Even Quantum Computers Need to Keep Their Cool, But How To Make Cool?

Quantum computers are very powerful machines and all that power produces a lot of heat. So, in order for quantum computers to work at their most efficient, researchers have built a nanoscale refrigerator that’s been designed especially to keep qubits cool. Where traditional computers have to use built-in fans to dissipate heat, quantum computers have the same requirements. The difference between the two comes down to the way in which they both deal with information. Traditional computers use bits of data that can be either a 0 or a 1, whereas quantum computers use qubits that can be both at the same time!

Another difference between traditional computers and quantum computers is that in order for qubits to run an algorithm they must first start in low-temperature ground states. Carrying out complex calculations makes the qubits heat up so running several at once or after a quick succession of one another will definitely require more than a standard fan to keep things cool. So, Mikko Mottonen and colleagues at Aalto University in Finland decided to build the world’s first standalone cooling device for quantum circuits. They did it by building a circuit with an energy gap that divided two channels. One was a superconducting fast lane, and the other was a slow resistive lane. Only those electros with enough energy to hop across the gap can join the superconductor lane. Sometimes an electron can get a boost from a nearby photon allowing it to cross lanes. As this happens the resonator in which the photon came from begins to cool.

This is exactly what happens to the electrons too. The hotter ones cross over while the cooler ones are left behind. As it takes place heat is removed from the system. Moving forward, the next step is to build a device that will cool the qubits as well and Mottonen is already in the process of applying for a patent for this, so watch this space. “Maybe in 10 to 15 years, this might be commercially useful,” he says. “It’s going to take some time, but I’m pretty sure we’ll get there.”

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