arXiv subjects

B. D. Hauer

Publications and source records attributed to B. D. Hauer.

At least 19 recordsLinked to original sources

arXiv2020

Wavelength transduction from a 3D microwave cavity to telecom using piezoelectric optomechanical crystals

Microwave to optical transduction has received a great deal of interest from the cavity optomechanics community as a landmark application for electro-optomechanical systems. In this Letter, we demonstrate a novel transducer that combines high-frequency mechanical motion and a microwave cavity for the first time. The system consists of a 3D microwave cavity and a gallium arsenide optomechanical crystal, which has been placed in the microwave electric field maximum. This allows the microwave cavity to actuate the gigahertz-frequency mechanical breathing mode in the optomechanical crystal through the piezoelectric effect, which is then read out using a telecom optical mode. The gallium arsenide optomechanical crystal is a good candidate for low-noise microwave-to-telecom transduction, as it has been previously cooled to the mechanical ground state in a dilution refrigerator. Moreover, the 3D microwave cavity architecture can naturally be extended to couple to superconducting qubits and to create hybrid quantum systems.

cond-mat.mes-hall↗

arXiv2019

Elimination of Thermomechanical Noise in Piezoelectric Optomechanical Crystals

Mechanical modes are a potentially useful resource for quantum information applications, such as quantum-level wavelength transducers, due to their ability to interact with electromagnetic radiation across the spectrum. A significant challenge for wavelength transducers is thermomechanical noise in the mechanical mode, which pollutes the transduced signal with thermal states. In this paper, we eliminate thermomechanical noise in the GHz-frequency mechanical breathing mode of a piezoelectric optomechanical crystal using cryogenic cooling in a dilution refrigerator. We optically measure an average thermal occupancy of the mechanical mode of only $0.7\pm0.4 ~ \mathrm{phonons}$, providing a path towards low-noise microwave-to-optical conversion in the quantum regime.

quant-ph↗

arXiv2019

Coherent Magneto-Optomechanical Signal Transduction and Long-Distance Phase-Shift Keying

A transducer capable of converting quantum information stored as microwaves into telecom-wavelength signals is a critical piece of future quantum technology as it promises to enable the networking of quantum processors. Cavity optomechanical devices that are simultaneously coupled to microwave fields and optical resonances are being pursued in this regard. Yet even in the classical regime, developing optical modulators based on cavity optomechanics could provide lower power or higher bandwidth alternatives to current technology. Here we demonstrate a magnetically-mediated wavelength conversion technique, based on mixing high frequency tones with an optomechanical torsional resonator. This process can act either as an optical phase or amplitude modulator depending on the experimental configuration, and the carrier modulation is always coherent with the input tone. Such coherence allows classical information transduction and transmission via the technique of phase-shift keying. We demonstrate that we can encode up to eight bins of information, corresponding to three bits, simultaneously and demonstrate the transmission of an 52,500 pixel image over 6 km of optical fiber with just 0.67% error. Furthermore, we show that magneto-optomechanical transduction can be described in a fully quantum manner, implying that this is a viable approach to signal transduction at the single quantum level.

physics.app-ph↗

arXiv2019

Dueling Dynamical Backaction in a Cryogenic Optomechanical Cavity

Dynamical backaction has proven to be a versatile tool in cavity optomechanics, allowing for precise manipulation of a mechanical resonator's motion using confined optical photons. In this work, we present measurements of a silicon whispering-gallery-mode optomechanical cavity where backaction originates from opposing radiation pressure and photothermal forces, with the former dictating the optomechanical spring effect and the latter governing the optomechanical damping. At high enough optical input powers, we show that the photothermal force drives the mechanical resonator into self-oscillations for a pump beam detuned to the lower-frequency side of the optical resonance, contrary to what one would expect for a radiation-pressure-dominated optomechanical device. Using a fully nonlinear model, we fit the hysteretic response of the optomechanical cavity to extract its properties, demonstrating that this non-sideband-resolved device exists in a regime where photothermal damping could be used to cool its motion to the quantum ground state.

cond-mat.mes-hall↗

arXiv2018

Two-Level System Damping in a Quasi-One-Dimensional Optomechanical Resonator

Nanomechanical resonators have demonstrated great potential for use as versatile tools in a number of emerging quantum technologies. For such applications, the performance of these systems is restricted by the decoherence of their fragile quantum states, necessitating a thorough understanding of their dissipative coupling to the surrounding environment. In bulk amorphous solids, these dissipation channels are dominated at low temperatures by parasitic coupling to intrinsic two-level system (TLS) defects, however, there remains a disconnect between theory and experiment on how this damping manifests in dimensionally-reduced nanomechanical resonators. Here, we present an optomechanically-mediated thermal ringdown technique, which we use to perform simultaneous measurements of the dissipation in four mechanical modes of a cryogenically-cooled silicon nanoresonator, with resonant frequencies ranging from 3 - 19 MHz. Analyzing the device's mechanical damping rate at fridge temperatures between 10 mK - 10 K, we demonstrate quantitative agreement with the standard tunneling model for TLS ensembles confined to one dimension. From these fits, we extract the defect density of states ($P_0 \sim$ 1 - 4 $\times$ 10$^{44}$ J$^{-1}$ m$^{-3}$) and deformation potentials ($γ\sim$ 1 - 2 eV), showing that each mechanical mode couples on average to less than a single thermally-active defect at 10 mK.

