From 7605b69e2093386eea0f634a20cb617093233b7f Mon Sep 17 00:00:00 2001
From: Yi-Te Huang <44385685+ytdHuang@users.noreply.github.com>
Date: Mon, 23 Sep 2024 00:22:42 +0800
Subject: [PATCH] fix `rand_unitary` (#230)

---
 src/qobj/operators.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/qobj/operators.jl b/src/qobj/operators.jl
index 008f2943..feb15780 100644
--- a/src/qobj/operators.jl
+++ b/src/qobj/operators.jl
@@ -48,7 +48,7 @@ function rand_unitary(dimensions::Union{AbstractVector{Int},Tuple}, ::Val{:haar}
     # Because inv(Λ) ⋅ R has real and strictly positive elements, Q · Λ is therefore Haar distributed.
     Λ = diag(R) # take the diagonal elements of R
     Λ ./= abs.(Λ) # rescaling the elements
-    return QuantumObject(dense_to_sparse(Q * Diagonal(Λ)); type = Operator, dims = dimensions)
+    return QuantumObject(sparse_to_dense(Q * Diagonal(Λ)); type = Operator, dims = dimensions)
 end
 function rand_unitary(dimensions::Union{AbstractVector{Int},Tuple}, ::Val{:exp})
     N = prod(dimensions)
@@ -59,7 +59,7 @@ function rand_unitary(dimensions::Union{AbstractVector{Int},Tuple}, ::Val{:exp})
     # generate Hermitian matrix
     H = QuantumObject((Z + Z') / 2; type = Operator, dims = dimensions)
 
-    return exp(-1.0im * H)
+    return sparse_to_dense(exp(-1.0im * H))
 end
 rand_unitary(dimensions::Union{AbstractVector{Int},Tuple}, ::Val{T}) where {T} =
     throw(ArgumentError("Invalid distribution: $(T)"))