nb = CreateDocument[{
    ExpressionCell[Defer[2+2],"Input"],
    ExpressionCell[4, "Output"],
    ExpressionCell[Defer[SparseArray[RandomInteger[10,10]]],"Input"],
    ExpressionCell[SparseArray[RandomInteger[10,10]],"Output"]
}];
NotebookSave[nb, FileNameJoin[{$TemporaryDirectory,"example.nb"}]]

NotebookImport[FileNameJoin[{$TemporaryDirectory,"example.nb"}], "Output"] //InputForm