Steele and co-authors coupled two superconducting circuits and transferred heat from one to the other to achieve their stunning cold radio waves. The adapted process is known as photon pressure coupling and uses the radiation pressure of photons at one frequency to draw heat from those elsewhere on the electromagnetic spectrum.

They used an adaptation of the laser cooling techniques that recently set a world record of 38 picoKelvins (38 trillionths of a degree above absolute zero). ItвЂ™s this part of the spectrum Professor Gary Steele and co-authors are seeking to cool. Optical, infrared and gigahertz frequency telescopes have used quantum techniques to cool electromagnetic radiation, but these have failed for frequencies in the hundreds of megahertz, coincidentally those used by FM radio stations. When even colder temperatures are required, such as to remove heat that might overpower signals from an MRI machine, liquid helium is used instead, bringing temperatures down to just 2.2 degrees above absolute zero.Д®ven that is far too warm some research purposes, however. A team from Delft University of Technology have announced in Science Advances they have brought radio waves to near the coolest temperatures possible.ДЇor ordinary cooling purposes an object can be bathed in a very cold medium, such as liquid nitrogen, that draws heat away. However, when trying to tap into radio waves at the edge of our capacity to hear, cooling the antenna, and thus the waves themselves, is vital to avoid being overwhelmed with static. Since the movements reflect the antennaвЂ™s temperature physicists refer to affected radio signals as hot.ДЄ nearby powerful radio signal can overwhelm any heat in the system, so we can listen to our favorite music with clarity. However, the antenna with which we detect radio waves are made up of atoms that, like everything else in the universe, move around randomly, introducing noise in the system. Radio stations may aspire to be cool, but for most people the idea of the radio waves themselves having a temperature feels like a category error.

Cool radio clock