d-Wave superconductors and quantum computers

Quantum algorithms promise enormous speed up in dealing with certain problem classes, but only in large enough quantum computers (about thousand qubits). Therefore the scalability of solid state devices make solid-state-based qubit prototypes an attractive choice. On the other side, it is difficult to preserve quantum coherence in such devices, in the presence of macroscopic number of degrees of freedom. The coherent ground state and suppression of low-energy excitations in superconductors could help solve the problems. Recent experiments on several mesoscopic qubit prototypes, using conventional superconductors, demonstrated coherent quantum behavior. Here I review the current results on qubit prototypes based on high-T-c superconductors, and discuss the open questions and the further directions of research. (C) 2001 Elsevier Science B.V. All rights reserved.