Topological quantum computers a step closer with a new method to ‘split’ electrons.
Electrons, once thought to be indivisible, may display behaviors suggesting they can split into two halves under quantum interference. Groundbreaking research explores how nanoelectronic circuits, governed by quantum mechanics, allow electrons to choose pathways and interfere with themselves, creating effects akin to the mysterious Majorana fermion.
Quantum Physics Meets Nano-Scale Electronics
Scientists have long understood electrons as indivisible, fundamental particles. However, groundbreaking research reveals that a peculiar feature of quantum mechanics can create states that mimic the behavior of half an electron. These so-called “split-electrons” could be pivotal in advancing quantum computing.
The discovery, recently published in Physical Review Letters, was led by Professor Andrew Mitchell from University College Dublin’s School of Physics and Dr. Sudeshna Sen from the Indian Institute of Technology in Dhanbad. Both are theoretical physicists specializing in the quantum properties of nanoscale electronic circuits.
Quantum Mechanics Redefines Miniaturized Electronics
“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,” said Dr. Sen. “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.”
When a nanoelectronic circuit is designed to give electrons the ‘choice’ of two different pathways, quantum interference takes place. 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’s Wave-Like Insights
The double-slit experiment demonstrates the wave-like properties of quantum particles like the electron, which led to the development of quantum mechanics in the 1920s. Individual electrons are fired at a screen with two tiny apertures, and the place they end up is recorded on a photographic plate on the other side. Because the electrons can pass through either slit, they interfere with each other. In fact, a single electron can interfere with itself, just like a wave does when it passes through both slits at the same time. The result is an interference pattern of alternating high and low-intensity stripes on the back screen. The probability of finding an electron in certain places can be zero due to destructive interference – think of the peaks and troughs of two waves colliding and canceling each other out.
Electrons Behaving as Majorana Fermions
Professor Mitchell said: “It’s the same thing 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.”
Majorana Fermions and Quantum Computation Potential
The result is a so-called ‘Majorana fermion’ – a particle first theorized by mathematicians in 1937 but as yet not isolated experimentally. The finding is potentially important for the development of new quantum technologies, if the Majorana particle can be created in an electronic device and manipulated.
“There has been a big search for Majoranas over the last few years because they are a key ingredient for proposed topological quantum computers,” Professor Mitchell said. “We might have found a way to produce them in nanoelectronics devices by using the quantum interference effect.”
Reference: “Many-Body Quantum Interference Route to the Two-Channel Kondo Effect: Inverse Design for Molecular Junctions and Quantum Dot Devices” by Sudeshna Sen and Andrew K. Mitchell, 12 August 2024, Physical Review Letters.
DOI: 10.1103/PhysRevLett.133.076501
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