World’s largest quantum cryo system

Technology News |
By Nick Flaherty

IBM has developed the world’s largest cryogenic dilution fridge to house larger quantum computers.

Project Goldeneye pushes the limits of low-temperature refrigeration while laying the groundwork for the quantum industry’s ability to scale to larger experiments.

Goldeneye is a concept system, and IBM says it will not be used for production quantum computer systems, But the project is pushing the limits of low temperature systems.

Current dilution refrigerators are limited in a number of ways: the size of the quantum physics experiments we can fit inside them; the number of input/output ports; and the cooling power.

Goldeneye contains 1.7 cubic meters’ worth of experimental volume, more than twice the size of today’s systems, cooling a volume larger than three home kitchen refrigerators to temperatures as low as 25mK with a quantum processor inside.

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

Dilution refrigerators perform the cooling by using a number of steps to remove heat from the helium isotope mixture, and then use vacuum pumps to circulate and dilute He-3 into the He-3/He-4 mixture until a target temperature is reached.

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

Project Goldeneye has a new construction of the frame and cryostat to maximize experimental volume while reducing noise and achieving the temperatures required for cooling experimental quantum hardware. The design is modular, which made prototyping, assembly, and disassembly a much easier lift for just a team of four IBM engineers.

The cryostat also features a clamshell design, allowing the outer vacuum chamber to open sideways and eliminating the need to remove the entire external shell to access the hardware inside. Most dilution refrigerators in use today require a team of operators to function properly, but Goldeneye’s fully automated system includes a specially designed jib crane that could one day allow even a single person to run the fridge which can be monitored remotely with the help of an open-source visualization platform.

The inside of the cryostat features the ability to install a set of 10 internal plates for mounting components in its top and bottom half: five “regular” units on top and five inverted units on the bottom. It can also hold up to six individual dilution refrigerator units, enabling close to ~10 mW at 100 mK cooling power, and over 24 W of cooling power at 4 K temperatures.

Finally, the weight of the entire system — 6.7 metric tons — also helps dampen vibrations, reducing the need for other commonly used dampening techniques.

The fridge supported coherence times of around 450 microseconds for the quantum processor, similar to those measured on other commercial dilution refrigeration systems.

IBM’s Quantum System Two, to be deployed next year, will first be realized with Bluefors’ Kide cryogenic platform, a smaller, modular system that can connect multiple processors together.

Goldeneye will inform the roadmap for quantum processors beyond 2025 for tomorrow’s quantum data centres.

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