Initial implementation (#1)

Author: mtfishman

README.md

@@ -7,6 +7,21 @@
 [![Code Style: Blue](https://img.shields.io/badge/code%20style-blue-4495d1.svg)](https://github.com/invenia/BlueStyle)
 [![Aqua](https://raw.githubusercontent.com/JuliaTesting/Aqua.jl/master/badge.svg)](https://github.com/JuliaTesting/Aqua.jl)
 
+Quantum operator algebra system. This is mostly meant to be used as a backend in [ITensorMPS.jl](https://github.com/ITensor/ITensorMPS.jl)
+and [ITensorNetworks.jl](https://github.com/ITensor/ITensorNetworks.jl) for lazily representing operator expressions
+that will be turned into quantum circuits and tensor networks.
+
+See also:
+- [ITensorQuantumOperatorDefinitions.jl](https://github.com/ITensor/ITensorQuantumOperatorDefinitions.jl) for operator definitions
+compatible with this system.
+- [Yao.jl](https://github.com/QuantumBFS/Yao.jl)
+- [Quac.jl](https://github.com/bsc-quantic/Quac.jl)
+- [QuantumAlgebra.jl](https://github.com/jfeist/QuantumAlgebra.jl)
+- [QuantumCumulants.jl](https://github.com/qojulia/QuantumCumulants.jl)
+- [QuantumSymbolics.jl](https://github.com/QuantumSavory/QuantumSymbolics.jl)
+- [QuantumOptics.jl](https://github.com/qojulia/QuantumOptics.jl), [QuantumInterface.jl](https://github.com/qojulia/QuantumInterface.jl)
+- [QuantumLattices.QuantumOperators](https://github.com/Quantum-Many-Body/QuantumLattices.jl/blob/master/src/QuantumOperators.jl)
+
 ## Installation instructions
 
 This package resides in the `ITensor/ITensorRegistry` local registry.
@@ -32,10 +47,39 @@ julia> Pkg.add("QuantumOperatorAlgebra")
 ## Examples
 
 ````julia
-using QuantumOperatorAlgebra: QuantumOperatorAlgebra
-````
+using QuantumOperatorAlgebra: Op, Prod, Scaled, Sum, coefficient, sites, terms, which_op
+using Test: @test
+
+o1 = Op("X", 1)
+o2 = Op("Y", 2)
+
+@test which_op(o1) == "X"
+@test sites(o1) == (1,)
+
+o = o1 + o2
 
-Examples go here.
+@test o isa Sum{Op}
+@test terms(o)[1] == o1
+@test terms(o)[2] == o2
+
+o *= 2
+
+@test o isa Sum{Scaled{Int,Op}}
+@test terms(o)[1] == 2 * o1
+@test terms(o)[2] == 2 * o2
+@test coefficient(terms(o)[1]) == 2
+@test coefficient(terms(o)[2]) == 2
+
+o3 = Op("Z", 3)
+
+o *= o3
+
+@test o isa Sum{Scaled{Int,Prod{Op}}}
+@test terms(o)[1] == 2 * o1 * o3
+@test terms(o)[2] == 2 * o2 * o3
+@test coefficient(terms(o)[1]) == 2
+@test coefficient(terms(o)[2]) == 2
+````
 
 ---
 

examples/README.jl

@@ -6,6 +6,21 @@
 # [![Coverage](https://codecov.io/gh/ITensor/QuantumOperatorAlgebra.jl/branch/main/graph/badge.svg)](https://codecov.io/gh/ITensor/QuantumOperatorAlgebra.jl)
 # [![Code Style: Blue](https://img.shields.io/badge/code%20style-blue-4495d1.svg)](https://github.com/invenia/BlueStyle)
 # [![Aqua](https://raw.githubusercontent.com/JuliaTesting/Aqua.jl/master/badge.svg)](https://github.com/JuliaTesting/Aqua.jl)
+#
+# Quantum operator algebra system. This is mostly meant to be used as a backend in [ITensorMPS.jl](https://github.com/ITensor/ITensorMPS.jl)
+# and [ITensorNetworks.jl](https://github.com/ITensor/ITensorNetworks.jl) for lazily representing operator expressions
+# that will be turned into quantum circuits and tensor networks.
+#
+# See also:
+# - [ITensorQuantumOperatorDefinitions.jl](https://github.com/ITensor/ITensorQuantumOperatorDefinitions.jl) for operator definitions
+# compatible with this system.
+# - [Yao.jl](https://github.com/QuantumBFS/Yao.jl)
+# - [Quac.jl](https://github.com/bsc-quantic/Quac.jl)
+# - [QuantumAlgebra.jl](https://github.com/jfeist/QuantumAlgebra.jl)
+# - [QuantumCumulants.jl](https://github.com/qojulia/QuantumCumulants.jl)
+# - [QuantumSymbolics.jl](https://github.com/QuantumSavory/QuantumSymbolics.jl)
+# - [QuantumOptics.jl](https://github.com/qojulia/QuantumOptics.jl), [QuantumInterface.jl](https://github.com/qojulia/QuantumInterface.jl)
+# - [QuantumLattices.QuantumOperators](https://github.com/Quantum-Many-Body/QuantumLattices.jl/blob/master/src/QuantumOperators.jl)
 
 # ## Installation instructions
 
@@ -37,5 +52,35 @@ julia> Pkg.add("QuantumOperatorAlgebra")
 
 # ## Examples
 
-using QuantumOperatorAlgebra: QuantumOperatorAlgebra
-# Examples go here.
+using QuantumOperatorAlgebra: Op, Prod, Scaled, Sum, coefficient, sites, terms, which_op
+using Test: @test
+
+o1 = Op("X", 1)
+o2 = Op("Y", 2)
+
+@test which_op(o1) == "X"
+@test sites(o1) == (1,)
+
+o = o1 + o2
+
+@test o isa Sum{Op}
+@test terms(o)[1] == o1
+@test terms(o)[2] == o2
+
+o *= 2
+
+@test o isa Sum{Scaled{Int,Op}}
+@test terms(o)[1] == 2 * o1
+@test terms(o)[2] == 2 * o2
+@test coefficient(terms(o)[1]) == 2
+@test coefficient(terms(o)[2]) == 2
+
+o3 = Op("Z", 3)
+
+o *= o3
+
+@test o isa Sum{Scaled{Int,Prod{Op}}}
+@test terms(o)[1] == 2 * o1 * o3
+@test terms(o)[2] == 2 * o2 * o3
+@test coefficient(terms(o)[1]) == 2
+@test coefficient(terms(o)[2]) == 2