In addition to having an extremely high voice, filling balloons or scuba diving, the most widespread use of helium is in refrigeration, a crucial task in countless tasks ranging from magnets for magnetic resonance imaging to particle accelerators (with conventional helium or Helium-4) to cryogenic cooling for quantum computing or neutron detectors (Helium -3). Critical industries.
Because yes, everything is helium, but the circumstances change depending on the isotope. Thus, while Helium-4 is abundant in the atmosphere but difficult to retain (it escapes into the atmosphere due to its lightness), Helium-3 is scarce on Earth and is also difficult to obtain: it is a byproduct of the aging of tritium nuclear warheads. Simply put: the helium needed to cool quantum computers and cutting-edge physics acts as a bottleneck to research.
A Chinese research team has published in Nature a solution: a metal alloy that cools almost to absolute zero without needing helium.
The invention. It is a metallic alloy, EuCo₂Al₉ (ECA), a rare earth intermetallic compound capable of reaching 106 millikelvin (–273.05 °C), thus establishing a record: it is the lowest temperature achieved by a metallic magnetocaloric material without using helium-3.
Another peculiarity is that it combines two seemingly antagonistic properties: it acts like a sponge that absorbs heat from the environment and its thermal conduction is between 50 and 100 times greater than other similar materials. A combination that postulates it to be the definitive supercoolant.
The network structure, its interactions and the resulting supersolid spin state. Chinese Academy of Sciences
Why is it important. We have already seen that helium-3 is a rare commodity and its usefulness in advanced physics and quantum computing. Finding an alternative opens the door to alleviating that bottleneck, although it is still in an early stage. Historically the largest global suppliers of helium-3 They have been the United States and Russiaas a byproduct of its nuclear programs. With this invention, China is one step closer to achieving independence of this strategic resource because it currently imports almost all of the helium-3 it consumes (95%, according to this paper 2024).
But the United States is also interested: at the end of January, the Defense Advanced Research Projects Agency launched a call to develop a modular helium-3-free cooling system for quantum and defense technologies. In less than two weeks I had the solution, yes, from China.
Context. The superconducting quantum computers They require working below 1 Kelvin and in that scenario the standard for decades has been dilution refrigeration technology. In a few words and in a simplified way: expensive refrigeration contraptions that occupy cubic meters and need helium-3 continuously. This limits its scalability, practically limiting it to specialized laboratories.
Adiabatic demagnetization cooling on which the ECA is based is not new, in fact the concept is a century oldbut its features have never been up to par. As explains the CASthe endemic problem was its poor thermal conductivity. According to the South China Morning PostPeking University already built two refrigerators using this principle in 2024, which have been operational for several months.
How have they done it. The cooling technique is called adiabatic demagnetization (ADR): a magnetic field is applied to the cold material, so that the internal “magnets” of the material align and release heat to the outside. When the magnetic field is removed, they return to their natural disordered state, absorbing heat from the surroundings, thereby lowering the temperature.
To solve the historical problem of low conductivity, ECA enters an unusual “metallic spin supersolid” physical state, which combines high heat absorption capacity with thermal conductivity similar to a conventional metal.
Yes, but. Being able to drop the temperature to 106 mK is remarkable, but the reality is that classic dilution systems in their most advanced version are capable of reaching 10 mK or less. And this is where much of quantum computing operates. In short: there is still a thermal gap to overcome.
On the other hand, it is a first step: going from laboratory material and even a prototype to the industrial or military environment is a long road. Scalability and costs will be decisive. Finally, it should be noted that the composition of the ECA includes Europium (in addition to cobalt and aluminum), a rare earth that makes the operation difficult and expensive. Nevertheless, China starts from a privileged positionas long as it is the absolute leader in this industry.
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