diff --git a/.github/workflows/downgrade.yml b/.github/workflows/downgrade.yml
index 9af107d..5b12d9d 100644
--- a/.github/workflows/downgrade.yml
+++ b/.github/workflows/downgrade.yml
@@ -21,7 +21,7 @@ jobs:
       - uses: julia-actions/setup-julia@v1
         with:
           version: ${{ matrix.version }}
-      - uses: cjdoris/julia-downgrade-compat-action@v1
+      - uses: julia-actions/julia-downgrade-compat@v2
         with:
           skip: Pkg,TOML,InteractiveUtils,Random,LinearAlgebra
       - uses: julia-actions/cache@v2
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c4d3e8d..c536612 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## v0.4.12 - dev
 
 - Add Gabs extension for numerical translations of symbolic Gaussian states and operators.
+- Add QuantumToolbox extension for state vector translations.
 
 ## v0.4.11 - 2025-06-22
 
diff --git a/Project.toml b/Project.toml
index 8decb87..718f2cc 100644
--- a/Project.toml
+++ b/Project.toml
@@ -17,23 +17,26 @@ TermInterface = "8ea1fca8-c5ef-4a55-8b96-4e9afe9c9a3c"
 Gabs = "0eb812ee-a11f-4f5e-b8d4-bb8a44f06f50"
 QuantumClifford = "0525e862-1e90-11e9-3e4d-1b39d7109de1"
 QuantumOpticsBase = "4f57444f-1401-5e15-980d-4471b28d5678"
+QuantumToolbox = "6c2fb7c5-b903-41d2-bc5e-5a7c320b9fab"
 
 [extensions]
 GabsExt = "Gabs"
 MixedCliffordOpticsExt = ["QuantumClifford", "QuantumOpticsBase"]
 QuantumCliffordExt = "QuantumClifford"
 QuantumOpticsExt = "QuantumOpticsBase"
+QuantumToolboxExt = "QuantumToolbox"
 
