Additivity of disjoint interval entanglement in quasiparticle excited states
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866916062843371520 |
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| author | Guo, Zhouhao Zhang, Jiaju |
| author_facet | Guo, Zhouhao Zhang, Jiaju |
| contents | We investigate mixed-state entanglement measures, namely reflected entropy, mutual information and logarithmic negativity, for two disjoint intervals in one-dimensional systems excited by a finite number of quasiparticles. While whole system is in a pure state, the two disjoint intervals are in a generically mixed state. To address the problem that natural subsystem bases are generically non-orthonormal in such excited states, we use a general and efficient algorithm that computes these measures directly from the density matrix expressed in an arbitrary non-orthonormal basis. Applying this method to classical, bosonic, and fermionic quasiparticle excitations on a circle, we discover a universal additivity property: in the limit of large momentum differences, the mixed-state entanglement of a multi-quasiparticle state decomposes exactly into the sum of independent contributions. This additivity unifies the entanglement behavior across classical and quantum statistics, with the classical result emerging naturally as a special case. Our findings establish a robust computational framework for mixed-state entanglement in excited many-body systems and reveal a generic decoupling mechanism that governs entanglement distribution beyond the ground state. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2601_03651 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Additivity of disjoint interval entanglement in quasiparticle excited states Guo, Zhouhao Zhang, Jiaju Quantum Physics Statistical Mechanics High Energy Physics - Theory We investigate mixed-state entanglement measures, namely reflected entropy, mutual information and logarithmic negativity, for two disjoint intervals in one-dimensional systems excited by a finite number of quasiparticles. While whole system is in a pure state, the two disjoint intervals are in a generically mixed state. To address the problem that natural subsystem bases are generically non-orthonormal in such excited states, we use a general and efficient algorithm that computes these measures directly from the density matrix expressed in an arbitrary non-orthonormal basis. Applying this method to classical, bosonic, and fermionic quasiparticle excitations on a circle, we discover a universal additivity property: in the limit of large momentum differences, the mixed-state entanglement of a multi-quasiparticle state decomposes exactly into the sum of independent contributions. This additivity unifies the entanglement behavior across classical and quantum statistics, with the classical result emerging naturally as a special case. Our findings establish a robust computational framework for mixed-state entanglement in excited many-body systems and reveal a generic decoupling mechanism that governs entanglement distribution beyond the ground state. |
| title | Additivity of disjoint interval entanglement in quasiparticle excited states |
| topic | Quantum Physics Statistical Mechanics High Energy Physics - Theory |
| url | https://arxiv.org/abs/2601.03651 |