Successful test of a dilution refrigerator for quantum computers

IBM scientists have succeeded in cooling a quantum computer chip to a temperature of 25 mK using a large-scale dilution refrigerator. 

Quantum computing is a rapidly emerging technology that harnesses the laws of quantum mechanics to solve problems that are too complex for classical computers.[1] Quantum computers must be cooled to cryogenic temperatures, just a fraction of a degree above absolute zero, in order to keep systems in a quantum state. These states are very sensitive to interference from the environment and the slightest temperature increase can render the entire system unworkable.[2, 3] 


A team of IBM scientists have built a proof-of-concept for a dilution refrigerator, capable of cooling future generations of quantum experiments.[4] Dilution refrigerators are experimental cryogenic devices that cool a space volume to the milli-Kelvin (mK) regime by diluting helium-3 (He-3) into a He-3/He-4 mixture. In a recent press release, IBM announced that after three years of research, its “super-fridge” has successfully reached an operating temperature of about 25 mK, with a functioning quantum processor wired inside. 


Until recently, all dilution refrigerators were “wet” systems, requiring cryogenic fluids such as liquid nitrogen to begin the cooling. Today’s fridges are more commonly “dry,” employing a mechanical component called a cryo-cooler to provide the initial 50 K and 4 K temperatures for pre-cooling the helium mixture. The IBM dilution refrigerator features an innovative construction of the frame and cryostat — the main, barrel-shaped component responsible for the cooling — to maximise the experimental volume while reducing noise and achieving the temperatures required for cooling experimental quantum hardware. 


This “super fridge” has an experimental volume of 1.7 cubic meters, which is two to three times bigger than previous dilution refrigerators.  It can be fitted with different refrigerator units that cool to different temperatures, and its 6.7-ton weight helps dampen vibrations that can interfere with the quantum equipment. Importantly, it only takes up one-10th the space of existing dilution refrigerators of equivalent power. 


According to IBM, this “super fridge” may not be slated for use with the quantum processors currently under development. Nevertheless, it contributes to further conceptualise the cryogenic infrastructure of tomorrow's quantum data centres. 



Left: Interior of the "super fridge".
Right: The IBM team with the instrument's outer shell closed (source: Connie Zhou for IBM) [4]




[1] What is quantum computing?  
[2] Cooling quantum computers. 

[3] IBM builds huge super-fridge colder than space to chill quantum computers. 

[4] IBM scientists cool down the world’s largest quantum-ready cryogenic concept system.