A gold prospector first sifts sand through a sieve, tossing out the barren rock. In much the same way, scientists decided to hunt for useful defects in silicon carbide, a tough crystal already used in electronics and possibly, in the future, in quantum computers.
A defect is a point-like disruption of order in a crystal: either an empty spot where an atom is missing, or a foreign atom sitting in the wrong place. Such defects sometimes keep devices from working, and sometimes, on the contrary, turn into qubits, the quantum units of memory. The trouble is that there are thousands of defect variants, and an exact calculation of each one takes a lot of time. Hence the need for a sieve.
It used to seem that a full calculation of the defect structure was indispensable. Now it has become clear that even without complex computations you can get reasonable estimates. This approach lowers the barrier to entry: no giant computing cluster is needed, just an ordinary computer with a trained model. The sieve does not replace exact verification, but it saves effort: precise calculations go only to promising candidates, not to thousands of random variants.
In 4H-SiC there are more than 200 polytypes, but it is 4H that is used in most commercial devices. Point defects in it can emit single photons, making them candidates for quantum cryptography.