QuOI Theory

Can a physically motivated symmetry make many-body magic analytically solvable? If so, at what cost? We answer this question (arxiv.org/abs/2609.38319), by looking at pairwise parity symmetry. This gives rise to a family of quantum states known as X-states. (continue..)/n

How does memory help to count? Using n bits, one can count perfectly up to 2^n. Higher numbers can only be counted on average, with an uncertainty growing with the number to be counted. We looked at how this uncertainty can be reduced when using qubits instead: arxiv.org/abs/2608.26240

Today on the arXiv with @itsmealeale.bsky.social we provide insights into the question of whether the presence of quantum entanglement at equilibrium can influence how an interacting system responds to changes in temperature. scirate.com/arxiv/2608.2...

New from Klára. With superactivation of genuinely multipartite entanglement, how much extra entanglement can you get from local projections of multiple copies of a state? Here it's shown that an optimal number can exist arxiv.org/abs/2608.19427

New preprint from Phila, teaming up with a group of experimentalists to design and test a new adaptive scheme for accurately reconstructing bosonic states (in particular Wigner functions) using fewer measurements arxiv.org/abs/2608.02049

New from Simon (can you tell admin recently came back from holiday and is catching up? 😅) Here we have a preprint showing how to apply the framework of quantum hypothesis testing to the sequential (continuous) parameter regime arxiv.org/abs/2608.01248

New preprint from Manu. They show the circumstances under which the quantum jump formalism is valid and effective when the dissipators in the quantum master equation are non-additive, finding that imperfect jumps can make additive unravellings possible arxiv.org/abs/2608.14469

New preprint from Shuheng, showing how indefinite causal order can be used to extend the parameter range over which entanglement remains certifiable after being transmitted through a noisy channel arxiv.org/abs/2608.14110

New preprint! Continuing on our work of describing quantum measurements as a dynamical, unitary process, here we apply these principles to numerical simulations of a more realistic many-body system -- a lattice of hopping particles arxiv.org/abs/2608.11319

New from Philipp in PRA, showing how to perform high-harmonic generation in the classically forbidden region, and produce super-Poissonian photon statistics in so doing. This allows them to test quantum properties of the driving field journals.aps.org/pra/abstract...

In our group we love the Landauer bound on dissipation. So in this new preprint from Jan, Jake, Pharnam, and Marcus, they explore how the cost of erasure can increase when one has access only to finite resources, in both the classical and quantum cases arxiv.org/abs/2607.27341

New preprint from Dani, Marcus, and Alberto: Working out how much work quantum systems do is hard work! In this new work, the team work up the courage to work through a new definition of the quantum work operator arxiv.org/abs/2607.20602

New preprint! Erik, Pharnam, Moha & co. They look at quantum thermometry when the dynamics are non-Markovian, deriving expressions for the Fisher information and the scaling of the precision in this scenario arxiv.org/abs/2607.15978

New in Reports on Progress in Physics by Florian, Marcus, Pauli, and Jake: they develop a self-contained model of a quantum processor without external control, to figure out what thermodynamic resources a quantum computer fundamentally needs to operate iopscience.iop.org/article/10.1...

New in Sciences Advances from Nicky, Florian, Pauli, and Marcus: A new way to characterise high-dimensional, time-frequency entanglement in photons for use in quantum key distribution, all with methods that can use commercial telecom components! www.science.org/doi/10.1126/...

This is now out in PRX Quantum! journals.aps.org/prxquantum/a...

