Jens Eisert @jenseisert.bsky.social · 30/09/2026Quantum coding schemes typically rely on knowing the underlying state or channel. In “Universal quantum coding,” we show how to distil entanglement and communicate quantum information without this prior knowledge. scirate.com/arxiv/2609.3... 131
Jens Eisert @jenseisert.bsky.social · 30/09/2026In our new work, “Ultra-high-distance quantum memories from amplified #qLDPC codes,” we introduce distance amplifiers: a modular way to increase both code distance and certified protection against circuit faults. The key is a rigorous fault-response certificate. scirate.com/arxiv/2609.3... 030
Jens Eisert @jenseisert.bsky.social · 04/09/2026We codesign quantum error correcting codes and decoders in quantum low-density lattice codes. scirate.com/arxiv/2609.0... 181
Jens Eisert @jenseisert.bsky.social · 04/09/2026Does computational pseudorandomness require statistical randomness? Surprisingly, no. scirate.com/arxiv/2609.0... 020
Jens Eisert @jenseisert.bsky.social · 28/08/2026How far can noise “dequantize” quantum circuits? We introduce a highly parallelizable tensor-network algorithm that optimally unravels arbitrary single-qubit noise to minimize entanglement, with rigorous simulation-error guarantees. journals.aps.org/pra/abstract... 160
Jens Eisert @jenseisert.bsky.social · 14/08/2026Random quantum circuits are a central tool in quantum information and many-body physics. But how random should the individual gates actually be? Perhaps surprisingly: less random local gates can generate more global randomness. journals.aps.org/pra/abstract... 040
Reposted by Jens EisertGreg White @gregswhitenoise.bsky.social · 16/07/2026My good friend and famed lover of questionnaires @eliesgf.bsky.social has a simple question for the quantum info community: what do you think when you hear the terms "strong" and "weak simulation? He (and by extension, me) would love it if you filled in this Google Form! forms.gle/wfFcwBPdaafv...docs.google.comWhat does it mean to simulate a quantum computation?Dear colleagues, We are some quantum researchers at FU Berlin. We were recently surprised among ourselves that we used the same words in very different incompatible ways when it comes to classically... 063
Jens Eisert @jenseisert.bsky.social · 01/08/2026Dynamical codes for hardware with noisy readouts We investigate the performance of dynamical stabilizer codes when measurements are noisy, as expected in many quantum computing platforms, with surprising outcomes. quantum-journal.org/papers/q-202... 051
Jens Eisert @jenseisert.bsky.social · 31/07/2026Quantum computers offer #quantumadvantage for combinatorial #optimization, but the practical advantage remains to be quantified. We study decoded quantum interferometry and show that classical sampling can closely emulate its performance across numerical benchmarks. scirate.com/arxiv/2607.2... 030
Jens Eisert @jenseisert.bsky.social · 30/07/2026I am delighted to see that our review "Artificial intelligence for representing and characterizing quantum systems" is now published in Nature Reviews Physics. www.nature.com/articles/s42... 163
Jens Eisert @jenseisert.bsky.social · 24/07/2026Complete theory of the Clifford commutant quantum-journal.org/papers/q-202... The Clifford group is central to quantum information. We develop a complete theory of its commutant, with explicit bases, dimension formulas, and a graphical calculus - and show a wealth of applications. 181
Jens Eisert @jenseisert.bsky.social · 27/06/2026Rigorous no-go theorems for heralded linear-optical state generation tasks: Algebraic geometry in applied mathematics meets design choices in linear optical state preparation for photonic quantum computing. journals.aps.org/pra/abstract... 230
Jens Eisert @jenseisert.bsky.social · 19/06/2026Experimental measurement and a physical interpretation of quantum shadow enumerators We show that Rains' quantum shadow enumerators - a powerful tool from #quantumerrorcorrection - admit a direct physical interpretation in terms of two-copy Bell measurements. journals.aps.org/prresearch/a... 051
Jens Eisert @jenseisert.bsky.social · 19/06/2026Nearest-neighbour gates are all you need: High-rate quantum low-density parity-check codes on a planar grid. scirate.com/arxiv/2606.1... 1204
Jens Eisert @jenseisert.bsky.social · 27/05/2026What role do #measurements play in quantum algorithms? We systematically explore this question in the context of a greatly simplified #quantumalgorithm for the abelian hidden subgroup problem for states (#StateHSP), featuring a reduced circuit complexity. journals.aps.org/prxquantum/a... 170
Jens Eisert @jenseisert.bsky.social · 08/05/2026For generating #pseudorandomness using doped #Clifford circuits, fundamental bounds on the resource cost show that extensive doping levels are necessary. go.aps.org/3RjBHQP 040
Jens Eisert @jenseisert.bsky.social · 05/05/2026I generally keep politics out of my social media—that is a space better suited to others. But what is happening here? I primarily use Bluesky to share scientific content, and I still find X reasonably functional for that purpose. Yet there seem to be significant shifts underway. What is going on? 210
