From CIQC PI Hartmut Haeffner’s research group:

Researchers at UC Berkeley have coupled the motion of two ions spaced by
0.6 mm to each other by literally placing a wire between them. The wire
and the electrodes used to trap remain at room temperature while the
ions are at temperatures near absolute zero at -273 degrees Celsius. One
ion was kept "hot" at 250 mK while another ion was kept cold at 2 mK. By
measuring the temperature of the hot ion, the researchers could detect
that the cold ion coupled to the hot ion slowing its heating. Laser
cooling ions is important both for quantum information applications and
precision measurements, however, most ion species can not be laser
cooled. Using the method demonstrated here, we can now cool remote
trapped charges by coupling them to an ion species which can be laser
cooled, thereby opening up a host of applications in precision metrology
and coupling disparate quantum systems to each other.

Read more in Phys. Rev. Lett. 128, 063201 (2022), arXiv:2107.00851.
and the Physics Viewpoint by Christian Tomás Schmiegelow:
“Tin-Can Telephone” Connects Two Ions”, Physics 15, 16.