Eliminate type parameters from abstract types and add fullbasis function

CHANGELOG.md

@@ -1,5 +1,11 @@
 # News
 
+## v0.4.0 - 2024-11-26
+
+- Add `OperatorBasis` and `SuperOperatorBasis` abstract types along with corresponding `fullbasis` function to obtain these from instances of subtypes of `AbstractOperator` and `AbstractSuperOperator`.
+- Change type parameters for `StateVector`, `AbstractKet` `AbstractBra` `AbstractOperator` `AbstractSuperOperator` to elimitate all type parameters.
+
+
 ## v0.3.6 - 2024-09-08
 
 - Add `coherentstate`, `thermalstate`, `displace`, `squeeze`, `wigner`, previously from QuantumOptics.

Project.toml

@@ -1,7 +1,7 @@
 name = "QuantumInterface"
 uuid = "5717a53b-5d69-4fa3-b976-0bf2f97ca1e5"
 authors = ["QuantumInterface.jl contributors"]
-version = "0.3.6"
+version = "0.4.0"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/QuantumInterface.jl

@@ -1,14 +1,144 @@
 module QuantumInterface
 
-import Base: ==, +, -, *, /, ^, length, one, exp, conj, conj!, transpose, copy
-import LinearAlgebra: tr, ishermitian, norm, normalize, normalize!
-import Base: show, summary
-import SparseArrays: sparse, spzeros, AbstractSparseMatrix # TODO move to an extension
+##
+# Basis specific
+##
+
+"""
+    basis(a)
+
+Return the basis of an object.
+
+If it's ambiguous, e.g. if an operator or superoperator has a different
+left and right basis, an [`IncompatibleBases`](@ref) error is thrown.
+"""
+function basis end
+
+"""
+    fullbasis(a)
+
+Return the full basis of an object.
+
+Returns subtype of `Basis` when a is a subtype of `StateVector`.
+Returns a subtype of `OperatorBasis` a is a subtype of `AbstractOperator`.
+Returns a subtype of `SuperOperatorBasis` when a is a subtype of `AbstractSuperOperator`.
+"""
+function fullbasis end
+
+"""
+    length(b::Basis)
+
+Total dimension of the Hilbert space.
+"""
+function length end
+
+function bases end
+
+function spinnumber end
+
+function cutoff end
+
+function offset end
+
+##
+# Standard methods
+##
+
+"""
+    multiplicable(a, b)
+
+Check if any two subtypes of `StateVector`, `AbstractOperator`,
+or `AbstractSuperOperator` can be multiplied in the given order.
+
+Spcefically this checks whether the right basis of a is equal
+to the left basis of b
+"""
+function multiplicable end
+
+"""
+    check_multiplicable(a, b)
+
+Throw an [`IncompatibleBases`](@ref) error if the objects are
+not multiplicable as determined by `multiplicable(a, b)`.
+
+If the macro `@compatiblebases` is used anywhere up the call stack,
+this check is disabled.
+"""
+function check_multiplicable end
+
+"""
+    addible(a, b)
+
+Check if any two subtypes of `StateVector`, `AbstractOperator`,
+or `AbstractSuperOperator` can be added together.
+
+Spcefically this checks whether the left basis of a is equal
+to the left basis of b and whether the right basis of a is equal
+to the right basis of b.
+"""
+function addible end
+
+"""
+    check_addible(a, b)
+
+Throw an [`IncompatibleBases`](@ref) error if the objects are
+not addible as determined by `addible(a, b)`.
+
+If the macro `@compatiblebases` is used anywhere up the call stack,
+this check is disabled.
+"""
+function check_addible end
+
+"""
+    issquare(a)
+
+Check if any two subtypes of `StateVector`, `AbstractOperator`,
+or `AbstractSuperOperator` are square.
+
+Spcefically this checks whether the left basis of a is equal
+to the right basis of a.
+For subtypes of `StateVector` this is always false.
+"""
+function addible end
+
+"""
+    check_issquare(a, b)
+
+Throw an [`IncompatibleBases`](@ref) error if the objects are
+not addible as determined by `addible(a, b)`.
+
+If the macro `@compatiblebases` is used anywhere up the call stack,
+this check is disabled.
+"""
+function check_addible end
+
+const BASES_CHECK = Ref(true)
+
+"""
+    @compatiblebases
+
+Macro to skip checks for compatible bases. Useful for `*`, `expect` and similar
+functions.
+"""
+macro compatiblebases(ex)
+    return quote
+        BASES_CHECK.x = false
+        local val = $(esc(ex))
+        BASES_CHECK.x = true
+        val
+    end
+end
 
