Montag, 10.03.2025 – 15:00 Uhr

Dr. Christoph Wolf
Center for Quantum Nanoscience (QNS), Institute for Basic Science, Seoul, EWHA Womans University Seoul, Korea

Abstract: After the development of electron-spin resonance (ESR) in a scanning tunneling microscope in 2015 [1] a myriad of potential applications appeared, exploiting the extremely high spatial resolution of the STM and high energy resolution of ESR.

For example, ESR-STM has been used to probe the energy levels of individual atoms and molecules using continuous wave spectroscopy [2-3], or as movable quantum sensor by functionalizing the STM tip with a molecule [4]. By applying a pulsed signal it has also been demonstrated that the quantum states can be coherently manipulated and the quantum state can be read out by the time-averaging current measurement inherent to the ESR-STM.[5]

In this talk I want to give an overview over our recent activity at QNS related to the latter part: the coherent manipulation of individual spins in interacting spin systems built using the atom manipulation technique of the STM. We have demonstrated that combining only a handful of atoms we can build atomic scale structures with quantum-coherent properties, which, in principle, can be developed towards quantum bits (qubits). By demonstrating single qubit arbitrary phase and multi-qubit controlled-NOT gates we have established a universal gate set and performed rudimentary quantum gate operations. More recently, we have estimated fidelity and entanglement in such systems by using open quantum systems simulations and parameters typical for ESR-STM experiments.

[1] Baumann et al., Science 350, 6259, 2015
[2] Willke et al., Science 362, 3412, 2018
[3] Zhang et al., Nat. Chem., 14, 59-65, 2022
[4] Esat et al., Nat. Nanotech., 19, 1466-1471, 2024
[5] Zang et al., Science 366, 6464, 2019

Seminarraum 3-1, Geb. 30.23