First observation of the phenomenon of Cherenkov radiation in two-dimensional space

A single free electron spreads over the special layered structure the researchers designed, a few tens of nanometers above it, and as it moves, the electron emits discrete beams of radiation called “photons.” Between the electron and the photons it emits, a “quantum entanglement” link is formed. Credit: Ella Maru Studio

Researchers from the Andrew and Erna Viterbi School of Electrical and Computer Engineering at the Technion – Israel Institute of Technology made the first experimental observation of Cherenkov radiation confined to two dimensions. The results represent a new record in the coupling strength of electron radiation, revealing the quantum properties of radiation.

Cherenkov radiation is a unique physical phenomenon, which has been used for many years in medical imaging and particle detection applications, as well as in laser-powered electron accelerators. The breakthrough by the Technion researchers links this phenomenon to future photonic quantum computing applications and free-electron quantum light sources.

The study published in X physical review, headed by Dr. Students Yuval Adiv and Shai Tsis of the Technion, with Hao Ho of Nanyang Technological University in Singapore (today a professor at Nanjing University in China). It was supervised by Prof. Edu Kamener and Prof. Guy Bartal of the Technion, in collaboration with colleagues from China: Prof. Hongsheng Chen and Prof. Xiaolin from Zhejiang University.

The interaction of free electrons with light forms the basis of many known radiation phenomena and has led to many applications in science and industry. One of the most important of these interaction effects is Cherenkov radiation — the electromagnetic radiation emitted when a charged particle, such as an electron, travels through a medium at a speed greater than the phase velocity of light in that particular medium. It is the optical equivalent of supersonic thrust, which occurs when, say, an aircraft is moving faster than the speed of sound. Hence, Cherenkov radiation is sometimes called an “optical shock wave”. This phenomenon was discovered in 1934. And in 1958 the scientists who discovered it were awarded the Nobel Prize in Physics.

Since then, through more than 80 years of research, the investigation of Cherenkov radiation has led to the development of a wide range of applications, mostly for particle detectors and medical imaging. However, despite the intense preoccupation with the phenomenon, the bulk of the theoretical research and all experimental demonstrations concerned Cherenkov radiation in three-dimensional space and based its description on classical electromagnetism.

Now, Technion researchers have provided the first experimental observation of two-dimensional Cherenkov radiation, showing that in two-dimensional space, radiation behaves in a completely different way — and for the first time, a quantum description of light is necessary to explain the results of the experiment.

The researchers designed a special layered structure that allows interaction between free electrons and light waves traveling along the surface. The clever engineering of the structure allowed the first measurement of two-dimensional Cherenkov radiation. The effect’s low dimensions allowed insight into the quantum nature of the process of radiation emission from free electrons: the number of photons (quantum particles of light) emitted by a single electron and indirect evidence of the entanglement of electrons with the light waves they emit.

In this context, ‘entanglement’ means the correlation between the properties of an electron and the properties of the emitted light, such that a measurement of one provides information about the other. It is worth noting that the 2022 Nobel Prize in Physics was awarded for performing a series of experiments demonstrating the effects of quantum entanglement (in systems different from those shown in the current research).

“The result of the study that surprised us the most is related to the efficiency of electron radiation emission in the experiment,” says Yuval Adiv: “While the most advanced experiments that preceded the current experiment achieved a system in which almost one electron out of a hundred radiation emission, here, we succeeded in achieving a reaction system in which every In other words, we were able to show an improvement of more than two orders of magnitude in the reaction efficiency (also called coupling strength). This result helps advance the recent developments of effective electron-driven radiation sources.”

Professor Kaminer says, “The radiation emitted by electrons is an ancient phenomenon that has been researched for over 100 years and was absorbed into technology a long time ago, for example the household microwave oven. For many years, it seemed that we had already discovered all there was to know about radiation Thus, the idea that this type of radiation has been fully described by classical physics has become firmly established.In stark contrast to this concept, the experimental apparatus we have created allows the quantum nature of electronic radiation to be revealed.

“The new experiment, now published, explores the photonic quantum nature of electron radiation. The experiment is part of a paradigm shift in the way we understand this radiation and, more broadly, the relationship between electrons and the radiation they emit. For example, we now understand that free electrons can entangle with the photons it emits. It is surprising and exciting to see signs of this phenomenon in the experiment.”

Shai Tsis says: “In Yuval Adif’s new experiment we forced electrons to travel near a photonic plasmonic surface that I planned based on a technique developed in the laboratory of Professor Jay Bartal. The electron speed was finely tuned to obtain a large coupling strength, greater than that obtained “In ordinary situations, coupling to radiation is three-dimensional. At the heart of the process, we observe the spontaneous quantum nature of radiation emissions, which are captured in discrete bundles of energy called photons. In this new way, the experiment sheds new light on the quantum nature of photons.”

more information:
Yuval Adiv et al., Observing 2D Cherenkov radiation, X physical review (2023). DOI: 10.1103/PhysRevX.13.011002

Provided by the Technion – Israel Institute of Technology

the quote: The first observation of the phenomenon of Cherenkov radiation in 2D space (2023, January 18) retrieved on January 18, 2023 from

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