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lkdvos merged 1 commit into from
Jan 12, 2026
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entanglement_spectrum docstring #371

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13 changes: 7 additions & 6 deletions src/algorithms/toolbox.jl
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
"""
entropy(state, [site::Int])

Calculate the Von Neumann entanglement entropy of a given MPS. If an integer `site` is
Calculate the von Neumann entanglement entropy of a given MPS. If an integer `site` is
given, the entropy is across the entanglement cut to the right of site `site`. Otherwise, a
vector of entropies is returned, one for each site.
"""
Expand Down Expand Up @@ -85,7 +85,7 @@ overlap of a given `above` state and a `below` state. The `sector` keyword argum
used to specify a non-trivial total charge for the transfer matrix eigenvectors.
Specifically, an auxiliary space `ℂ[typeof(sector)](sector => 1)'` will be added to the
domain of each eigenvector. The `tol` and `num_vals` keyword arguments are passed to
`KrylovKit.eigolve`
`KrylovKit.eigsolve`
"""
function transfer_spectrum(
above::InfiniteMPS; below = above, tol = Defaults.tol, num_vals = 20,
Expand All @@ -110,15 +110,16 @@ function transfer_spectrum(
end

"""
entanglement_spectrum(ψ, site::Int) -> SectorDict{sectortype(ψ),Vector{<:Real}}
entanglement_spectrum(ψ, site::Int) -> SectorVector{T, sectortype(ψ), AbstractVector{T}}

Compute the entanglement spectrum at a given site, i.e. the singular values of the gauge
matrix to the right of a given site. This is a dictionary mapping the charge to the singular
values.
matrix to the right of a given site. This is a vector containing the singular
values. The contributions from specific sectors can be viewed by indexing accordingly, i.e.
`entanglement_spectrum(ψ, site)[sector]`.

For `InfiniteMPS` and `WindowMPS` the default value for `site` is 0.

For `FiniteMPS` no default value for `site` is given, it is up to the user to specify.
For `FiniteMPS` no default value for `site` is given; it is up to the user to specify.
"""
function entanglement_spectrum(st::Union{InfiniteMPS, WindowMPS}, site::Int = 0)
checkbounds(st, site)
Expand Down