Laser, Offspring and Powerful Enabler of Quantum Science

Article published in Physical Review X Quantum

Abstract

Among all the inventions that quantum physics has produced, the laser holds a particularly important place, both for the rich story of successive discoveries that led to its birth, and for the role it has played in fundamental and applied research. I recall here the lineage of theoretical discoveries and experiments that have marked this history, restricting myself to the contribution of lasers to blue sky science and leaving apart its well-known role in various domains of technology. This story started from advances in the old quantum theory, from Einstein’s theoretical description of stimulated emission to O. Stern’s experimental discovery of the spatial quantization of the electron spin. Nuclear magnetic resonance, atomic clocks, optical pumping, and masers followed and the pace of discoveries accelerated with the appearance of the laser in 1960. This extraordinary light source has since enabled breakthroughs in fundamental physics and opened up fields of research that could not even have been imagined at the time of its birth. I was fortunate to begin my career in physics at this crossroad of atomic physics and optics. I give in this article my personal view of the great adventures in fundamental research in which I participated as an actor or spectator, from the cooling and trapping of atoms by light, to the physics of quantum gases of bosons and fermions, the manipulation of individual quantum particles and quantum simulations. Many other areas of fundamental physics, which I will only mention briefly, owe their development to lasers and further advances are still to be expected in the years to come.

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Featured Image: An optical molasses: a cloud of cold sodium atoms fluoresce at the intersection of three pairs of red-detuned counterpropagating laser beams. The laser beam used for the Zeeman slowing of the atoms is visible above the horizontal molasses beam. (Courtesy of W. Phillips.)

About the author: Serge Haroche works at the Laboratoire Kastler Brossel, École Normale Supérieure and Collège de France, Paris, France. He received the Nobel Prize in Physics in 2012.