1,077 research outputs found

    Minimum requirements for feedback enhanced force sensing

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    The problem of estimating an unknown force driving a linear oscillator is revisited. When using linear measurement, feedback is often cited as a mechanism to enhance bandwidth or sensitivity. We show that as long as the oscillator dynamics are known, there exists a real-time estimation strategy that reproduces the same measurement record as any arbitrary feedback protocol. Consequently some form of nonlinearity is required to gain any advantage beyond estimation alone. This result holds true in both quantum and classical systems, with non-stationary forces and feedback, and in the general case of non-Gaussian and correlated noise. Recently, feedback enhanced incoherent force sensing has been demonstrated [Nat. Nano. \textbf{7}, 509 (2012)], with the enhancement attributed to a feedback induced modification of the mechanical susceptibility. As a proof-of-principle we experimentally reproduce this result through straightforward filtering.Comment: 5 pages + 2 pages of Supplementary Informatio

    Carbon nanotubes adhesion and nanomechanical behavior from peeling force spectroscopy

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    Applications based on Single Walled Carbon Nanotube (SWNT) are good example of the great need to continuously develop metrology methods in the field of nanotechnology. Contact and interface properties are key parameters that determine the efficiency of SWNT functionalized nanomaterials and nanodevices. In this work we have taken advantage of a good control of the SWNT growth processes at an atomic force microscope (AFM) tip apex and the use of a low noise (1E-13 m/rtHz) AFM to investigate the mechanical behavior of a SWNT touching a surface. By simultaneously recording static and dynamic properties of SWNT, we show that the contact corresponds to a peeling geometry, and extract quantities such as adhesion energy per unit length, curvature and bending rigidity of the nanotube. A complete picture of the local shape of the SWNT and its mechanical behavior is provided

    Optomechanics with an electrodynamically levitated oscillator

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    In this work I report on a hybrid trap platform for sensitive optomechanics experiments with applications in quantum physics, thermodynamics and material science. We characterise a miniature linear Paul trap which can be used in combination with an optical cavity. The low-frequency harmonic motion of a nanoparticle levitated in a Paul trap can be detected with competitive sensitivities using a super-resolution imaging technique. This same method can be applied to characterise trap stability and nanosphere parameters such as mass with a 3% uncertainty. Using this same method at room temperature and at pressure of 3×10⁻⁷ mbar, we were able to measure an ultra-narrow mechanical linewidth of ∌80 ”Hz with a novel phase sensitive scheme which removes slow drifts in the mechanical frequency. We used this measurement to place new bounds on dissipative versions of wavefunction collapse models. Using two optical cavity modes with different frequencies interacting with a nanoparticle levitated within a Paul trap realises a versatile optomechanical system, which can be operated in regimes dominated by either linear or quadratic optomechanical coupling. We demonstrated cooling of the centre-of-mass motion of the nano-oscillator exclusively provided by the quadratic coupling. This nonlinear interaction gives rise to a highly non-thermal state of motion which matches well with theoretical predictions. In the linear regime, we report cooling down to Teff=21±4 mK limited by Paul trap noise, demonstrating stable trapping in the cavity standing-wave down to pressures ∌10⁻⁶ mbar. Using the same technique, we show that in theory, near ground state cooling could be achieved with better electronics used in conjunction with the filtering cavity developed as part of this work

