Implement Chain normalization by mixed canonization

src/Ansatz/Chain.jl

@@ -406,6 +406,18 @@ function mixed_canonize!(::Open, tn::Chain, center::Site) # TODO: center could b
     return tn
 end
 
+"""
+    LinearAlgebra.normalize!(tn::Chain, center::Site)
+
+Normalizes the input [`Chain`](@ref) tensor network by transforming it
+to mixed-canonized form with the given center site.
+"""
+function LinearAlgebra.normalize!(tn::Chain, root::Site; p::Real=2)
+    mixed_canonize!(tn, root)
+    normalize!(select(Quantum(tn), :tensor, root), p)
+    return tn
+end
+
 """
     evolve!(qtn::Chain, gate)
 

test/Ansatz/Chain_test.jl

@@ -208,5 +208,16 @@
         end
     end
 
+    @testset "normalize" 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]
+        roots = [Site(3), Site(2)]
+        for (qtn, root) in zip(qtns, roots)
+            normalize!(qtn, root)
+            @test isapprox(norm(qtn), 1.0)
+        end
+    end
+
     # TODO test `evolve!` methods
 end