Two tunnelling labs report different times. What most likely differs?

Answer: Different clock variable

Random lab scatter — Random noise can blur any experiment, but the famous tunnelling-time disagreement is not just sloppiness. Communications Physics notes that conflicting claims can both be correct under different species, laser intensities, and methods. The deeper point is that precision alone does not make two clocks read the same observable.

Different clock variable ✓ — Correct. In tunnelling, there is no single classical stopwatch hidden inside the barrier; experiments often read phase delay, arrival delay, spin precession, or weak-measurement values. These can agree for a classical particle and diverge for a quantum wavepacket, splitting the old question into several operational ones.

Longer path length — A longer path is the classical instinct: more distance should mean more time. In tunnelling, however, the question is not always a path length divided by speed. Phase delay, arrival delay, spin response, and weak values can all carry time units while referring to different physical readouts and different clocks.