Photon
Definition:
A photon is the quantum of electromagnetic radiation, the smallest possible amount of light energy that can be emitted, transmitted, or absorbed at a given wavelength. It is a massless, neutral particle that travels at the speed of light in a vacuum.
Scientific context:
Photons are fundamental particles in the Standard Model of particle physics and the force carriers of the electromagnetic interaction. They exhibit both particle-like and wave-like behaviour, a feature known as wave-particle duality. The energy of a photon is proportional to its frequency, given by the relation:
E=hν
where E is energy, h is Planck’s constant, and ν is the frequency.
In quantum technologies, photons play a central role:
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In quantum communication, they are used to encode and transmit quantum bits (qubits).
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In quantum optics, single-photon sources and detectors are essential tools for experiments and protocols like QKD, quantum teleportation, and entanglement distribution.
Example in practice:
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In Quantum Key Distribution, single photons are used to securely transmit encryption keys.
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In laser systems, photons are generated in coherent states, where many photons share the same frequency and phase.
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In quantum imaging, photon-level sensitivity enables detection beyond classical resolution limits.
Did you know?
Although photons are massless, they carry momentum and can exert measurable pressure, known as radiation pressure, which has practical applications in areas like solar sails and optical tweezers.
