EPFL News Breaks Barrier in Measuring Quantum Tunneling
For years, quantum time has been one of science' biggest mysteries. The exact time of a quantum transition, such an electron tunneling over a barrier, is notoriously difficult to establish, even if basic quantum physics may predict its possibility. A team of EPFL researchers has developed a new method to quantify these extremely fast events, showing that quantum tunneling's "speed" depends on the material's symmetry and form.
The Newton journal published the groundbreaking subatomic research. By using electrons as a "clock," the scientists avoided interference issues that hinder high-precision quantum experiments.
The Attosecond Timing Challenge
Humans cannot comprehend quantum processes like tunneling and photon absorption. Occurrences often occur in quintillionths or tens of attoseconds (10-18 seconds). Consider that light cannot flow through a virus in the time it takes for these conversions.
Hugo Dil, EPFL professor and physicist, says the observer effect has prevented quantification of these gaps. “Measuring time intervals of this magnitude is notoriously difficult,” explains Dil, “particularly because any external timing device can interfere with the very phenomenon one aims to observe”. The 2023 Nobel Prize in Physics proved that humans can access these short periods, although utilizing an external reference can introduce “artefacts” or mistakes.
EPFL solved this with SPERS, a clever method. Synchrotron light excites electrons and drives them away.
As they are evacuated, these electrons carry quantum spin information. When light hits the electron, numerous interfering quantum paths form a superposition. This interference gives the electron's spin a distinctive pattern that changes with the quantum process.
By observing these small spin pattern variations in relation to electron energy, the researchers were able to establish the transition length without a clock. This internal “spin clock” shows how the electron's wavefunction evolves from initial to greater energy.
Symmetry and Quantum Leap Speed
The most surprising discovery of the study is that the material's atomic-level “shape” or symmetry considerably affects these quantum events' length.
Researchers examined many materials with varied geometries:
3D Copper: This typical, highly symmetric three-dimensional structure's quantum transition took 26 attoseconds.
Bilayer Materials (TiSe2 and TiTe2): Loosely linked layers behave as flat sheets. This procedure took 140–175 attoseconds, a significant delay.
Copper Telluride (CuTe) is a one-dimensional chain. The transition time approached 200 attoseconds in this low-symmetry scenario.
The model was clear: the longer the quantum transition, the simpler and smaller the material. Lower symmetry “slows down” quantum leaps.
This discovery sheds light on whether quantum transitions are immediate or have a time. Understanding these timescales can benefit technology beyond theoretical physics.
Researchers said “understanding the duration of a quantum transition can assist researchers in creating materials with targeted quantum characteristics.” Future technologies like high-speed electronics and quantum computing require precision quantum state manipulation.
The EPFL researchers revealed the link between material symmetry and quantum timing, which helped them understand subatomic time.
