414 research outputs found
Beating quantum limits in optomechanical sensor by cavity detuning
We study the quantum limits in an optomechanical sensor based on a detuned
high-finesse cavity with a movable mirror. We show that the radiation pressure
exerted on the mirror by the light in the detuned cavity induces a modification
of the mirror dynamics and makes the mirror motion sensitive to the signal.
This leads to an amplification of the signal by the mirror dynamics, and to an
improvement of the sensor sensitivity beyond the standard quantum limit, up to
an ultimate quantum limit only related to the mechanical dissipation of the
mirror. This improvement is somewhat similar to the one predicted in detuned
signal-recycled gravitational-waves interferometers, and makes a high-finesse
cavity a model system to test these quantum effect
Evanescent straight tapered-fiber coupling of ultra-high Q optomechanical micro-resonators in a low-vibration helium-4 exchange-gas cryostat
We developed an apparatus to couple a 50-micrometer diameter
whispering-gallery silica microtoroidal resonator in a helium-4 cryostat using
a straight optical tapered-fiber at 1550nm wavelength. On a top-loading probe
specifically adapted for increased mechanical stability, we use a
specifically-developed "cryotaper" to optically probe the cavity, allowing thus
to record the calibrated mechanical spectrum of the optomechanical system at
low temperatures. We then demonstrate excellent thermalization of a 63-MHz
mechanical mode of a toroidal resonator down to the cryostat's base temperature
of 1.65K, thereby proving the viability of the cryogenic refrigeration via heat
conduction through static low-pressure exchange gas. In the context of
optomechanics, we therefore provide a versatile and powerful tool with
state-of-the-art performances in optical coupling efficiency, mechanical
stability and cryogenic cooling.Comment: 8 pages, 6 figure
Resolved-sideband cooling and measurement of a micromechanical oscillator close to the quantum limit
The observation of quantum phenomena in macroscopic mechanical oscillators
has been a subject of interest since the inception of quantum mechanics.
Prerequisite to this regime are both preparation of the mechanical oscillator
at low phonon occupancy and a measurement sensitivity at the scale of the
spread of the oscillator's ground state wavefunction. It has been widely
perceived that the most promising approach to address these two challenges are
electro nanomechanical systems. Here we approach for the first time the quantum
regime with a mechanical oscillator of mesoscopic dimensions--discernible to
the bare eye--and 1000-times more massive than the heaviest nano-mechanical
oscillators used to date. Imperative to these advances are two key principles
of cavity optomechanics: Optical interferometric measurement of mechanical
displacement at the attometer level, and the ability to use measurement induced
dynamic back-action to achieve resolved sideband laser cooling of the
mechanical degree of freedom. Using only modest cryogenic pre-cooling to 1.65
K, preparation of a mechanical oscillator close to its quantum ground state
(63+-20 phonons) is demonstrated. Simultaneously, a readout sensitivity that is
within a factor of 5.5+-1.5 of the standard quantum limit is achieved. The
reported experiments mark a paradigm shift in the approach to the quantum limit
of mechanical oscillators using optical techniques and represent a first step
into a new era of experimental investigation which probes the quantum nature of
the most tangible harmonic oscillator: a mechanical vibration.Comment: 14 pages, 4 figure
Observation of a phononic Mollow triplet in a hybrid spin-nanomechanical system
Reminiscent of the bound character of a qubit's dynamics confined on the
Bloch sphere, the observation of a Mollow triplet in the resonantly driven
qubit fluorescence spectrum represents one of the founding signatures of
Quantum Electrodynamics. Here we report on its observation in a hybrid
spin-nanomechanical system, where a Nitro-gen Vacancy spin qubit is
magnetically coupled to the vibrations of a Silicon Carbide nanowire. A
resonant microwave field turns the originally parametric hybrid interac-tion
into a resonant process, where acoustic phonons are now able to induce
transitions between the dressed qubit states, leading to synchronized
spin-oscillator dynamics. We further explore the vectorial character of the
hybrid coupling to the bidimensional de-formations of the nanowire. The
demonstrated microwave assisted synchronization of the spin-oscillator dynamics
opens novel perspectives for the exploration of spin-dependent forces, the
key-ingredient for quantum state transfer
Synchronizing the dynamics of a single NV spin qubit on a parametrically coupled radio-frequency field through microwave dressing
A hybrid spin-oscillator system in parametric interaction is experimentally
emulated using a single NV spin qubit immersed in a radio frequency (RF) field
and probed with a quasi resonant microwave (MW) field. We report on the MW
mediated locking of the NV spin dynamics onto the RF field, appearing when the
MW driven Rabi precession frequency approaches the RF frequency and for
sufficiently large RF amplitudes. These signatures are analog to a phononic
Mollow triplet in the MW rotating frame for the parametric interaction and
promise to have impact in spin-dependent force detection strategies
Optical frequency comb generation from a monolithic microresonator
Optical frequency combs provide equidistant frequency markers in the
infrared, visible and ultra-violet and can link an unknown optical frequency to
a radio or microwave frequency reference. Since their inception frequency combs
