quantum optics
Quantum optics is a branch of physics that studies the interaction of light and matter in a regime where quantum effects become decisive. Unlike classical optics, where light is described by electromagnetic waves, here it is considered as a stream of photons. Experiments achieve control at the level of single quanta, demonstrating phenomena such as photon antibunching (photons avoid arriving in pairs) and squeezed light (suppressed quantum noise in one of the characteristics). In practice, this leads to quantum cryptography and high-precision interferometers.
History
It all began with the invention of the laser in 1960 by Charles Townes and his colleagues. The laser provided a pure stream of identical photons, which made it possible to conduct experiments with single particles. Later, Alain Aspect in the 1980s demonstrated the reality of quantum entanglement of photons.
How it works
Imagine shooting single photon bullets from a light gun. Upon hitting a special crystal, one bullet sometimes splits into two smaller entangled ones. If you send one to a friend and keep the other, then by measuring yours, you instantly know what your friend received — even without a phone call. This is how quantum communication works.
💡 There exists light 'quieter' than absolute darkness — squeezed vacuum, in which quantum fluctuations of the field can be smaller than in empty space.