Non-zero momentum requires long-range entanglement
- URL: http://arxiv.org/abs/2112.06946v2
- Date: Tue, 31 May 2022 18:04:51 GMT
- Title: Non-zero momentum requires long-range entanglement
- Authors: Lei Gioia, Chong Wang
- Abstract summary: We show that a quantum state in a lattice spin (boson) system must be long-range entangled if it has non-zero lattice momentum.
The statement can also be generalized to fermion systems.
- Score: 6.018940870331878
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: We show that a quantum state in a lattice spin (boson) system must be
long-range entangled if it has non-zero lattice momentum, i.e. if it is an
eigenstate of the translation symmetry with eigenvalue $e^{iP}\neq1$.
Equivalently, any state that can be connected with a non-zero momentum state
through a finite-depth local unitary transformation must also be long-range
entangled. The statement can also be generalized to fermion systems. Some
non-trivial consequences follow immediately from our theorem: (1) several
different types of Lieb-Schultz-Mattis-Oshikawa-Hastings (LSMOH) theorems,
including a previously unknown version involving only a discrete $\mathbb{Z}_n$
symmetry, can be derived in a simple manner from our result; (2) a gapped
topological order (in space dimension $d>1$) must weakly break translation
symmetry if one of its ground states on torus has nontrivial momentum - this
generalizes the familiar physics of Tao-Thouless; (3) our result provides
further evidence of the "smoothness" assumption widely used in the
classification of crystalline symmetry-protected topological (cSPT) phases.
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