A novel solid-state qubit platform with electron spins on a surface

Abstract:  

 

Addressability to individual atoms and atom-by-atom position control [1] using a scanning tunneling microscope (STM) opens the bottom-up design of functional quantum devices. As an extension of such potential to atomic/molecular spins, STM can provide a platform of solid-state qubits [2], which is unique in the sense of qubit platform design at a scale of ~1 nm, with an advantage of atom precision control of its structure and inter-qubit couplings. Here we demonstrate atom-by-atom construction, coherent operations, and readout of coupled electron-spin qubits using an STM combined with pulsed electron spin resonance (ESR) [3]. To enable the coherent control of "remote" qubits that are outside the tunnel junction, we complement each electron spin with a local magnetic field gradient from a nearby single-atom magnet [4]. Readout is achieved by employing a sensor qubit in the tunnel junction and implementing double electron-electron spin resonance [5]. Single-, two-, and three-qubit operations are thereby demonstrated in an all-electrical fashion [6,7]. Our work marks the creation of an angstrom-scale qubit platform, where quantum functionalities using electron spin arrays, built atom-by-atom on a surface, are now within reach.