Studying tunneling times using Bose-condensed atoms

The question of how long a particle spends in a tunnel barrier – like most questions about the “history” of quantum systems – has been contentious for the greatest part of a century.  I will describe our ongoing experiments(2), which use a “Larmor clock” to measure the time ultracold Rubidium atoms spend inside a 1-micron tunnel barrier formed by a focused laser beam.   In particular, we observe that contrary to intuition, lower-energy particles tunnel through the barrier “faster” than higher-energy ones, and faster than they would through a lower barrier(3).  I will discuss our plans to probe where within a barrier atoms spend their time, as well as recent theory concluding that mere observation of particles inside the barrier can “collapse” them, enhancing their transmission probability.  This latest work suggests a definition for a new, position-dependent, escape time, which we will undertake to measure in future experiments.

(1) - work carried out by Ramón Ramos, David Spierings, Isabelle Racicot, and AMS

(2) - Measurement of the time spent by a tunnelling atom within the barrier region, Ramón Ramos, David Spierings, Isabelle Racicot, & Aephraim M. Steinberg, Nature 583, 529 (2020)

(3) - Tunneling takes less time when it’s less probable, David C. Spierings & Aephraim M. Steinberg, quant-ph/2101.12309