outer product express in quantum optics (#104)

Author: Krastanov

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## v0.4.7 - 2025-02-25
 
+- Proper expression of outer products in QuantumOptics.
+
+## v0.4.7 - 2025-02-25
+
 - Improvements to default flattening of expressions having nested sums and scalings.
 
 ## v0.4.6 - 2025-01-18

Project.toml

@@ -1,7 +1,7 @@
 name = "QuantumSymbolics"
 uuid = "efa7fd63-0460-4890-beb7-be1bbdfbaeae"
 authors = ["QuantumSymbolics.jl contributors"]
-version = "0.4.7"
+version = "0.4.8"
 
 [deps]
 Latexify = "23fbe1c1-3f47-55db-b15f-69d7ec21a316"

ext/QuantumOpticsExt/QuantumOpticsExt.jl

@@ -96,6 +96,8 @@ express_nolookup(x::IdentityOp, r::QuantumOpticsRepr) = identityoperator(finite_
 express_nolookup(p::PauliNoiseCPTP, ::QuantumOpticsRepr) = LazySuperSum(SpinBasis(1//2), [1-p.px-p.py-p.pz,p.px,p.py,p.pz],
                                                                [LazyPrePost(_id,_id),LazyPrePost(_x,_x),LazyPrePost(_y,_y),LazyPrePost(_z,_z)])
 
+express_nolookup(s::SOuterKetBra, r::QuantumOpticsRepr) = projector(express(s.ket, r), express(s.bra, r))
+
 include("should_upstream.jl")
 
 end

src/QSymbolicsBase/express.jl

@@ -74,4 +74,4 @@ function express_nolookup(s, repr::AbstractRepresentation)
     else
         error("Encountered an object $(s) of type $(typeof(s)) that can not be converted to $(repr) representation") # TODO make a nice error type
     end
-end
+end

test/test_outerprod.jl

@@ -0,0 +1,8 @@
+@testitem "Outer Product" begin
+    using QuantumOpticsBase
+
+    @test isequal(L1*dagger(L0), SOuterKetBra(L1,dagger(L0)))
+
+    @test isequal(express(L1*dagger(L0)), projector(express(L1), express(dagger(L0))))
+
+end