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Alex Pozas-Kerstjens @alexpozas.com · 30/09/2026

The first @quarc-csic.bsky.social workshop is on! quarc.csic.es/events/quantum-optics-for-quantum-technologies-workshop

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Alex Pozas-Kerstjens @alexpozas.com · 24/09/2026

Spending a very stimulating week at @uni-muenster.de on the Structure of Quantum Theory workshop. First time I'm using my new @quarc-csic.bsky.social -themed slides! Thanks @hippoquantum.bsky.social and Matthias Kleinmann for the invitation and for putting up such a good event

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Alex Pozas-Kerstjens @alexpozas.com · 14/05/2026

Indeed, this is what you find after a one-hour hike from the campus

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Alex Pozas-Kerstjens @alexpozas.com · 12/05/2026

This week I am visiting @quaintum.bsky.social at @univ-amu.fr. This is definitely the most beautiful campus I've been to so far. Looking forward to the exciting discussions!

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Alex Pozas-Kerstjens @alexpozas.com · 05/05/2026

To look for this realization, we use quantum testers, that are objects that encompass the union of a quantum state and a measurement device. They originate in the field of higher order quantum theory, and we use them to do efficient, stable optimization loops. 5/n

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Alex Pozas-Kerstjens @alexpozas.com · 05/05/2026

In particular, within this construction we look for realizations of mixtures of the W distribution (where the only events with nonzero -and uniform- probability are those in which only one of the parties output 1) with white noise. 4/n

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Alex Pozas-Kerstjens @alexpozas.com · 05/05/2026

Why is it the simplest? Because we just need one source that distributes (two-qubit) entangled states. The other sources distribute classical shared randomness! And, because of this, the parties need to perform (at most) single-qubit measurements. 3/n

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Alex Pozas-Kerstjens @alexpozas.com · 05/05/2026

Why is it the smallest? Because it is a just tripartite distribution over binary outcomes, for which we find a realization in the so-called triangle network. If you take a party, a source, or an outcome out, then you end up in a situation where you can always find a local hidden variable model. 2/n

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Alex Pozas-Kerstjens @alexpozas.com · 09/03/2026

Today I spoke about quantum nonlocality in networks at the "Nonlocality: Driver for Quantum Advantage?" workshop at the @lorentzcenter.bsky.social. After the first day of the workshop, I'm eager to see what the rest of the week brings. @snsf.ch

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Alex Pozas-Kerstjens @alexpozas.com · 14/06/2025

I've spent this week celebrating the 100th birthday of quantum mechanics in the island of Helgoland, where Werner Heisenberg write his pioneering work. It's been so refreshing to see the impressive things that we can do, and all the exciting challenges that still lie ahead.

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Alex Pozas-Kerstjens @alexpozas.com · 22/05/2025

Seeing snow in May was definitely not in my year's plan... But it happened. Thanks to Isaac Smith and the rest of the organizing committee of the @uniinnsbruck.bsky.social DK-ALM Summer (?) School for inviting me to lecture on quantum information theory here at Obergurgl!

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Alex Pozas-Kerstjens @alexpozas.com · 24/03/2025

In order to figure out, we compared with (and improved upon) the distributions that can be created in the triangle network in any physical theory. And we see some regions of distributions that are very promising for observing this quantum advantage. We will focus on these in further work.

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Alex Pozas-Kerstjens @alexpozas.com · 24/03/2025

And here is the result. There are only two types of non locality in this scenario: the shared-random-bit (aka GHZ) type, and the all-but-one-parties-agree (aka W) type. The other part is an effect of relabeling the outcomes of the parties. What does this tell us about quantum advantage?

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Alex Pozas-Kerstjens @alexpozas.com · 24/03/2025

So we parameterized all possible distributions achievable classically, and we looked for such form for all the distributions that are invariant under permutations of the parties (doing it in full generality would be too much) In one meme for @dulwichquantum.bsky.social, this was (kind of) it

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Alex Pozas-Kerstjens @alexpozas.com · 24/03/2025

Some scientists care about observing phenomena in quantum networks that cannot reproduced in classical mechanics. One of the simplest scenarios is the triangle network with where all the parties perform a fixed, binary outcome measurement. Is there any hope that we observe a quantum advantage here?

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Alex Pozas-Kerstjens @alexpozas.com · 24/03/2025

📢📢 New paper out! 📢📢 www.scirate.com/arxiv/2503.16654 We've computed all the tripartite probability distributions over binary events that 1) are invariant under permutation of parties, and 2) can be created in the triangle network within classical physics Why should we care about this? Read on! 🧵

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Alex Pozas-Kerstjens @alexpozas.com · 24/02/2025

We give an explicit example for this, that we found when investigating quantum nonlocality in my beloved triangle network (heh).

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Alex Pozas-Kerstjens @alexpozas.com · 24/02/2025

In physics, we care about how and why things happen. We make models for this, which we capture in equations. For example, these are the Navier-Stokes equations, that describe the dynamics of fluids.

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Alex Pozas-Kerstjens @alexpozas.com · 14/01/2025

And, most importantly, if we tensorize one of these non-private models and we post-process the resulting TN using its gauge freedom, we obtain a model that works fine and does not leak unwanted attributes. 7/n

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Alex Pozas-Kerstjens @alexpozas.com · 14/12/2024

It seems like a tradition is emerging here, and it is out duty to maintain it. So here is my part announcing the publication of our review in semidefinite programming for characterizing quantum correlations @dulwichquantum.bsky.social journals.aps.org/rmp/abstract...

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Alex Pozas-Kerstjens @alexpozas.com · 09/12/2024

Alrighty! I'm spending a few days at @ethzurich.bsky.social. Looking forward towards the discussions with @carrasqu.bsky.social and his group!

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