Experimental investigation of tunneling times using Bose-Einstein condensates

TL;DR

This study measures the tunneling times of Bose-Einstein condensates in optical lattices during Landau-Zener transitions, providing insights into quantum tunneling dynamics and potential applications in quantum control.

Contribution

It presents the first time-resolved measurements of Landau-Zener tunneling in Bose-Einstein condensates, comparing adiabatic and diabatic bases to explore tunneling probabilities.

Findings

Resolved the steplike time dependence of band populations.

Accessed tunneling probabilities in two different bases.

Paved the way for quantitative studies of tunneling times.

Abstract

The time it takes a quantum system to complete a tunneling event (which in the case of cross-barrier tunneling can be viewed as the time spent in a classically forbidden area) is related to the time required for a state to evolve to an orthogonal state, and an observation, i.e., a quantum mechanical projection on a particular basis, is required to distinguish one state from another. We have performed time-resolved measurements of Landau-Zener tunneling of Bose-Einstein condensates in accelerated optical lattices, clearly resolving the steplike time dependence of the band populations. The use of different protocols enabled us to access the tunneling probability, in two different bases, namely, the adiabatic basis and the diabatic basis. The adiabatic basis corresponds to the eigenstates of the lattice, and the diabatic one to the freeparticle momentum eigenstates. Our findings pave the way towards more quantitative studies of the tunneling time for LZ transitions, which are of current interest in the context of optimal quantum control and the quantum speed limit.