The Qalypso School on Quantum Science in Malta returns for its 3rd edition Aug 31 - Sep 4 this year! 🏖️
We have a great line up of lecturers covering Quantum Optimisation, Quantum Thermodynamics and Quantum Gibbs Sampling.
Pre-registrations opens today at forms.gle/3NkMJ3Br9V8b...
Do Share!
new paper!
how can one predict and detect magic of many-body quantum states using few body measurements ? what are the fundamental complexity-theoretic limitations ?
we tackle this question in arxiv.org/abs/2602.18939 1/n
Happy to see our paper Uniqueness of Purifications Is Equivalent to Haag Duality with @arrr.de and @stotti-alex.bsky.social published in PRL! 🥳
doi.org/10.1103/d7nm...
Amazing! Congrats Lauritz.
Disclaimer: this is a very bad thread from someone who never writes threads and is currently on the bus (checking my stop every 10 seconds)… But the paper itself is nicely written 😅
This was a really nice collaboration with the brilliant master’s student Xiaotian Yang, which started with Ulrik and me during a visit to Japan, and really took shape when Santiago Zamoras and Rafael Chaves spent time with Jonatan and me. Also: my first paper as last author. Hope you enjoy!
This allowed us to probe the nonlocality of two paradigmatic states: W and GHZ. And we found that GKP states provide strong and robust multipartite nonlocality: not high critical squeezing, tolerance to loss, and robustness to noise - all treated almost analytically. (5/n)
…no Bell violation in the bipartite case using only homodyne (and stabilizer resources, of course). For the multipartite case, however, we found a nice analytical way of computing the conditional probabilities! (4/n)
(3/n) This is exactly where GKP changes the picture. It turns homodyne + classical binning into effective qubit measurements, while keeping all the experimental advantages. To start with, we looked at finite-energy (i.e. “realistic”?) GKP states and proved a no-go result:
Homodyne detection is a natural candidate when talking about Bell nonlocality: it closes the detection loophole, is easy to implement, and comes with high efficiency… But it is also strongly constrained in continuous-variable (CV) systems. 2/n
Can Gottesman–Kitaev–Preskill (GKP) encoding turn homodyne detection into a practical tool for revealing Bell nonlocality?
The answer is yes, and in fact GKP states also lead to strong and robust multipartite nonlocality with homodyne detection!
Today on arXiv: arxiv.org/abs/2601.16189 1/n.
Chain of quantum two level systems. Excitations traveling from left to right, each time marking a tick when they leave on the right.
From one tick to the next, small timing uncertainties in clocks usually add up because of the independence of errors. Using fermions tunneling through a quantum wire as clock ticks, we found a way to build a clock where errors cancel out rather than accumulate. arxiv.org/abs/2601.10785
Save the date: sun, sea & science, where wave–particle duality means talks in the morning, surf in the afternoon. Quantum at the Dunes (IIP, Natal 🇧🇷) — School 23–27 Feb 2026 → Workshop 2–6 Mar 2026. www.even3.com.br/quantum-at-t...
Posted a joint work with Naoto Shiraishi on quantum thermodynamics. We managed to characterize the state transformability (for general coherent states!) with a correlated catalyst by the single free energy ordering. arxiv.org/abs/2510.05642
Thank you very much, Jake!!!! You’re awesome.
Quantum metrology in the finite-sample regime
journals.aps.org/prxquantum/a...
We propose an operational framework of #quantummetrology in the practically meaningful regime of a few measurement samples, introducing probably approximately correct (#PAC) metrology.
Thank you for the very kind words, Jake!!!
Our tutorial "A friendly guide to exorcising Maxwell's demon" (journals.aps.org/prxquantum/p...) is out!
The big question after the tutorial is whether I’m finally done drawing demons?
When I grow up I wanna be like Kristian: talk about quantum gravity while wearing a black-flag t-shirt.
(arxiv.org/abs/2503.03585)
Whether or not you're a fan of thermal operations, there's something fundamentally special about them: by pinning down what it means to equilibrate, thermal operations uniquely emerge! With this, we also uncover nice hierarchy of unital channels, in contrast with the classical Birkhoff theorem.
Very beautiful results, Nelly! Already started my late morning reading it 😍
My happiest memories are tied to this university, this office, and that chapter of my life. Even cooler to see my old office mate getting his PhD tomorrow! Finally get to use this picture (taken in 2021, just sitting in my gallery waiting for this moment):
Back in Krakow after 1.5 years. First stop: my old office (just had to see it). Somehow got in and boom 💥: everything was exactly the same: Kamil’s notes on my desk, unfinished (now finished) calcs from Marti’s project, old running gear, and the cactus I bought when I started my PhD!
Entangled exit strategies
Hmm… The only quantum aspect is assuming a closed system evolving under energy-preserving unitaries. This leads to a partial order on state transformations. Replacing unitaries with Gibbs-preserving stochastic matrices gives the same result-nothing uniquely quantum. But maybe I’m missing the point.
Sorry for not being clearer - I’m in a shelter at the top of a mountain in Japan right now. Hard to type and be coherent haha
I was referring to the first one showing the partial order for classical states (diagonal in the energy eigenbasis): „Nat. Commun. 4, 2059 (2013)”.
For the cones: „Phys. Rev. E 106, 064109 (2022)”.
But yes, Kamil & Matteo also showed this for Markovian thermal processes…
(1/n) Today on the arXiv, we examine the folklore that cooling a quantum system with access to another requires one to order their joint state eigenvalues in decreasing order and find that this sorting is actually dictated by a simple set of inequalities.
scirate.com/arxiv/2506.1...
In the video you can see the set of achievable states under thermodynamic transformations for a given an out of equilibrium state (4D state) in contact with a bath: green is the achievable states, blue the set that I achieve the initial state and red the set of incomparable states….
This was formally proven a few years ago! The set of states achievable under thermodynamic transformation follows a partial-order relation called “thermomajorisation”. This is a beautiful result that illustrates your point.