    Mesoscopic Quantum Thermo-mechanics: a new frontier of experimental physics

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    Within the last decade, experimentalists have demonstrated their impressive ability to control mechanical modes within mesoscopic objects down to the quantum level: it is now possible to create mechanical Fock states, to entangle mechanical modes from distinct objects, store quantum information or transfer it from one quantum bit to another, among the many possibilities found in today's literature. Indeed mechanics is quantum, very much like spins or electromagnetic degrees of freedom. And all of this is in particular referred to as a new engineering resource for quantum technologies. But there is also much more beyond this utilitarian aspect: invoking the original discussions of Braginsky and Caves where a quantum oscillator is thought of as a quantum detector for a classical field, namely a gravitational wave, it is also a unique sensing capability for quantum fields. The subject of study is then the baths to which the mechanical mode is coupled to, let them be known or unknown in nature. This Letter is about this new potentiality, that addresses stochastic thermodynamics, potentially down to its quantum version, the search for a fundamental underlying (random) field postulated in recent theories that can be affiliated to the class of the Wave-function Collapse models, and more generally open questions of Condensed Matter like the actual nature of the elusive (and ubiquitous) Two-Level Systems present within all mechanical objects. But such research turns out to be much more demanding than the usage of a few quantum mechanical modes: all the known baths have to be identified, experiments have to be conducted in-equilibrium, and the word "mechanics" needs to be justified by a real ability to move substantially the centre-of-mass when a proper drive tone is applied to the system

    A Low-Noise Electrically Levitated Oscillator for Investigating Fundamental Physics

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    This thesis describes the creation of a low-noise, electrodynamically levitated nanoparticle oscillator for applications in optomechanics and quantum physics. The harmonic motion of a nanoparticle trapped in a linear Paul trap was measured and characterized. Velocity damping and parametric feedback cooling methods were implemented to cool the centre-of-mass motion of an oscillator. Experiments were conducted on the same particle so that a direct comparison between both methods could be done. Theory and simulations were developed to fully understand these processes. It was shown that velocity damping achieves lower temperatures due to the greater backaction from measurement noise in the parametric feedback scheme. A minimum temperature of 26±626\pm6\,mK was reached in these experiments limited only by detection noise. Low-noise electronics, designed to prevent motional heating of the levitated nanoparticle due to fluctuations in the confining electric fields, were studied. At low pressures down to 3×10⁻⁷ mbar, where minimal thermal noise is present from gas collisions, no heating effect from voltage fluctuations was observed in two of the oscillator modes. This work demonstrated the utility of this trap for future low-noise experiments including investigations into wave function collapse with preliminary results presented here. The cooling and dynamics of two co-trapped nanoparticles strongly coupled by their mutual Coulomb repulsion was also studied. The normal modes in both the axial and radial motion of the trapped nanoparticle were measured and characterized. Sympathetic cooling and squeezing of one particle were achieved through interaction with the other trapped nanoparticle. Temperatures down to 200±10 mK and 190±40 mK were reached in the axial normal modes. Additionally, a measurement-based scheme was used to couple the axial normal modes which were shown to display the characteristics of strong coupling. Energy exchange between the two modes was demonstrated alongside sympathetic cooling of one mode through this coupling

