Rafael Wagner

Always nice to see that quantum foundations have survived the wave of capitalism that has swept through quantum.

Today Hausmann and Renner from ETH show that quantum states are more than just a few probability distributions in a trenchcoat.

arxiv.org/abs/2601.18872

I wonder if, internally, the organizers of the annual conferences of Quantum Information in Spain [Informacion Cuantica en Espana] have conceived changing the acronym of the conference due to recent events.

indico.ific.uv.es/event/7934/

We also show other neat results (e.g. higher order real-valued invariants of multi-states featuring set imaginarity)

Thanks to professors Mao-Sheng Li and Lin Zhang for this collaboration! Hopefully the first of many :)

#QuantumInformation #QuantumResources #Coherence #BargmannInvariant

The only extra information needed is the sign of its imaginary part, which is a truly higher-order information that is not present in two-state overlaps alone.

The information of this sign is the single relational information that requires higher-order invariants.

A major technical results we present is the following:

For qubits, every complex-valued multivariate trace of states (aka Bargmann invariant), like Tr(ρ1ρ2ρ3ρ4), is almost entirely determined by simple two-state overlaps.

One of the main results is beautifully geometric and extremely natural.

For a set of qubit states (think points on the Bloch sphere):

1) The set is incoherent if all their Bloch vectors lie on a single line.
2) The set is imaginarity-free if all vectors lie in a single plane

Fresh from the press! 📃🎆

journals.aps.org/pra/abstract...

We advance the study of basis-independent formulations of quantum resources that are based on multi-states (equivalently sets of states, or yet classical-quantum channels).

Always a good talk

Thanks! :)

I'm happy to join PRA's editorial team as an Early Career Board Member!

The journal has been a (if not *the most*) crucially important scientific source for quantum information, foundations, and computation.

It's a huge honour!

@apsphysics.bsky.social #PRA #Quantum

Has quantum advantage been achieved? Recently, I gave a couple of perspective talks on quantum advantage, one at the annual retreat of the CIQC and one at a recent KITP programme. I started off by polling the audience on who believed …

Dominik Hangleiter weighs in with an informative post about a much debated question: Has quantum advantage been achieved? This is the first post in a three-part series.
quantumfrontiers.com/2026/01/06/h...

A dream job opportunity! Our team is hiring a Senior Research Scientist in Quantum Error Mitigation Theory on the Quantum AI team, and we get to be colleagues.

www.google.com/about/caree...

Why are academic societies still on X it must violate all their code of conducts?

The Institute of Physics (@iop.org), its publishing arm @ioppublishing.bsky.social, and its flagship magazine @physicsworld.bsky.social (which I work for) figured this out a long time ago. If you’re a physicist/astronomer/science teacher/something else relevant, follow them & show them some love!

New paper published in @physreva.bsky.social, jointly with Kyrylo Simonov (Vienna) and Rafael Wagner (INL/Minho/Ulm)! We simplify the estimation of multivariate traces/Bargmann invariants using partial classical info. Thanks @quantumrw.bsky.social and Kyrylo! journals.aps.org/pra/abstract...

Jonte R. Hance - IYQ 2025 Dr. Jonte R. Hance is an early-career researcher already making notable advances to foundational and applied quantum science. Despite only completing their PhD in March 2023, they have published 26 ar...

Deeply honoured to have been named one of the Quantum 100 for the UN'S International Year of Quantum Science and Technology (IYQ)! quantum2025.org/quantum-100/...

Thrilled to share that I have been awarded the very prestigious Alexander von Humboldt Postdoctoral Fellowship! :) #HumboldtFellowship

The @ccbpp.bsky.social Spring School on near-term quantum computing is back! If you are a young (PhD/MSc) researcher in quantum science and want to get exposed to the recent developments on quantum computing, do not hesitate coming to Benasque on March 15 - 21 next year!

www.benasque.org/2026ntqc/

I have also received one (particularly bad and generic) from a PRA report. It is becoming increasingly common I think

We recently received a referee report from Phys. Rev. Lett. @apsphysics.bsky.social that was obviously written by generative AI. It is so bizarre to read it; I have never received anything like it before. What measures is @apsphysics.bsky.social taking to ensure the integrity of the review process?

Peter Shor: we haven't found many new quantum algorithms, in part, because we need larger quantum devices for testing our heuristics. He gives several examples of algorithms that were discovered computationally, including turbo codes, @fermilab.bsky.social quantum symposium by the SQMS center.

Consistent circuits for indefinite causal order Augustin Vanrietvelde, Nick Ormrod, Hlér Kristjánsson, and Jonathan Barrett, Quantum 9, 1923 (2025). Over the past decade, a number of quantum processes have been proposed which are logically consistent,...

Newly published in Quantum: Consistent circuits for indefinite causal order by Augustin Vanrietvelde, Nick Ormrod, Hlér Kristjánsson, and Jonathan Barrett doi.org/10.22331/q-2...

Quantum-Classical Separation in Bounded-Resource Tasks Arising from Measurement Contextuality The prevailing view is that quantum phenomena can be harnessed to tackle certain problems beyond the reach of classical approaches. Quantifying this capability as a quantum-classical separation and de...

Probably -- as far as I know -- the first contextuality-based quantum information advantage from the Google Quantum AI team.

scirate.com/arxiv/2512.0...

Comments are very welcome!

Although it’s not really possible to revise a PhD thesis after submission, I’m always glad to receive thoughtful feedback.

At least, (critical) comments will help me improve how I present the topic in future work.

Coherence and contextuality as quantum resources In this thesis, we explore the intersection of two fundamental subfields of quantum information theory: quantum coherence and contextuality. Despite their apparent differences, both areas address key ...

New preprint out! 🎉

I’ve just submitted my #PhD_thesis to the #arXiv.

Chapter 7 contains several new constructions and a few new results on the geometry of sets of Bargmann invariants. Most notably, in Theorem 7.13 I prove the convexity of a broad class of sets of (tuples of) unitary invariants.

arxiv.org/abs/2511.15806

If correct, that's a huge result!

Ultrafast physics with structured light - Nature Reviews Physics Spatiotemporal structuring of optical fields offers opportunities to probe and control electron motions in light–matter interactions. This Review discusses the recent advances in both fundamental phys...

Review: Ultrafast physics with structured light ⚛️

by Yiqi Fang, Zijian Lyu & Yunquan Liu
www.nature.com/articles/s42...

Separating QMA from QCMA with a classical oracle We construct a classical oracle proving that, in a relativized setting, the set of languages decidable by an efficient quantum verifier with a quantum witness (QMA) is strictly bigger than those decid...

My student @johnbostanci.bsky.social, Chinmay Nirkhe, Jonas Haferkamp, and Mark Zhandry have put out a tour-de-force paper that shows, relative to a classical oracle, QMA is stronger than QCMA -- i.e., quantum proofs >> classical proofs. Congratulations to the authors! arxiv.org/abs/2511.09551

Well-informed and accurate takes on the current state of quantum computing by @dangaristo.bsky.social. Good listen if you're outside the field or just entering it and want to get an honest picture.

Kudos for using the term "physics experiment" instead of "computer", and for coining "quantum FOMO".

Classical gravity cannot mediate entanglement In Nature, 646, 813 (2025), Aziz and Howl claim that classical (unquantised) gravity produces entanglement. We show that their model does not produce entanglement. Even if the model produced entanglem...

A recent @nature.com article claims that classical (unquantised) gravity produces entanglement. We show that their model does not produce entanglement. Even if the model produced entanglement, it would be mediated by the quantised matter interaction, and not gravity. scirate.com/arxiv/2511.0... 🧪⚛️