Bounding Entanglement Entropy Using Zeros of Local Correlation Matrices

Unravelling the quantum-entanglement effect of noble gas coordination on the spin ground state of CUO

The accurate description of the complexation of the CUO molecule by Ne and Ar noble gas matrices represents a challenging task for present-day quantum chemistry. Especially, the accurate prediction of the spin ground state of different CUO--noble-gas complexes remains elusive. In this work, the interaction of the CUO unit with the surrounding noble gas matrices is investigated in terms of complexation energies and dissected into its molecular orbital quantum entanglement patterns. Our analysis elucidates the anticipated singlet--triplet ground-state reversal of the CUO molecule diluted in diff…

Kitaev自旋液体中密度矩阵的精确组织与纠缠结构

Exact Organization of Density Matrices and Entanglement Structure in the Kitaev Spin Liquid

本文研究了Kitaev自旋液体中密度矩阵的精确形式及其纠缠结构，通过弦算符等价类组织密度矩阵，并揭示了其与规范对称性的关系，进一步证明了纠缠谱的退化性和熵分离性。

拓扑缺陷中的纠缠：理论与数值的调和

Entanglement Through Topological Defects: Reconciling Theory with Numerics

本文通过引入新的减少密度矩阵制备方法，解决了拓扑缺陷与纠缠熵理论预测之间的矛盾，并展示了其在Ising模型中对群状和对偶缺陷的有效性。

Discarded weight and entanglement spectra in the Numerical Renormalization Group

A quantitative criterion to prove and analyze convergence within the numerical renormalization group (NRG) is introduced. By tracing out a few further NRG shells, the resulting reduced density matrices carry relevant information on numerical accuracy as well as entanglement. Their spectra can thus be analyzed twofold. The smallest eigenvalues provide a sensitive estimate of how much weight is discarded in the low energy description of later iterations. As such, the discarded weight is a clear indicator of the accuracy of a specific NRG calculation. In particular, it indicates in a site-specifi…

Entanglement scaling in critical two-dimensional fermionic and bosonic systems

We relate the reduced density matrices of quadratic bosonic and fermionic models to their Green's function matrices in a unified way and calculate the scaling of bipartite entanglement of finite systems in an infinite universe exactly. For critical fermionic 2D systems at T=0, two regimes of scaling are identified: generically, we find a logarithmic correction to the area law with a prefactor dependence on the chemical potential that confirms earlier predictions based on the Widom conjecture. If, however, the Fermi surface of the critical system is zero-dimensional, we find an area law with a …

Boundary topological entanglement entropy in two and three dimensions

The topological entanglement entropy is used to measure long-range quantum correlations in the ground state of topological phases. Here we obtain closed form expressions for topological entropy of (2+1)- and (3+1)-dimensional loop gas models, both in the bulk and at their boundaries, in terms of the data of their input fusion categories and algebra objects. Central to the formulation of our results are generalized $\mathcal{S}$-matrices. We conjecture a general property of these $\mathcal{S}$-matrices, with proofs provided in many special cases. This includes constructive proofs for categories…