5 research outputs found
Coherent Signal Amplification in Bistable Nanomechanical Oscillators by Stochastic Resonance
Stochastic resonance is a counter-intuitive concept[1,2], ; the addition of
noise to a noisy system induces coherent amplification of its response. First
suggested as a mechanism for the cyclic recurrence of ice ages, stochastic
resonance has been seen in a wide variety of macroscopic physical systems:
bistable ring lasers[3], SQUIDs[4,5], magnetoelastic ribbons[6], and
neurophysiological systems such as the receptors in crickets[7] and
crayfish[8]. Although it is fundamentally important as a mechanism of coherent
signal amplification, stochastic resonance is yet to be observed in nanoscale
systems. Here we report the observation of stochastic resonance in bistable
nanomechanical silicon oscillators, which can play an important role in the
realization of controllable high-speed nanomechanical memory cells. Our
nanomechanical systems were excited into a dynamic bistable state and modulated
in order to induce controllable switching; the addition of white noise showed a
marked amplification of the signal strength. Stochastic resonance in
nanomechanical systems paves the way for exploring macroscopic quantum
coherence and tunneling, and controlling nanoscale quantum systems for their
eventual use as robust quantum logic devices.Comment: 18 pages, 4 figure
Quantum Friction in Nanomechanical Oscillators at Millikelvin Temperatures
We report low-temperature measurements of dissipation in megahertz-range,
suspended, single-crystal nanomechanical oscillators. At millikelvin
temperatures, both dissipation (inverse quality factor) and shift in the
resonance frequency display reproducible features, similar to those observed in
sound attenuation experiments in disordered glasses and consistent with
measurements in larger micromechanical oscillators fabricated from
single-crystal silicon. Dissipation in our single-crystal nanomechanical
structures is dominated by internal quantum friction due to an estimated number
of roughly 50 two-level systems, which represent both dangling bonds on the
surface and bulk defects.Comment: 5 pages, two-column format. Related papers available at
http://nano.bu.ed
Temperature dependence of a nanomechanical switch
We present the effect of temperature on the switching characteristics of a
bistable nonlinear nanomechanical beam. At MHz-range frequencies, we find that
it is possible to controllably change the state of the system between two
stable mechanical states defined by the hysteresis brought on by nonlinear
excitation. We find that the introduction of increased temperature results in a
loss of switching fidelity, and that temperature acts as an effective source of
external noise on the dynamics of the system
Evidence for Quantized Displacement in Macroscopic Nanomechanical Oscillators
We report the observation of discrete displacement of nanomechanical
oscillators with gigahertz-range resonance frequencies at millikelvin
temperatures. The oscillators are nanomachined single-crystal structures of
silicon, designed to provide two distinct sets of coupled elements with very
low and very high frequencies. With this novel design, femtometer-level
displacement of the frequency-determining element is amplified into collective
motion of the entire micron-sized structure. The observed discrete response
possibly results from energy quantization at the onset of the quantum regime in
these macroscopic nanomechanical oscillators.Comment: 4 pages, two-column format. Related papers available at
http://nano.bu.edu