Scanning Tunnelling Microscope

A scanning tunnelling microscope similar to this one captured an atom as it lost its quantum state. Credit: Stan Olszewski for IBM/CC BY-ND 2.0

Quantum physics

Bearing witness as an atom loses its quantum ‘fuzziness’

A single electron kicks an iron atom out of multiple quantum states.

A single iron atom has been observed in unprecedented detail as it sheds the ‘fuzziness’ of its quantum states.

Quantum computers perform calculations on the basis of quantum properties that allow atoms to be ‘fuzzy’ — that is, to exist in multiple states at once. But as an atom interacts with its environment over time, it loses this quantum feature and occupies only one state. This loss of fuzziness limits the capabilities of quantum computers.

To better understand this process, a team led by Andreas Heinrich of the IBS Center for Quantum Nanoscience in Seoul and Christopher Lutz of the IBM Almaden Research Center in San Jose, California, used a scanning tunnelling microscope to study single iron atoms. After delivering a stream of electrons through the microscope’s tip, the team saw that, in most cases, interaction with an individual electron was enough to shift the atom to only one quantum state.

Changes to the magnetic properties of the microscope’s tip also affected how long the atom remained in multiple quantum states. Such techniques could be used to design and build nanostructures atom by atom to improve the performance of quantum devices, the authors write.