Emergent Distance from Mutual Information in the Critical 1D XXZ Spin Chain

Abstract: The possibility that spatial geometry may emerge from the entanglement structure of a quantum many-body system is a subject of fundamental interest. Here, we propose and numerically test a candidate distance metric in 1D, d_E, defined purely from quantum mutual information (I) via the relation d_E = K_0 / sqrt(I). Using large-scale density-matrix renormalization group (DMRG) simulations, we compute this emergent distance for the ground state of the 1D spin-1/2 XXZ chain, a canonical model system. Our simulations show that in the quantum critical phase at anisotropy $\Delta = 1.0$, the mutual information exhibits a power-law decay consistent with the emergence of a valid metric space. In stark contrast, within the gapped, antiferromagnetic phase ($\Delta = 2.0$), where mutual information decays exponentially, the emergent distance grows exponentially, a behavior inconsistent with the triangle inequality. These results provide numerical evidence that this information-theoretic definition can yield a well-behaved geometry in critical systems, offering a quantitative tool for probing quantum phases and motivating further analytical investigation into the foundations of emergent space.