Coherent control of individual spins

In search of new architectures for quantum information processing, we study spin qubits using scanning probe microscopy in combination with electron spin resonance.

The performance of any qubit, be it a superconducting or a spin qubit, is limited by the interaction with the environment, which destroys the well-prepared quantum state of the qubit through relaxation or decoherence processes. In the case of solid-state qubits, this interaction can be due to the macroscopic environment, such as the arrangement of the gate electrodes, or at the atomic level, due to impurity atoms. These interactions, which cannot be eliminated, are a major problem and a reason for the intensive research on fault-tolerant qubits.

Single atomic and molecular spins on thin insulating layers on metal surfaces have only recently become relevant for quantum information by coherent spin manipulation using scanning tunneling microscopy (STM) in combination with electron spin resonance (ESR) [1]. These systems are particularly suited for building quantum architectures with atomic precision [2] and for studying the effects of the environment on the performance of qubits, since the perturbative environment can be tailored by arbitrarily positioning perturbative atoms using the manipulation capabilities of the STM.

We build artificial quantum architectures from single atoms and molecules on surfaces [2][3][4] and on probe tips [5], control their spin states [1][6], and study stationary and mobile (multi-)qubit systems.

References

[1] K. Yang, W. Paul, S.-H. Phark, P. Willke, Y. Bae, T. Choi, T. Esat, A. Ardavan, A. J. Heinrich, C. P. Lutz, Coherent spin manipulation of individual atoms on a surface. Science 366, 509–512 (2019)

[2] K. Yang, S.-H. Phark, Y. Bae, T. Esat, P. Willke, A. Ardavan, A. J. Heinrich, C. P. Lutz, Probing resonating valence bond states in artificial quantum magnets. Nat Commun. 12, 993 (2021)

[3] T. Esat, N. Friedrich, F. S. Tautz, R. Temirov, A standing molecule as a single-electron field emitter. Nature 558, 573–576 (2018)

[4] T. Esat, M. Ternes, R. Temirov, F. S. Tautz, Electron spin secluded inside a bottom-up assembled standing metal-molecule nanostructure. Phys. Rev. Research 5, 033200 (2023)

[5] T. Esat, D. Borodin, J. Oh, A. J. Heinrich, F. S. Tautz, Y. Bae, R Temirov, A quantum sensor for atomic-scale electric and magnetic fields. Nat. Nanotechnol. (2024)

[6] P. Willke, A. Singha, X. Zhang, T. Esat, C. P. Lutz, A. J. Heinrich, T. Choi, Tuning Single-Atom Electron Spin Resonance in a Vector Magnetic Field. Nano Lett. 19, 8201–8206 (2019)