Quantum materials always get talked about like futuristic technology, but the reality is that they are here and they are being used. Simulating molecular interactions for drug discovery, AI optimization, and advanced semi/super conductors are just a few areas where new materials are being utilized for quantum computing. One thing that each of these uses shares in common with one another is their temperature dependence. These tiny electronic chips will only show quantum material behavior at temperatures close to 0K, or absolute zero, a notoriously difficult temperature to reach.
The most common method of cooling in the lab past the 173K temperature of ice is liquid nitrogen, which reaches a temperature of 77K, which is nowhere near cold enough to eliminate the amount of thermal motion necessary for quantum materials to work effectively. Current quantum computers have begun utilizing liquid helium to achieve a temperature range of 4-0.22K, which is much closer to the ideal 0K. More specifically, Helium-3 is used, a rare isotope that contains 3 neutrons instead of the standard 2 that Helium-2 has. This creates the challenge of scarcity, where Helium-3 is very difficult to acquire.
Helium-2 on its own is rare enough, only taking up 5ppm of the Earth's atmosphere, and Helium-3 is only 0.0001% of that amount, so natural methods of acquiring this gas are not feasible for the industrial scale. During the Cold War in 1955, the development of Hydrogen Bombs as an improvement to the Atomic Bombs led to the creation of Tritium, or Hydrogen-3. This unstable isotope of Hydrogen will slowly decay into Helium-3 through beta decay, where a neutron is converted into a proton, releasing an electron and an antineutrino
Cooling quantum computers with liquid Helium functions by using Helium-4 to cool down to 4K, which boils off, with Helium-3 then being introduced and compressed, which cools down the mixture even more. At this point, the mixture separates into two layers: helium-3 on top of a mixture of both. As some atoms of helium-3 leave the mixture, replacements diffuse down from the layer of pure Helium-3, resulting in heat being drawn from the environment. Boiled off Helium can be captured and reused, allowing the process to continue until temperatures near absolute zero are reached.
Possible solutions for the Helium-3 supply issue have been theorized, such as extracting it from the tritium made in certain heavy water nuclear power plants or harvesting it from the Moon, where solar wind does not get deflected like it does for Earth, resulting in a buildup on the surface. Other cooling options are available, but this method will be left behind if a better source of Helium-3 is not found, because the demand for quantum computers will only continue to rise.
https://www.science.org/content/article/helium-3-runs-scarce-researchers-seek-new-ways-chill-quantum-computers
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