yksittäisfotoni
Yksittäisfotoni refers to a single quantum of electromagnetic radiation, essentially the smallest possible packet of light or any other electromagnetic wave. The concept of the photon was first introduced by Albert Einstein in 1905 to explain the photoelectric effect, where light shining on a metal surface can eject electrons. He proposed that light energy is not continuous but is instead quantized into discrete packets, which he called "quanta."
Later, the term "photon" was coined by Gilbert N. Lewis. Photons exhibit dual properties, behaving as both
Detecting a single photon is a challenging but achievable feat in quantum optics and experimental physics.