Along with research teams from Korea, Japan, and the United States, an international research team led by Deung-Jang Choi and Cristina Mier from the Centro de Física de Materiales (CSIC-UPV/EHU) and the Donostia International Physics Centre (DIPC) has effectively put forward a new quantum platform that employs the electron spin of a single atom on a solid surface and achieved ‘a multiple qubit (quantum bit)’ system using three electron spins. The study’s findings were just released in a renowned Science publication. (Autor: Elda Campos Lavín)
The fundamental unit for information storage and computation in computers is the bit, which can have a value of either 0 or 1. In contrast, quantum computers operate with qubits as their fundamental unit, which can perform computations in a superposition of 0 and 1 states, meaning that they can exist simultaneously in both states, like the paradox of the Schrodinger cat. This capacity results in significantly enhancing the performance in terms of information storage and processing speed compared to classical computers.
To commercialize quantum computers, various types of qubits have been proposed using superconducting junctions, ion traps, quantum dots, and quantum phase states. However, due to the relatively short history of quantum information science, the challenge to design an optimal qubit system is still on. For decades, scientists have aspired to construct a quantum-coherent architecture at the atomic scale, a realm where the fundamental properties of atoms, like electron spin, holds its way. Such an achievement could revolutionize quantum science and nanotechnology. Yet, building an atomic-scale quantum architecture, capable of precise assembly, controlled coupling, and coherent operation of multiple electron-spin qubits, has remained an extraordinary challenge.
In fact, there is a need for fundamental scientific research to implement a new quantum platform that addresses the shortcomings of existing qubits while increasing their integration and reliability.
Using scanning tunneling microscopy (STM) have proven very useful to measure and control the electronic states of individual atoms, exploiting quantum mechanical phenomena. In this work combining STM and ESR (electron spin resonance) technology, projecting microwave pulses onto individual titanium atoms on the surface lead to successfully controlling and measuring the spin states. As a result, precise control of the spin of a single atom and setting it to the desired quantum state became possible. The remaining challenge was to implement a multi-qubit system capable of controlling several qubits simultaneously. The qubit platform presented in this work consists of multiple titanium atoms placed on the surface of a thin insulator (magnesium oxide) and has succeeded in the challenge.
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