Tunnelling times, Larmor clock,and the elephant in the room

TL;DR

This paper examines the quantum tunnelling time problem, highlighting the limitations of Larmor clocks due to the Uncertainty Principle and arguing that these times cannot be interpreted as physical durations.

Contribution

It demonstrates the fundamental limitations of using Larmor clocks to measure tunnelling times and clarifies the theoretical nature of the quantities involved.

Findings

Larmor clock application is hindered by the quantum Uncertainty Principle.

Larmor times cannot be interpreted as physical time intervals.

Provides a theoretical description of measured quantities.

Abstract

A controversy surrounding the "tunnelling time problem" stems from the seeming inability of quantum mechanics to provide, in the usual way, a definition of the duration a particle is supposed to spend in a given region of space. For this reason the problem is often approached from an "operational" angle. Typically, one tries to mimic, in a quantum case, an experiment which yields the desired result for a classical particle. One such approach is based on the use of a Larmor clock. We show that the difficulty with applying a non-perturbing Larmor clock in order to "time" a classically forbidden transition arises from the quantum Uncertainty Principle. We also demonstrate that for this reason a Larmor time (in fact, none of the Larmor times) cannot be interpreted as a physical time interval. We also provide a theoretical description of the quantities measured by the clock.