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Josu Etxezarreta Martinez

@katutxakur.bsky.social
131 followers 148 following 9 posts

PhD in Quantum Information. Trying to make quantum computers less noisy. I am a reseacher at Tecnun. Former visitor at the Cavendish Laboratory (Cambridge). Rugby player. Rock&Roll. Opinions are my own.

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Reposted by Josu Etxezarreta Martinez
Lorena Fernández Álvarez @loretahur.bsky.social · 21/09/2026
A un teatro de Barcelona se le ha prohibido promocionar en Instagram y Facebook una obra teatral de Virginia Woolf. Según Meta: «cualquier mención a derechos civiles, feminismo o reforma social suele clasificarse como "tema social" por nuestro sistema automático» y se filtra. 🤬🤬🤬
theguardian.com
Meta bans ads for Virginia Woolf play in Spain because they relate to feminism
Theatre told that Facebook and Instagram filter out ads mentioning ‘social topics’ such as civil rights or feminism
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Hannibal Lecter 🦋 @hannibal.bsky.social · 17/06/2026
Garamendi habla de absentismo, pero no habla de esto:
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Maris Ozols @marisozols.bsky.social · 13/06/2026
The goal was to expose them to some of the quantum nonsense that's out there (thank you @dulwichquantum.bsky.social), help them understand the incentives of all the parties involved, and teach them critical thinking skills. I hope this will be helpful in their future careers!
Hype incentives

Companies
* profit
* promote a product
* personal profit

Journalists
* attractic readers (clickbait)
* early access

Politicians
* appear innovative
* national prestige

Scientists
* funding
* career prospects

General public
* appear smart
* play expert
* pump up stock
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Christopher K. Long @christopher-k-long.bsky.social · 11/06/2026
In our recent arXiv (arxiv.org/abs/2605.28936) we benchmarked QEC and magic state factories for spin qubits. By computing magic state production overheads as a function of initialization, gate, measurement, and decoherence times we estimated the runtimes for typical algorithms—see Fig.
Figure 2 from

Songqinghao Yang, Christopher K. Long, Rubén M. Otxoa, Prakash Murali, Crispin H. W. Barnes, & David R. M. Arvidsson-Shukur, Hardware-Tailored Resource Estimation for Magic-State Distillation on Silicon Spin Qubits, arXiv preprint arXiv:2605.28936 (2026).

Used under a CC-BY-4.0 license: https://creativecommons.org/licenses/by/4.0/

Caption:

