Â鶹´«Ã½

News — The Korea Research Institute of Standards and Science (KRISS, President: Dr. Lee Ho Seong) has developed a technology that controls the energy of single electrons in the desired form. This technology reduces the instability of electrons caused by external environments and enables stable quantum state implementation, making it a foundational technology to enhance the performance of single-electron qubits.

Electrons are fundamental particles that make up atoms, and when their paths are divided, they exhibit the quantum superposition phenomenon, passing through both paths (0 and 1) simultaneously. This characteristic can be utilized in information processing to create qubits. Single-electron qubits are highly regarded as a technology for scaling quantum computing due to their excellent integration, with the theoretical potential to implement dozens of qubits in a small area.

However, improving the performance of single-electron qubits has been challenging due to their extreme sensitivity to external environments. The stability and accuracy of a qubit’s quantum state directly determine its performance, yet electrons, being incredibly small and sensitive, make it difficult to achieve a stable quantum state. Additionally, their energy state is highly susceptible to interactions with the surrounding environment and other electrons, often leading to instability and a rapid loss of quantum properties.

The Quantum Device Group at KRISS has developed an advanced technology that precisely controls the energy of single electrons and reduces their instability using an energy filter. The newly developed energy filter is strategically placed within a conductive channel and functions similarly to a kitchen sieve. It selectively allows only electrons with energy above a specific threshold to pass through, while reflecting the rest. The researchers created single electrons in a quantum dot, then applied an appropriate voltage to a quantum point contact to form an energy filter. This approach successfully enabled the passage of only high-energy electrons, reducing energy uncertainty by more than half.

This technology is expected to be widely used in the development of single-electron-based quantum information processing technologies, including high-performance qubits. By eliminating unnecessary energy distributions and manipulating electrons within a specific energy range, the quantum phenomena of the electrons can be implemented more stably, while minimizing interactions with external environments and other electrons.

In addition, the research team has developed a technology to visualize the shape of single electrons controlled by the energy filter on a 2D graph. They devised a method to compare the shape of the single electron before and after passing through the energy filter using Wigner distribution*. By intuitively observing the time-energy information of the single electron, which changes depending on the conditions, on a digital 2D graph, the researchers can precisely identify the quantum properties of the single electron that were previously overlooked in earlier experiments.

^{* Wigner Distribution: A method of visually analyzing the quantum state of an electron by converting it into a distribution function of time (position) and energy (momentum). In this experiment, the research team developed a technique to compare the energy changes of single electrons using Wigner distribution and analyze it in detail by converting it into digital signals.}

Dr. Bae Myung-Ho stated, "This achievement will contribute to enhancing the applicability of quantum information technologies based on single electrons."

This research was conducted in collaboration with Jeonbuk National University, Korea Advanced Institute of Science and Technology (KAIST), and Korea Institute of Science and Technology (KIST), and the results were published in Nano Letters (IF: 9.6) in October 2024.