Overview of QNS
QNS focuses on a basic exploration of our world on the atomic scale with an eye towards harnessing these quantum behaviors for high-density data storage and quantum computation.
Breakthrough in Accessing the Tiny Magnet within the Core of a Single Atom
The two elements that were investigated in this work, iron and titanium, are atoms that can have a different number of neutrons in the atom’s core, these are the so-called isotopes. Only certain isotopes of each element have a core with a nuclear spin. It is normally exceedingly hard to measure nuclear spins of individual atoms. Traditionally large numbers of nuclear spins are required, making this advancement so noteworthy.
In order to detect the presence of a nuclear spin within the core of a single atom, the team made use of the hyperfine interaction. This phenomenon describes the coupling between a single atom’s nuclear spin and its electron counterpart, that is generally much easier to access. Dr. Philip Willke of the Center for Quantum Nanoscience (QNS), first author of the study, says: “We found that the hyperfine interaction of an atom changed when we moved it to a different position on the surface or if we moved other atoms next to it. In both cases, the electronic structure of the atom changes and the nuclear spin allows us to detect that.”
A step closer to single-atom data storage
Physicists of QNS and EPFL used Scanning Tunneling Microscopy to successfully test the stability of a magnet made up of a single atom. Despite the rise of solid-state drives, magnetic storage devices such as conventional hard drives and magnetic tapes are still very common. But as our data-storage needs are increasing at a rate of almost 15 million gigabytes per day, scientists are turning to alternative storage devices. One of these are single-atom magnets: storage devices consisting of individual atoms stuck (“adsorbed”) on a surface, each atom able to store a single bit of data that can be written and read using quantum mechanics. And because atoms are tiny enough to be packed together densely, single-atom storage devices promise enormous data capacities. But although they are no longer science fiction, single-atom magnets are still in basic research, with many fundamental obstacles to be overcome before they can be implemented into commercial devices. EPFL has been at the forefront of the field, overcoming the issue of magnetic remanence, and showing that single-atom magnets can be used to read and write data. Fabio Donati of the IBS Center for Quantum Nano Science, coauthor of the publication, says that “the intriguing behavior of single-atom magnets is interesting both for fundamental science and for future applications. Exploring the limiting factors of their magnetic stability is crucial for engineering future nanoscale devices that can use single atoms as building blocks.”
One Atom Bit
Utilizing Scanning Tunnelling Microscope
One bit of digital information can now be successfully stored in an individual atom, according to a study just published in Nature. Current commercially-available magnetic memory devices require approximately one million atoms to do the same. Andreas Heinrich, newly appointed Director of the Center for Quantum Nanoscience, within the Institute of Basic Science (IBS, South Korea), led the research effort that made this discovery at IBM Almaden Research Center (USA). This result is a breakthrough in the miniaturization of storage media and has the potential to serve as a basis for quantum computing.
A Quantum Sensor Made from Individual Iron Atoms
QNS researchers, in collaboration with a team of IBM researchers in the USA have succeeded in using individual iron atoms as quantum sensors. Using this sensor, they were able to measure the small magnetic field created by neighboring magnetic atoms, an effect that was previously not measurable in scanning tunneling microscopy.
This work is the first application of a recent breakthrough invention of the same team, which demonstrated electron spin resonance – a quantum mechanical measurement of single spins – in the STM. “We believe that this quantum sensor can be used to measure the spins in complex molecules with atomic-scale spatial resolution, sort of like a nano-GPS”, suggests Taeyoung Choi, first author of the recent study.
Scanning Tunneling Microscope
The Scanning Tunneling Microscope is a conceptually rather simple tool that has amazing capabilities. It ‘images’ the surface of a material – here labelled as sample – by bringing a really sharp metal needle – here labelled as tip – very close. The actual distance between the last atom on the tip and the atoms on the surface of the sample is about one nanometer, which corresponds to only about 4 atom spacings in most solid materials. At this close approach, electrons can jump from tip to sample and from sample to tip by using the quantum mechanical effect called tunneling. When a small voltage is applied between tip and sample, a current flows, which we measure. This current is extremely sensitive to the distance: for example it become 10 times smaller when the distance is increased from 1 to 1.1nm.
At QNS, we are using STM not only to image surfaces with atomic resolution but also to move the atoms into desired configurations. This enable us to engineer these nanostructures and then build them with ultimate precision. Finally, we use very high resolution spectroscopic measurements to investigate the electronic and magnetic properties of such systems.