Regensburg Team Measures Electron Space-Time Limit at Attosecond Resolution

The experiment deployed a custom dual-pulse ultrafast laser system to drive single-electron tunneling across a few atomic diameters. By scanning the delay between pulses while recording tunneling current, the team mapped how spatial localization trades off against temporal precision, confirming the space-time limit in a solid-state junction. Sample size consisted of repeated measurements on atomically sharp tungsten tips at cryogenic temperatures, with timing jitter below 100 attoseconds.

This result extends Heisenberg's principle into the joint space-time domain for matter waves, overturning assumptions that position and time remain independently measurable at quantum scales. It directly constrains design of next-generation quantum sensors and petahertz electronics, where switching speeds near 100,000 times current silicon limits would require simultaneous attosecond timing and sub-angstrom spatial control.

Connections to earlier molecular movies from the same group and to Rubio's real-time TDDFT simulations reveal a consistent pattern: quantum motion at these scales is governed by non-classical trajectories that classical device models ignore. The limit implies that any attempt to shrink both spatial and temporal uncertainty below the observed threshold will increase back-action on the electron wavefunction.

Future work must incorporate active feedback or entangled reference pulses to test whether the bound can be approached more closely in engineered heterostructures. Within three years, integration with on-chip waveguides could translate the finding into practical petahertz logic prototypes.