Hilbert Chronicle

Four developments from the quantum-tech industry worth your attention today — a team-curated summary from our editorial desk.

Stony Brook Researchers Resolve an Open Question on the Limits of Quantum Search

Two researchers at Stony Brook University, David Miloschewsky and Supartha Podder, report a proof that no quantum algorithm can efficiently find an actual route through a “welded-tree” maze, even though quantum computers can locate the maze’s exit exponentially faster than classical ones. The question had been listed as an open problem in 2021, and the new result removes two restrictions from an earlier 2023 proof. A separate proof by another group reached the same conclusion, and the teams are now working together to pin down the exact bound. The work is a preprint and has not yet been peer reviewed.

Source: Stony Brook University News

Telefónica and IQM to Install Madrid’s First On-Premises Quantum Computer

Telefónica and IQM Quantum Computers announced on October 23 that they will deploy an IQM Spark system at the Universidad Politécnica de Madrid, with installation due before the end of 2026. It is the third IQM–Telefónica deployment in Spain, following two at CESGA, Galicia’s supercomputing center. The system is meant to give universities, hospitals, research centers and startups direct access to real quantum hardware; the companies did not disclose the investment or qubit count.

Source: Telefónica press release

Leiden and Riverlane Find a Distance-Losing Flaw in Correlated Decoding

A joint team from Leiden University and Riverlane reports a structural flaw in the re-weighting step used by two-pass correlated decoders for surface codes. Deep below threshold, the flaw effectively costs one unit of code distance and raises logical failure rates. The authors propose an error-rate-dependent regularization parameter that restores the expected distance scaling and can be precomputed at decoder initialization, so it adds no runtime overhead.

Source: arXiv preprint, “Correlated decoding loses the surface code’s effective distance below threshold”

Theory Proposal: Reading Out an Andreev Qubit Through Its Own Supercurrent

Researchers at the University of São Paulo and the Beijing Institute of Technology, with support from FAPESP (São Paulo Research Foundation), propose reconstructing an Andreev qubit’s state from the oscillating supercurrent it produces, sensed by a nearby SQUID. The scheme would avoid the ancilla qubits and resets other non-destructive readout approaches require. Simulations suggest reconstruction accuracies of up to 99.85%, but the work is purely theoretical and untested in experiments.

Source: Physical Review B

This digest was researched and written by our AI editorial team (Quark & Prism), supervised by Mischa Hammann. Learn more on our team page. Not investment advice.