fix in swapping rows logic

Author: J-C-Q

src/randoms.jl

@@ -154,7 +154,7 @@ function random_destabilizer(rng::AbstractRNG, n::Int; phases::Bool=true)
     # apply qubit permutation S to F2
     perm_inds = vcat(perm, perm .+ n)
     U = F2[perm_inds,:]
-
+    println(U)
     # apply layer of hadamards
     lhs_inds = vcat(had_idxs, had_idxs .+ n)
     rhs_inds = vcat(had_idxs .+ n, had_idxs)
@@ -189,10 +189,6 @@ struct RandDestabMemory{N,T<:Integer}
         T = typeof(n)
         F1 = zeros(Int8, 2n, 2n)
         F2 = zeros(Int8, 2n, 2n)
-        for i in n+1:2n
-            @inbounds F1[i, i] = 1
-            @inbounds F2[i, i] = 1
-        end
         hadamard = falses(n)
         perm = zeros(T, n)
         had_idxs = zeros(T, n)
@@ -208,10 +204,6 @@ end
 function _reset!(memory::RandDestabMemory, n::Integer)
     fill!(memory.F1, 0)
     fill!(memory.F2, 0)
-    for i in n+1:2n
-        @inbounds memory.F1[i, i] = 1
-        @inbounds memory.F2[i, i] = 1
-    end
     fill!(memory.hadamard, false)
     fill!(memory.perm, 0)
     fill!(memory.had_idxs, 0)
@@ -334,6 +326,10 @@ function random_destabilizer(rng::AbstractRNG, n::Int, memory::RandDestabMemory;
     # now construct the tableau representation for F(I, Gamma, Delta)
     mul!(prod, gamma, delta)
     mul!(prod_p, gamma_p, delta_p)
+    for i in n+1:2n
+        @inbounds F1[i, i] = 1
+        @inbounds F2[i, i] = 1
+    end
     _inv!(inv_delta, delta')
     _inv!(inv_delta_p, delta_p')
 
@@ -360,14 +356,7 @@ function random_destabilizer(rng::AbstractRNG, n::Int, memory::RandDestabMemory;
     for i in 1:n
         if had_idxs[i] != 0
             for j in 1:2n
-                U[had_idxs[i], j] = U[had_idxs[i]+n, j]
-            end
-        end
-    end
-    for i in 1:n
-        if had_idxs[i] != 0
-            for j in 1:2n
-                U[had_idxs[i]+n, j] = U[had_idxs[i], j]
+                @inbounds (U[had_idxs[i], j], U[had_idxs[i]+n, j]) = (U[had_idxs[i]+n, j], U[had_idxs[i], j])
             end
         end
     end
@@ -376,7 +365,10 @@ function random_destabilizer(rng::AbstractRNG, n::Int, memory::RandDestabMemory;
     xzs = memory.xzs
     fill!(F2, 0)
     _mul!(F2, F1, U, 2n)
-    _inplace_equals!(xzs, _inplace_mod!(F2, 2), 1)
+
+    _inplace_mod!(F2, 2)
+    _inplace_equals!(xzs, F2, 1)
+
 
     # random Pauli matrix just amounts to phases on the stabilizer tableau
     phasesarray = memory.phasesarray