diff --git a/src/utils.jl b/src/utils.jl index 25ddc27..b673d45 100644 --- a/src/utils.jl +++ b/src/utils.jl @@ -9,11 +9,11 @@ Check whether a matrix `A` is symmetric with a zero diagonal. -Supposing that `A` is the adjacency matrix of a graph representing a quantum spin network, a -nonzero diagonal would indicate couplings between qubits and themselves, which is physically -nonsensical. On the other hand, symmetry (or rather Hermicity in the general case, but we -only consider here real-valued adjacency matrices) is required for the walk Hamiltonian -``eⁱᵗᴬ`` to be unitary. +Supposing that `A` is the adjacency (and walk Hamiltonian) of a graph representing a quantum +spin network, a nonzero diagonal would indicate couplings between qubits and themselves, +which is physically nonsensical. On the other hand, symmetry (Hermicity in the general case, +but we only consider here real-valued adjacency matrices) is required for the transition +matrix ``eⁱᵗᴬ`` to be unitary. # Arguments - `A::AbstractMatrix{<:Real}`: The matrix to check. @@ -37,10 +37,10 @@ end Check whether a graph `g` is simple (i.e., undirected with no self-loops). -Supposing that `g` represents a quantum spin network, self-loops would indicate couplings -between qubits and themselves, which is physically nonsensical. On the other hand, -undirectedness is required for the walk Hamiltonian ``eⁱᵗᴬ`` to be unitary, where `A` is the -adjacency matrix of `g`. +Supposing that `g` represents a quantum spin network (whose walk Hamiltonian is the +adjacency matrix `A` of `g`), self-loops would indicate couplings between qubits and +themselves, which is physically nonsensical. On the other hand, undirectedness is required +for the transition matrix ``eⁱᵗᴬ`` to be unitary. # Arguments - `g::AbstractGraph`: The graph to check.