Sympathetic cooling and squeezing of two co-levitated nanoparticles

We demonstrate sympathetic cooling of a silica nanoparticle coupled via the Coulomb interaction to a second silica nanoparticle to which feedback cooling is directly applied. We also implement sympathetic squeezing through a similar process showing non-thermal motional states can be transferred through the Coulomb interaction. This work establishes protocols for cooling and manipulating arrays of nanoparticles for sensing and minimising the effect of optical heating in future experiments.