A single-photon source you can make with household bleach

Quantum computing and quantum cryptography are expected to give much higher capabilities than their classical counterparts. For example, the computation power in a quantum system may grow at a double exponential rate instead ...

Evidence found for cloaked black hole in early universe

A group of astronomers, including Penn State scientists, has announced the likely discovery of a highly obscured black hole existing only 850 million years after the Big Bang, using NASA's Chandra X-ray Observatory. This ...

Heterostructure crystals could light the way to optical circuits

It may be possible to reach new levels of miniaturization, speed, and data processing with optical quantum computers, which use light to carry information. For this, we need materials that can absorb and transmit photons. ...

The mechanism for gamma-ray bursts from space is decoded

Gamma-ray bursts, short and intense flashes of energetic radiation coming from outer space, are the brightest explosions in the universe. As gamma rays are blocked by the atmosphere, the bursts were discovered accidentally ...

Quantum photonics by serendipity

A photonic chip with no less than 128 tunable components proves to be a true computing "Swiss army knife" with a variety of applications. During her research on measuring light wavelengths using this photonic chip, Caterina ...

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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.

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