Circumvent unsupported tensorkit feature

Author: lkdvos

src/algorithms/toolbox.jl

@@ -275,7 +275,7 @@ function periodic_boundary_conditions(mpo::InfiniteMPO{O},
         F_right = i == L ? cup :
                   isomorphism(ST, V_right ← V_wrap' * right_virtualspace(mpo, i))
         # account for fermionic boundary conditions
-        o = i == L ? twist(mpo[i], 4) : mpo[i]
+        o = i == L ? _twist(mpo[i], 4) : mpo[i]
         @plansor output[i][-1 -2; -3 -4] = F_left[-1; 1 2] *
                                            τ[-3 1; 4 3] *
                                            o[2 -2; 3 5] *
@@ -424,8 +424,8 @@ function periodic_boundary_conditions(H::InfiniteMPOHamiltonian, L=length(H))
             k′ = indmap[j, k, chi]
             k′ == size(output[end], 1) && continue
             # apply twist for fermionic boundary conditions
-            h′ = twist(h, 4)
-            @plansor o[-1 -2; -3 -4] := F_left[-1; 1 2 6] * h′[1 3; -3 4] * τ[3 2; 4 5] *
+            h = _twist(h, 4)
+            @plansor o[-1 -2; -3 -4] := F_left[-1; 1 2 6] * h[1 3; -3 4] * τ[3 2; 4 5] *
                                         τ[5 6; -4 -2]
             output[end][k′, 1, 1, 1] = o
         end

src/utility/utility.jl

@@ -133,6 +133,15 @@ function fuser(::Type{T}, V1::S, V2::S) where {T,S<:IndexSpace}
     return isomorphism(T, fuse(V1 ⊗ V2), V1 ⊗ V2)
 end
 
+# TODO: remove once TensorKit supports this
+_twist(t::AbstractTensorMap, i::Int) = _twist(BraidingStyle(t), t, i)
+_twist(::SymmetricBraiding, t::AbstractTensorMap, i::Int) = t
+function _twist(::NoBraiding, t::AbstractTensorMap, i::Int)
+    check_ambiguous_braiding(space(t, i))
+    return t
+end
+_twist(::BraidingStyle, t::AbstractTensorMap, i::Int) = twist(t, i)
+
 # Verify that the braiding is unambiguous: either through symmetric braiding or because the
 # sectors are all trivial
 function check_ambiguous_braiding(::Type{Bool}, V::VectorSpace)