Illustration from Scientific Research

Functional and structural scheme of the assembled quantum sensor. The PTCDA molecule (white, hydrogen; grey, carbon; red, oxygen) is attached in standing configuration to an STM tip, consisting of Ag (light blue) and Fe (orange) atoms. The Fe atoms provide spin polarization. In a (B) field (in-plane B || and out-of-plane B orientations are shown in green), the spin of PTCDA with its magnetic moment (m) (blue arrow), a quantum two-level system, serves as a sensing qubit. It is addressable by ESR, for which an RF signal V RF is added to the DC bias voltage V DC. The spin-polarized tip reads out the sensor’s quantum state magnetoresistively.

DOI