I have a question about entanglement in condensed matter physics. It seems that topological order origins from long range entanglement, but what is long range entanglement? It is the same as long range correlation? I am interested in this issue and I am happy to have any discussion.
Long range entanglements are defined through local unitary transformations which is discussed in arXiv:1004.3835 Local unitary transformation, long-range quantum entanglement, wave function renormalization, and topological order by Chen, Gu, and Wen.
Basically, long range entangled states are states which are very different from product states and cannot be changed to product states through local unitary transformations.