A groundbreaking study led by physicists from NTT Research, ETH Zurich, and Stanford University has unveiled a method for creating electrically defined quantum dots. Published in Science Advances, the research marks a significant milestone in the field of quantum photonics, opening new avenues for light-based quantum information processing and beyond.
Quantum dots are nanoscale semiconductor structures with unique properties that have long been heralded for their potential in various applications, including quantum computing, display technology, photovoltaics, and microscopy. However, traditional methods for creating quantum dots rely on chemical synthesis or epitaxial growth of materials, limiting their scalability and precision. The breakthrough achieved by the collaborative team introduces a novel approach to defining optically active quantum dots completely electrically, leveraging precisely patterned electrodes and strong electric fields.
“With conventional methods, quantum dots end up at random positions and have a broad distribution of energies,” ETH Zurich, Nanoscale Quantum Optics group, senior co-author Prof. Puneet Murthy said. “Our work shows how we can create quantum dots just by placing electrodes with the right shape, close to a semiconductor material. We can not only define where we want the quantum dot, but also tune the wavelength of light emitted from it by tuning the voltage applied on the electrodes.” The versatility of this technique is highlighted by the fact that simply by modifying the structure of electrodes, the precise shape of the quantum emitters can be changed, for instance, from a quantum dot to a ring or a one-dimensional wire.
Scalability is another breakthrough of this work. The researchers leveraged the electrode design to define not only single dots or rings but arrays of them. Most importantly, they showed that by using the right voltages on each electrode in the array, they can bring multiple quantum dots to the same energy, which holds promise for future applications.
“For cutting-edge technologies, such as photonic quantum computing, we need an architecture that can scale up to thousands of identical quantum dots that act as sources of single photons,” PHI Lab Scientist and senior co-author Dr. Thibault Chervy said. “This is why electrical control is so important, because we know how to pattern nanoscale electrodes and tune voltages on large scales. For instance, in CMOS technology that is used in many of our devices, billions of transistors are controlled with voltages. Our architecture is not different in nature from a transistor – we are just keeping a well-defined voltage potential across a tiny little junction.”
The researchers believe their work opens up several new directions, not only for future technological applications but also for exploring fundamental physics. “We have shown the versatility of our technique in defining quantum dots and rings electrically,” primary co-author and Stanford University Ph.D. student Jenny Hu (in Professor Tony Heinz’s Research Group) said. “This gives us an unprecedented level of control over the properties of the semiconductor at the nanoscale. The next step will be to investigate deeper the nature of light emitted from these structures and find ways of integrating such structures into cutting-edge photonics architectures.”
For more information, please read the accompanying press release: NTT Research PHI Lab Scientists Achieve Quantum Control of Excitons in 2D Semiconductors – NTT Research (ntt-research.com)
Image: Ella Maru Studio
