Coherent Quantum Control and Magnetism on atoms – Trapped ion and ESR STM

From QCLab
Prof. Taeyoung Choi (Ewha Womans Univ.)
  • Speaker: Prof. Taeyoung Choi (Ewha Womans Univ.)
  • Date: Wednesday, May 24, 2017, at 17:00
  • Place: BK Seminar Room

Understanding, controlling, and utilizing nanoscale quantum systems have been one of major research interests across fields of physics, chemistry, and material science. In atomic molecular optics (AMO) physics, the ultracold trapped ion system has been one of leading and successful architectures for coherent quantum control and has demonstrated key ingredients for quantum computation and simulation. Such quantum control has been applied to condensed matter systems which promise scalable Quantum information processing.

Recently, we successfully combined microwave technique to a Scanning Tunneling Microscopy (STM) and demonstrated electron spin resonance (ESR) of individual Fe atoms on ultrathin insulating MgO. Coherent Quantum control of atoms on surfaces using STM is a highly interesting and a new Quantum architecture, enabling us to position qubits and control their interaction in nano-meter and nano-electron-volt resolution.

With this new tool (ESR-STM), we studied magnetic interaction of artificially built nanostructures. We found that an ESR signal from single Fe atom split into two different frequencies when we position an additional Fe atom nearby. We measure ESR energy splittings that decay as 1/r³ (where r is the separation of the two Fe atoms), indicating that the atoms are coupled through magnetic dipole-dipole interaction. This energy and distance relation enables us to determine magnetic moments of atoms and molecules on a surface with high precision in energy (~10 MHz = ~40 neV). Unique and advantageous aspects of ESR-STM compared to other quantum magnetic sensors (such as NV centers) are the atom manipulation and imaging capabilities, which allow us to build atomically precise nanostructures and examine their interactions. For instance, we construct a dice cinque arrangement of five Fe atoms, and probe their magnetic interaction and energy degeneracy.

We demonstrate the ESR-STM technique can be utilized for quantum magnetic sensors and may serve as an alternative architecture for scalable quantum computation and simulation.