Czech physicists have been able to "move" a quasi-particle soliton

Scientists from the Institute of Physics of the Czech Academy of Sciences in collaboration with their Korean colleagues successfully demonstrated an experiment to create and destroy solitons with non-integer charge. They achieved this by using electrical pulses from the tip of a scanning microscope. The new procedure is an important step in the development of quantum computers based on solitons. The result was published in the Nature Nanotechnology journal.

In classical physics, solitons are stable waves that propagate in a material without energy loss and thus retain their velocity or amplitude. In 1834, engineer Scott Russel was the first to notice strange waves propagating in an unchanging shape at constant velocity in a canal. He was so intrigued that he chased them along the canal near Edinburgh for miles.

The study of solitons in quantum physics was of great importance for understanding the behavior of conductive polymers, for which the Nobel Prize in Chemistry was awarded in 2000. In recent years, it has been demonstrated that solitons can also be used in the construction of quantum computers. One of the basic preconditions for the development of this technology, however, was to prove the ability to manipulate individual solitons, i.e. to create, destroy and move them in a controlled manner, which was not possible before.

Pavel Jelínek's team focused on the study of solitons with non-integer charge. From the point of view of quantum information technologies, they are more interesting than the ones with the charge containing just one electron. Non-integer charge significantly facilitates their mobility and allows a longer life, which is a necessary condition for quantum computing.

A new way to process and store information

"While studying the atomic structure of gold-decorated silicon chains using a scanning microscope, we observed regular changes in the arrangement of atoms. This observation led us to the possibility of controlling solitons,” Pavel Jelínek from the Division of Solid State Physics of the Institute of Physics of the Czech Academy of Sciences explains how the idea to control solitons in 1D atomic chains came about.

The age of quantum informatics

The ability to arbitrarily manipulate solitons with non-integer charge is a basic prerequisite for the implementation of quantum information technologies based on solitons.

"In recent years, we have witnessed amazing experimental progress in controlled manipulations of various quantum objects. These results, including those related to quantum solitons, bring us closer to the age of quantum informatics, when the peculiarities of the quantum world will serve for more efficient computational and simulation procedures and advanced communication techniques,” explains Professor Pavel Cejnar of the Faculty of Mathematics and Physics of Charles University.

Quasiparticles

Quasiparticles, as their name suggests, are different from elementary particles such as electrons or quarks. In solids, the concept of quasiparticles is associated with an electron the energy of which is altered by interaction with the surrounding matter / field. The concept of a quasi-particle in solids can be compared to a running horse surrounded by a cloud of dust, which is kicked up by its movement. The horse itself represents an electron, and the cloud interaction with the surrounding matter, which effectively changes the energy of the electron itself. The introduction of the concept of such a quasiparticle greatly facilitates the description of quantum phenomena in solids.

Soliton

A soliton is a quasiparticle that is associated with an electron which is bound to a certain structural defect in the arrangement of individual atoms. Importantly, this structural defects with the electron  can move through the respective material with virtually no energy loss.

Solitons – animation:

Animation: https://youtu.be/4XtWoWtjYN4  Credit:  neuroncollective.com  / Tomáš Holub

Link to the publication: www.nature.com/articles/s41565-021-01042-8

More information:

doc. Ing. Pavel Jelínek, Ph.D.
Institute of Physics of the Czech Academy of Sciences
Email: jelinekp@fzu.cz

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