2020/06/29 by Saranyo Moitra, Rajdeep Sensarma
Computer Science · Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #Entropy (arrow of time) #Fermion #Fock space #Physics #Quantum #Quantum Information and Cryptography #Quantum discord #Quantum entanglement #Quantum many-body systems #Quantum mechanics #Squashed entanglement #Statistical physics #Von Neumann entropy #cond-mat.quant-gas #cond-mat.stat-mech #quant-ph
paper · pdf · doi:10.1103/physrevb.102.184306
14+5 pages, 7+3 figures
arxiv created 2020/06/29 · openalex publication_date 2020/11/25 · arxiv updated 2020/12/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We formulate a new ``Wigner characteristics''-based method to calculate entanglement entropies of subsystems of Fermions using Keldysh field theory. This bypasses the requirements of working with complicated manifolds for calculating R'enyi entropies for many-body systems. We provide an exact analytic formula for R'enyi and von Neumann entanglement entropies of noninteracting open quantum systems, which are initialized in arbitrary Fock states. We use this formalism to look at entanglement entropies of momentum Fock states of one-dimensional Fermions. We show that the entanglement entropy of a Fock state can scale either logarithmically or linearly with subsystem size, depending on whether the number of discontinuities in the momentum distribution is smaller or larger than the subsystem size. We also use this formalism to describe entanglement dynamics of an open quantum system starting with a single domain wall at the center of the system. Using entanglement entropy and mutual information, we understand the dynamics in terms of coherent motion of the domain wall wavefronts, creation and annihilation of domain walls, and incoherent exchange of particles with the bath.