Algorithmic resource requirements. We plot the wall-clock time (horizontal axis) and the number of physical qubits (vertical axis) needed to run three different quantum algorithms. The color map indicates the fraction of the qubits used for MSD. The circles label the sparse SpinBus architecture with the standard surface code; the triangles label the SpinBus architecture with the XZZX surface code; and the squares label the dense architecture with the standard surface code. The logical operations are implemented with lattice surgery and the ‘grow-and-distill’ MSD protocol is chosen to minimize the space-time overhead.
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Zoe Holmes @qzoeholmes.bsky.social · 22/05/2026
Me to my students:
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Rochelle @uberwensch.bsky.social · 19/05/2026
The trick is, when among mathematicians, to say you are a physicist so that they forgive you for not knowing very much math. Then, when among physicists, say you are a mathematician so that they forgive you for not knowing very much physics. In especially dire cases I might say I am a philosopher.
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Josu Etxezarreta Martinez @katutxakur.bsky.social · 09/05/2026
Check out our latest preprint: scirate.com/arxiv/2605.0...
scirate.com
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Joschka Roffe @qec.codes · 07/05/2026
📢 TartanQEC Workshop. The deadline for abstract submission is tomorrow. Submit your best work now 👇 qec.codes/tartan2026
qec.codes
TartanQEC Workshop
TartanQEC Workshop, 24-26 June 2026, School of Informatics, University of Edinburgh.
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Clément Canonne @ccanonne.github.io · 02/05/2026
Three paper rejections in two days (in two conferences), for works I am genuinely proud of and enthusiastic about. You'd think you get used to it, after a while (you don't, it still stings).
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Dulwich Quantum Computing @dulwichquantum.bsky.social · 18/04/2026
Fun twist in Google's zero knowledge proof of quantum circuit.
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The Conversation ES @es.theconversation.com · 14/04/2026
En el #DíaMundialdelaCuántica celebramos los logros de la primera revolución cuántica y miramos a la computación cuántica como el motor de la nueva era que empieza. ✍️  @katutxakur.bsky.social (@unav.edu) 
bit.ly
Día Mundial de la Cuántica: estado actual, retos y perspectivas de la computación cuántica
En el Día Mundial de la Cuántica, celebramos los logros de la primera revolución cuántica y miramos a la computación cuántica como el motor de la nueva era que empieza.
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The Hilbert Space Post @hilbertspacepost.bsky.social · 16/03/2026
The GUESS quantum error mitigation method leverages Hamiltonian symmetries to improve accuracy and reduce variance in noisy quantum computations, achieving around 10% relative error for circuits with up to 8000 CZ gates. @joanafrx.bsky.social, @katutxakur.bsky.social arxiv.org/abs/2603.13060
arxiv.org
Noise mitigation of quantum observables via learning from Hamiltonian symmetry decays
We present a new quantum error mitigation technique (QEM), called GUiding Extrapolations from Symmetry decayS (GUESS), which exploits Hamiltonian symmetries to improve accuracy of noisy quantum comput...
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arxiv quant-ph @arxiv-quant-ph.bsky.social · 16/03/2026
Javier Oliva del Moral, Olatz Sanz Larrarte, Joana Fraxanet, Dmytro Mishagli, Josu Etxezarreta Martinez Noise mitigation of quantum observables via learning from Hamiltonian symmetry decays arxiv.org/abs/2603.13060
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Josu Etxezarreta Martinez @katutxakur.bsky.social · 16/03/2026
Check out our latest preprint on quantum error mitigation. The meme summarizes the work. scirate.com/arxiv/2603.1...
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Xavi Cugat - Energía @revenergetica.com · 01/03/2026
Cambios en la generación eléctrica en China y EE.UU. entre 2024 y 2025. Un solo año. Por cierto, detalle, al margen de lo obvio. China es el país del mundo con una apuesta más fuerte por la nuclear.
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Graeme Smith @graemesmith.bsky.social · 21/02/2026
Scientific conferences must not be held in the US until it is safe to travel there. www.theguardian.com/us-news/2026...
theguardian.com
‘Don’t go to the US – not with Trump in charge’: the UK tourist with a valid visa detained by ICE for six weeks
Karen Newton was in America on the trip of a lifetime when she was shackled, transported and held for weeks on end. With tourism to the US under increasing strain, she says, ‘If it can happen to me, i...