 [compat]
-Gabs = "1.3.1"
+Gabs = "1.3.2"
 Latexify = "0.16"
 LinearAlgebra = "1.9"
 MacroTools = "0.5.13"
 PrecompileTools = "1.2"
-QuantumClifford = "0.8.19, 0.9, 0.10"
-QuantumInterface = "0.3.7, 0.4.1"
-QuantumOpticsBase = "0.4.22, 0.5"
-SymbolicUtils = "3.7"
+QuantumClifford = "0.9.4, 0.10"
+QuantumInterface = "0.4.1"
+QuantumOpticsBase = "0.5.6"
+QuantumToolbox = "0.34.0"
+SymbolicUtils = "3.13"
 Symbolics = "6"
 TermInterface = "2"
 julia = "1.10"
diff --git a/ext/QuantumToolboxExt/QuantumToolboxExt.jl b/ext/QuantumToolboxExt/QuantumToolboxExt.jl
new file mode 100644
index 0000000..d2eca05
--- /dev/null
+++ b/ext/QuantumToolboxExt/QuantumToolboxExt.jl
@@ -0,0 +1,85 @@
+module QuantumToolboxExt
+
+using QuantumToolbox
+using QuantumSymbolics
+using QuantumSymbolics:
+    HGate, XGate, YGate, ZGate, CPHASEGate, CNOTGate, PauliP, PauliM,
+    XCXGate, XCYGate, XCZGate, YCXGate, YCYGate, YCZGate, ZCXGate, ZCYGate, ZCZGate,
+    XBasisState, YBasisState, ZBasisState,
+    NumberOp, CreateOp, DestroyOp,
+    FockState,
+    MixedState, IdentityOp, STensor,
+    qubit_basis
+import QuantumSymbolics: express, express_nolookup
+using TermInterface
+using TermInterface: isexpr, head, operation, arguments, metadata
+
+const _l0 = QuantumToolbox.basis(2,0)
+const _l1 = QuantumToolbox.basis(2,1)
+const _s₊ = (_l0+_l1)/√2
+const _s₋ = (_l0-_l1)/√2
+const _i₊ = (_l0+im*_l1)/√2
+const _i₋ = (_l0-im*_l1)/√2
+const _σ₊ = QuantumToolbox.sigmap()
+const _σ₋ = QuantumToolbox.sigmam()
+const _l00 = QuantumToolbox.proj(_l0)
+const _l11 = QuantumToolbox.proj(_l1)
+const _id = QuantumToolbox.qeye(2)
+const _z = QuantumToolbox.sigmaz()
+const _x = QuantumToolbox.sigmax()
+const _y = QuantumToolbox.sigmay()
+const _hadamard = (_z+_x)/√2
+const _cnot = QuantumToolbox.tensor(_l00,_id) + QuantumToolbox.tensor(_l11,_x)
+const _cphase = QuantumToolbox.tensor(_l00,_id) + QuantumToolbox.tensor(_l11,_z)
+const _phase = _l00 + im*_l11
+const _iphase = _l00 - im*_l11
+
+const _f0₂ = QuantumToolbox.basis(2, 0)
+const _f1₂ = QuantumToolbox.basis(2, 1)
+const _ad₂ = QuantumToolbox.create(2)
+const _a₂ = QuantumToolbox.destroy(2)
+const _n₂ = QuantumToolbox.num(2)
+
+express_nolookup(::HGate, ::QuantumToolboxRepr) = _hadamard
+express_nolookup(::XGate, ::QuantumToolboxRepr) = _x
+express_nolookup(::YGate, ::QuantumToolboxRepr) = _y
+express_nolookup(::ZGate, ::QuantumToolboxRepr) = _z
+express_nolookup(::CPHASEGate, ::QuantumToolboxRepr) = _cphase
+express_nolookup(::CNOTGate, ::QuantumToolboxRepr) = _cnot
+
+const xyzopdict = Dict(:X=>_x, :Y=>_y, :Z=>_z)
+const xyzstatedict = Dict(:X=>(_s₊,_s₋),:Y=>(_i₊,_i₋),:Z=>(_l0,_l1))
+for control in (:X, :Y, :Z)
+    for target in (:X, :Y, :Z)
+        k1, k2 = xyzstatedict[control]
+        o = xyzopdict[target]
+        gate = QuantumToolbox.tensor(proj(k1),_id) + QuantumToolbox.tensor(proj(k2),o)
+        structname = Symbol(control,"C",target,"Gate")
+        let gate=copy(gate)
+            @eval express_nolookup(::$(structname), ::QuantumToolboxRepr) = $gate
+        end
+    end
+end
+
+express_nolookup(::PauliM, ::QuantumToolboxRepr) = _σ₋
+express_nolookup(::PauliP, ::QuantumToolboxRepr) = _σ₊
+
+express_nolookup(s::XBasisState, ::QuantumToolboxRepr) = (_s₊,_s₋)[s.idx]
+express_nolookup(s::YBasisState, ::QuantumToolboxRepr) = (_i₊,_i₋)[s.idx]
+express_nolookup(s::ZBasisState, ::QuantumToolboxRepr) = (_l0,_l1)[s.idx]
+
+express_nolookup(s::FockState, r::QuantumToolboxRepr) = fock(r.cutoff, s.idx)
+express_nolookup(s::CoherentState, r::QuantumToolboxRepr) = coherent(r.cutoff,s.alpha)
+express_nolookup(s::SqueezedState, r::QuantumToolboxRepr) = (c = r.cutoff; squeeze(c, s.z)*fock(c, 0))
+express_nolookup(o::NumberOp, r::QuantumToolboxRepr) = num(r.cutoff)
+express_nolookup(o::CreateOp, r::QuantumToolboxRepr) = create(r.cutoff)
+express_nolookup(o::DestroyOp, r::QuantumToolboxRepr) = destroy(r.cutoff)
+express_nolookup(o::DisplaceOp, r::QuantumToolboxRepr) = displace(r.cutoff, o.alpha)
+express_nolookup(o::SqueezeOp, r::QuantumToolboxRepr) = squeeze(r.cutoff, o.z)
+express_nolookup(x::MixedState, r::QuantumToolboxRepr) = (l = length(x.basis); return qeye(l)/l)
+express_nolookup(x::IdentityOp, r::QuantumToolboxRepr) = qeye(length(x.basis))
+
+express_nolookup(s::SOuterKetBra, r::QuantumToolboxRepr) = proj(express(s.ket, r), express(s.bra, r))
+express_nolookup(s::STensor, r::QuantumToolboxRepr) = QuantumToolbox.tensor((express(i, r) for i in s.terms)...)
+
+end
diff --git a/src/QSymbolicsBase/QSymbolicsBase.jl b/src/QSymbolicsBase/QSymbolicsBase.jl
index 8b9da55..1d842f7 100644
--- a/src/QSymbolicsBase/QSymbolicsBase.jl
+++ b/src/QSymbolicsBase/QSymbolicsBase.jl
@@ -22,7 +22,7 @@ import QuantumInterface:
 
