Implement Base.copy for AbstractQuantumObject (#486)

Author: ytdHuang

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Introduce `Lanczos` solver for `spectrum`. ([#476])
 - Add Bloch-Redfield master equation solver. ([#473])
 - Implement Bloch Sphere rendering and align style with qutip. ([#472], [#480])
+- Add `Base.copy` method for `AbstractQuantumObject`. ([#486])
 
 ## [v0.31.1]
 Release date: 2025-05-16
@@ -236,3 +237,4 @@ Release date: 2024-11-13
 [#473]: https://github.com/qutip/QuantumToolbox.jl/issues/473
 [#476]: https://github.com/qutip/QuantumToolbox.jl/issues/476
 [#480]: https://github.com/qutip/QuantumToolbox.jl/issues/480
+[#486]: https://github.com/qutip/QuantumToolbox.jl/issues/486

src/qobj/quantum_object_base.jl

@@ -1,6 +1,6 @@
 #=  
 This file defines the AbstractQuantumObject structure, all the type structures for AbstractQuantumObject, and fundamental functions in Julia standard library:  
-    - Base: show, length, size, eltype, getindex, setindex!, isequal, :(==), isapprox  
+    - Base: show, length, size, copy, eltype, getindex, setindex!, isequal, :(==), isapprox  
 =#
 
 export AbstractQuantumObject
@@ -93,6 +93,8 @@ Optionally, you can specify an index (`idx`) to just get the corresponding dimen
 Base.size(A::AbstractQuantumObject) = size(A.data)
 Base.size(A::AbstractQuantumObject, idx::Int) = size(A.data, idx)
 
+Base.copy(A::AbstractQuantumObject) = get_typename_wrapper(A)(copy(A.data), A.type, A.dimensions)
+
 Base.getindex(A::AbstractQuantumObject, inds...) = getindex(A.data, inds...)
 Base.setindex!(A::AbstractQuantumObject, val, inds...) = setindex!(A.data, val, inds...)
 

test/core-test/quantum_objects.jl

@@ -186,9 +186,12 @@
         a2 = Qobj(a)
         a3 = Qobj(a, type = SuperOperator())
         a4 = to_sparse(a2)
+        a4_copy = copy(a4)
+        a4_copy[1] = rand(ComplexF64)
         @test isequal(a4, a2) == true
         @test isequal(a4, a3) == false
         @test a4 ≈ a2
+        @test a4 != a4_copy
 
         @test real(a2).data == real(a)
         @test imag(a2).data == imag(a)