About the Cover

As quantum computation and other quantum applications speed toward real-world uses, understanding the underlying physics is important for overcoming the technologies’ performance challenges. On page 26, Christopher Anderson and David Awschalom explore progress on and opportunities for quantum systems based on solid-state defects. And on page 34, José Aumentado, Gianluigi Catelani, and Kyle Serniak discuss one of the primary limits on superconducting qubit performance. (Image courtesy of Peter Allen.)