 export SymQObj,QObj,
        AbstractRepresentation,AbstractUse,
-       QuantumOpticsRepr,QuantumMCRepr,CliffordRepr,GabsRepr,
+       QuantumOpticsRepr,QuantumMCRepr,CliffordRepr,GabsRepr,QuantumToolboxRepr,
        UseAsState,UseAsObservable,UseAsOperation,
        apply!,
        express,
@@ -52,6 +52,15 @@ export SymQObj,QObj,
        isunitary,
        KrausRepr,kraus
 
+
+
+
+# TODO: move this to QuantumInterface
+"""Representation using kets, bras, density matrices, and superoperators governed by `QuantumToolbox.jl`."""
+Base.@kwdef struct QuantumToolboxRepr <: AbstractRepresentation 
+    cutoff::Int = 2
+end
+
 ##
 # Metadata cache helpers
 ##
diff --git a/test/Project.toml b/test/Project.toml
index e33cd01..83838e2 100644
--- a/test/Project.toml
+++ b/test/Project.toml
@@ -12,6 +12,7 @@ QuantumClifford = "0525e862-1e90-11e9-3e4d-1b39d7109de1"
 QuantumInterface = "5717a53b-5d69-4fa3-b976-0bf2f97ca1e5"
 QuantumOptics = "6e0679c1-51ea-5a7c-ac74-d61b76210b0c"
 QuantumOpticsBase = "4f57444f-1401-5e15-980d-4471b28d5678"
+QuantumToolbox = "6c2fb7c5-b903-41d2-bc5e-5a7c320b9fab"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Reexport = "189a3867-3050-52da-a836-e630ba90ab69"
 Revise = "295af30f-e4ad-537b-8983-00126c2a3abe"
diff --git a/test/test_conditional_cliffords.jl b/test/test_conditional_cliffords.jl
index 4b19245..7daf531 100644
--- a/test/test_conditional_cliffords.jl
+++ b/test/test_conditional_cliffords.jl
@@ -1,15 +1,22 @@
 @testitem "Conditional Cliffords" begin
     using QuantumClifford
     using QuantumOpticsBase
+    using QuantumToolbox
     using LinearAlgebra
 
