Doped resonating valence bond states: a quantum information study

Sudipto Singha Roy, Harisch-Chandra Research Institute, Allahabad, India

19.06.2017 at 10:00 

Resonating valence bond states have played a crucial role in the description of exotic phases in strongly correlated systems, especially in the realm of Mott insulators and the associated high­Tc superconducting phase transition. In particular, RVB states are considered to be an important system to study the ground state properties of the doped
quantum spin­1/2 ladder. It is therefore interesting to understand how quantum correlations are distributed among the constituents of these composite systems. In this regard, we formulate an analytical recursive method to generate the wave function of doped short­range resonating valence bond (RVB) states as a tool to efficiently estimate multisite entanglement as well as other physical quantities in doped quantum spin ladders. Importantly, our results show that within a specific doping concentration and model parameter regimes, the doped RVB state essentially characterizes the trends of genuine multiparty entanglement in the exact ground states of a Hubbard model with large onsite interactions. Moreover, we consider an isotropic RVB network of spin­1/2 particles with a finite fraction of defects, where the corresponding wave function of the network is rotationally invariant under the action of local unitaries. By using quantum information­theoretic concepts like strong subadditivity of von Neumann entropy and approximate quantum telecloning, we prove analytically that in the presence of defects, caused by loss of a finite fraction of spins, the RVB network
sustains genuine multisite entanglement, and at the same time may exhibit finite moderate­range bipartite entanglement, in contrast to the case with no defects.