In a work published in Physical Review Letters (2020), D. Khomenko, C. Scalliet, L. Berthier, D. R. Reichman and F. Zamponi show that the density of two-level systems in a glass depends on its stability, i.e. its degree of annealing. In particular, they evidenced a strong depletion of two-level systems in ultrastable glasses prepared with SWAP, a state-of-the-art algorithm.
The work was notably featured in Physics Magazine and Quanta Magazine.