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Craig Gidney @craiggidney.bsky.social · 14/02/2026
I've been asked several times to comment on arxiv.org/abs/2602.11457, which claims to reduce the qubit cost of factoring by 10x. My take is that they demand a *lot* more qubit connectivity for that number. Your mileage depends entirely on how plausible you find those demands.
arxiv.org
The Pinnacle Architecture: Reducing the cost of breaking RSA-2048 to 100 000 physical qubits using quantum LDPC codes
The realisation of utility-scale quantum computing inextricably depends on the design of practical, low-overhead fault-tolerant architectures. We introduce the \textit{Pinnacle Architecture}, which us...
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Dulwich Quantum Computing @dulwichquantum.bsky.social · 06/02/2026
Just LOVE the "Advanced Quantum Algorithms" lecture notes of Stacey Jeffery!!! homepages.cwi.nl/~jeffery/not... Everyone teaching quantum computing should read this paragraph out loud to their students! homepages.cwi.nl/~jeffery/not...
Many of the potential applications of Hamiltonian simulation are not algorithms themselves, but
rather, the idea that having a better understanding of certain physical or chemical systems would likely
lead to new scientific and technological breakthroughs. Some of these are well worked out ideas (for
example, nitrogen fixation [RWS+17]), but many of them are very tenuous, which unfortunately does
not stop popular science news, and technology-enthusiasts who have decided to make a career talking
a lot about quantum computing without really understanding it, from treating such applications as
being just around the corner. You will find headlines and ted talks claiming quantum computers can
solve every futuristic-sounding problem, including fixing climate change [mtl], curing cancer [Kak24],
and finding the secret to immortality [Gre20]. I mean, science could solve any of these (but could it?),
and faster Hamiltonian simulation would mean we can do better science, so. . . The reality is, there
probably will be many applications to being able to simulate physical systems, but we do not yet know
what they will be. We will not discuss applications of Hamiltonian simulation in this course, but it
is important to understand that there is a lot of hype around quantum computing, some of which is
justified, and some of which is not.
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Henry Legg @henrylegg.bsky.social · 26/01/2026
Fun fact I learnt preparing my condensed matter lectures for this semester: Arnold Sommerfeld was nominated 84 times for the Nobel prize in physics, but never won. Interestingly, despite his lifelong Nobel prize disappointment, Sommerfeld never threatened to invade Greenland (as far as I know).
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Dulwich Quantum Computing @dulwichquantum.bsky.social · 09/01/2026
The promise of solving the electronic structure of FeMo-co has long been central to the narrative that quantum computers will one day solve world hunger. Now we can finally put the "solving world hunger" part to test since Garnet Chan just solved FeMo-co *classically*! arxiv.org/abs/2601.04621
arxiv.org
Classical solution of the FeMo-cofactor model to chemical accuracy and its implications
The main source of reduced nitrogen for living things comes from nitrogenase, which converts N2 to NH3 at the FeMo-cofactor (FeMo-co). Because of its role in supporting life, the uncertainty surroundi...
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Mark M. Wilde @markwilde.bsky.social · 10/12/2025
We recently received a referee report from Phys. Rev. Lett. @apsphysics.bsky.social that was obviously written by generative AI. It is so bizarre to read it; I have never received anything like it before. What measures is @apsphysics.bsky.social taking to ensure the integrity of the review process?
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Información y Tecnologías Cuánticas en España @qipcspain.bsky.social · 05/12/2025
"Antonio de Marti i Olius, premio GEITC a la mejor tesis doctoral en información y tecnologías cuánticas". #cuantica2025 www.cuantica2025.es/antonio-de-mart…
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Sophien Kamoun @kamounlab.bsky.social · 03/12/2025
I just published: ERC-Plus: jackpot science or missed chance to fix academia? My reflections on ERC-Plus, Europe’s newest ultra-competitive research grant and what it tells us about the academic culture we’re building. medium.com/p/erc-plus-j...
medium.com
ERC-Plus: jackpot science or missed chance to fix academia?
My reflections on ERC-Plus, Europe’s newest ultra-competitive research grant and what it tells us about the academic culture we’re…
