"Researchers solve a foundational problem in transmitting quantum information" (2024) https://phys.org/news/2024-02-foundational-problem-transmitt... :

They developed a new technology for transmitting quantum information over perhaps tens to a hundred micrometers [...,] "In our work, we couple a few electrons in the quantum dot to an electrical circuit known as a terahertz split-ring resonator," explains Kazuyuki Kuroyama, lead author of the study. "The design is simple and suitable for large-scale integration."

"Coherent interaction of a-few-electron quantum dot with a terahertz optical resonator" (2023) https://arxiv.org/abs/2204.10522 :

Abstract: We have investigated light-matter hybrid excitations in a quantum dot (QD)-terahertz (THz) optical resonator coupled system. We fabricate a gate-defined QD in the vicinity of a THz split-ring resonator (SRR) by using a AlGaAs/GaAs two-dimensional electron system (2DES). By illuminating the system with THz radiation, the QD shows a current change whose spectrum exhibits coherent coupling between the electrons in the QD and the SRR as well as coupling between the 2DES and the SRR. The latter coupling enters the ultrastrong coupling regime and the coupling between the QD and the SRR is also very close to the ultrastrong coupling regime, despite the fact that only a few electrons reside in the QD.