An ordinary kitchen thermometer shows the temperature at which mercury stops resisting electricity. For superconductors used in quantum computers, the critical temperature is like a quality passport: the higher, the better. Tantalum in the alpha form is a star student, while its twin beta was considered a slacker. But as it turns out, even a slacker can solve problems.
Physicists took a film of beta-tantalum on a sapphire substrate and built 11 qubits — the basic cells of a quantum processor. The average qubit quality (a measure of how long it holds a quantum state) was 5.6 million, and the best sample reached 10.1 million. This is comparable to good qubits made from the alpha phase. Energy losses mainly occur due to surface defects, so-called two-level systems that act like tiny traps for microwave photons. The beta phase has about twice as many of these traps, but that's not fatal.
The beta phase of tantalum forms at room temperature, while alpha requires heating. This makes production simpler and cheaper. The result opens the door to scaling up quantum processors: you don't need to chase a perfect crystal structure if the "wrong" phase works well enough. After all, even a slacker can become an engineer.
The critical temperature of beta-tantalum is about 0.5 kelvin — colder than outer space, but sufficient for qubit operation in modern refrigerators.
In the series "Devs," a quantum computer is built from exotic materials, but here ordinary tantalum is used, just in a less known crystalline form.