The Les Houches Summer School in August 2015 covered the emerging fields of cavity optomechanics and quantum nanomechanics. Optomechanics is flourishing and its concepts and techniques are now applied to a wide range of topics. Modern quantum optomechanics was born in the late 1970s in the framework of gravitational wave interferometry, with an initial focus on the quantum limits of displacement measurements.

Carlton Caves, Vladimir Braginsky, and others realized that the sensitivity of the anticipated large-scale gravitational-wave interferometers (GWI) was fundamentally limited by the quantum fluctuations of the measurement laser beam. After tremendous experimental progress, the sensitivity of the upcoming next generation of GWI will effectively be limited by quantum noise. In this way, quantum-optomechanical effects will directly affect the operation of what is arguably the world's most impressive precision experiment. However, optomechanics has also gained a life of its own with a focus on the quantum aspects of moving mirrors. Laser light can be used to cool mechanical resonators well below the temperature of its environment. After proof-of-principle demonstrations of this cooling in 2006, a number of systems were used as the field gradually merged with its condensed matter cousin (nanomechanical systems) to try to reach the mechanical quantum ground state, eventually demonstrated in
2010 by pure cryogenic techniques and just one year later by a combination of cryogenic and radiation-pressure cooling.

The book covers all aspects -- historical, theoretical, experimental -- of the field, with its applications to quantum measurement, foundations of quantum mechanics and quantum information. It is an essential read for any new researcher in the field.

About the Author:
Pierre-Francois Cohadon, Associate Professor of Physics, Ecole Normale Superieure, Paris, France, Jack Harris, Professor of Physics, Yale University, New Haven, USA, Florian Marquardt, Director and Head of Theory Division, Max Planck Institute for the Science of Light, Erlangen, Germany, Leticia Cugliandolo, Professor of Physics, Sorbonne Universite, Paris, France

Pierre-Francois Cohadon's current research activity is split in two distinct areas. He works on optomechanics experiments at LKB on micro- or nanomechanical systems, which aim to demonstrate quantum properties of both light (under the effect of the motion of a movable mirror) and of a mechanical resonator (under the effect of radiation pressure of a laser beam). He also works in the Virgo Collaboration on the expected radiation-pressure effects in the gravitational interferometer Advanced Virgo, as well as on the sensitivity gain achieved using squeezed light. Despite orders of magnitude between the characteristics of the different systems under study, both activities are surprisingly related.

Jack Harris studies the quantum aspects of motion in macroscopic objects that combine mechanical, optical, and fluid components. His experiments use ultrasensitive force detectors to measure quantum fluctuations of objects that are visible to the naked eye, to reveal the counterintuitive behavior of apparently simple systems. These experiments are also used to study novel topological features in the dynamics of coupled oscillators.

Florian Marquardt applies tools from condensed matter theory and from quantum optics to a range of questions at the interface of nanophysics and quantum optics, addressing both quantum and classical dynamics, paying particular attention to the direct contact with experiments, down to designing the classical electromagnetic and acoustic properties of specific structures. His current interests include cavity optomechanics and nanomechanics, quantum information processing, quantum many body physics, and machine learning for physics.

Leticia Cugliandolo is Professor at Pierre and Marie Curie University, where she works on statistical physics and field theory with applications to soft and hard condensed matter. She has written more than 130 scientific papers, and has been a coeditor of the Les Houches book series since 2007, when she assumed the directorship of the Les Houches Summer School of Physics.