Coherence freeze in an optical lattice investigated via pump-probe spectroscopy

TL;DR

This paper investigates the unexpected coherence freeze in an optical lattice using pump-probe spectroscopy, revealing insights into vibrational state dynamics and the system's memory effects in ultracold rubidium atoms.

Contribution

It introduces a pump-probe spectroscopy method to analyze vibrational coherence and models the frequency trajectory distribution to explain coherence freeze phenomena.

Findings

Observed coherence freeze in ultracold rubidium atoms

Inferred frequency distribution predicts echo decay features

Characterized memory dynamics of vibrational states

Abstract

Motivated by our observation of fast echo decay and a surprising coherence freeze, we have developed a pump-probe spectroscopy technique for vibrational states of ultracold $^{85}$Rb atoms in an optical lattice to gain information about the memory dynamics of the system. We use pump-probe spectroscopy to monitor the time-dependent changes of frequencies experienced by atoms and to characterize the probability distribution of these frequency trajectories. We show that the inferred distribution, unlike a naive microscopic model of the lattice, correctly predicts the main features of the observed echo decay.