ua nt - p h / 04 01 15 9 v 1 2 6 Ja n 20 04 ’ Superluminal ’ tunnelling as a quantum measurement effect

We exploit the analogy between tunnelling across a potential barrier and Aharonov's weak measurements to resolve the long standing paradox between the impossibility to exceed the speed of light and the seemingly 'superlumi-nal' behaviur of the tunnelling particle in the barrier. We demonstrate that 'superluminality' occurs when the value of the duration τ spent in the barrier is uncertain, whereas when τ is known accurately, no 'superluminal' behaviur is observed. In all cases only subluminal durations contribute to the transmission across the barrier.