Entanglement entropy has played an important role in characterizing many-body quantum states. In this pedagogical lecture, I will discuss numerical techniques for calculating entanglement entropy in the spin-1/2 XY chain, which includes the XX chain and the Ising chain as special cases, as well as in the harmonic chain. For the XY chain, I will show how to perform analytical diagonalization and then calculate the entanglement entropy of eigenstates using the correlation matrix method. For the harmonic chain, I will explain how to construct eigenstate wave functions and compute their entanglement entropy.

Reference: 

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[7] J. Zhang and M. A. Rajabpour, Excited state Rényi entropy and subsystem distance in two-dimensional non-compact bosonic theory. Part I. Single-particle states, JHEP 12 (2020) 160, [arXiv:2009.00719].

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Inviter: Jie-Qiang Wu