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Quantum Spain @quantumspain-project.es · 04/12/2025
📺 We’ve just released the recording of our latest Quantum Spain Seminar on YouTube! 💡 Advances in low-overhead quantum error correction 🗣️ Josu Etxezarreta Martinez , researcher @tecnun.bsky.social - Universidad de Navarra Watch it now! www.youtube.com/watch?v=_UW5...
youtube.com
Quantum Spain Seminar: Advances in low-overhead quantum error correction
YouTube video by Quantum Spain
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Quantum Spain @quantumspain-project.es · 01/12/2025
📢 Tomorrow: new Quantum Spain Seminar with Josu Etxezarreta Martinez - @tecnun.bsky.social Topic: Advances in low-overhead quantum error correction 👉 Register here: events.teams.microsoft.com/event/f76507...
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Información y Tecnologías Cuánticas en España @qipcspain.bsky.social · 27/11/2025
"Seminar | Josu Etxezarreta". #cuantica2025 www.cuantica2025.es/seminar-josu-et…
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Krista Koeller @kristalerista.bsky.social · 14/10/2025
Dear funding agencies, I know we all want to discover the wonder drug that will cure the horrible diseases, but to do that, we need to invest in basic, unsexy, foundational research on how the systems work. Funding can’t all be drug development. Sincerely, Looking for basic research grants.
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Christopher K. Long @christopher-k-long.bsky.social · 18/09/2025
Ever wanted to use virtual Z gates with arbitrary powers of SWAP? Introducing the virtual Z pulse: arxiv.org/abs/2509.13453. In our new article, we present a method for distorting a pulse sequence to implement single-qubit Z controls virtually.
arxiv.org
From virtual Z gates to virtual Z pulses
Virtual $Z$ gates have become integral for implementing fast, high-fidelity single-qubit operations. However, virtual $Z$ gates require that the system's two-qubit gates are microwave-activated or nor...
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Josu Etxezarreta Martinez @katutxakur.bsky.social · 06/08/2025
Check out the V2 of our qLDPC decoding paper "An almost-linear time decoding algorithm for quantum LDPC codes under circuit-level noise". The meme summarizes our approach. @qec.codes
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Christopher K. Long @christopher-k-long.bsky.social · 05/07/2025
How fast can quantum processors run? My coauthors and I answer in our new npj Quantum Information article! Utilising pulse engineering, we prepare molecular ground states in a few nanoseconds, ~100× faster than with gates. Back-of-the-envelope: Simulations can now tolerate T₁ and T₂ ~100× smaller.
nature.com
Minimal state-preparation times for silicon spin qubits - npj Quantum Information
npj Quantum Information - Minimal state-preparation times for silicon spin qubits
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Christopher K. Long @christopher-k-long.bsky.social · 17/06/2025
Hi all! I am excited to finally share this suite of quantum optimal control libraries that run up to 100× faster than QuTiP for some tasks. We developed these libraries while working on our preprint arxiv.org/abs/2406.10913, which was recently accepted into npj Quantum Information—keep tuned! (1/7)
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Sergey Frolov🇺🇦 @spinespresso.bsky.social · 05/06/2025
I remember getting a $300k grant 10 years ago to perform non-abelian braiding in 2 years It is funny, but it is also sad. "The people" want miracles from science, right now, and for free. If one is achieved, they move on immediately and just want more, different, fresh like distracted children.
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Dulwich Quantum Computing @dulwichquantum.bsky.social · 02/06/2025
👇
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Dulwich Quantum Computing @dulwichquantum.bsky.social · 26/05/2025
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Riverlane @riverlane.com · 26/05/2025
An open call for all #QuantumErrorCorrection researchers to now summarise their work in the form of memes please 🙂 - nice work @katutxakur.bsky.social et al (both the paper and meme!) #QECpapers
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Josu Etxezarreta Martinez @katutxakur.bsky.social · 26/05/2025
Check out our latest preprint! The meme summarizes it.
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Craig Gidney @craiggidney.bsky.social · 23/05/2025
I'm often asked if I'll redo the 2019 quantum factoring estimate. Denser storage by yokes, smaller magic factories by cultivation, slimmer approx arithmetic by Chevignard et al… surely the cost is lower now? Yes, it's lower now. security.googleblog.com/2025/05/trac... arxiv.org/abs/2505.15917