+    P = [1. 0. 0. 0.;   # Maps QuantumOptics to QuantumToolbox basis
+         0. 0. 1. 0.;
+         0. 1. 0. 0.;
+         0. 0. 0. 1.]
     for control in (:X, :Y, :Z)
         for target in (:X, :Y, :Z)
             structname = Symbol(control,"C",target,"Gate")
             gate = eval(structname)()
             gate_qo = express(gate, QuantumOpticsRepr())
-            gate_qc = Operator(CliffordOperator(express(gate, CliffordRepr(), UseAsOperation())(1,2),2))
+            gate_qc = QuantumOpticsBase.Operator(CliffordOperator(express(gate, CliffordRepr(), UseAsOperation())(1,2),2))
+            gate_qt = express(gate, QuantumToolboxRepr())
             @test gate_qo ≈ gate_qc
+            @test P * gate_qo.data * P' ≈ gate_qt.data atol = 1e-10
         end
     end
 end
diff --git a/test/test_quantumtoolbox.jl b/test/test_quantumtoolbox.jl
new file mode 100644
index 0000000..a9de735
--- /dev/null
+++ b/test/test_quantumtoolbox.jl
@@ -0,0 +1,49 @@
+@testitem "QuantumToolbox objects" begin
+    using QuantumSymbolics
+    using QuantumToolbox
+
+    α = rand(ComplexF64)
+    n = rand(1:9)
+
+    @testset "Fock states and operators" begin
+        repr = QuantumToolboxRepr(cutoff = 10)
+        @test express(vac, repr) ≈ fock(10, 0)
+        @test express(FockState(n), repr) ≈ fock(10, n)
+        @test express(CoherentState(α), repr) ≈ coherent(10, α)
+        @test express(SqueezedState(α), repr) ≈ squeeze(10, α) * fock(10, 0)
+        @test express(NumberOp(), repr) ≈ num(10)
+        @test express(CreateOp(), repr) ≈ create(10)
+        @test express(DestroyOp(), repr) ≈ destroy(10)
+        @test express(DisplaceOp(α), repr) ≈ displace(10, α)
+    end
+
+    @testset "Quantum gates" begin
+        repr = QuantumToolboxRepr()
+        @test express(H, repr) ≈ to_sparse(Qobj([1.0+0.0im 1.; 1. -1.]/√2))
+        @test express(X, repr) ≈ sigmax()
+        @test express(Y, repr) ≈ sigmay()
+        @test express(Z, repr) ≈ sigmaz()
+        @test express(CPHASE, repr) ≈ Qobj([1.0+0.0im 0. 0. 0.; 0. 1. 0. 0.; 0. 0. 1. 0.; 0. 0. 0. -1.], dims = (2,2))
+        @test express(CNOT, repr) ≈ Qobj([1.0+0.0im 0. 0. 0.; 0. 1. 0. 0.; 0. 0. 0. 1.; 0. 0. 1. 0.], dims = (2,2))
+        @test express(QuantumSymbolics.PauliM(), repr) ≈ sigmam()
+        @test express(QuantumSymbolics.PauliP(), repr) ≈ sigmap()
+    end
+
+    @testset "Pure states" begin
+        repr = QuantumToolboxRepr()
+        @test express(XBasisState(1, SpinBasis(1//2)), repr) ≈ Qobj([1.0+0.0im, 1.0]/√2)
+        @test express(XBasisState(2, SpinBasis(1//2)), repr) ≈ Qobj([1.0+0.0im, -1.0]/√2)
+        @test express(YBasisState(1, SpinBasis(1//2)), repr) ≈ Qobj([1.0+0.0im, 1.0im]/√2)
+        @test express(YBasisState(2, SpinBasis(1//2)), repr) ≈ Qobj([1.0+0.0im, -1.0im]/√2)
+        @test express(ZBasisState(1, SpinBasis(1//2)), repr) ≈ Qobj([1.0+0.0im, 0.0])
+        @test express(ZBasisState(2, SpinBasis(1//2)), repr) ≈ Qobj([0.0+0.0im, 1.0])
+    end
+
+    @testset "Linear algebra" begin
+        repr = QuantumToolboxRepr()
+        @test express(QuantumSymbolics.tensor(X, Y) + QuantumSymbolics.tensor(Z, X), repr) ≈ QuantumToolbox.tensor(express(X, repr), express(Y, repr)) + QuantumToolbox.tensor(express(Z, repr), express(X, repr))
+        @test express(CreateOp() * (FockState(1) + CoherentState(α)), repr) ≈ express(CreateOp(), repr) * (express(FockState(1), repr) + express(CoherentState(α), repr))
+        @test express(IdentityOp(QuantumSymbolics.tensor(X, Y)), repr) ≈ qeye(4)
+        @test express(MixedState(QuantumSymbolics.tensor(X, Y)), repr) ≈ qeye(4) / 4
+    end
+end
\ No newline at end of file