nLab short-range entanglement




In solid state physics, where the nature of quantum materials depends crucially on the entanglement of their ground states, it has been proposed (Kitaev 11, 13) that “short-range entanglement” (SRE) in a quantum material means or implies that the “ground state is non-degenerate”, hence that the Hilbert space of quantum states with the same lowest energy has dimension 11. See also Chen, Gu & Wen 10, Sec. II.

If such an SRE material is in a topological phase of matter, with the ground state separated by an energy gap from the excited states, then this means (Freed 14, cf. G & JF 19, ftn 2) that the (extended) topological field theory which describes the topological phase is an invertible topological field theory, hence one also speaks of an invertible topological phase.

In particular, short-range entanglement thus implies the absence of “topological order” (at least by two of three common definitions of the latter, see there).

In contrast, long-range entanglement in the ground state is supposedly the hallmark of topological order (Chen, Gu & Wen 10, Sec. V)


Short-range entanglement

The notion was introduced (only) in a series of talks:

  • Alexei Kitaev, Toward Topological Classification of Phases with Short-range Entanglement, talk at KITP (2011) [[video]]

  • Alexei Kitaev, On the Classification of Short-Range Entangled States, talk at Simons Center (2013) [[video]]

Formalization in terms of invertible topological field theories:

See also around footnote 2 of

Long-range entanglement

The opposite notion of long-range entanglement:

Further discussion:

  • Tsung-Cheng Lu, Sagar Vijay, Characterizing Long-Range Entanglement in a Mixed State Through an Emergent Order on the Entangling Surface [[arXiv:2201.07792]]

Last revised on May 26, 2022 at 06:18:42. See the history of this page for a list of all contributions to it.