Physicists at the University of Regensburg and the Max Planck Institute in Hamburg report that an electron’s position in time and its position in space cannot both be pinned down without limit, a boundary related to Heisenberg’s uncertainty principle. Their experiment followed single electrons hopping across a gap of just a few atomic diameters, driven by laser pulses that last attoseconds. The more sharply the timing is fixed, the more energy the measurement demands.
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One attosecond is a billionth of a billionth of a second. Simulations in the paper put the lag of the electrons behind the driving light field at about 500 attoseconds, and they matched the experiment closely.
A sharp metal tip, a silver surface and two laser pulses
The study, “Tracking electrons at the space-time limit,” ran in Nature Photonics in 2026. The University of Regensburg release of July 3 says the work came out of the Regensburg Center for Ultrafast Nanoscopy, with groups led by Jascha Repp, Rupert Huber, Franz Giessibl and Klaus Richter, while Angel Rubio’s team at the Max Planck Institute in Hamburg ran the quantum simulations. Simon Maier is lead author. ScienceDaily carried the story on Nov. 7.
A new laser system with finer time resolution than earlier setups produces infrared pulses that push electrons from an atomically sharp metal tip toward a silver surface. A single atom on that surface confines the electron wave packet to a very small region just before the pulses arrive, and the transfer is read out as an electrical current. By varying the delay between two light pulses, Maier explained, the team can observe directly how the electrons respond. Doctoral student Katharina Glöckl compared the arrangement to a high-speed camera for electron wave packets.
Rubio’s simulations did more than check the data. By the release’s account they showed the light behaving as both a wave and a stream of particles, and the calculated electron motion followed the measured signal closely enough that the group treats the 500-attosecond figure as a description of what happened in the experiment. The Regensburg release says the team observed the position-and-timing limit for the first time.
Heisenberg’s position and momentum rule versus a timing and location rule
Heisenberg’s own statement of the idea comes from his Nobel lecture of Dec. 11, 1933, a talk that traced how quantum mechanics grew out of Bohr’s correspondence principle and its statistical character, where he said the product of the probable errors in measuring location and momentum is never smaller than Planck’s constant divided by 4 pi. Sharper knowledge of where a particle is means blurrier knowledge of how it moves.
The Regensburg result concerns a different pairing. According to the release, an electron’s location and its behavior over time cannot both be known with arbitrary precision. Co-author Raffael Spachtholz put the cost in energy terms: sharper pinning of an electron’s position in time requires providing more energy. That cost is what the team ran into as it pushed its timing sharper, and it is why the researchers describe the result as a limit instead of a technical shortfall.
Attosecond tools have already earned a Nobel; the 2023 Nobel Prize in Physics recognized experimental methods that generate attosecond pulses of light for studying electron dynamics. The Regensburg group works at a scale where, by the release’s account, electron motion runs roughly a thousand times faster than the movement of atoms and molecules, and where a single tightly confined electron can reach a local peak current density of up to about 1 trillion amperes per square centimeter.
The 500-attosecond lag and the hundred-thousand-fold speed claim
Two caveats matter for anyone reading beyond the physics. First, the 500-attosecond delay comes from simulations that reproduced the experimental results closely, not from a direct reading of the delay. Second, the prospect of electronics running hundreds of thousands of times faster than today’s CMOS technology, the transistor design inside most processors is described by Repp and Huber as a long-term goal. The experiments did not demonstrate it, and ScienceDaily’s report treats it that way.
The framing differs between the two accounts. The university release stresses the first observation of the limit and the prospect of steering chemistry, while the ScienceDaily version leans harder on speed. Anyone weighing the claims should keep the measured result, an electron lag and an energy cost for sharper timing, apart from the long-range engineering hopes attached to it.
What the group does claim is a new kind of access. Repp said the team wants to use such wave packets to trigger chemical reactions in a targeted way, and Huber spoke of eventually operating electronics at the intrinsic speed limit of electron motion itself. Whether the energy cost Spachtholz describes caps how far that ambition can go is not settled by this paper, which establishes the trade-off but leaves the engineering open.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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