Support different length for to and from on GeneralDImensions (#448)

Author: albertomercurio

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://github.com/qutip/QuantumToolbox.jl/tree/main)
 
+- Support different length for `to` and `from` on GeneralDimensions. ([#448])
+
 ## [v0.30.0]
 Release date: 2025-04-12
 
@@ -201,3 +203,4 @@ Release date: 2024-11-13
 [#438]: https://github.com/qutip/QuantumToolbox.jl/issues/438
 [#440]: https://github.com/qutip/QuantumToolbox.jl/issues/440
 [#443]: https://github.com/qutip/QuantumToolbox.jl/issues/443
+[#448]: https://github.com/qutip/QuantumToolbox.jl/issues/448

src/entropy.jl

@@ -149,7 +149,7 @@ Here, ``S`` is the [Von Neumann entropy](https://en.wikipedia.org/wiki/Von_Neuma
 - `kwargs` are the keyword arguments for calculating Von Neumann entropy. See also [`entropy_vn`](@ref).
 """
 function entropy_mutual(
-    ρAB::QuantumObject{ObjType,<:AbstractDimensions{N}},
+    ρAB::QuantumObject{ObjType,<:AbstractDimensions{N,N}},
     selA::Union{Int,AbstractVector{Int},Tuple},
     selB::Union{Int,AbstractVector{Int},Tuple};
     kwargs...,
@@ -182,7 +182,7 @@ Here, ``S`` is the [Von Neumann entropy](https://en.wikipedia.org/wiki/Von_Neuma
 - `kwargs` are the keyword arguments for calculating Von Neumann entropy. See also [`entropy_vn`](@ref).
 """
 entropy_conditional(
-    ρAB::QuantumObject{ObjType,<:AbstractDimensions{N}},
+    ρAB::QuantumObject{ObjType,<:AbstractDimensions{N,N}},
     selB::Union{Int,AbstractVector{Int},Tuple};
     kwargs...,
 ) where {ObjType<:Union{KetQuantumObject,OperatorQuantumObject},N} =

src/qobj/dimensions.jl

@@ -4,16 +4,16 @@ This file defines the Dimensions structures, which can describe composite Hilber
 
 export AbstractDimensions, Dimensions, GeneralDimensions
 
-abstract type AbstractDimensions{N} end
+abstract type AbstractDimensions{M,N} end
 
 @doc raw"""
-    struct Dimensions{N,T<:Tuple} <: AbstractDimensions{N}
+    struct Dimensions{N,T<:Tuple} <: AbstractDimensions{N, N}
         to::T
     end
 
 A structure that describes the Hilbert [`Space`](@ref) of each subsystems.
 """
-struct Dimensions{N,T<:Tuple} <: AbstractDimensions{N}
+struct Dimensions{N,T<:Tuple} <: AbstractDimensions{N,N}
     to::T
 
     # make sure the elements in the tuple are all AbstractSpace
@@ -24,7 +24,7 @@ function Dimensions(dims::Union{AbstractVector{T},NTuple{N,T}}) where {T<:Intege
     L = length(dims)
     (L > 0) || throw(DomainError(dims, "The argument dims must be of non-zero length"))
 
-    return Dimensions(NTuple{L,Space}(Space.(dims)))
+    return Dimensions(Tuple(Space.(dims)))
 end
 Dimensions(dims::Int) = Dimensions(Space(dims))
 Dimensions(dims::DimType) where {DimType<:AbstractSpace} = Dimensions((dims,))
@@ -42,14 +42,14 @@ Dimensions(dims::Any) = throw(
 
 A structure that describes the left-hand side (`to`) and right-hand side (`from`) Hilbert [`Space`](@ref) of an [`Operator`](@ref).
 """
-struct GeneralDimensions{N,T1<:Tuple,T2<:Tuple} <: AbstractDimensions{N}
+struct GeneralDimensions{M,N,T1<:Tuple,T2<:Tuple} <: AbstractDimensions{M,N}
     # note that the number `N` should be the same for both `to` and `from`
     to::T1   # space acting on the left
     from::T2 # space acting on the right
 
     # make sure the elements in the tuple are all AbstractSpace
-    GeneralDimensions(to::NTuple{N,T1}, from::NTuple{N,T2}) where {N,T1<:AbstractSpace,T2<:AbstractSpace} =
-        new{N,typeof(to),typeof(from)}(to, from)
+    GeneralDimensions(to::NTuple{M,T1}, from::NTuple{N,T2}) where {M,N,T1<:AbstractSpace,T2<:AbstractSpace} =
+        new{M,N,typeof(to),typeof(from)}(to, from)
 end
 function GeneralDimensions(dims::Union{AbstractVector{T},NTuple{N,T}}) where {T<:Union{AbstractVector,NTuple},N}
     (length(dims) != 2) && throw(ArgumentError("Invalid dims = $dims"))
@@ -59,14 +59,10 @@ function GeneralDimensions(dims::Union{AbstractVector{T},NTuple{N,T}}) where {T<
 
     L1 = length(dims[1])
     L2 = length(dims[2])
-    ((L1 > 0) && (L1 == L2)) || throw(
-        DomainError(
-            (L1, L2),
-            "The length of the arguments `dims[1]` and `dims[2]` must be in the same length and have at least one element.",
-        ),
-    )
-
-    return GeneralDimensions(NTuple{L1,Space}(Space.(dims[1])), NTuple{L1,Space}(Space.(dims[2])))
+    (L1 > 0) || throw(DomainError(L1, "The length of `dims[1]` must be larger or equal to 1."))
+    (L2 > 0) || throw(DomainError(L2, "The length of `dims[2]` must be larger or equal to 1."))
+
+    return GeneralDimensions(Tuple(Space.(dims[1])), Tuple(Space.(dims[2])))
 end
 
