From waves to quantum light

The lecture takes place in Uppsala, Ångström laboratory, 20th of May 17h30

Lecturer: Dr. Vitaliy Goryashko

Waves are our main tool to interact with the outside world. We hear sound waves, our ear is a delicate device that decomposes sound into different frequencies. By interpreting them, we enjoy music. Other animals use echolocation to determine their position. We see with our eyes a visible part of the electromagnetic wave spectrum. The human eye can distinguish three different colours, some birds can distinguish four, and mantis shrimp can distinguish twelve. Outside of the visible range, we have both high-energetic waves coming for instance from distant pulsars, and low-energetic waves used in microwave ovens and mobile phones. There are also waves of very low energy that travelled 13.6 billion years to reach the Earth and they tell us secrets of the Universe how it was shortly after the Big Bang. People even recently confirmed experimentally the existence of gravitational waves: waves due to fluctuations of space-time geometry.

When we consider waves of very low intensity, we discover that they should be more properly described as a collection of massless particles - photons. This is explained in the particle-wave duality of quantum mechanics. Humanity learned how to operate with single photons, and this becomes a basis for the technology of the nearest future.