How Did a Laser Cool This Semiconductor to Almost Absolute Zero?

By Andrew Liszewski on at

It's completely counterintuitive, but scientists at the Niels Bohr Institute have succeeded in cooling a semiconductor membrane to −269°C, almost four degrees above absolute zero, using a powerful laser we usually think of as only being able to burn.

With a thickness of just 160 nanometres and a surface area of 1 millimetre square, the semiconductor membrane is incredibly small by most standards. But compared to previous laser cooling experiments which have been conducted on clouds of particles, it's downright gigantic. And it's composed of a material called gallium arsenide, which has a unique crystal structure giving it special electronic and optical properties.

Now how exactly the scientists were able to cool it to near absolute zero by blasting it with a laser is a bit on the complicated side. But the gist of the experiment involves bouncing the laser light between the membrane and a mirror, and as some of the light is absorbed by the membrane it expands and contracts. But by constantly adjusting and controlling this expansion and contraction, which essentially cause the membrane to vibrate, the material can actually be radically cooled.

So besides producing a lengthy research paper, why is this important? Well at some point quantum computers are going to revolutionise computing as we know it, but they can be very finicky beasts. Extra particles whizzing about inside can hinder their calculations, so cooling components to near absolute zero, where there's no particle motion, will help to create an environment where a quantum computer can function more accurately. Also, how cool would a laser-powered fridge be? [Niels Bohr Institute via Gizmag]