Researchers have been able to produce the first experimental pulse-generation of a single-particle electron. The team of scientists in France named the single electron a leviton, in honour of physicist Leonid Levitov and its resemblance to the soliton - a solitary wave that behaves like a "particle” and maintains its shape while it travels at constant speed. The team published their findings in the journal Nature.
In 1996, Levitov and colleagues proposed that a voltage applied to a nanocircuit and varied over time according to the mathematical expression of a Lorentzian distribution should be able to excite a single electron peak in a sea of electrons. Lorentzian distribution is also referred to as the Cauchy distribution and is a continuous probability distribution: a probability distribution that has a probability density function. A probability density function is a function that describes the relative likelihood for this random variable to take on a given value. The new research has proved Levitov’s theory to be true, opening the door to a new subfield of physics that involves using quantum excitations.
The team built a nanocircuit which acted as a nanoscale electrode and created a Fermi Sea, which is where electrons are held in a tiny device. The circuit was then cooled to near absolute zero and applied voltage that varied in time to stir the electrons; this created chaotic peaks and valleys. Changing the time variations to fit the Lorentzian distribution meant one single peak was created: the leviton.
The experiment can be compared to a tub of water, where stirring causes chaotic waves to form. Adding more water (electrons) causes the water level to rise, while pouring out some water causes the water level to fall. If the water is stirred the right way, a soliton can form as a tsunami type wave where the energy is not dispersed as it moves across the surface.
Though this is not the first time single-electron excitations have been caused to come about, it is the first time it has occurred without the need to build a special nanostructure. The team therefore think it will be possible to scale up the circuit so larger structures can be built that could carry quantum information. The technique could be applied to cold atomic gases, leading to the possibility of atomic levitons.