Engineers and physicists at University College London (UCL) in the UK have devised a novel technique, demonstrating for the first time the reliable positioning of individual atoms within an array with near 100% accuracy and scalability. This breakthrough paves the way for manufacturing quantum computers with nearly zero failure rates, significantly enhancing the prospects for building universal quantum computers. The findings are detailed in the latest issue of the journal Advanced Materials.
Dr. Taylor Stark loads samples into a scanning tunneling microscope (STM) for atomic-level operations. Image Source: University College London.
In theory, quantum computing holds the promise of solving complex problems that traditional computers could never tackle. One approach to creating quantum gates in a universal quantum computer involves placing individual atoms within silicon, cooling them to extremely low temperatures to maintain their quantum properties stable, and then manipulating them with electrical and magnetic signals to process information, akin to manipulating binary transistors in classical computers to output 0s and 1s.
Various methods for building quantum computers are under development, but none have yet achieved the required scale and low error rates.
A precise positioning of individual "impurity" atoms in a silicon crystal manipulates their quantum properties to form quantum bits. This approach boasts low quantum bit error rates and is based on scalable silicon microelectronics technology. The standard method employs phosphorus as the impurity atom, but with a success rate of only 70% in positioning single phosphorus atoms, the system still falls short of the near-zero fault rate needed to establish a quantum computer.
In this study, researchers hypothesized that arsenic might be a more reliable material than phosphorus. They used a microscope capable of identifying and manipulating single atoms to precisely insert arsenic atoms into silicon crystals. They then repeated this process, establishing a 2×2 array of single arsenic atoms that could be used as quantum bits.
The researchers claim they were able to place atoms in silicon with near-perfect precision and in a scalable manner, marking a significant advancement in the field of quantum computing. They demonstrated, for the first time, a method for achieving the precision and scale required for quantum computers.
Currently, the methods developed in the study require manual positioning of each atom, one at a time, which takes several minutes. Theoretically, this process can be repeated infinitely. However, to build a universal quantum computer, it is necessary to automate and industrialize this process. This entails creating arrays of millions, billions, or even trillions of quantum bits. The method needs to be highly compatible with current semiconductor processes and integrated after solving some engineering challenges.
The development of quantum computers involves interdisciplinary fields, with materials science being one of them. What materials are best suited for making quantum computers to fully unleash their potential? Researchers are continuously experimenting and exploring in this regard. Currently, superconducting materials, photonic materials, atomic materials, etc., are all candidate materials for developing quantum computers. One thing is certain: regardless of the material used, the core principle is to adhere to the operating rules of quantum computers.
