Process tomography of dynamical decoupling in a dense optically trapped atomic ensemble

TL;DR

This paper demonstrates that applying a dynamical decoupling sequence significantly prolongs coherence times in dense optically trapped atomic ensembles, enabling their use as long-lived quantum memories.

Contribution

The study provides experimental evidence of extended coherence times using dynamical decoupling in dense atomic ensembles, with quantum process tomography confirming high-fidelity quantum memory operation.

Findings

20-fold increase in coherence time with >200 pi-pulses

Dense ensemble with optical depth 230 used as quantum memory

Coherence times exceeding 3 seconds achieved

Abstract

Atomic ensembles have many potential applications in quantum information science. Owing to collective enhancement, working with ensembles at high densities increases the overall efficiency of quantum operations, but at the same time also increases the collision rate and leads to faster decoherence. Here we report on experiments with optically trapped 87Rb atoms demonstrating a 20-fold increase of the coherence time when a dynamical decoupling sequence with more than 200 pi-pulses is applied. We perform quantum process tomography and demonstrate that using the decoupling scheme a dense ensemble with an optical depth of 230 can be used as an atomic memory with coherence times exceeding 3 sec.