Gave a talk at the University of Vienna today, in a room once used by the great logician Kurt Gödel!
However, my treatment of the subject - holographic fault tolerance - remains incomplete.
Why does this charging station remind me of a certain American president?
Since Rydbergs work at room temperature, they're literally much hotter than all the dilution-refrigerated qubits out there!
I hope they still build some golden chandeliers around them for promo photos, though.
It's not often that I do breaking news! Today, Charles Bennett and Gilles Brassard received the Turing Award for helping lay the foundations of quantum information science. Read more in @quantamagazine.bsky.social!
Berlin's pubs are already adjusting to new geopolitical realities:
"Beer now cheaper than gasoline -
Don't drive away, drink and stay!"
Indeed, because he's still missing the Dulwich Peace Prize.
If you are interested in doing a postdoc with me, please apply to the IQC postdoctoral fellowship here: iqc-uwaterloo.slideroom.com#/login/progr...
(I/III) We're excited to announce a new tenure track opening! The position is called 'quantum informatics' and is affiliated with our QUICK group within the CS+AI division at @jku.at 🇦🇹. Application deadline is November 30th, 2025: www.jku.at/en/the-jku/w...
This week, we're in beautiful Kraków for a conference on tensor networks and all their applications. My PhD students Dimitris and Lev already gave amazing talks about discrete-holographic boundary symmetries and von Neumann algebras in holographic codes!
Or dare we say... Engineering? 😬
You can tell that the #QIP2026 deadline has not yet passed, since @zoltanzimboras.bsky.social has not given word on his submission yet.
Postdoc job! I expect to have an opening at Johns Hopkins for a postdoctoral researcher working somewhere in the broad realms of physics, philosophy, and complexity. Apply at Academic Jobs Online:
academicjobsonline.org/ajo/jobs/30496
Thanks Zoltan! You should petition the museum to add some hyperbolic tilings as well, there's plenty of material in our papers. 😁
It would be a lost opportunity if they didn't call it the Ministry of Magic (state distillation).
Looking for a postdoc to work on bosonic quantum error correction!
Join me and the QAT team at ENS & INRIA Paris — flexible start date.
Details here 👉 recrutement.inria.fr/public/class... or feel free to reach out!
For more details, you'll have to read our paper! As always, many thanks for the support of Berlin Quantum for our work at @freieuniversitaet.bsky.social.
arxiv.org/abs/2103.02634
This suggests a deep relationship between equilibration strength and entanglement phases in many-body quantum systems! The main idea: More entanglement = stronger equilibration.
For the condensed-matter theorists among you, our work also leads to an interesting conjecture: RTNs on different geometries describe different phases of entanglement scaling. We show that D_eff follows a sharp hierarchy between area- and volume-law phases.
This means that random tensor networks know a lot more about holographic dynamics than we expected, and may be able to hold more insights into (holographic) quantum gravity.
And surprisingly, the result matches gravitational degree-of-freedom counting in holography: If we "fuse" tensors together, i.e., replace part of the bulk geometry by a "black hole", D_eff always *increases*. Just as in gravity, where a black hole is the highest-entropy state!
This brings us to holography: For holographic RTNs, we can now compute the minimum effective dimension D_eff that describes late-time dynamics! From the geometry and bond dimension of the RTN alone, we can determine how complex its dynamics must be.
Now here's the kicker: For random ensembles, we can strictly lower-bound D_eff *without knowing H*! In a sense, the randomness cancels out its exact eigenstate structure. This is a trick we learned from Haferkamp et al., who used it on random MPS:
arxiv.org/abs/2103.02634
The key quantity to describe the strength of equilibration is the "effective dimension" D_eff, which basically counts how many (energy) states are needed to describe late-time dynamics.
Here's how it works: In a quantum system, expectation values of observables fluctuate. At late times, even a pure state will *equilibrate*, meaning that local expectation values will fluctuate within a fixed window. This happens for all Hamiltonians H with "non-degenerate gaps".
In our paper, we bring in ideas from quantum statistical mechanics to show that the opposite is true: Thanks to the randomness in RTNs, we can probe late-time dynamics without knowing the explicit Hamiltonian! The key concept that enables this is called *equilibration*.
That makes choosing a Hamiltonian that performs time evolution on the boundary difficult: Any choice, e.g. motivated from AdS/CFT arguments, would time-evolve different RTN samples differently. Thus, it seemed that randomness made time evolution impossible to describe!
This sparked hundreds of follow-up papers - many of which refined the original proposal - but there was one limitation: Random tensor networks (RTNs) produce an *ensemble* of states, with every random sample looking quite different locally.
Some background: In a seminal paper from 2016, Hayden et al. showed that tensor networks with locally random tensors, if put on a hyperbolic geometry, reproduce quantum states that very closely resemble boundary states of the AdS/CFT duality.
arxiv.org/abs/1601.01694
Very happy to have this paper with @jenseisert.bsky.social and his PhD student Shozab Qasim out on the @arxiv.bsky.social!
It achieves something that, until recently, I thought to be impossible: To use random tensor networks to study holographic *dynamics*.
They've obviously been best friends for years, I don't know why this is so hard for the media to acknowledge.