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Joschka Roffe @qec.codes · 19/06/2026

performance for the <500 qubit regime we consider.

Joschka Roffe @qec.codes · 19/06/2026

Hi. Good question. The BPT bounds impose restrictions on code parameters in the asymptotic limit, but they leave open the possibility that high-rate local codes might exist at finite-size. So the favourable encoding rate would eventually disappear for larger code distances, but we still see good ...

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Joschka Roffe @qec.codes · 19/06/2026

This is not a marginal improvement: instances of the code family we introduce can reduce qubits by up to an order of magnitude relative to the rotated surface code, and our circuit-level numerical simulations demonstrate improvements in logical error rate suppression by a factor of up to 1000x. 3/3

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Joschka Roffe @qec.codes · 19/06/2026

But this has always come with the caveat that they require long-range interactions, making them far harder to engineer into practical quantum computing systems. In this work we show we can have the best of both worlds: efficient qLDPC codes that can be implemented on a planar 2D grid of qubits. 2/3

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Joschka Roffe @qec.codes · 19/06/2026

📢 New paper. 𝗡𝗲𝗮𝗿𝗲𝘀𝘁-𝗻𝗲𝗶𝗴𝗵𝗯𝗼𝘂𝗿 𝗴𝗮𝘁𝗲𝘀 𝗮𝗿𝗲 𝗮𝗹𝗹 𝘆𝗼𝘂 𝗻𝗲𝗲𝗱: 𝗛𝗶𝗴𝗵-𝗿𝗮𝘁𝗲 𝗾𝘂𝗮𝗻𝘁𝘂𝗺 𝗹𝗼𝘄-𝗱𝗲𝗻𝘀𝗶𝘁𝘆 𝗽𝗮𝗿𝗶𝘁𝘆-𝗰𝗵𝗲𝗰𝗸 𝗰𝗼𝗱𝗲𝘀 𝗼𝗻 𝗮 𝗽𝗹𝗮𝗻𝗮𝗿 𝗴𝗿𝗶𝗱. scirate.com/arxiv/2606.1... 𝘁𝗹𝗱𝗿; For several years now, we have been advocating for qLDPC codes as a resource-efficient alternative to the surface code. 1/3

scirate.com

Nearest-neighbour gates are all you need: High-rate quantum low-density parity-check codes on a planar grid

High-performance quantum low-density parity-check codes promise substantial reductions in the overhead of fault-tolerant quantum computation, but most constructions require long-range connectivity or ...

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Joschka Roffe @qec.codes · 08/06/2026

Back in Santa Barbara this week for #QEC2026. Looking forward to meeting colleagues, old and new, and hearing about the latest and greatest in QEC!

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Joschka Roffe @qec.codes · 01/06/2026

🚨Registration deadline today! TartanQEC Workshop 24-26 June. Poster submissions remain open until end-of-day (AOE). Sign up now 👇 qec.codes/tartan2026

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Joschka Roffe @qec.codes · 20/05/2026

TartanQEC Workshop | University of Edinburgh 24-26 June. The full programme is now available. Poster submissions are still being accepted & registration deadline is 1st June. Sign up now 👇 qec.codes/tartan2026/t...

qec.codes

TartanQEC Timetable

TartanQEC Workshop timetable, 24-26 June 2026, School of Informatics, University of Edinburgh.

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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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Joschka Roffe @qec.codes · 29/04/2026

📢 TartanQEC Workshop, 24-26 June, University of Edinburgh. Along with @jdpritchard.bsky.social, I am organising an event on practical methods for quantum error correction. See details and submit your best work for poster/talk before 8th May 👇 qec.codes/tartan2026/

qec.codes

TartanQEC Workshop

TartanQEC Workshop, 24-26 June 2026, School of Informatics, University of Edinburgh.

