Johannes Jakob Meyer @jjmeyer.bsky.social · 25/09/2026Can people please stop to write that they "take full responsibility for the results" in their AI disclosures? You posted a paper on the arXiv. With your name on it. 293
Johannes Jakob Meyer @jjmeyer.bsky.social · 17/09/2026Thanks! Yes, Berlin only, that's a hard requirement. 000
Johannes Jakob Meyer @jjmeyer.bsky.social · 10/09/2026At the end of the day this would also be loosely tied to recent research but would IMHO result in much more entertaining and interesting talks. 000
Johannes Jakob Meyer @jjmeyer.bsky.social · 10/09/2026I agree with this. I also think it would make sense to go a step further and decouple submissions from papers. Then people can also submit more overview-ish and inspirational/aspirational talks. 130
Johannes Jakob Meyer @jjmeyer.bsky.social · 04/08/2026These don't look that egregious to me. More like a case where people have been working on the problem for quite some time and ChatGPT then supplied the breakthrough. I think that it is fine then to put it out in that form. 010
Johannes Jakob Meyer @jjmeyer.bsky.social · 30/07/2026static.klipy.comErrol Flynn as Robin HoodALT: Errol Flynn as Robin Hood 010
Johannes Jakob Meyer @jjmeyer.bsky.social · 30/07/2026I added my two cents! Thanks for initiating this. 130
Johannes Jakob Meyer @jjmeyer.bsky.social · 09/05/2026For an overview of my research, consider my Google Scholar: scholar.google.com/citations?us... My current focus is to merge quantum information theory with computational complexity, but I have very broad interests all across quantum information.scholar.google.com 230
Johannes Jakob Meyer @jjmeyer.bsky.social · 09/05/2026I recently submitted my PhD thesis 🎉 I am now planning the next step of my journey. I will stay in Berlin for personal reasons, which makes me curious which research groups and companies would hire postdocs or equivalent for remote positions. If you have any leads, please DM! 2233
Johannes Jakob Meyer @jjmeyer.bsky.social · 18/03/2026Such a well-deserved honor! Taking Gilles Brassard's quantum info course at UdeM is what got me into the field. It is still the best course I ever attended. 081
Johannes Jakob Meyer @jjmeyer.bsky.social · 23/01/2026Our work shows that there is a need for quantum communication theory and computational complexity to converge more fully, with many more exciting questions ahead! 010
Johannes Jakob Meyer @jjmeyer.bsky.social · 23/01/2026First, we show that there exists a nearly maximal separation between the computational and unbounded two-way quantum capacity. Second, we show a transition in computational capacity from nearly maximal to zero when the complexity (in terms of Choi rank) goes from polynomial to super-polynomial. 100
Johannes Jakob Meyer @jjmeyer.bsky.social · 23/01/2026We give a first definition of a computational capacity measure and show that it related to computational distillable entanglement for "efficiently stretchable" channels. We give a channel model for which we can tightly bound these quantities to establish two key results: 100
Johannes Jakob Meyer @jjmeyer.bsky.social · 23/01/2026Last year, I became interested in the question what happens if we impose computational efficiency onto information theory. In our latest paper, we analyze how this changes the amount of information that can be transmitted over a channel -- spoiler alert: a lot! scirate.com/arxiv/2601.1...scirate.comThe computational two-way quantum capacityQuantum channel capacities are fundamental to quantum information theory. Their definition, however, does not limit the computational resources of sender and receiver. In this work, we initiate the st... 1141
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025I also wanted to add a shout-out to Álvaro, Thomas and Jan who put out a work with similar mindset today: arxiv.org/abs/2509.21308. It turns out that our results mostly complement each other quite nicely, so please have a look there as well!arxiv.orgEfficient Quantum Measurements: Computational Max- and Measured Rényi Divergences and ApplicationsQuantum information processing is limited, in practice, to efficiently implementable operations. This motivates the study of quantum divergences that preserve their operational meaning while faithfull... 050
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025A big thanks to my coauthors Asad, Jacopo, Lorenzo, Sofiene and Jens. 120
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025This is in stark contrast to how people approached computational information theory to date, where the approaches focused on single-shot statements. These are of course more exact, but also much more complicated to manipulate and build intuition for. 140
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025We believe that our definition has a nice level of abstraction that captures the essence of information theory under computational constraints while at the same time having the look and feel of unbounded information theory. 120
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025I invite you to discover many exciting things in the paper, like computationally measured divergences and a computational Stein's Lemma or a computational Rains bound on efficiently distillable entanglement. 220
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025Another highlight is the fact that we can obtain separations in hypothesis testing, both between bounded and unbounded observers as well as classical-quantum separations. This means there exist classical distributions testable when having access to a quantum computer but not classically. 130
