add code review suggestions - when the invsparity is 1, just do norma…

…lization.

src/nonclifford.jl

@@ -236,7 +236,7 @@ julia> prob₁ = (real(χ′)+1)/2
 
 See also: [`expect`](@ref)
 """
-function projectrand!(sm::GeneralizedStabilizer, p::PauliOperator)
+function _projectrand_notnorm(sm::GeneralizedStabilizer, p::PauliOperator)
     # Returns the updated `GeneralizedStabilizer` state sm′ = (χ′, B(S′, D′)),
     # where (S′, D′) is derived from (S, D) through the traditional stabilizer update,
     # and χ′ is the updated density matrix after measurement. Note: Λ(χ′) ≤ Λ(χ).
@@ -285,6 +285,19 @@ function projectrand!(sm::GeneralizedStabilizer, p::PauliOperator)
     end
 end
 
+function projectrand!(sm::GeneralizedStabilizer, p::PauliOperator)
+    sm, res = _projectrand_notnorm(sm, p)
+    dict = sm.destabweights
+    if sm |> QuantumClifford.invsparsity == 1
+        for ((dᵢ, dⱼ), χ) in dict
+            χ′ = χ/LinearAlgebra.tr(χ) # normalization
+            sm.destabweights[(dᵢ, dⱼ)] = χ′
+        end
+        return sm, res
+    end
+    return sm, res
+end
+
 function project!(s::GeneralizedStabilizer, p::PauliOperator)
     throw(MethodError(project!, (s, p)))
 end

test/test_nonclifford_quantumoptics.jl

@@ -1,5 +1,5 @@
 using QuantumClifford
-using QuantumClifford: GeneralizedStabilizer, rowdecompose, PauliChannel, mul_left!, mul_right!, invsparsity
+using QuantumClifford: GeneralizedStabilizer, rowdecompose, PauliChannel, mul_left!, mul_right!, invsparsity, _projectrand_notnorm
 using QuantumClifford: @S_str, random_stabilizer
 using QuantumOpticsBase
 using LinearAlgebra
@@ -156,7 +156,7 @@ end
             genstab = GeneralizedStabilizer(s)
             apply!(genstab, pcT) # in-place
             prob1 = (real(expect(p, genstab))+1)/2
-            projectrand!(genstab, p)[1] # in-place
+            _projectrand_notnorm(genstab, p)[1] # in-place
             dict = genstab.destabweights
             trace_χ′ = real(tr(collect(values(dict))[1])) # Tr[χ′]
             @test isapprox(prob1, trace_χ′; atol=1e-5)