Qiskit Fall Fest 2026: MalaysiaBraids, memories and regional momentum

Researchers from the University of Chicago, Harvard, Stony Brook University and Quantinuum used 54 physical qubits on the H2 trapped-ion processor to create emergent non-Abelian anyons associated with the symmetry group S3. Pairs of anyons encoded topological qutrits. Braiding supplied an entangling gate, while fusion measurements completed a set that is universal in principle and directly prepared a magic state.

The peer-reviewed Nature experiment turns a theoretical construction into working quantum operations and suggests a possible route around costly magic-state distillation. Its protection is topological at the encoding level, but the experiment did not perform active error correction. The authors explicitly frame it as a proof of principle. Scaling will require stabilising non-Abelian memories, repeatedly detecting faults and showing that logical error rates improve as code size grows; this is not yet a fault-tolerant computer.

A Duke-led international team encoded a string-breaking model in 13 trapped ions and tracked the appearance of effective particle–antiparticle charges as an initially stretched field evolved. Separately, S. Saner, O. Băzăvan and collaborators used electronic qubits for gauge fields and ion vibrations for bosonic matter, building a two-link loop that obeyed Gauss’s law and exhibited flux-dependent Aharonov–Bohm interference.

Both Nature Physics experiments show why hybrid digital–analogue simulators are attractive for real-time lattice gauge theories, which become difficult for conventional numerical methods in larger regimes. The present devices are deliberately small: classical calculations reproduced the 13-ion string-breaking result, and the loop used only two qubits and two oscillators. They establish faithful encodings and observables, not quantum advantage. The second peer-reviewed paper↗ maps a route toward higher-dimensional simulations.

Nasser Gohari Kamel, Sourabh Kumar and collaborators demonstrated random access across eight spectral modes in a ytterbium-doped crystal. Their photon-echo memory uses rapid adiabatic-passage rephasing pulses to imprint controlled phases. That lets the device suppress unwanted echoes and retrieve a chosen subset of spectro-temporal modes while requiring less intense rephasing pulses than conventional schemes.

Selective recall matters for repeaters and network processors: a useful quantum memory must route stored photonic information, not simply return every mode in sequence. The Communications Physics result is an experimental proof of concept rather than a quantum-network-ready RAM. It covers eight modes in one material platform, and larger systems must preserve efficiency, coherence and state fidelity while adding longer storage times, more channels and low-loss interfaces. It should not be confused with the superconducting random-access memory featured two weeks ago; this is an optical, frequency-multiplexed approach.

Xiao-Long Zhou, Jian Wang and colleagues at the University of Science and Technology of China isolated higher-order scattering events from the resonance fluorescence of a single rubidium-87 atom in a cavity. They resolved third- and fourth-order processes and showed that the three-photon component was genuinely energy–time entangled through a violation of Svetlichny’s inequality. The team also used the source in a laboratory quantum secret-sharing demonstration.

The Nature Photonics result expands the familiar one- and two-photon picture of resonance fluorescence and offers a conceptually simple source of multiphoton quantum correlations. It remains a carefully controlled cavity-QED experiment, not a turnkey network component. Collection efficiency, event rates, indistinguishability and integration must all improve before such emissions can support scalable communication or metrology. The secret-sharing demonstration validates an application principle; it does not establish a deployed secure network.

Paolo Abiuso, Alberto Rolandi, John Calsamiglia, Pavel Sekatski and Martí Perarnau-Llobet derived a model-independent lower bound on how quickly a finite-temperature quantum system can thermalise. By treating thermalisation as the preparation of states close to thermal ensembles for distinct Hamiltonians, then applying quantum information geometry and metrology, they obtained τ ≥ ℏ/(2kBT). At low temperature, the gap between the ground and first excited states becomes the relevant energy scale.

The peer-reviewed proof gives operational footing to the long-discussed “Planckian” timescale and connects many-body physics with limits on Hamiltonian estimation. It is a theoretical speed limit, not a claim that every material or quantum processor reaches it. Real systems may relax much more slowly because of conservation laws, disorder, weak coupling or other bottlenecks, and the result depends on the paper’s defined thermalisation task and distinguishability criteria.

Zhenzhong Xing, Hamim Mahmud Rivy and Cornell colleagues positioned a calcium-40 ion at a node of an integrated 397-nanometre standing wave and demonstrated electromagnetically induced-transparency cooling across roughly five megahertz of motional bandwidth. The revised preprint reports cooling to about 0.05 phonons in the target mode within 150 microseconds—3.3 times faster than the comparable running-wave protocol—while cooling all three motional modes.

Rapid, broadband recooling could reduce operational delays in trapped-ion architectures that shuttle ions between zones. Integrated optical delivery also makes the phase-stable geometry relevant to scale-up. The evidence is still a single-ion experiment described in an unreviewed preprint, and the comparison is against the team’s matched running-wave implementation. Multi-ion chains, repeated transport cycles and long-run calibration will test whether the advantage survives in a working processor.

New reporting this week highlighted a peer-reviewed Nanjing University experiment in which three users established the same secure key through an untrusted measurement station. Yifeng Du, Yang Hu, Xiao-Song Ma and collaborators paired detection events asynchronously and corrected laser-frequency and phase drift in post-processing, avoiding global phase locking. The measured key rate scaled ideally with single-link transmittance rather than its N-user power.

At 59.6 decibels of total loss, the experiment produced 4.470 × 10⁻⁹ secret bits per pulse. Better loss scaling and measurement-device independence address real network bottlenecks, especially for multi-party links. The absolute rate at maximum loss is nevertheless low, and the test involved three laboratory nodes. Field fibre, finite-key effects, authentication, more users and independently engineered components remain necessary before the protocol becomes an intercity conference network.