 function apply! end
 
 function dagger end
 
+"""
+    directsum(x, y, z...)
+
+Direct sum of the given objects. Alternatively, the unicode
+symbol ⊕ (\\oplus) can be used.
+"""
 function directsum end
 const ⊕ = directsum
 directsum() = GenericBasis(0)
@@ -86,8 +216,9 @@ function squeeze end
 function wigner end
 
 
-include("bases.jl")
 include("abstract_types.jl")
+include("bases.jl")
+include("show.jl")
 
 include("linalg.jl")
 include("tensor.jl")

src/abstract_types.jl

@@ -1,3 +1,18 @@
+"""
+Abstract base class for all specialized bases.
+
+The Basis class is meant to specify a basis of the Hilbert space of the
+studied system. Besides basis specific information all subclasses must
+implement a shape variable which indicates the dimension of the used
+Hilbert space. For a spin-1/2 Hilbert space this would be the
+vector `[2]`. A system composed of two spins would then have a
+shape vector `[2 2]`.
+
+Composite systems can be defined with help of the [`CompositeBasis`](@ref)
+class.
+"""
+abstract type Basis end
+
 """
 Abstract base class for `Bra` and `Ket` states.
 
@@ -6,9 +21,9 @@ in respect to a certain basis. These coefficients are stored in the
 `data` field and the basis is defined in the `basis`
 field.
 """
-abstract type StateVector{B,T} end
-abstract type AbstractKet{B,T} <: StateVector{B,T} end
-abstract type AbstractBra{B,T} <: StateVector{B,T} end
+abstract type StateVector end
+abstract type AbstractKet <: StateVector end
+abstract type AbstractBra <: StateVector end
 
 """
 Abstract base class for all operators.
@@ -21,7 +36,7 @@ For fast time evolution also at least the function
 implemented. Many other generic multiplication functions can be defined in
 terms of this function and are provided automatically.
 """
-abstract type AbstractOperator{BL,BR} end
+abstract type AbstractOperator end
 
