Disrupting the quantum computing industry! Fermilab creates the world's largest dilution chiller

In September, IBM announced that it had successfully cooled the world's largest dilution chiller, the Goldeneye, to operating temperature (~25 mK). Although the Goldeneye has not yet been officially put into use, but its "world's first" name has been lost, because Fermilab is developing a dilution cooler Colossus is three times the size of the Goldeneye.

Currently, researchers at the U.S. Department of Energy's Fermilab National Accelerator Laboratory announced that they are building Colossus - which will be the largest and most powerful dilution cooler to date at mK temperatures. Fermilab says, "When completed Colossus will it will provide 5 cubic meters of space and cool components to about 0.01 K. This is 10 times the cooling capacity and 15 times the volume of a standard commercial dilution chiller." The standard dilution chiller is about 0.4-0.7 cubic meters, and the GoldenEye is 1.7 cubic meters, just one-third the size of the Colossus.

Colossus, the largest dilution chiller of 5 m3

01The world's largest dilution chiller

Researchers from Fermilab's Center for Superconducting Quantum Materials and Systems (SQMS) needed plenty of room at low temperatures to achieve their goal of building a state-of-the-art quantum computer. Unlike kitchen refrigerators, dilution chillers use a mixture of helium isotopes to produce temperatures close to absolute zero.

Once we have accomplished our goal of building this giant machine, with the cooling capacity and volume that Colossus will provide, SQMS researchers will have unprecedented space for our future quantum computers and many other quantum computing and physics experiments," said Matt Hollister, the project's chief technologist. 'Colossus' is named after the first electronically programmable computer, which was built in the 1940s to break codes. It was a historic milestone in the history of computing and seemed an appropriate name for our new dilution cooler."

SQMS scientists and engineers are tackling the challenge of quantum decoherence. Decoherence is a phenomenon that occurs when quantum information is masked by signal noise or lost through the materials that make up physical quantum bits.The metal-niobium cavities used by SQMS to develop better physical quantum bits originated in Fermilab's famous particle gas pedal program. The lab's expertise in superconducting cavities and cryogenics was critical to building the modern, powerful particle gas pedal that made Fermilab the primary home of one of the U.S. Department of Energy's National Center for Quantum Information Science and Research.

To build a quantum computer, researchers not only need interconnected, high-quality quantum bits, they also need a large amount of peripheral equipment.

Most dilution coolers operating at mK temperatures provide only a fraction of the space compared to Colossus, making scalability a major obstacle to building useful quantum computers. colossus is so huge that it will be able to hold hundreds to thousands of highly coherent cavities and quantum bits.

The new dilution cooler will be built around a redesigned facility that was originally used to test components of the Fermilab Mu2e experiment at temperatures near 4K. When the Colossus is fully built, it will provide 5 cubic meters of space and cool components to about 0.01 K. That's 10 times the cooling capacity and 15 times the volume of a standard commercial dilution chiller at that temperature.

At SQMS, we use metal cavities made of superconducting materials to conduct our research," Hollister said. Superconducting materials are excellent at storing electromagnetic energy with very low losses, but the biggest challenge is that they have to be very cold. Fortunately, we are building a space to store hundreds to thousands of cavities and quantum bits, depending on the geometry and size, of course."

Colossus faces many challenges in its construction, as it is about 2 meters in diameter. Like an inverted wedding cake, about seven disks with smaller and smaller diameters and lower and lower temperatures will be suspended from each other to form the cryogenic structure of Colossus.

Chris James, Grzegorz Tatkowski and Matt Hollister stand on top of the redesigned cooling tank for Colossus.

A dilution chiller of this size has never been built before," said Grzegorz Tatkowski, cryogenic engineer. This presented many technical challenges for our team. We were designing a payload of considerable mass for Colossus, and it was a challenge to ensure that each plate met the correct temperature specifications required for the project."

To build Colossus, technicians will redesign the cryogenic equipment and a control room that was originally used for Fermilab's famous collider detector, which provided data for researchers to discover top quarks and provided recent measurements of the W boson mass.

It's very different from the low-temperature challenges I faced when I worked in the neutrino division at Fermilab," said Chris James, a cryogenic engineer. There, we used large tanks that could hold tons of ultra-pure liquid argon to detect tiny particles called neutrinos. Here, I'm using liquid helium at about 0.01 K, which is about 10,000 times colder than liquid argon."

To finalize the design and specifications of Colossus, the SQMS team has conducted an in-depth review of the components of the dilution chiller. The team expects to begin mass procurement in the summer of 2023.

Once we accomplish our goal of building this large machine, we look forward to seeing the incredible physics and quantum computing experiments our researchers have planned with Colossus," said Hollister. the Colossus team is excited to build the first machine of its kind to support our upcoming experiments and to create enhance the knowledge and capabilities of computing devices."

02Disrupting the Quantum Computing Industry

On the day of the IBM GoldenEye launch, Uncle Box envisioned several questions and said the answers to those questions could even disrupt the quantum computing industry landscape. In fact, for the future emergence of Colossus, these questions are still worthy of our consideration.

First, does quantum bit scaling really require such a large dilution cooler? Is there an alternative scaling method that does not require such a large cooler? Or is there a new way of cooling (which might require a new kind of physics)?

Second, do other companies have the capability to manufacture dilution chillers of this size? If not, can they be procured from companies or research institutions that have the manufacturing capability? For domestic companies, will the purchase be banned like the AMSL lithography?

Third, do millions of quantum bits require a larger cooler? Both GoldenEye and Colossus have indicated that they can accommodate thousands of quantum bits, so how many times larger will the cooler accommodate millions of quantum bits in the future? This is actually contrary to the trend of miniaturization of computers.

Fourth, should we develop room-temperature quantum computers if we cannot solve the problem of increasingly large dilution coolers domestically?

Reference link：

https://news.fnal.gov/2022/12/its-colossal-creating-the-worlds-largest-dilution-refrigerator/