Observation of the Decrease of Larmor Tunneling Times with Lower Incident Energy

TL;DR

This study uses a Larmor clock to measure tunneling times of ultra-cold atoms, confirming that lower incident energy results in shorter tunneling durations and providing precise quantitative data on these times.

Contribution

It provides the first precise experimental measurements showing that tunneling times decrease with lower incident energies using ultra-cold atoms and a Larmor clock.

Findings

Tunneling times decrease with lower incident energies.

At least 90% of transmitted atoms tunnel through the barrier.

Tunneling time at lowest energy is approximately 0.59 ms, faster than higher energies.

Abstract

How much time does a tunneling particle spend in a barrier? A Larmor clock, one proposal to answer this question, measures the interaction between the particle and the barrier region using an auxiliary degree of freedom of the particle to clock the dwell time inside the barrier. We report on precise Larmor time measurements of ultra-cold $^{87}$Rb atoms tunneling through an optical barrier, which confirm longstanding predictions of tunneling times. We observe that atoms generally spend less time tunneling through higher barriers and that this time decreases for lower energy particles. For the lowest measured incident energy, at least $90\%$ of transmitted atoms tunneled through the barrier, spending an average of $0.59(2)$ms inside. This is $0.11(3)$ms faster than atoms traversing the same barrier with energy close to the barrier's peak and $0.21(3)$ms faster than when the atoms traverse a barrier with $23\%$ less energy.