Using a newly developed laser-base technique, scientists were able to cool a microscopic machine to previously unheard of temperatures.
Physicists at the National Institute of Standards and Technology (NIST) have just created the coldest piece of machinery on record, bringing it to a temperature lower than previously thought possible. The results of this supercooling study were published in the January 2017 edition of Nature.
When physicists attempt to cool an object, they usually turn to light – specifically, lasers. While we typically associate lasers with heat, laser cooling, also called “sideband cooling,” is a widely used technique in the world of physics. Here, highly organized light is used to slow the random motion of atoms, reducing the thermal energy – the heat – they produce. The more focused the laser, the more effective its cooling power. However, there will always be units of light called “photons” that are not perfectly focused. Typically, the “noise” that’s present in typical lasers and light sources agitates the atoms inside an object and heating it, which limits the temperature it can reach – this is known as the “quantum limit.”
A new technique developed by NIST researchers takes laser cooling one step further. They “squeeze light” to slow the atoms, rendering the end product much colder than could be accomplished with typical cooling techniques.
Squeezed light is a type of light that’s entirely focused in one direction. This removes the “quantum noise,” or fluctuations typically present in the light particles, making the overall laser more direct, and more powerful. Though the technique was previously studied in relation to other branches of physics, including gravitational wave detection and quantum entanglement, this is the first time it has been harnessed for its cooling properties.
“We are squeezing light as a ‘magic level,’ in a very specific direction and amount” said NIST physicist John Teufel, who led the experiment. He added that this has the potential to make perfectly correlated photons with a more stable intensity.
Teufel and his team shone this squeezed light onto a thin, vibrating aluminum membrane that closely resembled the head of a snare drum, and were able to lower its temperature to about 360 microkelvin – 10,000 times colder than the vacuum of space. The researchers suggest that this new technique is so powerful that it could be used to cool objects to absolute zero (zero Kelvin), the temperature at which all of an object’s atoms are at a standstill, and not producing any thermal energy.
Supercooled mechanical objects, like this drum, have the potential to create the super-fast electronics of the future. Because they register negligible amounts of random noise from their surroundings, they can be used to create extremely sensitive and precise sensors for measuring force or acceleration.
“The colder you can get the drum, the better it is for any application,” said Teufel. “Sensors would become more sensitive. You can store information longer. If you’re using a quantum computer, then you can compute without distortion.”