New preprint! Dorian and colleagues make a simple derivation of Wigner's Inequality and a basic quantum optical lab setup to test it, with data to go with it. If you're designing an undergrad program to teach QM and give students an intuition for it, this one's for you! arxiv.org/abs/2606.30255

New preprint! Philipp studies the implications of two-electron effects on the strong-field approximation and look at high-harmonic generation in this context arxiv.org/abs/2606.24765

New preprint! Shuheng looks at the implications for multipartite entanglement in many-body systems of exceptional points arxiv.org/abs/2606.24205

New preprint! Florian and Marcus propose a new, easily-implementable method for certifying entanglement in discrete time bin temporal superposition states arxiv.org/abs/2606.23817

New preprint! Philipp and colleagues show that bright-squeezed-vacuum-driven high-harmonic generation can lead to non-Gaussianity in the resulting states, or to Gaussian entanglement, or to non-classical Gaussian states arxiv.org/abs/2606.22714

New preprint! It's known that measurement error can make certifying quantum effects harder. But here, Simon and colleagues show that it's sometimes possible for an adversary to trick you into seeing entanglement using arbitrarily small errors! arxiv.org/abs/2606.20396

What a brilliant day, three consecutive defenses: It was an honor to serve on the PhD committee of Philipp Sohr (middle), and then very proud to see my student Nicky Kai Hong Li (second from right) defend valiantly, before leaning back as Marcus' (left) student Iraj (second from left) took the stage

What's better than celebrating a PhD defence? How about THREE? Congrats to Drs (L-R) Umesh, Sohr, and Li for finishing their doctorates (and organising a three-in-a-row defence day!)

My mom: What have you been doing all these years? Me:

@quoi-theory.at mods posted the defense pic where I look most dead - whilst I was tired, I was also very happy ❤️

New from Philipp: a Rep. Prog. Phys. about attosecond quantum optical interferometry! iopscience.iop.org/article/10.1... See also this write-up in Physics World: physicsworld.com/a/attosecond...

Congratulations, Dr. Xuereb! 🔥🧊🖥️👹

New preprint from Klára and Nico on genuinely multipartite entanglement: they show that all members of a certain kind of Gaussian state are both fully inseparable biseparable, and also GME. This raises the question: are ALL fully inseparable Gaussian states GME? arxiv.org/abs/2605.28404

New preprint! Here, Dorian, Marcus, and Eliza describe how to create a form of entanglement that has both discrete and continuous features in a quantum optical setting arxiv.org/abs/2605.26962

Well done, Phila and Tom!

This has now been published in PRA! journals.aps.org/pra/abstract...

New preprint! Dimpi, Shuheng, Giuseppe, and Konrad study the structure of covariance matrices for finite-dimensional position and momentum observables, expanding uncertainty relations to account for more complicated correlation structures arxiv.org/abs/2605.11876

Congratulations, Dr. Meier!

This is now out in PRE! journals.aps.org/pre/abstract...

This is now out in Quantum! quantum-journal.org/papers/q-202...

This is now published in PRL! journals.aps.org/prl/abstract...

New preprint! Carlos looks at the dynamics of an all-to-all quantum Ising model and finds that it expresses a wide range of behaviours, from integrable to chaotic arxiv.org/abs/2604.14798

New in PRA! Using analytic and numerical methods, Carlos and colleagues study how imperfections in a measuring device impact one's ability to characterise a quantum many-body state journals.aps.org/pra/abstract...

New preprint! Marcus and Nico from our team were involved in this huge roadmap on high-dimensional quantum photonics! arxiv.org/abs/2604.06528

A new, very serious preprint is out from Veronika and Alberto. No, don't look at today's date it's 100% legit we promise. It's a genuine proof that P=NP... (...if you believe in quantum many-worlds and are willing to destroy almost every observer in the multiverse 👀) arxiv.org/abs/2603.28869

This is now fully published in Reviews of Modern Physics. Congrats to all involved! journals.aps.org/rmp/abstract...

New preprint! Manu, Max, and Pharnam look at how long chaotic many-body systems take to equilibrate, with both analytics and a numerical model. They find both results that confirm random matrix theory and results that suggest it is lacking in places! arxiv.org/abs/2603.28587

New preprint! Philipp and colleagues show how quantum fluctuations can lead to symmetry-breaking and violation of classical selection rules in high harmonic generation, leading to squeezing-like behaviour arxiv.org/abs/2603.24377