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Jonathan Pritchard @jdpritchard.bsky.social · 29/04/2026

Interested in qauntum error correction? Join @qec.codes and I at the TartanQEC conference in Edinburgh 24-26 June 26 as part of the Quantum Fringe. Abstract submission open until 8th May - for details and registration see qec.codes/tartan2026/

qec.codes

TartanQEC Workshop

TartanQEC Workshop, 24-26 June 2026, School of Informatics, University of Edinburgh.

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Joschka Roffe @qec.codes · 06/03/2026

We show explicit examples where up to k/2 Pauli-product measurements can be performed simultaneously, saturating the same upper bound achieved by the surface code. The result is a single computational block that naturally supports parallel logical operations, i.e. a QGPU.

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Joschka Roffe @qec.codes · 06/03/2026

In this work we address this limitation through a code–logic co-design approach. First, we introduce a new family of codes that admits an addressable logical-qubit basis. Second, we develop a code surgery protocol that allows operations on this basis to be executed in parallel. 3/n

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Joschka Roffe @qec.codes · 06/03/2026

quantum computation. A key challenge, however, is that compiling logic is much more difficult than in surface codes: logical operators can overlap, meaning there limited scope for executing operations in parallel. 2/n

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Joschka Roffe @qec.codes · 06/03/2026

📢 New paper. 𝐐𝐆𝐏𝐔: 𝐏𝐚𝐫𝐚𝐥𝐥𝐞𝐥 𝐥𝐨𝐠𝐢𝐜 𝐢𝐧 𝐪𝐮𝐚𝐧𝐭𝐮𝐦 𝐋𝐃𝐏𝐂 𝐜𝐨𝐝𝐞𝐬. A great collaboration w/ Boren Gu, Andi Lui, Armanda Quintavalle, Xian Xu, & @jenseisert.bsky.social 𝐭𝐥𝐝𝐫; Quantum LDPC codes are an exciting architecture for fault-tolerant ... 1/n scirate.com/arxiv/2603.0...

scirate.com

QGPU: Parallel logic in quantum LDPC codes

Quantum error correction is critical to the design and manufacture of scalable quantum computing systems. Recently, there has been growing interest in quantum low-density parity-check codes as a resou...

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Joschka Roffe @qec.codes · 05/02/2026

detector matrix. @peter-jan.bsky.social's paper on detector models is a great intro to this arxiv.org/abs/2407.13826 At this point you'll have ample background to follow the STIM tutorials on surface code decoding and enough understanding to apply these tools to other QEC codes.

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Joschka Roffe @qec.codes · 05/02/2026

readout, as these are much easier to set up. The PyMatching documentation explains how you can do this for the Toric code pymatching.readthedocs.io/en/stable/to... Once your comfortable with this, it's time to start with more realistic circuit level simulations using STIM where you decode over a

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Joschka Roffe @qec.codes · 05/02/2026

stabiliser codes in terms of binary matrices via the GF2 mapping (this allows you to use classical coding machinery in the analysis of QEC). At this point you can start expereminting with decoding simulations. I would recommend beginning with code capacity simulations, where you assume perfect

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Joschka Roffe @qec.codes · 05/02/2026

I think it's best to learn the basic theory first: how QEC uses entanglement to create redundancy, how you can use stabilisers to nodestructively measure parities, and understand some of the classic codes such as the Shor and Steane codes. From there, it's important to learn how you can represent

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Joschka Roffe @qec.codes · 04/02/2026

Great day back in Durham visiting @durhamqlm.bsky.social to give a seminar on QEC and our recent work at Quantum Software Lab. Also fun to discuss the fault-tolerance of the Welsh towname Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch w/ @ifanghughes.bsky.social @tobifranzen.bsky.social

Opening slide of my presentation on Quantum Error Correction at Durham Uninversity. Slide features a picture of the Durham student union and Kingsgate bridge, famously designed by legendary North Eastern arcitect Ove Arup and considered to be one of the world's finest examples of brutalist architecture.

