The rules of physics suggest that it is impossible to cool objects to absolute zero, when all of the object's thermal energy is completely removed and the atoms come to a standstill.
Coldest Object On Record: 10,000 Times Colder Than Vacuum Of Space
Physicists from the National Institute of Standards and Technology, however, have managed to get really close to achieving this. They were able to cool an object to a temperature colder than what was once thought possible.
In a new study published in the journal Nature on Wednesday, Jan.11, the researchers reported how they used laser to make a microscopic drum colder than anything that has been cooled before.
Using a new technique that defied the quantum limit for supercooling mechanical objects, the researchers were able to chill the mechanical drum to 360 microKelvin, which is 10,000 times colder than the vacuum of space.
The breakthrough process, which made the microscopic drum the coldest object on record, involves using what is called "squeezed" light.
Sideband Cooling
The best technique that scientists currently use to remove thermal energy from an object is what is known as sideband cooling. The process uses lasers to slow the atoms of an object down. The angle and frequency of the light allow the photons to take away energy from the atoms when they interact.
There were, however, limits to how cold researchers can cool atoms using this technique and this has something to do with the behavior of light. Instead of flowing in a continuous stream, light travels in discrete packets known as quanta, each of which gives a little kick as it arrives.
What this means is that a little bit of heat gets added during the process even as the energies are removed. It is comparable to keeping a leaf suspended in the air using sputtering hoses. Whenever the stream falters, the leaf drifts.
Squeezing Light To Reduce Heat-Producing Kicks
To eliminate the kicks, the researchers "squeezed" light using a special superconducting circuit to produce a light beam with quanta that follow one another in an orderly fashion. Although this process did not completely eliminate all of the heat-producing kicks, it helped get rid of a lot of these.
"Noise gives random kicks or heating to the thing you're trying to cool," study researcher John Teufel said. "We are squeezing the light at a 'magic' level-in a very specific direction and amount-to make perfectly correlated photons with more stable intensity. These photons are both fragile and powerful."
The experiment showed that the microscopic mechanical drum can be cooled down to less than a fifth of a single packet of energy, which is lower than ordinarily predicted by theories of quantum physics.
The technique can theoretically cool objects to absolute zero, wherein matter can be devoid of nearly all energy and motion.
"Here we propose and experimentally demonstrate that squeezed light can be used to cool the motion of a macroscopic mechanical object below the quantum backaction limit," the researchers wrote in their study.