 """
 Base class for all super operator classes.
@@ -37,21 +52,4 @@ A_{bl_1,bl_2} = S_{(bl_1,bl_2) ↔ (br_1,br_2)} B_{br_1,br_2}
 A_{br_1,br_2} = B_{bl_1,bl_2} S_{(bl_1,bl_2) ↔ (br_1,br_2)}
 ```
 """
-abstract type AbstractSuperOperator{B1,B2} end
-
-function summary(stream::IO, x::AbstractOperator)
-    print(stream, "$(typeof(x).name.name)(dim=$(length(x.basis_l))x$(length(x.basis_r)))\n")
-    if samebases(x)
-        print(stream, "  basis: ")
-        show(stream, basis(x))
-    else
-        print(stream, "  basis left:  ")
-        show(stream, x.basis_l)
-        print(stream, "\n  basis right: ")
-        show(stream, x.basis_r)
-    end
-end
-
-show(stream::IO, x::AbstractOperator) = summary(stream, x)
-
-traceout!(s::StateVector, i) = ptrace(s,i)
+abstract type AbstractSuperOperator end

src/bases.jl

@@ -1,35 +1,10 @@
-"""
-Abstract base class for all specialized bases.
-
-The Basis class is meant to specify a basis of the Hilbert space of the
-studied system. Besides basis specific information all subclasses must
-implement a shape variable which indicates the dimension of the used
-Hilbert space. For a spin-1/2 Hilbert space this would be the
-vector `[2]`. A system composed of two spins would then have a
-shape vector `[2 2]`.
-
-Composite systems can be defined with help of the [`CompositeBasis`](@ref)
-class.
-"""
-abstract type Basis end
-
 """
     length(b::Basis)
 
 Total dimension of the Hilbert space.
 """
 Base.length(b::Basis) = prod(b.shape)
 
-"""
-    basis(a)
-
-Return the basis of an object.
-
-If it's ambiguous, e.g. if an operator has a different left and right basis,
-an [`IncompatibleBases`](@ref) error is thrown.
-"""
-function basis end
-
 
 """
     GenericBasis(N)
@@ -64,6 +39,7 @@ end
 CompositeBasis(bases) = CompositeBasis([length(b) for b ∈ bases], bases)
 CompositeBasis(bases::Basis...) = CompositeBasis((bases...,))
 CompositeBasis(bases::Vector) = CompositeBasis((bases...,))
+bases(b::CompositeBasis) = b.bases
 
 Base.:(==)(b1::T, b2::T) where T<:CompositeBasis = equal_shape(b1.shape, b2.shape)
 
@@ -142,8 +118,6 @@ Exception that should be raised for an illegal algebraic operation.
 """
 mutable struct IncompatibleBases <: Exception end
 
-const BASES_CHECK = Ref(true)
-
 """
     @samebases
 
@@ -283,6 +257,8 @@ struct FockBasis{T} <: Basis
         new{T}([N-offset+1], N, offset)
     end
 end
+cutoff(b::FockBasis) = b.N
+offset(b::FockBasis) = b.offset
 
 Base.:(==)(b1::FockBasis, b2::FockBasis) = (b1.N==b2.N && b1.offset==b2.offset)
 
@@ -348,6 +324,7 @@ struct SpinBasis{S,T} <: Basis
 end
 SpinBasis(spinnumber::Rational) = SpinBasis{spinnumber}(spinnumber)
 SpinBasis(spinnumber) = SpinBasis(convert(Rational{Int}, spinnumber))
+spinnumber(b::SpinBasis) = b.spinnumber
 
 Base.:(==)(b1::SpinBasis, b2::SpinBasis) = b1.spinnumber==b2.spinnumber
 
@@ -366,9 +343,9 @@ SumBasis(shape, bases::Vector) = (tmp = (bases...,); SumBasis(shape, tmp))
 SumBasis(bases::Vector) = SumBasis((bases...,))
 SumBasis(bases::Basis...) = SumBasis((bases...,))
 
-==(b1::T, b2::T) where T<:SumBasis = equal_shape(b1.shape, b2.shape)
-==(b1::SumBasis, b2::SumBasis) = false
-length(b::SumBasis) = sum(b.shape)
+Base.:(==)(b1::T, b2::T) where T<:SumBasis = equal_shape(b1.shape, b2.shape)
+Base.:(==)(b1::SumBasis, b2::SumBasis) = false
+Base.length(b::SumBasis) = sum(b.shape)
 
 """
     directsum(b1::Basis, b2::Basis)
@@ -393,62 +370,3 @@ function directsum(b1::SumBasis, b2::SumBasis)
     bases = [b1.bases...;b2.bases...]
     return SumBasis(shape, (bases...,))
 end
-
-embed(b::SumBasis, indices, ops) = embed(b, b, indices, ops)
-
-##
-# show methods
-##
-
-function show(stream::IO, x::GenericBasis)
-    if length(x.shape) == 1
-        write(stream, "Basis(dim=$(x.shape[1]))")
-    else
-        s = replace(string(x.shape), " " => "")
-        write(stream, "Basis(shape=$s)")
-    end
-end
-
-function show(stream::IO, x::CompositeBasis)
-    write(stream, "[")
-    for i in 1:length(x.bases)
-        show(stream, x.bases[i])
-        if i != length(x.bases)
-            write(stream, " ⊗ ")
-        end
-    end
-    write(stream, "]")
-end
-
-function show(stream::IO, x::SpinBasis)
-    d = denominator(x.spinnumber)
-    n = numerator(x.spinnumber)
-    if d == 1
-        write(stream, "Spin($n)")
-    else
-        write(stream, "Spin($n/$d)")
-    end
-end
-
-function show(stream::IO, x::FockBasis)
-    if iszero(x.offset)
-        write(stream, "Fock(cutoff=$(x.N))")
-    else
-        write(stream, "Fock(cutoff=$(x.N), offset=$(x.offset))")
-    end
-end
-
-function show(stream::IO, x::NLevelBasis)
-    write(stream, "NLevel(N=$(x.N))")
-end
-
-function show(stream::IO, x::SumBasis)
-    write(stream, "[")
-    for i in 1:length(x.bases)
-        show(stream, x.bases[i])
-        if i != length(x.bases)
-            write(stream, " ⊕ ")
-        end
-    end
-    write(stream, "]")
-end