Multipartite entanglement in the random Ising chain

Quantum entanglement is a distinguishing property that offers fundamentally stronger correlations than classical physics. Entanglement of a single subsystem is well understood through entanglement entropy, showing a term known as the "area law" and a logarithmic term with a universal prefactor that is unique at quantum phase transitions. However, quantifying entanglement across multiple subsystems is a challenging open problem in interacting quantum systems. Here, we consider two subsystems of length l separated by a distance r and quantify two measures of multipartite quantum correlations, entanglement negativity (?) and mutual information (Ι), in critical random Ising chains. The ground states of the random Ising chains are generated through the asymptotically exact strong disorder renormalization group method. By relating ? and Ι to a cluster counting problem and though numerical simulations, we find universal constants of ? and Ι over any distances when r = αl.