Tagging atoms in a gas can be achieved using different isotopes, as demonstrated in PET scans with oxygen isotopes. However, tracking atoms of the same type without isotopes poses significant challenges, as there are no known distinguishing quantum properties that can be consistently applied to individual atoms. While it is theoretically possible to prepare an atom in a unique quantum state, this state would likely decohere quickly, making long-term tracking impractical. The wave nature of matter complicates the ability to distinguish between identical atoms, as it relies on measuring their particle nature. Recent advancements in techniques have improved the investigation of single moving atoms, but practical tracking remains limited.
