G56: Quantum Spin Liquids, Theory I

Tue. March 7, 1:30 p.m. – 1:42 p.m. PST

Room 304

Entanglement and separability are two opposite yet intertwined notions in quantum mechanics. A quantum state is said to be entangled if it is not separable, and vice versa. Quantifying how entangled two subsystems are remains a challenging problem, which has led to important insights in the context of quantum many-body systems. In this talk, we discuss entanglement and separability of dimer Rokhsar-Kivelson (RK) states and resonating valence-bond (RVB) states. For dimer RK states on general tilable graphs, we prove the exact separability of the reduced density matrix of two disconnected subsystems, implying the absence of entanglement between the subsystems. For RVB states, we show separability for disconnected subsystems up to exponentially small terms in the distance d between the two subsystems. We argue that separability does hold in the scaling limit, even for arbitrarily small ratio d/L, where L is the characteristic size of the subsystems. Our results hold irrespective of the underlying graph (which include square and triangular lattices), and hence suggest that separability (up to exponentially small terms) between disjoint regions is a universal feature of quantum spin liquids. In the case of adjacent subsystems for the RK states, we derive exact results for the logarithmic negativity in terms of partition functions of the underlying statistical model, and recover the known result for the Rényi-1/2 entropy in the limit of complementary subsystems.