A slide from my presentation comparing surface codes to QLDPC codes. Background: surface codes are a leading approach to QEC, favoured for their local connectivity and straightforward ability to scale to arbitrary distance. However, from a coding theory perspective, they are far from optimal codes, owing to the fact that only a single logical qubit is encoded per patch. In practice, it is estimated that ~1000 qubits will be required per logical qubit in a surface code architecture, making them much less efficient than classical LDPC codes (of the type used in 5G and WiFi) where encoding ratios can be as low as 2-to-1. Quantum LDPC are modelled on classical codes, and it is has been shown (through simulation) that they code achieve encoding densities as low as 50-to-1 (some 20x improvement than surface codes). The tradeoff is that QLDPC codes are much less structured than surface codes, requiring long-range interactions between qubits. The QLDPC Tanner graph shown on the slide depicts a naive layout that I usefully refer to as the "spaghetti connectivity".

Language is redundant by design. The town of Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch in Anglesey Wales is probably the best error corrected placename in the world!

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Joschka Roffe @qec.codes · 04/02/2026

I wrote a "Zero to Surface Code Guide" a couple of years ago that doesn't require you to transform into Alexei Kitaev. arxiv.org/abs/1907.11157 There is also the legendary surface code review by Austin Fowler arxiv.org/abs/1208.0928 written in 2012 but is still excellent for learning the basics.

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Timo Hillmann @timohillmann.bsky.social · 03/09/2025

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...

nature.com

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....

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Joschka Roffe @qec.codes · 03/09/2025

A very enjoyable collaboration @timohillmann.bsky.social, @lucasberent.bsky.social, Armanda Quintavalle, Robert Wille, and @jenseisert.bsky.social

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Joschka Roffe @qec.codes · 03/09/2025

parity-check codes. Our LSD algorithm works as a post-processor for standard belief propagation algorithms and, crucially, is designed from the bottom-up with parallism in mind. This makes it a suitable for implementation on specialised hardware (e.g., GPUs, FPGAs, ASICS) for real-time decoding.

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Joschka Roffe @qec.codes · 03/09/2025

𝘁𝗹;𝗱𝗿; Any quantum error correction (QEC) protocol is only ever as good as its decoder: a classical co-processor tasked with intrepting stabiliser measurements in real-time. In this work, we propose localised statistics decoding (LSD) as a very general decoding algorithm for quantum low-density ...

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Joschka Roffe @qec.codes · 03/09/2025

📢 Our paper, 𝗟𝗼𝗰𝗮𝗹𝗶𝘀𝗲𝗱 𝘀𝘁𝗮𝘁𝗶𝘀𝘁𝗶𝗰𝘀 𝗱𝗲𝗰𝗼𝗱𝗶𝗻𝗴 𝗳𝗼𝗿 𝗾𝘂𝗮𝗻𝘁𝘂𝗺 𝗹𝗼𝘄-𝗱𝗲𝗻𝘀𝗶𝘁𝘆 𝗽𝗮𝗿𝗶𝘁𝘆-𝗰𝗵𝗲𝗰𝗸 𝗰𝗼𝗱𝗲𝘀, is now published in Nature Communications (Nature Portfolio). Great to see it in print! www.nature.com/articles/s41...

nature.com

Localized statistics decoding for quantum low-density parity-check codes - Nature Communications

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Joschka Roffe @qec.codes · 23/08/2025

Your wish will be fufilled: this will be in arXiv V2 👀

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Alexis Morvan @amorvan.bsky.social · 23/08/2025

Color code decoding with some big claim: arxiv.org/abs/2508.15743 I wish they could try to benchmark this decoder against the experimental color code data from arxiv.org/pdf/2412.14256 zenodo.org/records/1423... We are releasing experimental data so people can try out their decoding algorithms!

arxiv.org

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...

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John Preskill @preskill.bsky.social · 17/08/2025

The QEC25 conference hosted by @yaleqi.bsky.social was really excellent, and videos of all talks are available. So much recent progress on quantum error correction! qec25.yalepages.org

qec25.yalepages.org

QEC25

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Joschka Roffe @qec.codes · 12/08/2025

James Mills introducing Logical Accreditation to #QEC2025 at @yaleqi.bsky.social See our recent preprint here: arxiv.org/abs/2508.05523

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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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Jens Eisert @jenseisert.bsky.social · 28/05/2025

Hardware-tailored logical Clifford circuits for stabilizer codes scirate.com/arxiv/2505.2... This first first author paper of Eric appeared yesterday, but was not picked up by Scirate. It suggests novel strategies for implementing logical Cliffords of stabilizer codes under hardware constraints.

