Time moves differently at the quantum level — and now physicists have figured out how to measure it.
Researchers at EPFL have developed a method to track ultrafast quantum events without relying on external timing devices, which risk contaminating the very processes they're meant to measure. The breakthrough centers on a counterintuitive insight: electrons themselves can serve as the clock.
When electrons absorb light and escape from a material, they carry encoded information in their spin — the quantum equivalent of angular momentum. By analyzing how these spin patterns shift as the electron's energy changes, Hugo Dil's team calculated the duration of quantum transitions with unprecedented precision. No external clock needed. No interference with the process being studied.
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Start Your News Detox"Although the 2023 Nobel prize in physics shows we can access such short times, the use of such an external time scale risks to induce artifacts," Dil explains. The team's approach sidesteps this trap entirely.
What emerged was striking: quantum time isn't universal. It depends entirely on how atoms are arranged. In three-dimensional copper, an electron's transition from absorbing a photon to escaping the material takes about 26 attoseconds — that's 26 billionths of a billionth of a second. But in layered materials like TiSe₂ and TiTe₂, the same process stretches to between 140 and 175 attoseconds. In chain-like CuTe, it exceeds 200 attoseconds.
The pattern is clear: simpler, more reduced atomic structures slow down quantum transitions. Complexity speeds them up.
This matters because it rewrites what we thought we knew about quantum mechanics. The results suggest that time itself — or at least how we measure it — isn't a fixed backdrop to quantum events. It's woven into the material's structure. "Our experimental results provide further insight into what factors influence time on the quantum level, to what extent quantum transitions can be considered instantaneous, and might pave the way to finally understand the role of time in quantum mechanics," Dil says.
For now, this is fundamental physics — the kind of discovery that sits in laboratories and journals. But understanding what controls quantum time could eventually reshape how we design materials and build quantum technologies. Time, it turns out, is something we can finally measure from the inside.
