Reviewed by Danielle Ellis, B.Sc.Sep 20 2024
Physicists at the Indian Institute of Technology and the University College Dublin reveal that it is possible to create objects that behave like half of an electron by utilizing an odd property of quantum mechanics. Perhaps these "split-electrons" are the key to releasing the potential of quantum computing. The study was recently published in Physical Review Letters.
The most reliable and potent computer system in the world would be the "topological" quantum computer, albeit it currently only exists in theory. It does, however, call for a unique kind of "qubit," or quantum bit, which has not yet been realized or controlled.
Electrons are the fundamental particles that make up atoms, which are the building blocks of conventional matter. Scientists have long understood that electrons are indivisible. However, unexpected new research reveals that it is possible to create objects that behave like half of an electron by utilizing an odd property of quantum mechanics.
These "split-electrons" can function as topological qubits and could be the key to releasing quantum computation's full potential.
The theoretical physicists studying the quantum characteristics of nanoscale electronic circuits were Professor Andrew Mitchell at University College Dublin (UCD) School of Physics and Dr. Sudeshna Sen at the Indian Institute of Technology in Dhanbad.
The miniaturization of electronics has reached the point now where circuit components are just nanometers across. At that scale, the rules of the game are set by quantum mechanics, and you have to give up your intuition about the way things work. A current flowing through a wire is actually made up of lots of electrons, and as you make the wire smaller and smaller, you can watch the electrons go through one-by-one. We can now even make transistors which work with just a single electron.
Dr. Sudeshna Sen, Theoretical Physicist, Quantum Characteristics of Nanoscale Electronic Circuits, Indian Institute of Technology
States where electrons appear to split can result from the phenomenon of "quantum interference" between electrons in nanoscale electronic circuits.
In a nanoelectronic circuit, electrons going down different paths in the circuit can destructively interfere and block the current from flowing. This phenomenon has been observed before in quantum devices. The new thing that we found is that by forcing multiple electrons close enough together that they strongly repel each other, the quantum interference gets changed. Even though the only fundamental particles in the circuit are electrons, collectively they can behave as if the electron has been split in two.
Andrew Mitchell, Professor, School of Physics, University College Dublin
This led to the creation of a particle known as a "Majorana fermion," which mathematicians first theorized in 1937 but has not yet been isolated experimentally. If an electronic device can produce and manipulate the Majorana particle, then this discovery could be significant for the advancement of novel quantum technologies.
Professor Mitchell said: “There has been a big search for Majoranas over the last few years because they are a key ingredient for proposed topological quantum computers. We might have found a way to produce them in nanoelectronics devices by using the quantum interference effect.”
Quantum Interference Explained by the “Double-Slit” Experiment
Quantum interference occurs when a nanoelectronic circuit is built to allow electrons to have the "choice" between two distinct pathways.
Professor Mitchell explained, “The quantum interference we see in such circuits is very similar to that observed in the famous double-slit experiment.”
The double-slit experiment reveals the wave-like nature of quantum particles such as electrons, a discovery that contributed to the development of quantum mechanics in the 1920s. In the experiment, individual electrons are fired at a screen with two small apertures, and their landing positions are recorded on a photographic plate on the opposite side. Since the electrons can pass through either slit, they interfere with each other.
Remarkably, a single electron can even interfere with itself, much like a wave passing through both slits simultaneously. As the electrons pass through, the resulting waves on the other side interact and recombine, forming a complex interference pattern. When the peak of one wave meets the trough of another, they cancel each other out, preventing the electron from passing through certain areas.
It’s the same thing that is happening in a nanoelectronic circuit. Quantum interference can be used to produce the kinds of qubits we need for more powerful quantum computers.
Andrew Mitchell, Professor, School of Physics, University College Dublin
Journal Reference:
Sen, S. & Mitchell, K. A., (2024) Many-Body Quantum Interference Route to the Two-Channel Kondo Effect: Inverse Design for Molecular Junctions and Quantum Dot Devices. Physical Review Letters. doi.org/10.1103/PhysRevLett.133.076501