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Jens Eisert @jenseisert.bsky.social · 27/05/2025

Hardware-tailored logical Clifford circuits for stabilizer codes arxiv.org/abs/2505.20261 It is important to identify strategies for implementing Clifford unitaries at the logical level of stabilizer codes in #quantumerrorcorrection, respecting hardware constraints. Here is one such strategy.

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Joschka Roffe @qec.codes · 05/05/2025

📣 New pre-print on the arXiv today on generalisation of surface code lattice surgery to arbitrary CSS codes w/ Clément Poirson and Robert Booth. Congrats to @clemenson7.bsky.social on his first paper! 🎉

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Joschka Roffe @qec.codes · 14/04/2025

The group's research include: - Investigating new QEC protocols. - Designing QEC decoding algorithms for specialised hardware. - Logical gates for fault-tolerant logic. - Design and implementation of QEC experiments, - Developing open-source QEC software. More details soon!

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Joschka Roffe @qec.codes · 14/04/2025

My group will tackle both the theoretical and practical challenges of building fault-tolerant quantum computers. I'll be advertising postdoctoral research positions soon. Please get in touch if you're interested in joining or collaborating.

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Joschka Roffe @qec.codes · 14/04/2025

Happy World Quantum Day! I'm excited to announce that I will be starting a new group dedicated to quantum error correction (QEC) at The University of Edinburgh Quantum Software Lab, funded by an EPSRC Quantum Technology Career Acceleration Fellowship!

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Joschka Roffe @qec.codes · 12/02/2025

📣 New paper: Computing Efficiently in QLDPC Codes w/ @TeamPhotonic! Lots of great stuff here: - New subsystem codes w/ transversal gates that efficiently compile full Clifford Group. - Single-shot decoding - Huge circuit-level logic sims scirate.com/arxiv/2502.0...

scirate.com

Computing Efficiently in QLDPC Codes

It is the prevailing belief that quantum error correcting techniques will be required to build a utility-scale quantum computer able to perform computations that are out of reach of classical computer...

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Joschka Roffe @qec.codes · 14/01/2025

🚨Reminder: The deadline to apply for the Quantum Informatics CDT is tomorrow (15th Jan). Apply below 👇 www.quantuminformatics-cdt.ac.uk

quantuminformatics-cdt.ac.uk

QI CDT – EPSRC Centre for Doctoral Training in Quantum Informatics

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Steve Flammia @sflammia.bsky.social · 11/01/2025

Submissions for QEC 2025 are now open through March 28. This will easily be the most exciting conference on quantum error correction yet! Conference homepage: qec25.yalepages.org EasyChair submission page: easychair.org/my/conferenc...

qec25.yalepages.org

QEC25

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Joschka Roffe @qec.codes · 14/12/2024

@physicssteve.bsky.social's Inside Quantum Podcast has two seasons and over 20 episodes in total. Highly recommended insidequantum.org

insidequantum.org

insideQuantum

insideQuantum, telling the human stories behind quantum technologies.

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Joschka Roffe @qec.codes · 10/12/2024

Yes. They are two separate programmes. You can apply for both.

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Joschka Roffe @qec.codes · 07/12/2024

Ah wow. This is amazing! Is it in a Github repo so we can contribute?

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Joschka Roffe @qec.codes · 07/12/2024

I'll see if the repo can be moved to the Quantum-journal GitHub organisation. Arxiv PDF upload would work. You could also upload the typst source alongside that, so the experience wouldn't be much different than with LaTeX

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qctip2025.bsky.social @qctip2025.bsky.social · 05/12/2024

Submissions for QCTiP 2025 are now open.

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