Jens Eisert @jenseisert.bsky.social · 13/04/2026The term has started again at Freie Universität Berlin. This term, I am teaching my favourite subject, quantum information and quantum technologies. www.physik.fu-berlin.de/en/einrichtu... 0141
Jens Eisert @jenseisert.bsky.social · 03/04/2026We introduce a method for achieving high-threshold decoding of non-Pauli codes aimed at two-dimensional universality. Our results suggest that genuinely non-Clifford quantum operations in two-dimensional codes can perform comparably to those of a simple quantum memory. scirate.com/arxiv/2604.0... 1110
Jens Eisert @jenseisert.bsky.social · 02/04/2026In the absence of quantum error correction, circuits of #quantumcomputers can be logarithmically deep. www.nature.com/articles/s41... 082
Reposted by Jens EisertJoschka 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.comQGPU: Parallel logic in quantum LDPC codesQuantum 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... 1201
Reposted by Jens EisertElies Gil-Fuster @eliesgf.bsky.social · 25/03/2026New #QML paper alert! 📝🧠⚛️ 🧐 A PAC-Bayesian approach to generalization for quantum models arxiv.org/abs/2603.22964 This collaboration involved some seriously hard and fun work by @pablones8.bsky.social, Matthias Caro, Carlos Bravo-Prieto, @fjschreiber.bsky.social, and @jenseisert.bsky.socialarxiv.orgA PAC-Bayesian approach to generalization for quantum modelsGeneralization is a central concept in machine learning theory, yet for quantum models, it is predominantly analyzed through uniform bounds that depend on a model's overall capacity rather than the sp... 1113
Jens Eisert @jenseisert.bsky.social · 28/03/2026Measurement-induced non-commutativity in adaptive fermionic linear optics We show that mid-circuit measurements of fermions with internal degrees of freedom can induce the equivalent of "magic" to free fermionic circuits and render them classically hard to sample. scirate.com/arxiv/2603.2... 140
Jens Eisert @jenseisert.bsky.social · 28/03/2026What a week. A highlight for me has been the #quantumtechnologies segment of the Grand Challenges conference of the @berlinualliance.bsky.social. Jerry Chow blew everybody away with his talk. 021
Jens Eisert @jenseisert.bsky.social · 06/03/2026QGPU: Parallel logic in quantum LDPC codes scirate.com/arxiv/2603.0... We introduce #clusteredcycliccodes for #quantumerrorcorrection and show how to pursue highly parallelized surface-code style quantum logic with quantum low density parity check codes featuring simple logicals. 0100
Jens Eisert @jenseisert.bsky.social · 06/03/2026Tight inapproximability of max-LINSAT and implications for decoded quantum interferometry. scirate.com/arxiv/2603.0... Warm thanks to @mxkramer.bsky.social and Carsten Schubert for this collaboration. 030
Jens Eisert @jenseisert.bsky.social · 27/02/2026The unbearable hardness of deciding about magic We show that determining membership in the stabilizer polytope, which defines the free states of magic-state resource theory, requires super-exponential time exp(n2) in the number of qubits n, even approximately. scirate.com/arxiv/2602.2... 1130
Jens Eisert @jenseisert.bsky.social · 26/02/2026There are interesting separations in quantum learning theory depending on whether or not one has access to post-measurement states in quantum measurement. scirate.com/arxiv/2602.2... 142
Jens Eisert @jenseisert.bsky.social · 23/02/2026Mid-circuit measurements are a powerful tool for state preparation. In contrast, their usefulness for #quantumcomputation remains comparatively less well understood. We demonstrate that #midcircuitmeasurementscan enable quantum advantages even in shallow circuits. journals.aps.org/prl/abstract... 050
Jens Eisert @jenseisert.bsky.social · 17/02/2026Variational #quantumalgorithms and classical variational methods, such as #tensornetworks, provide upper bounds on ground-state energies. This work provides guarantees for lower bounds. journals.aps.org/pra/abstract... 080
Reposted by Jens EisertParityQC @parityqc.bsky.social · 27/01/2026We're excited to have kicked off a new project - together with Freie Universität Berlin, Technische Universität Berlin and NXP Semiconductors, and led by @jenseisert.bsky.social. Our goal is to advance the performance of quantum algorithms to solve real problems in semiconductor chip manufacturing.parityqc.comParityQC joins PraktiQOM project, developing advanced quantum algorithms for semiconductor chip design - ParityQCParityQC is a member of the PraktiQOM project, aiming to advance quantum algorithms to solve real-world optimization problems. 011
Jens Eisert @jenseisert.bsky.social · 23/01/2026This is a paper I very much like, for its foundational and somewhat "rebellious" character: We show that notions channel capacities are strongly altered if one simply assumes that all operations one can implement are efficient. scirate.com/arxiv/2601.1... 0101
Jens Eisert @jenseisert.bsky.social · 23/01/2026This is a paper I very much like, for its foundational and somewhat "rebellious" character: We show that notions channel capacities are strongly altered if one simply assumes that all operations one can implement are efficient. scirate.com/arxiv/2601.1... 040
