Fix evolve! function (#179)

* Fix evolve_2site! function

* Add tests for evolve! and expect

* Fix test

* Format tests

* Chnage testset names

src/Ansatz/Chain.jl

@@ -598,12 +598,21 @@ function evolve_2site!(qtn::Chain, gate::Dense; threshold, maxdim, iscanonical=f
         end,
     )
     replace!(
-        TensorNetwork(gate),
+        Quantum(gate),
         map(zip(inputs(gate), contracting_inds)) do (site, contracting_index)
             inds(gate; at=site) => contracting_index
         end,
     )
 
+    # replace output indices of the gate for gensym indices
+    output_inds = [gensym(:out) for _ in outputs(gate)]
+    replace!(
+        Quantum(gate),
+        map(zip(outputs(gate), output_inds)) do (site, out)
+            inds(gate; at=site) => out
+        end,
+    )
+
     # reindex output of gate to match TN sitemap
     for site in outputs(gate)
         if inds(qtn; at=site) != inds(gate; at=site)

test/Chain_test.jl

@@ -386,5 +386,63 @@
         @test isapprox(contract(TensorNetwork(qtn)), contract(TensorNetwork(adjoint_qtn)))
     end
 
-    # TODO test `evolve!` methods
+    @testset "evolve!" begin
+        @testset "one site" begin
+            i = 2
+            mat = reshape(LinearAlgebra.I(2), 2, 2)
+            gate = Dense(Tenet.Operator(), mat; sites=[Site(i), Site(i; dual=true)])
+
+            qtn = Chain(State(), Open(), [rand(2, 2), rand(2, 2, 2), rand(2, 2, 2), rand(2, 2, 2), rand(2, 2)])
+
+            @testset "canonical form" begin
+                canonized = canonize(qtn)
+
+                evolved = evolve!(deepcopy(canonized), gate; threshold=1e-14)
+                @test isapprox(contract(TensorNetwork(evolved)), contract(TensorNetwork(canonized)))
+                @test issetequal(size.(tensors(evolved)), [(2, 2), (2,), (2, 2, 2), (2,), (2, 2, 2), (2,), (2, 2)])
+                @test isapprox(contract(TensorNetwork(evolved)), contract(TensorNetwork(qtn)))
+            end
+
+            @testset "arbitrary chain" begin
+                evolved = evolve!(deepcopy(qtn), gate; threshold=1e-14, iscanonical=false)
+                @test length(tensors(evolved)) == 5
+                @test issetequal(size.(tensors(evolved)), [(2, 2), (2, 2, 2), (2, 2, 2), (2, 2, 2), (2, 2)])
+                @test isapprox(contract(TensorNetwork(evolved)), contract(TensorNetwork(qtn)))
+            end
+        end
+
+        @testset "two sites" begin
+            i, j = 2, 3
+            mat = reshape(kron(LinearAlgebra.I(2), LinearAlgebra.I(2)), 2, 2, 2, 2)
+            gate = Dense(Tenet.Operator(), mat; sites=[Site(i), Site(j), Site(i; dual=true), Site(j; dual=true)])
+
+            qtn = Chain(State(), Open(), [rand(2, 2), rand(2, 2, 2), rand(2, 2, 2), rand(2, 2)])
+
+            @testset "canonical form" begin
+                canonized = canonize(qtn)
+
+                evolved = evolve!(deepcopy(canonized), gate; threshold=1e-14)
+                @test isapprox(contract(TensorNetwork(evolved)), contract(TensorNetwork(canonized)))
+                @test issetequal(size.(tensors(evolved)), [(2, 2), (2,), (2, 2, 2), (2,), (2, 2, 2), (2,), (2, 2)])
+                @test isapprox(contract(TensorNetwork(evolved)), contract(TensorNetwork(qtn)))
+            end
+
+            @testset "arbitrary chain" begin
+                evolved = evolve!(deepcopy(qtn), gate; threshold=1e-14, iscanonical=false)
+                @test length(tensors(evolved)) == 5
+                @test issetequal(size.(tensors(evolved)), [(2, 2), (2, 2, 2), (2,), (2, 2, 2), (2, 2, 2), (2, 2)])
+                @test isapprox(contract(TensorNetwork(evolved)), contract(TensorNetwork(qtn)))
+            end
+        end
+    end
+
+    @testset "expect" begin
+        i, j = 2, 3
+        mat = reshape(kron(LinearAlgebra.I(2), LinearAlgebra.I(2)), 2, 2, 2, 2)
+        gate = Dense(Tenet.Operator(), mat; sites=[Site(i), Site(j), Site(i; dual=true), Site(j; dual=true)])
+
+        qtn = Chain(State(), Open(), [rand(2, 2), rand(2, 2, 2), rand(2, 2, 2), rand(2, 2, 2), rand(2, 2)])
+
+        @test isapprox(expect(qtn, [gate]), norm(qtn)^2)
+    end
 end