Particle physics experiments

IBM built the world’s largest and coldest refrigerator to cool quantum experiments

Studying the coldest, most distant, lowest and highest energies and smallest things in the universe is difficult. This requires building brand new devices that push the boundaries of modern technology.

Today, IBM has built the world’s largest dilution refrigerator – known internally as Project Goldeneye – capable of cooling future generations of quantum experiments. This “super-fridge”, a dilution refrigerator larger than any commercially available today – in experimental volume.

As stated in IBM’s official blog, “The super-fridge contains 1.7 cubic meters of experimental volume, which means it can cool a volume greater than three home kitchen refrigerators to temperatures colder than outer space, compared to refrigerators previous ones, which are between 0.4 and 0.7 cubic meters. .”

“These temperatures are needed to perform cutting-edge physics experiments and potentially run large quantum processors.”

During the experiments, the scientists cooled it down to operating temperature (~25 mK) and wired a quantum processor inside.

How did they build the biggest and coldest refrigerator in the world?

Dilution refrigerators are experimental cryogenic devices that use a mixture of helium-3 (He-3) and helium-4 to cool a volume of space to the milli-Kelvin (mK) regime (He-4).

Dilution refrigerators accomplish this cooling by first using a series of procedures to remove heat from the helium isotope mixture, then using vacuum pumps to circulate and dilute He-3 into the He-3 mixture. /He-4 until the desired temperature is reached.

Until recently, all dilution refrigerators were “wet” systems, requiring already cold substances like liquid nitrogen and other cryogenic fluids to begin cooling.

The Goldeneye project features an all-new construction of the frame and cryostat – the main barrel-shaped component responsible for cooling – to maximize experimental volume while reducing noise and achieving required temperatures.

L: Interior of the experimental Goldeneye super fridge. A: The IBM Quantum Goldeneye team.

The cryostat also has a clamshell design, which allows the outer vacuum chamber to open horizontally and eliminates the need to remove the entire outer shell to reach the internal components.

A specially designed jib crane in the system could one day allow a single person to operate the refrigerator. Moreover, it can be monitored remotely using an open source visualization platform.

Five “normal” units at the top and five “inverted” units at the bottom of the cryostat’s interior can be installed as ten internal plates to secure components in its upper and lower halves. Additionally, it can accommodate up to six separate dilution refrigerators, enabling cooling capacities of over 24 W at 4 K and up to 10 mW at temperatures of 100 mK. Finally, the system weight of 6.7 metric tons reduces the need for additional damping methods by helping to dampen vibration.

Scientists have noted, “The most important thing is that it works. After only three years from the start of the project to our recent 25 mK milestone, we performed one last characterization exercise: we put a qubit chip inside . »

“We were able to reproduce coherence times of approximately 450 microseconds, similar to those measured on other commercial dilution refrigeration systems. We did not observe any decrease in qubit performance despite the different internal environment and much larger experimental volume.

Although the largest, the super fridge requires less space than today’s full-scale dilution fridges.

Goldeneye will soon be moving to IBM Quantum Computation Center in Poughkeepsie, NY, where the team will explore large-scale cryogenic systems to develop the cooling needs of tomorrow’s quantum data centers, such as the Blues Kide platform under development. for use with IBM Quantum System Two.