[2112.13688] A Variational Approach to Quantum Spin Liquids in the Rydberg Atom Simulator

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overview: Recently, the Rydberg blockade effect has been exploited to realize quantum spin liquids on kagome lattices. Evidence for quantum spin liquids has been obtained experimentally by direct measurements of nonlocal string order. In this letter, we report his BCS-type variational wavefunction study of the spin liquid state in this model. This wavefunction is motivated by mapping the Rydberg blockade model to lattice gauge theory, where local gauge conservation replaces the role of constraints from the Rydberg blockade. We determine variational parameters from experimental measurements of the Rydberg atomic ensemble. We then compare this deterministic wavefunction prediction with experimental measurements of nonlocal string order. We combine both open-string and closed-string measurements to extract the variation related only to the closed loop as an index of topological order. The predictions from the wavefunction agree fairly well with the experimental data without fitting parameters. Our variational wavefunction provides a simple and intuitive picture of quantum spin liquids in this system that can be generalized to various generalizations of the current model.