000232441 001__ 232441
000232441 005__ 20190509132620.0
000232441 0247_ $$2doi$$a10.5075/epfl-thesis-8134
000232441 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis8134-7
000232441 02471 $$2nebis$$a11072436
000232441 037__ $$aTHESIS
000232441 041__ $$aeng
000232441 088__ $$a8134
000232441 245__ $$aQuantum optomechanics at room temperature
000232441 260__ $$bEPFL$$c2017$$aLausanne
000232441 269__ $$a2017
000232441 300__ $$a175
000232441 336__ $$aTheses
000232441 502__ $$aProf. Romuald Houdré (président) ; Prof. Tobias Kippenberg (directeur de thèse) ; Prof. Vincenzo Savona, Prof. Lukas Novotny, Prof. Pierre Verlot (rapporteurs)
000232441 520__ $$aWhy are classical theories often sufficient to describe the physics of our world even though everything around us is entirely composed of microscopic quantum systems? The boundary between these two fundamentally dissimilar theories remains an unsolved problem in modern physics. Position measurements of small objects allow us to probe the area where the classical approximation breaks down. In quantum mechanics, Heisenberg’s uncertainty principle dictates that any measurement of the position must be accompanied by measurement induced back-action---in this case manifested as an uncertainty in the momentum.  In recent years, cavity optomechanics has become a powerful tool to perform precise position measurements and investigate their fundamental limitations. The utilization of optical micro-cavities greatly enhances the interaction between light and state-of-the-art nanomechanical oscillators. Therefore, quantum mechanical phenomena have been successfully observed in systems far beyond the microscopic world. In such a cavity optomechanical system, the fluctuations in the position of the oscillator are transduced onto the phase of the light, while fluctuations in the amplitude of the light disturb the momentum of the oscillator during the measurement. As a consequence, correlations are established between the amplitude and phase quadrature of the probe light.  However, so far, observation of quantum effects has been limited exclusively to cryogenic experiments, and access to the quantum regime at room temperature has remained an elusive goal because the overwhelming amount of thermal motion masks the weak quantum effects. This thesis describes the engineering of a high-performance cavity optomechanical device and presents experimental results showing, for the first time, the broadband effects of quantum back-action at room temperature. The device strongly couples mechanical and optical modes of exceptionally high quality factors to provide a measurement sensitivity $\sim\!10^4$ times below the requirement to resolve the zero-point fluctuations of the mechanical oscillator. The quantum back-action is then observed through the correlations created between the probe light and the motion of the nanomechanical oscillator. A so-called “variational measurement”, which detects the transmitted light in a homodyne detector tuned close to the amplitude quadrature, resolves the quantum noise due to these correlations at the level of 10\% of the thermal noise over more than an octave of Fourier frequencies around mechanical resonance. Moreover, building on this result, an additional experiment demonstrates the ability to achieve quantum enhanced metrology. In this case, the generated quantum correlations are used to cancel quantum noise in the measurement record, which then leads to an improved relative signal-to-noise ratio in measurements of an external force. In conclusion, the successful observation of broadband quantum behavior on a macroscopic object at room temperature is an important milestone in the field of cavity optomechanics. Specifically, this result heralds the rise of optomechanical systems as a platform for quantum physics at room temperature and shows promise for generation of ponderomotive squeezing in room-temperature interferometers.
000232441 6531_ $$aquantum measurement
000232441 6531_ $$aroom temperature cavity optomechanics
000232441 6531_ $$ameasurement back-action
000232441 6531_ $$aquantum correlations
000232441 700__ $$0246956$$g230194$$aSchütz, Hendrik
000232441 720_2 $$aKippenberg, Tobias$$edir.$$g182444$$0244694
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000232441 920__ $$b2017$$a2017-11-24
000232441 970__ $$a8134/THESES
000232441 973__ $$sPUBLISHED$$aEPFL
000232441 980__ $$aTHESIS