18 research outputs found
Minimum requirements for feedback enhanced force sensing
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
Thin film superfluid optomechanics
Excitations in superfluid helium represent attractive mechanical degrees of
freedom for cavity optomechanics schemes. Here we numerically and analytically
investigate the properties of optomechanical resonators formed by thin films of
superfluid He covering micrometer-scale whispering gallery mode cavities.
We predict that through proper optimization of the interaction between film and
optical field, large optomechanical coupling rates kHz
and single photon cooperativities are achievable. Our analytical model
reveals the unconventional behaviour of these thin films, such as thicker and
heavier films exhibiting smaller effective mass and larger zero point motion.
The optomechanical system outlined here provides access to unusual regimes such
as and opens the prospect of laser cooling a liquid into its
quantum ground state.Comment: 18 pages, 6 figure
Optomechanical magnetometry with a macroscopic resonator
We demonstrate a centimeter-scale optomechanical magnetometer based on a
crystalline whispering gallery mode resonator. The large size of the resonator
allows high magnetic field sensitivity to be achieved in the hertz to kilohertz
frequency range. A peak sensitivity of 131 pT per root Hz is reported, in a
magnetically unshielded non-cryogenic environment and using optical power
levels beneath 100 microWatt. Femtotesla range sensitivity may be possible in
future devices with further optimization of laser noise and the physical
structure of the resonator, allowing applications in high-performance
magnetometry
Coherent vortex dynamics in a strongly-interacting superfluid on a silicon chip
Two-dimensional superfluidity and quantum turbulence are directly connected
to the microscopic dynamics of quantized vortices. However, surface effects
have prevented direct observations of coherent vortex dynamics in
strongly-interacting two-dimensional systems. Here, we overcome this challenge
by confining a two-dimensional droplet of superfluid helium at microscale on
the atomically-smooth surface of a silicon chip. An on-chip optical microcavity
allows laser-initiation of vortex clusters and nondestructive observation of
their decay in a single shot. Coherent dynamics dominate, with thermal vortex
diffusion suppressed by six orders-of-magnitude. This establishes a new on-chip
platform to study emergent phenomena in strongly-interacting superfluids, test
astrophysical dynamics such as those in the superfluid core of neutron stars in
the laboratory, and construct quantum technologies such as precision inertial
sensors.Comment: Main text - 12 pages, 4 figures. Supplementary materials - 25 pages,
13 figure
High bandwidth on-chip capacitive tuning of microtoroid resonators
We report on the design, fabrication and characterization of silica microtoroid based cavity opto-electromechanical systems (COEMS). Electrodes patterned onto the microtoroid resonators allow for rapid capacitive tuning of the optical whispering gallery mode resonances while maintaining their ultrahigh quality factor, enabling applications such as efficient radio to optical frequency conversion, optical routing and switching applications
Optomechanical Magnetometry with a Macroscopic Resonator
We demonstrate a centimeter-scale optomechanical magnetometer based on a crystalline whispering-gallery-mode resonator. The large size of the resonator, with a magnetic-field integration volume of 0.45  cm3, allows high magnetic-field sensitivity to be achieved in the hertz-to-kilohertz frequency range. A peak sensitivity of 131  pT  Hz−1/2 is reported, in a magnetically unshielded noncryogenic environment using optical power levels beneath 100  μW. Femtotesla-range sensitivity may be possible in future devices with the further optimization of laser noise and the physical structure of the resonator, allowing applications in high-performance magnetometry