ARTICLES

The problem of quantum entanglement has attracted muchattention since the early days of quantum mechanics. One of themost intriguing features of this phenomenon is that non-interacting parts of a system can show non-local correlations reflecting interactions that occurred in the past (see,for example,ref.1).Although techniques to entangle two particles and, in particular, two photons2 have been known for some time, it is only recently that many (up to four)-particle entanglements have been demonstrated experimentally3,4. Following developments in quantum cryptography, together with the discovery of quantum algorithms that outperform those of classical computation,research on the foundations of quantum mechanics has now moved to the centre of the new field of quantum information5. As a result, the question of entanglement has gained practical significance. In this work, we propose and demonstrate experimentally a novel method for many-particle entanglement involving Zeeman-split spin states of non-interacting paramagnetic impurities (Mn2+ and donors) i