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Riverlane @riverlane.com · 09/05/2025
We’d love to find more #QEC experts here on BlueSky and have created this starter pack to help connect the error correction community. It’s just a start – if you’re working QEC, please follow this account and message us. We’ll happily add you to the pack! go.bsky.app/RiZfVco 🧪 🧵[2/2]
go.bsky.app
Riverlane's Quantum Error Correction Pack
Join the conversation
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Dulwich Quantum Computing @dulwichquantum.bsky.social · 22/04/2025
"By the time we get to million qubits, I will be dead." --John Martinis Industry expectations vs actual progress in one of his slides:
Number of qubits plotted as a function of year. Industry expectations vs actual trajectory.
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Josu Etxezarreta Martinez @katutxakur.bsky.social · 07/04/2025
Check out our latest preprint: SpinHex: A low-crosstalk, spin-qubit architecture based on multi-electron couplers. scirate.com/arxiv/2504.0...
scirate.com
SpinHex: A low-crosstalk, spin-qubit architecture based on multi-electron couplers
Semiconductor spin qubits are an attractive quantum computing platform that offers long qubit coherence times and compatibility with existing semiconductor fabrication technology for scale up. Here, w...
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Juan José García-Ripoll @jjgarciaripoll.bsky.social · 06/04/2025
Estas cosas no hacen más que acentuar la desconfianza de los jóvenes en la carrera académica. Lo que necesitamos son inversiones recurrentes, planificadas y predecibles. 1/
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Michael Nielsen @michaelnielsen.bsky.social · 04/04/2025
"overcome your inner resistance; it is always a mistake to try to do things too cleverly" - Einstein in a letter to Leo Szilard
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Christophe Vuillot @christophe.vuillot.info · 21/03/2025
Two talks of Alice&Bob QEC team in parallel this morning: @diego-ruiz.bsky.social presented his new results on distillation with biased-noise qubits: with bias=30 he already gets 150x reduction! I talked about implementing rotor codes So many fun subjects to work on, join our team we are hiring!🐱
Diego presenting his work under the expert eye of Craig Gidney Summary slide of Diego's results
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Quantum Bullshit Detector @bullshitquantum.bsky.social · 30/01/2025
Improving devices before entering commercialization phase: not bullshit
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Julen Bollain @julenbollain.bsky.social · 26/01/2025
En España hay 11.914 personas con una fortuna superior a los 30 millones de dólares. ¿Sabías que gracias a Ayuso dos de cada tres ultrarricos españoles no pagan impuesto de patrimonio? No pagan nada porque tienen su fortuna en Madrid. Pero luego no tiene para la universidades.
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Dave Bacon @dabacon.tachyon.institute · 04/01/2025
I saw the best minds of my generation destroyed by madness, starving hysterical naked, dragging themselves through the academic halls at dawn applying for a new grant
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Graeme Smith @graemesmith.bsky.social · 26/12/2024
“The true measure of learning is not the time and energy you put in. It’s the knowledge and skills you take out.” By @adamgrant.bsky.social www.nytimes.com/2024/12/26/o...
nytimes.com
Opinion | No, You Don’t Get an A for Effort
High marks reward excellence, not grit.
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Josu Etxezarreta Martinez @katutxakur.bsky.social · 17/12/2024
Check out our latest preprint "Asymptotically good CSS-T codes exist". There is also a nice discussion about in on scirate.com/arxiv/2412.0...
scirate.com
Asymptotically good CSS-T codes exist
We give a new construction of binary quantum codes that enables the generation of a CSS-T code from any given CSS code. Using this construction, we prove the existence of asymptotically good binary CS...
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John Preskill @preskill.bsky.social · 14/12/2024
I created a transcript of my talk at the Q2B Conference: "Beyond NISQ: The Megaquop Machine." You can read it here: quantumfrontiers.com/2024/12/14/b...
quantumfrontiers.com
Beyond NISQ: The Megaquop Machine
On December 11, I gave a keynote address at the Q2B 2024 Conference in Silicon Valley. This is a transcript of my remarks. The slides I presented are here. NISQ and beyond I’m honored to be back at…
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