437 research outputs found
Control of Recoil Losses in Nanomechanical SiN Membrane Resonators
In the context of a recoil damping analysis, we have designed and produced a
membrane resonator equipped with a specific on-chip structure working as a
"loss shield" for a circular membrane. In this device the vibrations of the
membrane, with a quality factor of , reach the limit set by the intrinsic
dissipation in silicon nitride, for all the modes and regardless of the modal
shape, also at low frequency. Guided by our theoretical model of the loss
shield, we describe the design rationale of the device, which can be used as
effective replacement of commercial membrane resonators in advanced
optomechanical setups, also at cryogenic temperatures
Perspectivas para o uso de fungos entomopatogênicos no controle microbiano das pragas do coqueiro.
O controle de insetos-pragas por meio de agentes biológicos como os fungos entomopatogênicos e uma opção desejável para evitar aplicações químicas e aumentar a proteção ambiental.bitstream/item/68752/1/CPATC-CIR.-TEC.-26-01.pd
Calibrated quantum thermometry in cavity optomechanics
Cavity optomechanics has achieved the major breakthrough of the preparation
and observation of macroscopic mechanical oscillators in peculiarly quantum
states. The development of reliable indicators of the oscillator properties in
these conditions is important also for applications to quantum technologies. We
compare two procedures to infer the oscillator occupation number, minimizing
the necessity of system calibrations. The former starts from homodyne spectra,
the latter is based on the measurement of the motional sidebands asymmetry in
heterodyne spectra. Moreover, we describe and discuss a method to control the
cavity detuning, that is a crucial parameter for the accuracy of the latter,
intrinsically superior procedure
Optical self-cooling of a membrane oscillator in a cavity optomechanical experiment at room temperature
Thermal noise is a major obstacle to observing quantum behavior in
macroscopic systems. To mitigate its effect, quantum optomechanical experiments
are typically performed in a cryogenic environment. However, this condition
represents a considerable complication in the transition from fundamental
research to quantum technology applications. It is therefore interesting to
explore the possibility of achieving the quantum regime in room temperature
experiments. In this work we test the limits of sideband cooling vibration
modes of a SiN membrane in a cavity optomechanical experiment. We obtain an
effective temperature of a few mK, corresponding to a phononic occupation
number of around 100. We show that further cooling is prevented by the excess
classical noise of our laser source, and we outline the road toward the
achievement of ground state coolin
Control of Recoil Losses in Nanomechanical SiN Membrane Resonators
In the context of a recoil damping analysis, we have designed and produced a membrane resonator equipped with a specific on-chip structure working as a "loss shield" for a circular membrane. In this device the vibrations of the membrane, with a quality factor of , reach the limit set by the intrinsic dissipation in silicon nitride, for all the modes and regardless of the modal shape, also at low frequency. Guided by our theoretical model of the loss shield, we describe the design rationale of the device, which can be used as effective replacement of commercial membrane resonators in advanced optomechanical setups, also at cryogenic temperatures
Quantum signature of a squeezed mechanical oscillator
Some predictions of quantum mechanics are in contrast with the macroscopic
realm of everyday experience, in particular those originated by the Heisenberg
uncertainty principle, encoded in the non-commutativity of some measurable
operators. Nonetheless, in the last decade opto-mechanical experiments have
actualized macroscopic mechanical oscillators exhibiting such non-classical
properties. A key indicator is the asymmetry in the strength of the motional
sidebands generated in an electromagnetic field that measures
interferometrically the oscillator position. This asymmetry is a footprint of
the quantum motion of the oscillator, being originated by the non-commutativity
between its ladder operators. A further step on the path highlighting the
quantum physics of macroscopic systems is the realization of strongly
non-classical states and the consequent observation of a distinct quantum
behavior. Here we extend indeed the analysis to a squeezed state of a
macroscopic mechanical oscillator embedded in an optical cavity, produced by
parametric effect originated by a suitable combination of optical fields. The
motional sidebands assume a peculiar shape, related to the modified system
dynamics, with asymmetric features revealing and quantifying the quantum
component of the squeezed oscillator motion
Quantum motion of a squeezed mechanical oscillator attained via a optomechanical experiment
We experimentally investigate a mechanical squeezed state realized in a
parametrically-modulated membrane resonator embedded in an optical cavity. We
demonstrate that a quantum characteristic of the squeezed dynamics can be
revealed and quantified even in a moderately warm oscillator, through the
analysis of motional sidebands. We provide a theoretical framework for
quantitatively interpreting the observations and present an extended comparison
with the experiment. A notable result is that the spectral shape of each
motional sideband provides a clear signature of a quantum mechanical squeezed
state without the necessity of absolute calibrations, in particular in the
regime where residual fluctuations in the squeezed quadrature are reduced below
the zero-point level
REQUIRED COEFFICIENT OF FRICTION ANALYSES IN RUNNING
The purpose of this study was to analyze the possible alterations in the required coefficient of friction (RCOF) in running under the following conditions: a) barefoot against shod; b) self-selected velocity and cadence versus imposed cadence and c) along three running phases (initial contact, mid-stance and propulsion). Two Kistler force plates were used to measure the horizontal and vertical components of ground reaction forces in order to calculate the RCOF. Statistical differences were found for cadence and phase factors. Barefoot-Shod conditions did not present statistical differences. An interaction between velocity and phase of cycle was found. At propulsion phase, an increased RCOF were revealed, especially with the interaction of an imposed cadence. In conclusion, the present study supports the relevance of RCOF as a variable affecting and being affected during running to be taken into consideration at many experimental conditions
Mancha-anelar-do-fruto-do-coqueiro: agente causal e danos.
O aparecimento de determinadas necroses marrons sobre a epiderme dos frutos do coqueiro ocorreu de forma repentina, em meados de 1999, em plantios de coqueiro anão-verde de várias regiões do Brasil, causando prejuízos consideráveis à comercialização do coco-verde no mercado de fruto in natura pela má aparência deixada nos frutos.bitstream/item/64517/1/CPATC-DOCUMENTOS-27-MANCHA-ANELAR-DO-FRUTO-DO-COQUEIRO-AGENTE-CAUSAL-E-DANOS-FL-13176.pd
Silicon Nitride MOMS Oscillator for Room Temperature Quantum Optomechanics
IEEE Optomechanical SiN nano-oscillators in high-finesse Fabry-Perot cavities can be used to investigate the interaction between mechanical and optical degree of freedom for ultra-sensitive metrology and fundamental quantum mechanical studies. In this paper, we present a nano-oscillator made of a high-stress round-shaped SiN membrane with an integrated on-chip 3-D acoustic shield properly designed to reduce mechanical losses. This oscillator works in the range of 200 kHz to 5 MHz and features a mechanical quality factor of Q ≃10⁷ and a Q-frequency product in excess of 6.2 x 10¹² Hz at room temperature, fulfilling the minimum requirement for quantum ground-state cooling of the oscillator in an optomechanical cavity. The device is obtained by MEMS deep reactive-ion etching (DRIE) bulk micromachining with a two-side silicon processing on a silicon-on-insulator wafer. The microfabrication process is quite flexible such that additional layers could be deposited over the SiN membrane before the DRIE steps, if required for a sensing application. Therefore, such oscillator is a promising candidate for quantum sensing applications in the context of the emerging field of quantum technologies
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