Tag Archives: Photon

Scientists discover precise form of individual photon

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New research from the University of Birmingham examines the properties of photons (individual particles of light) in more detail than ever before.

Ben Yuen and Angela Demetriadou define the precise shape of a single photon. Image credit: Ben Yuen and Angela Demetriadou.

Professor Angela Demetriadou from the University of Birmingham said: “The geometry and optical properties of the environment have a significant impact on how photons are emitted, including defining their shape, color, and even the likelihood of their existence.” said.

The team's new research shows how photons are emitted by atoms and molecules and how they are shaped by their environment.

The nature of this interaction creates endless possibilities for light to exist and propagate, or travel, through the surrounding environment.

However, this infinite possibility makes modeling interactions extremely difficult, a challenge that quantum physicists have been grappling with for decades.

By grouping these possibilities into distinct sets, the authors explain not only the interaction between the photon and the emitter, but also how the energy from that interaction is transmitted far into the far field. I was able to create a model.

At the same time, they were able to use calculations to visualize the photons themselves.

“Our calculations have enabled us to transform a seemingly unsolvable problem into a computable problem,” said Dr. Benjamin Yuen from the University of Birmingham.

“And almost as a byproduct of the model, we were able to generate this image of a photon that physics had never seen before.”

This research is important because it opens new research avenues for quantum physicists and materials scientists.

Being able to precisely define how photons interact with matter and other elements of its environment allows scientists to discover ways to communicate securely, detect pathogens, control chemical reactions at the molecular level, and more. We can design new nanophotonics technologies that have the potential to change the world.

“This research will help us better understand the energy exchange between light and matter, which in turn will help us better understand how light radiates into nearby and distant environments,” Yuen said. Ta.

“A lot of this information used to be thought of as just noise, but there is so much information in it that we can now understand and use. .”

“By understanding this, we have established a foundation from which we can engineer light-matter interactions for future applications such as better sensors, improved photovoltaic cells, and quantum computing.”

of work Published in a magazine physical review letter.

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Ben Yuen and Angela Demetriadou. 2024. Precise quantum electrodynamics of synchrotron radiation environments. Physics. pastor rhett 133, 203604; doi: 10.1103/PhysRevLett.133.203604

Source: www.sci.news

Physicists develop one-dimensional photon gas

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In an experiment, physicists from the University of Bonn and the University of Kaiserslautern-Landau observed and studied the properties of a one- to two-dimensional crossover in a gas of harmonically confined photons (light particles). The photons were confined in dye microcavities, while polymer nanostructures provided the trapping potential for the photon gas. By varying the aspect ratio of the trap, the researchers tuned it from an isotropic two-dimensional confinement to a highly elongated one-dimensional trapping potential. The team paper Published in a journal Natural Physics.

A polymer applied to the reflective surface confines the photonic gas within the light's parabola. The narrower this parabola is, the more one-dimensional the gas behaves. Image courtesy of University of Bonn.

“To create a gas from photons, you need to concentrate a lot of photons in a limited space and cool them at the same time,” said Dr Frank Wevinger from the University of Bonn.

In their experiments, Dr. Wewinger and his colleagues filled a small container with a dye solution and used a laser to excite it.

The resulting photons bounced back and forth between the reflective walls of the container.

Each time they collided with a dye molecule they cooled, eventually condensing the photon gas.

By modifying the reflective surface, we can affect the gas's dimensions.

“We were able to coat the reflective surface with a transparent polymer and create tiny microscopic protrusions,” said Dr Julian Schulz, a physicist at the University of Kaiserslautern-Landau.

“These protrusions allow us to confine and condense photons into one or two dimensions.”

“These polymers act as a kind of channel for the light,” said Dr Kirankumar Kalkihari Umesh, a physicist at the University of Bonn.

“The narrower this gap becomes, the more one-dimensional the gas behaves.”

In two dimensions, there is a precise temperature limit where condensation occurs, just as water freezes at exactly 0 degrees – physicists call this a phase transition.

“But if you create a one-dimensional gas instead of two-dimensional, things are a bit different,” Dr Wewinger said.

“So-called thermal fluctuations do occur in the photon gas, but in two dimensions they are so small that they have no practical effect.”

“But on one level, these fluctuations can make waves, figuratively speaking.”

These fluctuations destroy the order in a one-dimensional system, causing different regions in the gas to no longer behave in the same way.

As a result, phase transitions that are still precisely defined in two dimensions become increasingly blurred as the system becomes one-dimensional.

However, their properties are still governed by quantum physics, just like for two-dimensional gases, and these types of gases are called degenerate quantum gases.

