Prof.  John G. Rarity

Quantum Photonics

Abstract

The discoveries of Newton revolutionised our understanding of light and his ideas were refined by others (including Young, Huygens, and Maxwell) to form the wave description of light. This description was rocked by the developments of quantum mechanics in the early part of the 20th century and in particular by Einstein’s discovery of the photon. This led on to concepts such as wave-particle duality and entanglement. These counter-intuitive properties even worried the likes of Einstein. Advances in technology now make it routine for us to isolate and detect individual photons, to test their quantum properties and illustrate Einstein’s paradoxes in the laboratory. Key experiments have shown that light can behave like a particle (photon) and a wave within the same experiment. Similarly, photon pair experiments show that the pairs have strongly correlated properties such that any measurement made on one instantaneously sets a value for the other even when they are separated by large distances (this is entanglement).

There comes a point when we have to accept that QM is a good description of nature at the microscopic level despite some bizarre properties. This then begs the question, how can we use these properties to our advantage. This search has led to ways of sending information encoded on single photons, to quantum teleportation schemes and eventually to the quantum computer. We are now trying to build the fundamental gates of such a machine based on single photons encoding bits of information. In this talk I will introduce the concept of the photon and its use to carry information. I will go on to discuss how it can be used for communication and computing and some technologies for creating single photons and photon pairs suitable for use in these schemes.