Creating direct electrical connections between metal electrodes and low-dimensional semiconductor nanostructures has recently become possible thanks to the development of new nanomaterials and nanofabrication methods. Hybrid devices can thus be made in which macroscopic properties, such as superconductivity or ferromagnetism, are combined with microscopic properties, such as the charge or the spin state of individual electrons. Such hybrid devices open a wide range of opportunities for the study of new quantum phenomena and, in the long term, they may lead to the development of useful electronic devices with quantum functionalities. In this talk, I will present recent experimental results obtained with hybrid devices consisting of zero-dimensional, quantum-dot structures coupled to superconducting electrodes. Special attention will be devoted to the magnetic properties of the sub-gap states in these hybrid systems and to the intriguing competition between Coulomb interactions, Kondo correlations, and the superconducting proximity effect.
 E. J. H. Lee, X. Jiang, R. Aguado, G. Katsaros, C. M. Lieber, and S. De Franceschi, “Zero-bias anomaly in a nanowire quantum dot coupled to superconductors”, Phys. Rev. Lett. 109, 186802 (2012).
 E. J. H. Lee, X. Jiang, M. Houzet, R. Aguado, C. M. Lieber, and S. De Franceschi, “Spin-resolved Andreev levels in hybrid superconductor-semiconductor nanostructures”, arXiv:1302.2611.