Remove ChainRulesCore for now

Author: mtfishman

Project.toml

@@ -4,12 +4,10 @@ authors = ["ITensor developers <[email protected]> and contributors"]
 version = "0.1.2"
 
 [deps]
-ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 ITensorBase = "4795dd04-0d67-49bb-8f44-b89c448a1dc7"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 
 [compat]
-ChainRulesCore = "1.25.1"
 ITensorBase = "0.1.8"
 LinearAlgebra = "1.10"
 julia = "1.10"

src/ITensorQuantumOperatorDefinitions.jl

@@ -16,8 +16,6 @@ include("sitetypes/tj.jl")
 include("sitetypes/qudit.jl")
 include("sitetypes/boson.jl")
 
-include("ITensorQuantumOperatorDefinitionsChainRulesCoreExt.jl")
-
 include("itensor/siteinds.jl")
 include("itensor/val.jl")
 include("itensor/state.jl")

src/ITensorQuantumOperatorDefinitionsChainRulesCoreExt.jl

@@ -1,4 +1,3 @@
-using ChainRulesCore: @ignore_derivatives
 using ITensorBase: Index, ITensor, dag, prime, tags
 
 op(::OpName, ::SiteType, ::Index...; kwargs...) = nothing

src/itensor/op.jl

@@ -149,6 +149,12 @@ alias(::OpName"a†a†") = OpName("a†") ⊗ OpName("a†")
 
 δ(x, y) = (x == y) ? 1 : 0
 
+# See:
+# https://en.wikipedia.org/wiki/Spin_(physics)#Higher_spins
+# https://en.wikipedia.org/wiki/Pauli_matrices
+# https://en.wikipedia.org/wiki/Generalizations_of_Pauli_matrices
+# https://en.wikipedia.org/wiki/Generalized_Clifford_algebra
+# https://github.com/QuantumKitHub/MPSKitModels.jl/blob/v0.4.0/src/operators/spinoperators.jl
 function Base.AbstractArray(n::OpName"σ⁺", domain_size::Tuple{Int})
   d = only(domain_size)
   s = (d - 1) / 2