In the face of mounting numerical evidence, Metlitski and Grover [arXiv:1112.5166] have given compelling analytical arguments that systems with spontaneous broken continuous symmetry contain a sub-leading contribution to the entanglement entropy that diverges logarithmically with system size. They predict that the coefficient of this log is a universal quantity that depends on the number of Goldstone modes. In this paper, we confirm the presence of this log term through quantum Monte Carlo calculations of the second Rényi entropy on the spin 1/2 XY model. Devising an algorithm to facilitate convergence of entropy data at extremely low temperatures, we demonstrate that the single Goldstone mode in the ground state can be identified through the coefficient of the log term. Furthermore, our simulation accuracy allows us to obtain an additional geometric constant additive to the Rényi entropy, that matches a predicted fully-universal form obtained from a free bosonic field theory with no adjustable parameters.Introduction -In condensed matter, the entanglement entropy of a bipartition contains an incredible amount of information about the correlations in a system. In spatial dimensions d ≥ 2, quantum spins or bosons display an entanglement entropy that, to leading order, scales as the boundary of the bipartition [1][2][3]. Subleading to this "area-law" are various constants and -particularly in gapless phases -functions that depend non-trivially on length and energy scales. Some of these subleading terms are known to act as informatic "order parameters" which can detect non-trivial correlations, such as the topological entanglement entropy in a gapped spin liquid phase [4][5][6][7]. At a quantum critical point, subleading terms contain novel quantities that identify the universality class, and potentially can provide constraints on renormalization group flows to other nearby fixed points [8][9][10][11][12][13][14].In systems with a continuous broken symmetry, evidence is mounting that the entanglement entropy between two subsystems with a smooth spatial bipartition contains a term, subleading to the area law, that diverges logarithmically with the subsystem size. First observed in spin wave [15] and finite-size lattice numerics [16], the apparently anomalous logarithm had no rigorous explanation until 2011, when Metlitski and Grover developed a comprehensive theory [17]. They argued that, for a finite-size subsystem with length scale L, the term is a manifestation of the two long-wavelength energy scales corresponding to the spin wave gap, and the "tower of states" arising from the restoration of symmetry in a finite volume [18][19][20][21]. Remarkably, their theory not only explains the subleading logarithm, but predicts that the * bkulchyt@uwaterloo.ca FIG. 1. Schematic energy level structure of the low energy tower of states for finite-size systems with spontaneous breaking of a continuous symmetry. The correction to the entanglement entropy may be approximated by the log of the number of quantum rotor states bel...