It's as if water gets cold but doesn't freeze completely, but turns into ice at low temperatures.

“We were able to investigate this behavior for the first time in the transition from a two-dimensional to a one-dimensional photon gas,” Dr. Wewinger said.

The authors were able to demonstrate that a one-dimensional photon gas indeed does not have a precise condensation point.

By making small changes to the polymer structure, it becomes possible to study in detail what happens during the transition between different dimensions.

Although this is still considered fundamental research at this point, it has the potential to open up new applications of quantum optical effects.

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K. Kalkihari Umesh othersDimensional crossover in a quantum gas of light. National Physical SocietyPublished online September 6, 2024; doi: 10.1038/s41567-024-02641-7

Source: www.sci.news

Physicists successfully transfer electron spin to photon

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A team of physicists led by Dr. Yuan Lu of the Jean Lamour Institute at the University of Lorraine used electrical pulses to manipulate magnetic information into polarized signals. This discovery could revolutionize long-distance optical communications, including between Earth and Mars. This breakthrough involves the field of spintronics, which aims to manipulate the spin of electrons to store and process information.

Structure of SOT Spin LED: Control of emission intensity and charging current is the basis of information transfer and processing. In contrast, robust information storage and magnetic random access memory are implemented using carrier spins and their associated magnetizations in ferromagnets. The missing link between the respective fields of photonics, electronics, and spintronics is modulating the circular polarization of emitted light rather than its intensity through electrically controlled magnetization.Dynon other. demonstrated that this missing link is established in light-emitting diodes at room temperature in the absence of an applied magnetic field through the transfer of angular momentum between photons, electrons, and ferromagnets.Image credit: Dynon other., doi: 10.1038/s41586-024-07125-5.

Spintronics has been successfully used in magnetic computer hard drives, where information is represented by the direction of electron spin and its proxy, magnetization.

Ferromagnetic materials such as iron and cobalt have an unequal number of electrons, with their spins oriented either along or against the magnetization axis.

Electrons with spins aligned with the magnetization move smoothly in a ferromagnetic material, while electrons with spins in the opposite direction bounce. This represents binary information of 0’s and 1’s.

The resulting change in resistance is a key principle in spintronic devices, where magnetic states can be maintained indefinitely, which can be considered stored information.

Just as a refrigerator magnet requires no power to stick to a door, spintronic devices require much less power than traditional electronics.

But like pulling a fish out of water, when an electron is removed from a ferromagnetic material, the spin information is quickly lost and can no longer travel far.

This major limitation can be overcome by utilizing circularly polarized light, also known as helicity, as another spin carrier.

Just as humans used homing pigeons centuries ago to carry written communication farther and faster than on foot, the trick is to transfer the spin of an electron to a photo, a quantum of light. That’s probably true.

Such transfer is possible due to the presence of spin-orbit coupling, which causes spin information loss outside the ferromagnetic material.

The key missing link is to electrically modulate the magnetization and thereby change the helicity of the emitted light.

“The concept of spin LEDs was first proposed at the end of the last century,” Dr. Lu said.

“But to move into practical use, it must meet three important criteria: it must operate at room temperature, it does not require a magnetic field, and it must be able to be electrically controlled.”

“After more than 15 years of dedicated work in this field, our collaborative team has managed to overcome all obstacles.”

In their research, Dr. Lu and his colleagues succeeded in switching the magnetization of a spin injector using an electric pulse that uses spin-orbit torque.

The electron spin is rapidly converted into information contained in the helicity of the emitted photon, allowing seamless integration of magnetization dynamics and photonic technology.

This electrically controlled spin-to-photon conversion is currently realized with electroluminescence in light-emitting diodes.

In the future, through implementation in semiconductor laser diodes, so-called spin lasers, this highly efficient information encoding will pave the way for high-speed communication across interplanetary distances, since the polarization of light is preserved in spatial propagation. It is possible and could potentially make it possible. The fastest mode of communication between Earth and Mars.

It also has significant benefits for the development of a variety of advanced technologies on Earth, including photonic quantum communications and optical computing, neuromorphic computing for artificial intelligence, and ultra-fast and highly efficient optical transmitters for data centers and light-fidelity applications. will bring about.

“The realization of spin-orbit torque spin injectors is a decisive step in the development of ultrafast and energy-efficient spin lasers for next-generation optical communications and quantum technologies,” said Professor Nils Gerhardt of Ruhr University. ” he said.

team's work It was published in the magazine Nature.

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PA Dynon other. 2024. Optical helicity control by electromagnetic switching. Nature 627, 783-788; doi: 10.1038/s41586-024-07125-5

Source: www.sci.news