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025We can use the computational relative entropy as a mother quantity. We exemplify this by defining a computational entropy S̲(ρₙ):=−D(ρₙ‖𝕀) and show that it quantifies the best rate at which we can compress a state under complexity restrictions -- just like the entropy in the unbounded setting. 140
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025For example, we obtain a computational version of Pinsker's inequality, which looks exactly like the unbounded relation only that the involved quantities carry underscores, marking them as computational quantities. 130
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025One of our main contributions is to turn this process of "polynomial regularization" into a rigorous notion. It allows us to reap the benefits of regularizing to obtain simpler expressions that closely resemble their counterparts from unbounded information theory. 130
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025Of course, talking about polynomial scaling only makes sense when there is a scaling parameter. Therefore, all our results pertain to families of quantum states indexed by some parameter n. This is often the number of qubits, but need not be. 120
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025We propose the following remedy: we define the computational relative entropy D̲(ρₙ‖σₙ) as the best error exponent in asymmetric hypothesis testing when restricted to polynomially many copies and polynomial-time tests and take the polynomials to be arbitrarily large. 130
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025But there is a catch! The connection between hypothesis testing and the relative entropy only holds if arbitrary tests can be performed. The optimal tests, however, could be exponentially complex to implement. We also need a large number of copies of the state to get sufficient statistics. 120
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025The fact that the relative entropy and its derived quantities appear so often in information theory is that it quantifies the best achievable error exponent in asymmetric hypothesis testing, a primitive many important information processing tasks can be reduced to. 140
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025The relative entropy D(ρ‖σ) is a fundamental quantity in classical and quantum information theory. It appears in many important theorems and serves as a mother quantity to derive other important measures from -- for example mutual information or entropy. 130
Johannes Jakob Meyer @jjmeyer.bsky.social · 26/09/2025You think we already have enough entropies and divergence measures? I don't think so! In our latest work (arxiv.org/abs/2509.20472), we introduce yet another information theoretic measure -- the computational relative entropy. Let's have a quick rundown👇 1183
Johannes Jakob Meyer @jjmeyer.bsky.social · 12/05/2025arxiv.org/abs/2410.18196arxiv.orgSimulating quantum chaos without chaosQuantum chaos is a quantum many-body phenomenon that is associated with a number of intricate properties, such as level repulsion in energy spectra or distinct scalings of out-of-time ordered correlat... 110
Johannes Jakob Meyer @jjmeyer.bsky.social · 20/04/2025I think the best bit is that they have a guy named "Clifford Mapp" on their team! 070
Johannes Jakob Meyer @jjmeyer.bsky.social · 27/03/2025Very nice! Michael Wolf also has some very good newer ones: mediatum.ub.tum.de/download/170...mediatum.ub.tum.de 171
Reposted by Johannes Jakob Meyerqctip2025.bsky.social @qctip2025.bsky.social · 17/02/2025Registrations are now open for #QCTiP2025: qctip2025.com/registration.... Don’t wait too long—spots for participants without a talk are first-come, first-served!qctip2025.comRegistrationsRegistrations Registrations close: 14 March To register please create an account on our ConfTool portal, accessible through the link below (or use the same account you created for submissions of ta… 052
Johannes Jakob Meyer @jjmeyer.bsky.social · 14/01/2025I guess that particular myth was formulated so that you can debunk it. I never heard anyone claim that error mitigation cannot be used, just that it is no scalable solution for the problem. 110
Johannes Jakob Meyer @jjmeyer.bsky.social · 09/12/2024We should all recall once in a while that we as a community are in a hamster wheel of our own making. This means we can also just choose to be nicer and more helpful to each other. 050
Johannes Jakob Meyer @jjmeyer.bsky.social · 09/12/2024That said, one line rejects should not happen. At the end of the day we've all been on the other side and justifiably annoyed by bad reviews. 120
Johannes Jakob Meyer @jjmeyer.bsky.social · 09/12/2024Therefore, it's more of an answer to the question: "how likely is this to cross the bar relative to the other submissions in your batch?". In that way, "weak reject" doesn't mean the submission is not good science, but just that there is so much other good stuff out there. 250
Johannes Jakob Meyer @jjmeyer.bsky.social · 09/12/2024Something that is important for context – and that I only realized after seeing the process from the inside – is that the scores are not meant to judge the quality of the submission. The task of the PC is to make a program. 260
Reposted by Johannes Jakob Meyerqctip2025.bsky.social @qctip2025.bsky.social · 05/12/2024Submissions for QCTiP 2025 are now open. 12315
Johannes Jakob Meyer @jjmeyer.bsky.social · 29/11/2024www.unicodeit.netunicodeit.netunicodeit.net 2100
