currents of energy

Weizmann Institute scientists have proven the existence of neutral particles that carry energy. The meaning: another step on the way to proving the feasibility of a quantum computer

The line between imagination and science is crossed only when ideas are tested and proven in experiments, are therefore raised in rank, and become the accepted scientific concept in their fields. Thus, with the assistance of the scientists of the Weizmann Institute of Science, this border was crossed in the past by "simulated particles". Now Prof. Motti Highblom and his research partners from the Department of Physics of Condensed Matter at the Institute have succeeded, for the first time in the world, in proving the existence of energy currents carried by particles lacking an electric charge. This proof is a significant step in the long journey to the development of quantum computers.

First step: simulated particles

It all started in 1982, when the American physicist Robert Leflin proposed an explanation for a certain phenomenon (the fractional quantum Hall effect). He proposed that, under the conditions of measurement, a kind of structures of electrons are formed in the electric current that function as "simulated particles", each of which carries an electric charge smaller than the "basic" charge of a single electron: a third of the electron's charge, a fifth of it, a seventh of it, and even smaller parts ( The name "simulated particles" should not mislead. In all practical respects, these particles behave like completely real particles). The first proof of the correctness of Leflin's theory was provided by members of the research group of Prof. Motty Highblum from the Department of Condensed Matter Physics at the Weizmann Institute of Science. This proof played an important role in the decision to award Robert Leflin, Horst Sturmer and Daniel Tsoi the 1998 Nobel Prize in Physics (for discovering and finding the explanation for the fractional quantum Hall effect).

Step Two: A New Type of Simulated Particles

The next step in the invasion of virtual particles into our perception of the world took place when experiments in which the fractional quantum Hall effect was examined under purer conditions indicated the possibility of the existence of virtual particles of a completely different type: those whose electric charge would be equal to a quarter of the charge of the electron (that is, the fractional charge is, in this case , has an even denominator - unlike in the simulated particles proposed by Leflin, whose denominator of their fractional charge is odd). Prof. Highblom and the members of his research group also proved the existence of these simulated particles, and were able to measure their electric charge, equal to a quarter of the charge of the electron.

Third step: attraction and rejection

In general, in a system where the quantum Hall effect takes place, electrons are placed in a two-dimensional system (surface), which is under the influence of a strong magnetic field. When electrons flow in this system, each individual electron "aspires" to continue moving straight - but the magnetic field acting on the system bends its path. When the tilt of the magnetic field balances against the repulsive forces of the electrons repelling each other (due to the fact that they all have a negative electric charge), the "new" electrons joining the system will continue to move in a straight line, despite the "attempts" of the magnetic field to tilt their path.

While the simulated particles move in one direction, there are cases where the theory proposed by several scientists included a prediction that other simulated particles, carrying no electric charge, but only energy, would move in the opposite direction. This prediction was made already in the 90s of the last century, but due to the difficulty of measuring such neutral particles, their existence was not proven until the current research carried out by the members of Prof. Highblom's research group.

Step four: measure noise

To measure and prove the existence of the neutral simulated particles, the energy carriers, the scientists built a unique experimental system in which they placed a semi-permeable quantum barrier in the path of these particles. The neutral particles that collided with the barrier were shattered and received positive and negative electric charges (in a random distribution). This creates a non-uniform current. The irregular motion created electrical noise (no mean electrical current). This electrical noise is measured using extremely sensitive measuring devices. This is how the scientists were able to prove the existence of the simulated neutral particles, the energy carriers.

The discovery of these unique particles provided new information about the quantum state of the system, and in fact opened a new field of research that focuses on the flow of energy currents. For example, the existence of energy currents in a system where the fractional quantum Hall effect takes place, where simulated particles with a charge equal to a quarter of the electron's charge are created, may indicate that the system is in a non-Abelian quantum state (see box), which means that such a system may serve as a quantum bit , on which quantum computers could be based.

This calculation possibility arises from the fact that in such a system a new phenomenon takes place: exchanging the positions of two simulated particles moves the entire system to a different quantum state. The ability to create such a fundamental difference in the system is what may allow this system to function as a quantum bit, which may serve as a basis for the development of a quantum computer.

A sad bunch

Nils Henry Abel was born in 1803 in Norway, as the son of a poor priest. He did not receive the recognition he deserved in his lifetime, and only after his death from tuberculosis at the age of 26 did he become famous, among other things, for defining a type of bruise that bears his name ("mourning bruises"). A mourning group maintains a symmetric exchange between the multiplication arrays of its members. That is: the result that will be obtained from multiplying AZ by AZ is equal to the result obtained when multiplying AZ by AZ.