Measurement-induced non-commutativity in adaptive fermionic linear optics We show that mid-circuit measurements of fermions with internal degrees of freedom can induce the equivalent of "magic" to free fermionic circuits and render them classically hard to sample. scirate.com/arxiv/2603.24950 Fermionic linear optics (FLO) with Gaussian resources is efficiently classically simulable. We show that this is no longer the case for such quantum circuits for fermions with internal degrees of freedom, equipped with #midcircuit number monitoring and classical feedforward. In our architecture, the measurement record routes the selected blocks into a fixed-order Bell-fusion pairing geometry. On the level of classical description, this implies realizing a situation in which the permutation sum no longer collapses to a single determinant or Pfaffian. Each post-selected branch expands as a signed sum of path-ordered products of typically non-commuting dressed blocks, and branch amplitudes are matrix elements of the resulting non-commutative trace polynomials. Numerically, we observe Porter-Thomas statistics as the output distribution and a rapid growth of the minimal order-respecting matrix product operator bond dimension. These results thus establish mid-circuit measurement-induced non-commutativity as a route to #samplinghardness for noninteracting #fermions under reasonable complexity assumptions, without introducing coherent two-body interactions into the FLO evolution. Warm thanks to Chenfeng Cao and Yifan Tang for the wonderful collaboration.

What a year! I feel extremely grateful to work in one of the most creative teams in quantum information science and the study of complex quantum systems in the world, consisting of wonderful postdocs and students. Once again, this year has been enormously productive, and many interesting ideas have emerged, often first on the blackboard. As a result of this, we had 11 papers in the Nature group this year, mostly in @NaturePhysics or @NatureComms, nature.com/articles/s41567-0… nature.com/articles/s41567-0… nature.com/articles/s41567-0… nature.com/articles/s41467-0… nature.com/articles/s41467-0… nature.com/articles/s42005-0… nature.com/articles/s41534-0… nature.com/articles/s41467-0… nature.com/articles/s43246-0… nature.com/articles/s41534-0… arxiv.org/abs/2403.13927 and 13 papers in the @PhysRevLett, @PRX_Quantum, or @PhysRevX of the @APSphysics. journals.aps.org/prl/abstrac… journals.aps.org/prl/abstrac… journals.aps.org/prxquantum/… journals.aps.org/prxquantum/… journals.aps.org/prxquantum/… journals.aps.org/prxquantum/… journals.aps.org/prxquantum/… journals.aps.org/prxquantum/… journals.aps.org/prxquantum/… journals.aps.org/prx/abstrac… among many others, physik.fu-berlin.de/en/einri…. I feel grateful and blessed. Thanks so much to all.

Over the recent weeks and months, @preskill and I sat down to think about where we are in quantum computing. While the noisy intermediate-scale quantum (#NISQ) era — a term coined by John in 2018 — is just unfolding as we speak, the time seems right to look ahead to the next steps to come. scirate.com/arxiv/2510.19928 In this perspectives article, we try to sketch the fraught road to quantum advantage — the path toward fault-tolerant, application-scale quantum (#FASQ) computers. There are several gaps ahead of us, and we try to faithfully and honestly hint at how one may be able to "mind those gaps", and suggest a few important intermediate steps along the way. I have been impressed by the ease and efficiency with which we have been able to put this together. Warm thanks to John for the great collaboration and wonderful team work.

Hardware-tailored logical Clifford circuits for stabilizer codes scirate.com/arxiv/2505.20261 This first first author paper of Eric Kuehnke appeared on the arXiv yesterday, but was not picked up by Scirate, but only today. It suggests novel strategies for implementing Clifford unitaries at the logical level of a given stabilizer code in #quantumerrorcorrection under hardware constraints.

In an exhibition entitled "We felt a star dying", the artist Laure Prouvost explores the connection between arts and quantum physics. Actually, @HartmutNeven of @GoogleQuantumAI has been involved in the making, with the help of @fzj_jsc. I wonder whether this would be a good venue for #QIP one day. 😉

"XYZ ruby code: Making a case for a three-colored graphical calculus for quantum error correction in spacetime" journals.aps.org/prxquantum/… In brief: This work presents a new highly attractive Floquet code in #quantumerrorcorrection and introduces - yet another - useful graphical calculus. In detail: Analyzing and developing new quantum error-correcting (#QEC) schemes is one of the most prominent tasks in quantum computing research. In such efforts, introducing time dynamics explicitly in both analysis and design of error-correcting protocols constitutes an important cornerstone. In this work, we present a #graphicalformalism based on #tensornetworks to capture the logical action and error-correcting capabilities of any #Cliffordcircuit with Pauli measurements. We showcase the functioning of the formalism on new #Floquetcodes derived from #topological subsystem codes, which we call XYZ ruby codes. Based on the projective symmetries of the building blocks of the tensor network we develop a framework of Pauli flows. Pauli flows allow for a graphical understanding of all quantities entering an error-correction analysis of a circuit, including different types of QEC experiments, such as memory and stability experiments. We lay out how to derive a well-defined #decoding problem from the tensor-network representation of a protocol and its Pauli flows alone, independent of any stabilizer code or fixed circuit. Importantly, this framework applies to all Clifford protocols and encompasses both measurement-based and circuit-based approaches to #faulttolerance. We apply our method to our new family of dynamical codes, which are in the same topological phase as the 2+1-dimensional #colorcode, making them a promising candidate for low-overhead logical gates. In contrast to its static counterpart, the dynamical protocol applies a ℤ₃ automorphism to the logical #Pauligroup every three time steps. We highlight some of its topological properties and comment on the anyon physics behind a planar layout. Lastly, we benchmark the performance of the XYZ ruby code on a torus by performing both memory and stability experiments and find competitive circuit-level noise thresholds of approximately equal to 0.18%, comparable with other Floquet codes and 2+1-dimensional color codes. Warm thanks to Julio Carlos Magdalena de la Fuente, @old_josias, @the_grass_beige, Manuel Rispler and Markus Müller for this wonderful @FU_Berlin-@fz_juelich-@RWTH-collaboration.