Nearest Neighbours in 2D lattices

[Adwait-Naravane]

Hi, when you call @mpoham to construct an MPO from interactions along nearest neighbours on a 2D lattice, isn't it supposed to receive the linearized_index of the nearest_neighbours? The nearest_neighbours in the square_lattice and triangular_lattice files seems to return the 2D coordinates instead of their linearized_index, is it supposed to be this way?

[lkdvos]

For square coordinates this works because we are implicitly linearizing based on the linear indexing of the matrix of physical spaces. I would have to double check that everything is being handled consistently, but that should just work.