I heard decoding qLDPC codes? Let’s see what we can do :)

Fast surgery for quantum LDPC codes Quantum LDPC codes promise significant reductions in physical qubit overhead compared with topological codes. However, many existing constructions for performing logical operations come with distance-...

happy to share this preprint from last week scirate.com/arxiv/2510.0... - my first with Iceberg!
big thanks to Larry and Nouedyn, who led this cool project ❄️

we have also written a short blogpost about it www.iceberg-quantum.com/blog/fast-su...
comments welcome 🧊

Thanks for this collaboration @lucasberent.bsky.social, Armanda Quintavalle, @jenseisert.bsky.social, Robert Wille, and @qec.codes (Joschka Roffe)

Colour Codes Reach Surface Code Performance using Vibe Decoding Two-dimensional quantum colour codes hold significant promise for quantum error correction, offering advantages such as planar connectivity and low overhead logical gates. Despite their theoretical ap...

LSD can get its soft information from a pre-processor like
BP or the device's noise model directly, see also VibeLSD. arxiv.org/abs/2508.15743
It matches the performance of the best decoders out there, like OSD-O, but with a reduced runtime complexity.

All of this is made possible through a novel parallel matrix factorization strategy, which we call on the-fly elimination, to identify, validate, and solve local decoding regions on the decoding graph.

Localized statistics decoding for quantum low-density parity-check codes - Nature Communications Quantum low-density parity-check (QLDPC) codes offer lower overhead than topological quantum error-correcting codes, but decoding remains a key challenge for scalable fault-tolerant quantum computing....

Working on LSD was fun! - Our paper on Localized statistics decoding (LSD) for qLDPC codes is now in print.
LSD is a highly parallelizable, reliability-guided inversion decoder that exploits the clustering of errors. Think of it as a parallel version of OSD.
www.nature.com/articles/s41...

Der Polizist behält seinen Job, denn: "Aus den Nachrichten ergebe sich noch keine eindeutig verfassungsfeindliche Gesinnung."

I think I’m missing :)

Since even for surface codes Relay-BP (Fig. 2) competes with matching-based decoders, it would be interesting to see whether Relay-BP outperforms known color code decoders, relevant, for example, to the performance of magic state cultivation.

As Gallager already noted, BP is often more art than science, justified “only by the fact that it works.” But it does work in many cases, and I think it’s worth exploring how far we can push it with careful heuristics and structured approaches.

Another thing I noticed: there has been only limited effort to combine different strategies to mitigate trapping sets. I had actually written this down as a future project idea but didn't get to it, so I’m glad to see that the IBM Quantum team has already shown that this direction is viable.

While writing my thesis, I revisited a lot of the BP literature and dug into the basics. One thing that stood out is that heuristics for trapping sets are rarely tested under circuit-level noise, even though decoding in that setting is significantly different from code capacity.

Improved belief propagation is sufficient for real-time decoding of quantum memory We introduce a new heuristic decoder, Relay-BP, targeting real-time quantum circuit decoding for large-scale quantum computers. Relay-BP achieves high accuracy across circuit-noise decoding problems: ...

Great work by the IBM Quantum team on Relay-BP, a BP-only heuristic decoder for general qLDPC codes. From a first look, the performance seems strong and further supports qLDPC architectures from a decoding-focused perspective.
arxiv.org/abs/2506.01779

GitHub - seokhyung-lee/tesseract-python: Python Wrapper for Tesseract Decoder Python Wrapper for Tesseract Decoder. Contribute to seokhyung-lee/tesseract-python development by creating an account on GitHub.

I recently created a simple Python wrapper for the Tesseract decoder for personal use, but I’ve decided to make it public in case others find it useful. Feel free to let me know if you encounter any issues!

github.com/seokhyung-le...

Protecting Science: TIB builds Dark Archive for arXiv - TIB-Blog Research and science are international; it is not for nothing that we speak of international specialist communities. Although a service such as arXiv is operated by an institution based in the USA, na...

There is now an official announcement: The TIB has archived the current status of the arXiv:

blog.tib.eu/2025/05/14/p...

Did the text change significantly? If I recall correctly the previous ones then they read very similar. Only the word „exceptional“ didn’t appear every time if my mind is not lying to me

Excerpt from APS article on the new AIP report on impact of funding cuts in physics & astro departments: "One cannot work like this - all energy goes in thinking how to survive and not in physics - it is like being in the war," another department chair wrote. "No one can be productive in a climate like this - it is the end of the US scientific and technical dominance in the world - we will not recover from this in a decade," they added.

New AIP report discusses impact of funding cuts in physics & astro depts: “No one can be productive in a climate like this—it is the end of the US scientific and technical dominance in the world—we will not recover from this in a decade...”. ⚛️🔭 physics.aps.org/articles/v18...

Ok, heute ARD-Brennpunkt zur AfD, auf einen der Gäste kommt ihr nie. Richtig, Tino Chrupalla. Vor 80 Jahren hätte der zumindest auf der Anklagebank gesessen. Woher diese unbändige Lust, weiter mit Nazis zu reden? Ist es Masochismus? Erinnerungskultur tm? Oder vermisst ihr einfach eure Omas und Opas?

Next up in session A is Lucas Berent telling us about LSD, a popular topic in Berlin.

This past week, I received a second stop work order on one of my grants. This now means that we can no longer spend on *two* of my major grants. Several of my group members will now graduate earlier than expected, I am looking into being a consultant for the summer, and students will do internships

Dass ausgerechnet die CSU-Politikerin Doro Bär, die noch vor wenigen Jahren den menschengemachten Klimawandel leugnete, jetzt neue Forschungsministerin werden soll - ein Job, bei dem es ganz besonders darauf ankommt, der Kraft der Wissenschaft zu vertrauen, ist m.E. hochproblematisch.

If now for subsystem codes we are measuring non-commuting gauge operators and combining them to get stabilizers, there is a way to look at the problem in the same way as for the ordering of operations in ordinary syndrome extraction circuits. Probably with even fewer constraints though. 2/2

I wonder if with hindsight we are just coming back to realize that the order of operations in the syndrome extraction circuit matters for the effective fault distance of ordinary codes. There we all agree that the order of operations matters. 1/2

Section 3 of the Extractor paper is a very good overview I find as a non-expert. arxiv.org/abs/2503.10390

Typing away on my PhD thesis - no matter where I go next, the views from my office will be hard to beat, unfortunately.

@arrr.de is working on something related.

Read the paper here: journals.aps.org/pra/abstract...

When we wrote the theory proposal for the dissipatively stabilized squeezed cat qubit, we got into an argument with the copy editors of the journal. I had a strong opinion against calling it „cat state qubit“ (as no one does) which got so far that we almost had to add a disclaimer, see the mail

cubeIP