Breakthrough Tracker record

A nonlinear fluorescence measurement confirms attosecond hard-X-ray pulses

Inoue, Robles, Halavanau and collaborators report the first direct experimental confirmation of hard-X-ray attosecond pulse generation at a free-electron laser, inferring shot-to-shot durations of about 100 to 400 attoseconds from amplified spontaneous emission in transition-metal foils.

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Stable ID: physics-attosecond-hard-xray-direct-demonstration-2026
Revision: physics-attosecond-hard-xray-direct-demonstration-2026.v1
Field: Physics · Ultrafast X-ray science and free-electron lasers
Evidence: Tier 1 · Peer reviewed: Yes
Record state: Current · Peer-reviewed experimental demonstration
Last checked: 2026-10-22

AI role

No substantive AI role was disclosed in the inspected paper or publication metadata. Beam-dynamics and Maxwell–Bloch simulations were treated as conventional computational methods.

Record details

Problem or result: Direct confirmation and duration measurement of hard-X-ray attosecond pulses
Authors: Ichiro Inoue, River Robles, Aliaksei Halavanau, Veronica Guo, Takahiro Sato, Agostino Marinelli and collaborators
Institutions: University of Tokyo; RIKEN SPring-8 Center; SLAC National Accelerator Laboratory; Stanford University; DESY and University of Hamburg; Osaka University; University of Wisconsin–Madison
Result date: Nature Photonics version of record published October 20, 2026; underlying preprint submitted June 9, 2025

Why it matters

The measurement extends directly confirmed attosecond operation to roughly 9-keV hard X-rays, combining electron-timescale resolution with atomic-scale wavelengths and establishing a diagnostic route for future ultrafast scattering experiments.

Limits

Pulse duration was inferred from collective fluorescence yield with simulations and statistical modelling rather than read from a general-purpose pulse meter. The reported 100-attosecond case was nearly transform limited, but routine user operation, damage-free structural imaging and broad experimental access remain future goals.

Sources

Primary: Nature Photonics attosecond hard-X-ray study
Open preprint: Inoue and collaborators experimental preprint

Correction and revision history

2026-10-22 — Added after primary-source, scope, status, AI-role and limitation review.

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