Denis Bernard - Real Time Imaging of Quantum and Thermal Fluctuations
Channel: Institut des Hautes Études Scientifiques (IHÉS)
Date: 2013-11-15

Denis Bernard (LPT, ENS-Paris)
Real Time Imaging of Quantum and Thermal Fluctuations
Tremendous progresses have been achieved in the last decade in realising and
manipulating stable and controllable quantum systems, and these made possible to
experimentally study fundamental questions posed in the early days of quantum
mechanics. We shall theoretical discuss recent cavity QED experiments on non-
demolition quantum measurements. While they nicely illustrate postulates of quantum
mechanics and the possibility to implement efficient quantum state manipulations, these
experiments pose a few questions such as: What does it mean to observe a progressive
wave function collapse in real time? How to describe it? What do we learn from them?
Their analysis will allow us one hand to link these experiments to basics notions of
probability or information theory, and on the other hand to touch upon notions of
quantum noise.
As an illustration, we shall look at quantum systems in contact with a heat bath subject to
quantum transitions between energy levels upon absorption or emission of energy quanta.
Isolating the two indispensable mechanisms in competition, we shall describe the main
physical features of thermally activated quantum jumps.