1. Dipartimento di Metodologie Fisiche e Chimiche (DMFCI), viale A. Doria 6, 95125 Catania, Italy
2. NEST-INFM, Piazza dei Cavaliezi 7, I-56126 Pisa, Italy
3. Scuola Normale Superiore, Piazza dei Cavaliezi 7, I-56126 Pisa, Italy

Correspondence to: Rosario Fazio^2,3 Correspondence and requests for materials should be addressed to R.F. (e-mail: Email: fazio@sns.it).

Classical phase transitions occur when a physical system reaches a state below a critical temperature characterized by macroscopic order¹. Quantum phase transitions occur at absolute zero; they are induced by the change of an external parameter or coupling constant², and are driven by quantum fluctuations. Examples include transitions in quantum Hall systems³, localization in Si-MOSFETs (metal oxide silicon field-effect transistors; ref. 4) and the superconductor–insulator transition in two-dimensional systems^{5, 6}. Both classical and quantum critical points are governed by a diverging correlation length, although quantum systems possess additional correlations that do not have a classical counterpart. This phenomenon, known as entanglement, is the resource that enables quantum computation and communication⁸. The role of entanglement at a phase transition is not captured by statistical mechanics—a complete classification of the critical many-body state requires the introduction of concepts from quantum information theory⁹. Here we connect the theory of critical phenomena with quantum information by exploring the entangling resources of a system close to its quantum critical point. We demonstrate, for a class of one-dimensional magnetic systems, that entanglement shows scaling behaviour in the vicinity of the transition point.