 _gen_dimensions(dims::AbstractDimensions) = dims

src/qobj/quantum_object_base.jl

@@ -263,25 +263,22 @@ function Base.getproperty(A::AbstractQuantumObject, key::Symbol)
 end
 
 # this returns `to` in GeneralDimensions representation
-get_dimensions_to(A::AbstractQuantumObject{KetQuantumObject,<:Dimensions{N}}) where {N} = A.dimensions.to
+get_dimensions_to(A::AbstractQuantumObject{KetQuantumObject,<:Dimensions}) = A.dimensions.to
 get_dimensions_to(A::AbstractQuantumObject{BraQuantumObject,<:Dimensions{N}}) where {N} = space_one_list(N)
-get_dimensions_to(A::AbstractQuantumObject{OperatorQuantumObject,<:Dimensions{N}}) where {N} = A.dimensions.to
-get_dimensions_to(A::AbstractQuantumObject{OperatorQuantumObject,<:GeneralDimensions{N}}) where {N} = A.dimensions.to
+get_dimensions_to(A::AbstractQuantumObject{OperatorQuantumObject,<:Dimensions}) = A.dimensions.to
+get_dimensions_to(A::AbstractQuantumObject{OperatorQuantumObject,<:GeneralDimensions}) = A.dimensions.to
 get_dimensions_to(
-    A::AbstractQuantumObject{ObjType,<:Dimensions{N}},
-) where {ObjType<:Union{SuperOperatorQuantumObject,OperatorBraQuantumObject,OperatorKetQuantumObject},N} =
-    A.dimensions.to
+    A::AbstractQuantumObject{ObjType,<:Dimensions},
+) where {ObjType<:Union{SuperOperatorQuantumObject,OperatorBraQuantumObject,OperatorKetQuantumObject}} = A.dimensions.to
 
 # this returns `from` in GeneralDimensions representation
 get_dimensions_from(A::AbstractQuantumObject{KetQuantumObject,<:Dimensions{N}}) where {N} = space_one_list(N)
-get_dimensions_from(A::AbstractQuantumObject{BraQuantumObject,<:Dimensions{N}}) where {N} = A.dimensions.to
-get_dimensions_from(A::AbstractQuantumObject{OperatorQuantumObject,<:Dimensions{N}}) where {N} = A.dimensions.to
-get_dimensions_from(A::AbstractQuantumObject{OperatorQuantumObject,<:GeneralDimensions{N}}) where {N} =
-    A.dimensions.from
+get_dimensions_from(A::AbstractQuantumObject{BraQuantumObject,<:Dimensions}) = A.dimensions.to
+get_dimensions_from(A::AbstractQuantumObject{OperatorQuantumObject,<:Dimensions}) = A.dimensions.to
+get_dimensions_from(A::AbstractQuantumObject{OperatorQuantumObject,<:GeneralDimensions}) = A.dimensions.from
 get_dimensions_from(
-    A::AbstractQuantumObject{ObjType,<:Dimensions{N}},
-) where {ObjType<:Union{SuperOperatorQuantumObject,OperatorBraQuantumObject,OperatorKetQuantumObject},N} =
-    A.dimensions.to
+    A::AbstractQuantumObject{ObjType,<:Dimensions},
+) where {ObjType<:Union{SuperOperatorQuantumObject,OperatorBraQuantumObject,OperatorKetQuantumObject}} = A.dimensions.to
 
 # functions for getting Float or Complex element type
 _FType(A::AbstractQuantumObject) = _FType(eltype(A))

test/core-test/quantum_objects.jl

@@ -86,6 +86,7 @@
         a2 = Qobj(a)
         a3 = Qobj(a, type = SuperOperator)
         a4 = Qobj(sprand(ComplexF64, 100, 10, 0.1)) # GeneralDimensions
+        a5 = QuantumObject(rand(ComplexF64, 2*3*4, 5), dims = ((2, 3, 4), (5,)))
         @test isket(a2) == false
         @test isbra(a2) == false
         @test isoper(a2) == true
@@ -116,6 +117,8 @@
         @test isconstant(a4) == true
         @test isunitary(a4) == false
         @test a4.dims == [[100], [10]]
+        @test isoper(a5) == true
+        @test a5.dims == [[2, 3, 4], [5]]
         @test_throws DimensionMismatch Qobj(a, dims = 2)
         @test_throws DimensionMismatch Qobj(a4.data, dims = 2)
         @test_throws DimensionMismatch Qobj(a4.data, dims = ((100,), (2,)))
@@ -351,7 +354,7 @@
         for T in [ComplexF32, ComplexF64]
             N = 4
             a = rand(T, N)
-            @inferred QuantumObject{KetQuantumObject,Dimensions{1},typeof(a)} Qobj(a)
+            @inferred Qobj(a)
             for type in [Ket, OperatorKet]
                 @inferred Qobj(a, type = type)
             end
@@ -367,7 +370,7 @@
             end
 
             UnionType2 = Union{
-                QuantumObject{OperatorQuantumObject,GeneralDimensions{1,Tuple{Space},Tuple{Space}},Matrix{T}},
+                QuantumObject{OperatorQuantumObject,GeneralDimensions{1,1,Tuple{Space},Tuple{Space}},Matrix{T}},
                 QuantumObject{OperatorQuantumObject,Dimensions{1,Tuple{Space}},Matrix{T}},
             }
             a = rand(T, N, N)