After an short introduction to the concepts of Conformal Field Theory (CFT) and quantum criticality, we will briefly review the universal properties exhibited by the entanglement of 1d critical systems in its ground state . The ground state entanglement of a 1d Hamiltonian follows a law which is given by the Conformal Field Theory describing its scaling regime. We will explain  how this relationship can be generalized to critical low-energy excitations, the n-th Rényi entanglement entropy being related in this case to a 2n-point correlator of the field describing the excitation. This result uncovers a new link between quantum information theory and CFT.
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