Fix ptrace and add extended methods for tensor and kron

README.md

@@ -144,8 +144,6 @@ We can extract the expectation value of the number operator $\hat{a}^\dagger \ha
 
 We can easily pass the computation to the GPU, by simply passing all the `Qobj`s to the GPU:
 
-> **_NOTE:_** The described feature requires `Julia 1.9+`.
-
 ```julia
 using QuantumToolbox
 using CUDA

docs/make.jl

@@ -21,14 +21,14 @@ const PAGES = [
     "Getting Started" => [
         "Introduction" => "index.md",
         "Key differences from QuTiP" => "qutip_differences.md",
+        "The Importance of Type-Stability" => "type_stability.md",
         # "Cite QuantumToolbox.jl" => "cite.md",
     ],
     "Users Guide" => [
         "Basic Operations on Quantum Objects" => [
             "users_guide/QuantumObject/QuantumObject.md",
             "users_guide/QuantumObject/QuantumObject_functions.md",
         ],
-        "The Importance of Type-Stability" => "users_guide/type_stability.md",
         "Manipulating States and Operators" => "users_guide/states_and_operators.md",
         "Tensor Products and Partial Traces" => "users_guide/tensor.md",
         "Time Evolution and Dynamics" => [

docs/src/index.md

@@ -97,9 +97,6 @@ We can extract the expectation value of the number operator ``\hat{a}^\dagger \h
 
 We can easily pass the computation to the GPU, by simply passing all the `Qobj`s to the GPU:
 
-!!! compat "Compat"
-    The described feature requires `Julia 1.9+`. See [CUDA extension](@ref doc:CUDA) for more details.
-
 ```julia
 using QuantumToolbox
 using CUDA

docs/src/users_guide/QuantumObject/QuantumObject.md

@@ -14,6 +14,9 @@ The key difference between classical and quantum mechanics is the use of operato
 - `CUDA.CUSPARSE.CuSparseMatrixCSR` (sparse GPU matrix)
 - and even more ...
 
+!!! note "Support for GPU arrays"
+    See [CUDA extension](@ref doc:CUDA) for more details.
+
 We can create a [`QuantumObject`](@ref) with a user defined data set by passing an array of data into the [`QuantumObject`](@ref):
 
 ```@setup Qobj
@@ -53,7 +56,7 @@ Qobj(rand(4, 4), type = SuperOperator)
 ```
 
 !!! note "Difference between `dims` and `size`"
-    Notice that `type`, `dims`, and `size` will change according to the input `data`. Although `dims` and `size` appear to be the same, `dims` keep tracking the dimension of individual Hilbert spaces of a multipartite system, while `size` does not. We refer the reader to the section [tensor products and partial traces](@ref doc:Tensor-products) for more information.
+    Notice that `type`, `dims`, and `size` will change according to the input `data`. Although `dims` and `size` appear to be the same, `dims` keep tracking the dimension of individual Hilbert spaces of a multipartite system, while `size` does not. We refer the reader to the section [Tensor Products and Partial Traces](@ref doc:Tensor-products-and-Partial-Traces) for more information.
 
 ## States and operators
 

docs/src/users_guide/extensions/cuda.md

@@ -4,9 +4,6 @@
 
 This is an extension to support `QuantumObject.data` conversion from standard dense and sparse CPU arrays to GPU ([`CUDA.jl`](https://github.com/JuliaGPU/CUDA.jl)) arrays.
 
-!!! note "Requirements"
-    The [`CUDA.jl`](https://github.com/JuliaGPU/CUDA.jl) extension for `QuantumToolbox.jl` requires `Julia 1.9+`.
-
 This extension will be automatically loaded if user imports both `QuantumToolbox` and [`CUDA.jl`](https://github.com/JuliaGPU/CUDA.jl):
 
 ```julia