have triggered major advances in optical frequency metrology and precision
measurements and in applications such as broadband laser-based gas sensing8 and
molecular fingerprinting. Early work generated frequency combs by intra-cavity
phase modulation while to date frequency combs are generated utilizing the
comb-like mode structure of mode-locked lasers, whose repetition rate and
carrier envelope phase can be stabilized. Here, we report an entirely novel
approach in which equally spaced frequency markers are generated from a
continuous wave (CW) pump laser of a known frequency interacting with the modes
of a monolithic high-Q microresonator13 via the Kerr nonlinearity. The
intrinsically broadband nature of parametric gain enables the generation of
discrete comb modes over a 500 nm wide span (ca. 70 THz) around 1550 nm without
relying on any external spectral broadening. Optical-heterodyne-based
measurements reveal that cascaded parametric interactions give rise to an
optical frequency comb, overcoming passive cavity dispersion. The uniformity of
the mode spacing has been verified to within a relative experimental precision
of 7.3*10(-18).Comment: Manuscript and Supplementary Informatio
Optomechanical sideband cooling of a micromechanical oscillator close to the quantum ground state
Cooling a mesoscopic mechanical oscillator to its quantum ground state is
elementary for the preparation and control of low entropy quantum states of
large scale objects. Here, we pre-cool a 70-MHz micromechanical silica
oscillator to an occupancy below 200 quanta by thermalizing it with a 600-mK
cold 3He gas. Two-level system induced damping via structural defect states is
shown to be strongly reduced, and simultaneously serves as novel thermometry
method to independently quantify excess heating due to the cooling laser. We
demonstrate that dynamical backaction sideband cooling can reduce the average
occupancy to 9+-1 quanta, implying that the mechanical oscillator can be found
(10+- 1)% of the time in its quantum ground state.Comment: 11 pages, 5 figure
Optomechanically induced transparency
Coherent interaction of laser radiation with multilevel atoms and molecules
can lead to quantum interference in the electronic excitation pathways. A
prominent example observed in atomic three-level-systems is the phenomenon of
electromagnetically induced transparency (EIT), in which a control laser
induces a narrow spectral transparency window for a weak probe laser beam. The
concomitant rapid variation of the refractive index in this spectral window can
give rise to dramatic reduction of the group velocity of a propagating pulse of
probe light. Dynamic control of EIT via the control laser enables even a
complete stop, that is, storage, of probe light pulses in the atomic medium.
Here, we demonstrate optomechanically induced transparency (OMIT)--formally
equivalent to EIT--in a cavity optomechanical system operating in the resolved
sideband regime. A control laser tuned to the lower motional sideband of the
cavity resonance induces a dipole-like interaction of optical and mechanical
degrees of freedom. Under these conditions, the destructive interference of
excitation pathways for an intracavity probe field gives rise to a window of
transparency when a two-photon resonance condition is met. As a salient feature
of EIT, the power of the control laser determines the width and depth of the
probe transparency window. OMIT could therefore provide a new approach for
delaying, slowing and storing light pulses in long-lived mechanical excitations
of optomechanical systems, whose optical and mechanical properties can be
tailored in almost arbitrary ways in the micro- and nano-optomechanical
platforms developed to date
Coding of shape from shading in area V4 of the macaque monkey
<p>Abstract</p> <p>Background</p> <p>The shading of an object provides an important cue for recognition, especially for determining its 3D shape. However, neuronal mechanisms that allow the recovery of 3D shape from shading are poorly understood. The aim of our study was to determine the neuronal basis of 3D shape from shading coding in area V4 of the awake macaque monkey.</p> <p>Results</p> <p>We recorded the responses of V4 cells to stimuli presented parafoveally while the monkeys fixated a central spot. We used a set of stimuli made of 8 different 3D shapes illuminated from 4 directions (from above, the left, the right and below) and different 2D controls for each stimulus. The results show that V4 neurons present a broad selectivity to 3D shape and illumination direction, but without a preference for a unique illumination direction. However, 3D shape and illumination direction selectivities are correlated suggesting that V4 neurons can use the direction of illumination present in complex patterns of shading present on the surface of objects. In addition, a vast majority of V4 neurons (78%) have statistically different responses to the 3D and 2D versions of the stimuli, while responses to 3D are not systematically stronger than those to 2D controls. However, a hierarchical cluster analysis showed that the different classes of stimuli (3D, 2D controls) are clustered in the V4 cells response space suggesting a coding of 3D stimuli based on the population response. The different illumination directions also tend to be clustered in this space.</p> <p>Conclusion</p> <p>Together, these results show that area V4 participates, at the population level, in the coding of complex shape from the shading patterns coming from the illumination of the surface of corrugated objects. Hence V4 provides important information for one of the steps of cortical processing of the 3D aspect of objects in natural light environment.</p
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