Speaker
Description
Coherent expansion of a quantum wavepacket is a necessary fundamental step in many experimental protocols to prepare, manipulate, and read out non-classical states, especially for levitated dielectric nanoparticles where the ground state extent is on the order of $10\,\text{pm}$. Free evolution is potentially the most straightforward technique to achieve this state expansion. While it is both a simple and effective expansion scheme, it does require compensation of static forces to avoid mean displacement of the wavepacket during the free evolution.
Using an optical trap-release-recapture sequence involving a charged nanoparticle we developed methods to measure and counteract static forces. Compensating gravity and stray electric fields, in three dimensions, we demonstrate free evolution for $1\,\text{ms}$ with subsequent recapture. Coupled with a short harmonic pulse in between two free expansions, we have performed recompression and time-of-flight protocols, speaking for the coherence of our approach as well as its usefulness to further generate squeezed mechanical states.