie…
28 August (2024)
18 August (2024)
Alain Delon, le dernier monstre sacré du cinéma Français, peut-être aussi le dernier tout court de l'esprit Français: laussy.org/wiki/Blog:Fabr…
Belle retrospective par Valentin Lagorio:
17 August (2024)
10 August (2024)
End of conference picture, taken specially for @AntnSo
9 August (2024)
8 August (2024)
7 August (2024)
Imamoglu on the latest LP (experimental) antibunching.
6 August (2024)
A quick thread on correlations in circular cascades, the topic of our latest preprint: arxiv.org/abs/2408.02068
Cascades are well-known to produce dramatic and sometimes even qualitatively new effects. We're interested in cascades that go around, with the final step triggering again the first one. Imagine for instance dominos springing back into position after knocking down their successor
We ourselves deal with photons, but the effect applies to everything. The formalism is simply rate equations. Whether you put photons, marbles, viruses or whatnot doesn't matter. The most difficult is to know if, by who, for what, where and when all this was already found.
The point is, usually people don't consider such simple, all-the-way down cascades. Photon cascades are a huge topic but since Einstein's A and B, we know that photons like to go both ways: down the ladder of energy levels as they emit, and up again as they get excited.
So from the huge literature on the topics, including big cascades, you always find essentially the physics of two-photon cascades. The pumping back breaks the beautiful effects that a full merry-go-round can bring to the story. The simpler the matrix, the prettier the physics!
But what 𝑖𝑠 this wonderful physics, I hear you ask? That which has been described by the Harvard and MIT people as "nonlinear quantum optics in its extreme, in which individual photons behave as impenetrable particles"! Looks great, doesn't it? A Tonks-Girardeau gas of photons.
Here is how such extreme stuff looks like, as pictured by Otterbach et al. [https://t.co/iaxnCxBK8r] who Wigner-crystallize their photons:
This physics, we ourselves described in terms of "liquids" (not crystals) and involving time (not space): pubs.aip.org/aip/apq/articl…
This is because we have a completely different mechanism. Our prestigious colleagues deal with strongly interacting cold Rydberg gas maintained in the tricky electromagnetically-induced transparency window, which, they showed, can generate those "extreme" correlations in space.
I should write "could generate", due to the system's complexity, with concerns about, e.g., "pollutants" that make the platform more similar to a nuclear reactor than to an optical device. They are thus still very far from producing something that looks remotely like a "crystal".
Our circular cascades, on the other hand, do that. They produce these "nonlinear, impenetrable photons" only by forcing them to go in one direction only. No EIT, no Rydberg nonlocal interactions, no cold-atomic gases, only the broad properties of compound random variables. Easy.
The simplicity already strikes at the theoretical level. No need of Density Matrix Renormalization Group (inset from Otterbach 2013): you can work out the exact result with pen and paper (formula & superimposed blue traces). I don't exclude departures are DMRG numerical errors!
Taking a taste of my own medicine, I should add that beyond such single-photon emission, the versatility of circular cascades delivers similarly a type of light that I've been advocating from steep routes. Consider indeed 2 contiguous transitions together, this is what you get:
and what this is, is a two-photon bundle liquid! Yes ma'am. Not only it's a better bundler than the elaborate, beautiful but also tricky cavity QED N-photon bundler, it's also much more configurable, and much purer: no fundamental restriction on the size of the bundles.
So circular cascades—which can do many other things—look worth realizing. How? They're not unphysical but require skilful engineering. Chiral optics & topological photonics could lend their services. Whoever builds such a cascade will have liquid light and unrestricted bundlers.
Replying to @RealSci_Nano, @INC_UAM, @ifimacuam, @QuantERA_EU, @ComphortQ, @HeindelTobias, @SchneiderQMat, @NQOLab and @BristolUni
Great logo
5 August (2024)
4 August (2024)
New manuscript on the arXiv. This should appear on Tuesday since arXiv doesn't work on week-ends, so on the day of my talk at the PEPS conference, although I won't be speaking about that (at least not at the conference, maybe here in the virtual world).
3 August (2024)
Replying to @55Bellechasse
Cet adversaire est de fait moins dominé que celui qui s'est pris un ippon en finale des poids lourds. Riner n'arrive pas à prendre prise. Une fois la main au collier, son poids et sa taille rendent le moindre déanché fatal. Ce judoka pourrait lui donner une bonne leçon de judo.
2 August (2024)