Jens Eisert @jenseisert.bsky.social · 17/01/2026It has been a great pleasure—and both fun and insightful—to speak with Dr. Thomas Ramge about the future of quantum technologies, broader aspects of science and technology, and what makes science so exciting in the first place. m.youtube.com/watch?si=mh2... 090
Jens Eisert @jenseisert.bsky.social · 12/01/2026This is the most technological paper I have been involved in for a while. It presents a below-threshold error reduction in single photons through photon #distillation. scirate.com/arxiv/2601.0... 090
Jens Eisert @jenseisert.bsky.social · 11/01/2026Variational optimization of projected entangled-pair states on the triangular lattice. journals.aps.org/prb/abstract... The “meta-message” is that the use of tools such as #automaticdifferentiation, and the co-design of the ansatz class and the physical system can improve #tensornetwork methods. 050
Jens Eisert @jenseisert.bsky.social · 09/01/2026To what extent can noisy quantum circuits be classically simulated? And at what point is this no longer true, so that one can hope for a quantum advantage? This is a compelling research question. Here, we suggest frames to do so, extending known Monte Carlo methods. scirate.com/arxiv/2601.0... 082
Jens Eisert @jenseisert.bsky.social · 05/01/2026Do Bose-Hubbard type systems have a speed of sound for particle propagation? scirate.com/arxiv/2601.001… Yes. This work proves a strikingly simple bound of this kind for particle propagation for generalized Bose–Hubbard models defined on general lattices. 182
Jens Eisert @jenseisert.bsky.social · 18/12/2025We suggest a shift in emphasis—namely, putting it on the representability of #functions—when thinking about quantum models aimed at achieving a quantum advantage for machine learning tasks. scirate.com/arxiv/2512.1... 031
Jens Eisert @jenseisert.bsky.social · 10/12/2025How can we classically simulate large-scale open quantum systems—effectively dequantizing them? I am delighted to see the results of this wonderfully fruitful collaboration published in @natureportfolio.nature.com Communications. www.nature.com/articles/s41... 170
Reposted by Jens EisertScience X / Phys.org @sciencex.bsky.social · 08/12/2025Recent analysis shows that quantum-state tomography faces significant challenges in accurately reconstructing continuous-variable quantum states, highlighting key limitations for quantum technologies. doi.org/hbdw67phys.orgQuantifying unknown quantum states: Study explores effectiveness of existing methodsReliably quantifying and characterizing the quantum states of various systems is highly advantageous for both quantum physics research and the development of quantum technologies. 031
Jens Eisert @jenseisert.bsky.social · 29/11/2025This is a publication I am extremely happy about. It is a bit rebellious, and yet it touches upon an old and important question: How can we learn an unknown continuous quantum state from data? www.nature.com/articles/s41... We prove that quantum state tomography is a lot harder than anticipated. 1111
Reposted by Jens EisertJens Eisert @jenseisert.bsky.social · 09/11/2025The results of the evaluation of the submissions to #QIP2026 are out. I am very happy to see eight accepted submissions from our team so far. arxiv.org/abs/2504.12263 arxiv.org/abs/2505.15770 arxiv.org/abs/2502.12284 arxiv.org/abs/2510.07305 arxiv.org/abs/2503.15751 arxiv.org/abs/2510.05531 and … 1151
Reposted by Jens EisertEman @nettarecosmico.bsky.social · 10/11/2025quantamagazine.orgPhysicists Take the Imaginary Numbers Out of Quantum Mechanics | Quanta MagazineQuantum mechanics has at last been formulated exclusively with real numbers, bringing a mathematical puzzle at the heart of the theory into a new era of inquiry. 041
Reposted by Jens EisertPerimeter Institute for Theoretical Physics @perimeterinstitute.bsky.social · 10/11/2025Congratulations to Kiana Salehi, Perimeter PhD student who was awarded the Blue Apple Award for her talk, Influence of observer’s inclination and spacetime structure on photon ring observables. Learn more: indico.global/event/14302/... 0111
Jens Eisert @jenseisert.bsky.social · 09/11/2025The results of the evaluation of the submissions to #QIP2026 are out. I am very happy to see eight accepted submissions from our team so far. arxiv.org/abs/2504.12263 arxiv.org/abs/2505.15770 arxiv.org/abs/2502.12284 arxiv.org/abs/2510.07305 arxiv.org/abs/2503.15751 arxiv.org/abs/2510.05531 and … 1151
Jens Eisert @jenseisert.bsky.social · 24/10/2025Over the recent weeks and months, John Preskill and I sat down to think about where we are in quantum computing. While the noisy intermediate-scale quantum (#NISQ) era is just unfolding as we speak, the time seems right to look ahead to the next steps to come. scirate.com/arxiv/2510.1... 1324
Jens Eisert @jenseisert.bsky.social · 22/10/2025This is a manuscript I am particularly happy with. It concerns topics I have been working on for my PhD, entanglement theory, going back to the work of Bennett et al. Yet it still has a fresh flavour, relating the subject to modern developments in quantum computing. www.nature.com/articles/s41... 0172