EPFL physicists have discovered that the speed of quantum events is controlled by a material’s atomic symmetry. By using electron spin as an internal clock, they measured transitions lasting just attoseconds, redefining quantum time
Physicists at EPFL have discovered that quantum transitions are not instantaneous and that their speed is governed by the atomic structure of the material. Published on 9 February 2026, the study reveals that events like electrons absorbing light happen over incredibly brief intervals—measured in attoseconds—and vary significantly depending on whether a material is 3D, layered, or chain-like.
Traditionally, measuring such speeds required external “clocks,” which can interfere with delicate quantum states. Professor Hugo Dil and his team bypassed this by using the electrons’ own spin as a built-in stopwatch, allowing them to observe time’s flow at the quantum level without external distortion.
The role of atomic symmetry
The research demonstrated that the geometry of a material directly controls the “speed” of its quantum processes. By testing different atomic arrangements, the team found a clear correlation between symmetry and time:
High symmetry (3D Copper):
Transitions were extremely rapid, lasting only about 26 attoseconds.
Layered structures (TiSe2):
The process slowed down to between 140 and 175 attoseconds.
Low symmetry (Chain-like CuTe):
The transition took the longest, exceeding 200 attoseconds.
This suggests that the more complex or “reduced” the atomic path an electron must navigate, the more time the quantum transition requires to unfold.
Quantum interference as a stopwatch
To capture these measurements, the team utilised “spin- and angle-resolved photoemission spectroscopy” (SARPES). When light hits the material, electrons follow multiple quantum paths simultaneously. These paths interfere with each other, leaving a specific “fingerprint” in the electron’s spin.
By analysing how this spin pattern changed across different energy levels, researchers could calculate the exact duration of the transition. This “clock-free” method provides a more accurate picture of quantum evolution by focusing on the accumulated phase of the electron’s wave function.
Implications for future technology
The discovery that quantum time is not a fixed constant but is dependent on material structure has major implications for the future of technology. Understanding these attosecond-scale delays will allow scientists to:
Tailor quantum materials:
Design materials with specific timing properties for faster computing.
Enhance precision sensors:
Improve the accuracy of devices that rely on sub-atomic timing.
Refine quantum computing:
Better control the fragile states required for processing complex calculations.
This work moves the study of quantum time from philosophical debate into a practical engineering tool, paving the way for a new era of materials science defined by attosecond precision.
