From e7a48db78f97385bd6a769c9b3385e288b8d9406 Mon Sep 17 00:00:00 2001
From: Claude Code <noreply@anthropic.com>
Date: Mon, 18 Aug 2025 22:44:56 +0000
Subject: [PATCH] Add commutator and anticommutator functions
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- Add commutator(A, B) function that computes [A, B] = AB - BA
- Add anticommutator(A, B) function that computes {A, B} = AB + BA
- These are fundamental quantum mechanical operations for operator algebra
- Includes comprehensive documentation with examples

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
---
 src/QuantumInterface.jl | 14 ++++++++++++++
 src/linalg.jl           | 43 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/src/QuantumInterface.jl b/src/QuantumInterface.jl
index 4af5dd7..a090ac5 100644
--- a/src/QuantumInterface.jl
+++ b/src/QuantumInterface.jl
@@ -53,6 +53,20 @@ function traceout! end
 
 function variance end
 
+"""
+    commutator(A, B)
+
+Compute the commutator [A, B] = AB - BA of two operators.
+"""
+function commutator end
+
+"""
+    anticommutator(A, B)
+
+Compute the anticommutator {A, B} = AB + BA of two operators.
+"""
+function anticommutator end
+
 ##
 # Qubit specific
 ##
diff --git a/src/linalg.jl b/src/linalg.jl
index 71833e3..10ad846 100644
--- a/src/linalg.jl
+++ b/src/linalg.jl
@@ -8,3 +8,46 @@ directsum(a::AbstractOperator...) = reduce(directsum, a)
 ptrace(a::AbstractOperator, index) = arithmetic_unary_error("Partial trace", a)
 _index_complement(b::CompositeBasis, indices) = complement(length(b.bases), indices)
 reduced(a, indices) = ptrace(a, _index_complement(basis(a), indices))
+
+# Commutator and anticommutator operations
+"""
+    commutator(A, B)
+
+Compute the commutator [A, B] = AB - BA of two operators.
+
+# Arguments
+- `A::AbstractOperator`: First operator
+- `B::AbstractOperator`: Second operator
+
+# Returns
+The commutator [A, B] = AB - BA
+
+# Examples
+```julia
+σx = sigmax()
+σy = sigmay()
+comm = commutator(σx, σy)  # Returns 2i*σz
+```
+"""
+commutator(A::AbstractOperator, B::AbstractOperator) = A*B - B*A
+
+"""
+    anticommutator(A, B)
+
+Compute the anticommutator {A, B} = AB + BA of two operators.
+
+# Arguments
+- `A::AbstractOperator`: First operator
+- `B::AbstractOperator`: Second operator
+
+# Returns
+The anticommutator {A, B} = AB + BA
+
+# Examples
+```julia
+σx = sigmax()
+σz = sigmaz()
+anticomm = anticommutator(σx, σz)  # Returns zero for Pauli matrices
+```
+"""
+anticommutator(A::AbstractOperator, B::AbstractOperator) = A*B + B*A