In a study published in Nature Communications, a research team led by Prof. YANG Kai from the Institute of Physics of the Chinese Academy of Sciences, along with Prof. FERNÁNDEZ-ROSSIER Joaquín from International Iberian Nanotechnology Laboratory, demonstrated the all-electrical control of quantum interference in individual atomic spins on a surface.
Quantum interference arises when a system exists in a superposition of states, with relative phases producing constructive or destructive interference. An example is Landau-Zener-Stückelberg-Majorana (LZSM) interference which arises when a quantum two-level system is repeatedly driven through an anticrossing in the energy-level diagram, and undergoes multiple non-adiabatic transitions.
This mechanism is a powerful tool for fast and reliable quantum control, but it remains a significant challenge to achieve tunable LZSM interference in an atomic-scale quantum architecture where multiple spins can be precisely assembled and controllably coupled on demand.
In this study, using a custom-built advanced microscope known as electron spin resonance-scanning tunnelling microscope (ESR-STM), the researchers developed an all-electrical method to control LZSM quantum interference in individual and coupled atomic spins on insulating films.
By modulating atomically confined tip-atom interactions with strong electric fields, they rapidly drove spin states through anticrossings and observed rich interference patterns, including multiphoton resonances and signatures of spin-transfer torque. Multi-level LZSM spectra measured on coupled spins with tunable interactions showed distinct interference patterns depending on their many-body energy landscapes.
These findings open new avenues for all-electrical quantum manipulation in spin-based quantum processors in the strongly driven regime. This study opens up new possibilities for fast and robust quantum-state manipulation at the atomic scale.
