Implement Chain normalization by mixed canonization

src/Ansatz/Chain.jl

@@ -406,6 +406,20 @@ function mixed_canonize!(::Open, tn::Chain, center::Site) # TODO: center could b
     return tn
 end
 
+"""
+    normalize_by_mixed_canonization(tn::Chain)
+
+Normalizes the input [`Chain`](@ref) tensor network by transforming it
+to a mixed-canonized form.
+"""
+function normalize_by_mixed_canonization(tn::Chain)
+    centersite = Site(((Quantum(tn) |> nsites) + 1) ÷ 2)
+    canonized = mixed_canonize(tn, centersite)
+    normalize!(select(Quantum(canonized), :tensor, centersite))
+
+    return canonized
+end
+
 """
     evolve!(qtn::Chain, gate)
 

src/Qrochet.jl

@@ -23,7 +23,7 @@ export Chain
 export MPS, pMPS, MPO, pMPO
 export leftindex, rightindex, isleftcanonical, isrightcanonical
 export canonize_site, canonize_site!, truncate!
-export canonize, canonize!, mixed_canonize, mixed_canonize!
+export canonize, canonize!, mixed_canonize, mixed_canonize!, normalize_by_mixed_canonization
 export observe
 
 export evolve!

test/Ansatz/Chain_test.jl

@@ -208,5 +208,18 @@
         end
     end
 
+    @testset "Normalization" begin
+        @testset "normalize_by_mixed_canonization" begin
+            odd_qtn = Chain(State(), Open(), [rand(4, 4), rand(4, 4, 4), rand(4, 4, 4), rand(4, 4, 4), rand(4, 4)])
+            even_qtn = Chain(State(), Open(), [rand(4, 4), rand(4, 4, 4), rand(4, 4, 4), rand(4, 4, 4), rand(4, 4, 4), rand(4, 4)])
+            qtns = [odd_qtn, even_qtn]
+            for qtn in qtns
+                norm_canonized = normalize_by_mixed_canonization(qtn)
+
+                @test isapprox(norm(norm_canonized), 1.0)
+            end
+        end
+    end
+
     # TODO test `evolve!` methods
 end