Related topics: quantum computing · quantum state

Real-time imaging for use in medicine

A new paper in Nature Photonics from researchers at CU Boulder details impressive improvements in the ability to control the propagation and interaction of light in complex media such as tissue—an area with many potential ...

New topological insulator reroutes photonic 'traffic' on the fly

Topological insulators are a game-changing class of materials; charged particles can flow freely on their edges and route themselves around defects, but can't pass through their interiors. This perfect surface conduction ...

Chameleon inspires 'smart skin' that changes color in the sun

A chameleon can alter the color of its skin so it either blends into the background to hide or stands out to defend its territory and attract a mate. The chameleon makes this trick look easy, using photonic crystals in its ...

Using correlated photons to enhance x-ray imaging

A team of researchers at Bar-Ilan University has found a way to use correlated photons to make sharper X-ray images. In their paper published in the journal Physical Review Letters, the group describes their process and suggest ...

Entanglement sent over 50 km of optical fiber

The quantum internet promises absolutely tap-proof communication and powerful distributed sensor networks for new science and technology. However, because quantum information cannot be copied, it is not possible to send this ...

page 1 from 23

Photon

In physics, a photon is an elementary particle, the quantum of the electromagnetic field and the basic "unit" of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force. The effects of this force are easily observable at both the microscopic and macroscopic level, because the photon has no rest mass; this allows for interactions at long distances. Like all elementary particles, photons are governed by quantum mechanics and will exhibit wave-particle duality – they exhibit properties of both waves and particles. For example, a single photon may be refracted by a lens or exhibit wave interference, but also act as a particle giving a definite result when its location is measured.

The modern concept of the photon was developed gradually by Albert Einstein to explain experimental observations that did not fit the classical wave model of light. In particular, the photon model accounted for the frequency dependence of light's energy, and explained the ability of matter and radiation to be in thermal equilibrium. It also accounted for anomalous observations, including the properties of black body radiation, that other physicists, most notably Max Planck, had sought to explain using semiclassical models, in which light is still described by Maxwell's equations, but the material objects that emit and absorb light are quantized. Although these semiclassical models contributed to the development of quantum mechanics, further experiments proved Einstein's hypothesis that light itself is quantized; the quanta of light are photons.

In the modern Standard Model of particle physics, photons are described as a necessary consequence of physical laws having a certain symmetry at every point in spacetime. The intrinsic properties of photons, such as charge, mass and spin, are determined by the properties of this gauge symmetry.

The photon concept has led to momentous advances in experimental and theoretical physics, such as lasers, Bose–Einstein condensation, quantum field theory, and the probabilistic interpretation of quantum mechanics. It has been applied to photochemistry, high-resolution microscopy, and measurements of molecular distances. Recently, photons have been studied as elements of quantum computers and for sophisticated applications in optical communication such as quantum cryptography.

This text uses material from Wikipedia, licensed under CC BY-SA