    Quantum Communication, Sensing and Measurement in Space

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    The main theme of the conclusions drawn for classical communication systems operating at optical or higher frequencies is that there is a well‐understood performance gain in photon efficiency (bits/photon) and spectral efficiency (bits/s/Hz) by pursuing coherent‐state transmitters (classical ideal laser light) coupled with novel quantum receiver systems operating near the Holevo limit (e.g., joint detection receivers). However, recent research indicates that these receivers will require nonlinear and nonclassical optical processes and components at the receiver. Consequently, the implementation complexity of Holevo‐capacityapproaching receivers is not yet fully ascertained. Nonetheless, because the potential gain is significant (e.g., the projected photon efficiency and data rate of MIT Lincoln Laboratory's Lunar Lasercom Demonstration (LLCD) could be achieved with a factor‐of‐20 reduction in the modulation bandwidth requirement), focused research activities on ground‐receiver architectures that approach the Holevo limit in space‐communication links would be beneficial. The potential gains resulting from quantum‐enhanced sensing systems in space applications have not been laid out as concretely as some of the other areas addressed in our study. In particular, while the study period has produced several interesting high‐risk and high‐payoff avenues of research, more detailed seedlinglevel investigations are required to fully delineate the potential return relative to the state‐of‐the‐art. Two prominent examples are (1) improvements to pointing, acquisition and tracking systems (e.g., for optical communication systems) by way of quantum measurements, and (2) possible weak‐valued measurement techniques to attain high‐accuracy sensing systems for in situ or remote‐sensing instruments. While these concepts are technically sound and have very promising bench‐top demonstrations in a lab environment, they are not mature enough to realistically evaluate their performance in a space‐based application. Therefore, it is recommended that future work follow small focused efforts towards incorporating practical constraints imposed by a space environment. The space platform has been well recognized as a nearly ideal environment for some of the most precise tests of fundamental physics, and the ensuing potential of scientific advances enabled by quantum technologies is evident in our report. For example, an exciting concept that has emerged for gravity‐wave detection is that the intermediate frequency band spanning 0.01 to 10 Hz—which is inaccessible from the ground—could be accessed at unprecedented sensitivity with a space‐based interferometer that uses shorter arms relative to state‐of‐the‐art to keep the diffraction losses low, and employs frequency‐dependent squeezed light to surpass the standard quantum limit sensitivity. This offers the potential to open up a new window into the universe, revealing the behavior of compact astrophysical objects and pulsars. As another set of examples, research accomplishments in the atomic and optics fields in recent years have ushered in a number of novel clocks and sensors that can achieve unprecedented measurement precisions. These emerging technologies promise new possibilities in fundamental physics, examples of which are tests of relativistic gravity theory, universality of free fall, frame‐dragging precession, the gravitational inverse‐square law at micron scale, and new ways of gravitational wave detection with atomic inertial sensors. While the relevant technologies and their discovery potentials have been well demonstrated on the ground, there exists a large gap to space‐based systems. To bridge this gap and to advance fundamental‐physics exploration in space, focused investments that further mature promising technologies, such as space‐based atomic clocks and quantum sensors based on atom‐wave interferometers, are recommended. Bringing a group of experts from diverse technical backgrounds together in a productive interactive environment spurred some unanticipated innovative concepts. One promising concept is the possibility of utilizing a space‐based interferometer as a frequency reference for terrestrial precision measurements. Space‐based gravitational wave detectors depend on extraordinarily low noise in the separation between spacecraft, resulting in an ultra‐stable frequency reference that is several orders of magnitude better than the state of the art of frequency references using terrestrial technology. The next steps in developing this promising new concept are simulations and measurement of atmospheric effects that may limit performance due to non‐reciprocal phase fluctuations. In summary, this report covers a broad spectrum of possible new opportunities in space science, as well as enhancements in the performance of communication and sensing technologies, based on observing, manipulating and exploiting the quantum‐mechanical nature of our universe. In our study we identified a range of exciting new opportunities to capture the revolutionary capabilities resulting from quantum enhancements. We believe that pursuing these opportunities has the potential to positively impact the NASA mission in both the near term and in the long term. In this report we lay out the research and development paths that we believe are necessary to realize these opportunities and capitalize on the gains quantum technologies can offer

    Light matter interaction in mesoscopic systems

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    The study of light-matter interaction has led to many fundamental discoveries as well as to the development of new technology. In this thesis, we investigate the interaction between light and matter in different mesoscopic systems such us Fabry-Perot cavities with fixed and/or moving mirrors (optomechanical cavities) and superconducting circuits. In the context of optomechanical cavities, we isolate genuine quantum contributions of the interaction between an optical field and a mechanical mirror and study how to probe nonlinearities of the mechanical motion. We also investigate dynamical corrections, arising from an initial non-equilibrium configuration of the system, to the Casimir energy induced by the interaction between a quantum multimode field and the quantum fluctuations of the movable mirror. In a cavity scenario, we further consider such kind of dynamical corrections for the Casimir-Polder force between an excited atom and a perfectly conducting mirror, finding new features that can allow for an easier way to single-out the dynamical Casimir-Polder effect. In the context of superconducting circuits, we explore the light-matter interaction between microwave fields and artificial atoms in the ultrastrong coupling regime, where the system displays a high degree of entanglement. We show how to extract these (otherwise inaccessible) quantum correlations, and how such correlations can potentially be exploited as a resource for entanglement-based applications. In all these investigations we provide feasible experimental scenarios where such new effects can be probed.Open Acces
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