Single atom creates new quantum computing platform!

Researchers at the IBS Center for Quantum Nanoscience (QNS) at Ewha Womans University have made a breakthrough in the field of quantum information science: in collaboration with teams from Japan, Spain, and the U.S., they have created a new type of electron-spin quantum bit platform that assembles atoms one by one on a surface.The breakthrough was published on October 5 in the journal Science.

Unlike previous surface atom quantum devices that could only control a single quantum bit, the QNS researchers have successfully demonstrated the ability to control multiple quantum bits at the same time, enabling single-quantum-bit, double-quantum-bit, and triple-quantum-bit gates.

Simultaneous control of multiple quantum bits

A quantum bit is the fundamental unit of quantum information and is key to quantum applications such as quantum computing, sensing and communication.Phark Soo-hyon, one of the principal investigators at QNS, emphasized the importance of the project, "To date, scientists have only been able to create and control a single quantum bit on the surface, and this is an important step towards multi-quantum bit systems. "

This technology is unlikely to rival leading quantum computing methods in the short term, including those used by Google and IBM, as well as many startups. But the researchers who developed the method say it could be used to study the quantum properties of various other chemical elements and even molecules.

To some extent, everything in nature is quantum, and quantum computation is in principle possible. The difficulty lies in separating quantum states (equivalent to storage bits in a classical computer) from environmental disturbances and controlling them finely enough to enable quantum computation.

Andreas Heinrich and his collaborators at the Institute for Basic Science in Seoul have utilized nature's "primitive" quantum bit, the electron spin, in their research. An electron is like a tiny compass needle, and measuring the direction of its spin only yields two possible values, "up" or "down," which correspond to the 0s and 1s of the classical bits. These states are called superpositions; this is the key to quantum computation.

Led by directors Bae Yujeong, Phark Soo-hyon and Andreas Heinrich, QNS has developed this novel platform, which consists of individual magnetic atoms placed on the pristine surface of a thin insulator. These atoms can be precisely positioned using the tip of a scanning tunneling microscope (STM) and manipulated with the aid of electron spin resonance (ESR-STM). This atomic-scale control enabled the researchers to coherently manipulate quantum states. They also identified the possibility of controlling remote quantum bits, opening the way for scaling up to tens or hundreds of quantum bits in a defect-free environment.

By manipulating the spins of individual atoms and molecular combinations, Heinrich said, scaling up this technique to about 100 quantum bits would be fairly straightforward. However, it could be difficult to scale it up to many more quantum bits - the current leading quantum bit technology can already scale up to hundreds of quantum bits. According to Heinrich, "We're doing more basic science, but multiple STM quantum computers could someday be connected to form a larger quantum computer."

Bae Yujeong said, "It is truly amazing that we can now control the quantum states of multiple individual atoms on the surface simultaneously." The platform's atomic-level precision allows the atoms to be remotely manipulated to perform quantum bit operations individually without moving the top of the STM.

This research marks a significant departure from other quantum bit platforms such as photonic devices, ion and atom traps, and superconducting devices. One of the unique advantages of this surface-based approach to electron spin is the myriad of available spin species and the variety of two-dimensional geometries that can be precisely assembled.

Going forward, the researchers anticipate that quantum sensing, computing, and simulation protocols will use these precisely assembled atomic architectures. In short, the work of the QNS researchers promises to usher in a new era of atomic-scale control in quantum information science.