A new paper in Nature Physics shows that by cramming lots of rare-earth ions into a crystal, some will form pairs that act as highly coherent qubits, thus debunking the idea that solid-state qubits need to be super dilute in an ultra-clean material to achieve long lifetimes.

According to the study’s authors, one of the major barriers to practical quantum computing has been how to make qubits that retain their quantum information long enough to be useful.