cond-mat.mes-hall↗

arXiv2018

Phonon Quantum Nondemolition Measurements in Nonlinearly Coupled Optomechanical Cavities

In the field of cavity optomechanics, proposals for quantum nondemolition (QND) measurements of phonon number provide a promising avenue by which one can study the quantum nature of nanoscale mechanical resonators. Here, we investigate these QND measurements for an optomechanical system whereby quadratic coupling arises due to shared symmetries between a single optical resonance and a mechanical mode. We establish a relaxed limit on the amount of linear coupling that can exist in this type of system while still allowing for a QND measurement of Fock states. This new condition enables optomechanical QND measurements, which can be used to probe the decoherence of mesoscopic mechanical Fock states, providing an experimental testbed for quantum collapse theories.

quant-ph↗

arXiv2017

Magnetic Actuation and Feedback Cooling of a Cavity Optomechanical Torque Sensor

We demonstrate the integration of a mesoscopic ferromagnetic needle with a cavity optomechanical torsional resonator, and its use for quantitative determination of the needle's magnetic properties, as well as amplification and cooling of the resonator motion. With this system we measure torques as small as 32 zNm, corresponding to sensing an external magnetic field of 0.12 A/m (150 nT). Furthermore, we are able to extract the magnetization (1710 kA/m) of the magnetic sample, not known a priori, demonstrating this system's potential for studies of nanomagnetism. Finally, we show that we can magnetically drive the torsional resonator into regenerative oscillations, and dampen its mechanical mode temperature from room temperature to 11.6 K, without sacrificing torque sensitivity.

cond-mat.mes-hall↗

arXiv2016

Approaching the Standard Quantum Limit of Mechanical Torque Sensing

Mechanical transduction of torque has been key to probing a number of physical phenomena, such as gravity, the angular momentum of light, the Casimir effect, magnetism, and quantum oscillations. Following similar trends as mass and force sensing, mechanical torque sensitivity can be dramatically improved by scaling down the physical dimensions, and therefore moment of inertia, of a torsional spring. Yet now, through precision nanofabrication and sub-wavelength cavity optomechanics, we have reached a point where geometric optimization can only provide marginal improvements to torque sensitivity. Instead, nanoscale optomechanical measurements of torque are overwhelmingly hindered by thermal noise. Here we present cryogenic measurements of a cavity-optomechanical torsional resonator cooled in a dilution refrigerator to a temperature of 25 mK, corresponding to an average phonon occupation of = 35, that demonstrate a record-breaking torque sensitivity of 2.9 yNm/Hz^{1/2}. This a 270-fold improvement over previous optomechanical torque sensors and just over an order of magnitude from its standard quantum limit. Furthermore, we demonstrate that mesoscopic test samples, such as micron-scale superconducting disks, can be integrated with our cryogenic optomechanical torque sensing platform, in contrast to other cryogenic optomechanical devices, opening the door for mechanical torque spectroscopy of intrinsically quantum systems.

cond-mat.mes-hall↗

arXiv2015

Optomechanics and thermometry of cryogenic silica microresonators

We present measurements of silica optomechanical resonators, known as bottle resonators, passively cooled in a cryogenic environment. These devices possess a suite of properties that make them advantageous for preparation and measurement in the mechanical ground state, including high mechanical frequency, high optical and mechanical quality factors, and optomechanical sideband resolution. Performing thermometry of the mechanical motion, we find that the optical and mechanical modes demonstrate quantitatively similar laser-induced heating, limiting the lowest average phonon occupation observed to just ~1500. Thermalization to the 9 mK thermal bath would facilitate quantum measurements on these promising nanogram-scale mechanical resonators.

cond-mat.mes-hall↗

arXiv2015

Nonlinear Power Spectral Densities for the Harmonic Oscillator

In this paper, we discuss a general procedure by which nonlinear power spectral densities (PSDs) of the harmonic oscillator can be calculated in both the quantum and classical regimes. We begin with an introduction of the damped and undamped classical harmonic oscillator, followed by an overview of the quantum mechanical description of this system. A brief review of both the classical and quantum autocorrelation functions (ACFs) and PSDs follow. We then introduce a general method by which the kth-order PSD for the harmonic oscillator can be calculated, where $k$ is any positive integer. This formulation is verified by first reproducing the known results for the $k = 1$ case of the linear PSD. It is then extended to calculate the second-order PSD, useful in the field of quantum measurement, corresponding to the $k = 2$ case of the generalized method. In this process, damping is included into each of the quantum linear and quadratic PSDs, producing realistic models for the PSDs found in experiment. These quantum PSDs are shown to obey the correspondence principle by matching with what was calculated for their classical counterparts in the high temperature, high-Q limit. Finally, we demonstrate that our results can be reproduced using the fluctuation-dissipation theorem, providing an independent check of our resultant PSDs.

cond-mat.mes-hall↗

arXiv2014

Optical microscope and tapered fiber coupling apparatus for a dilution refrigerator

We have developed a system for tapered fiber measurements of optomechanical resonators inside a dilution refrigerator, which is compatible with both on- and off-chip devices. Our apparatus features full three-dimensional control of the taper-resonator coupling conditions enabling critical coupling, with an overall fiber transmission efficiency of up to 70%. Notably, our design incorporates an optical microscope system consisting of a coherent bundle of 37,000 optical fibers for real-time imaging of the experiment at a resolution of $\sim$1 $μ$m. We present cryogenic optical and optomechanical measurements of resonators coupled to tapered fibers at temperatures as low as 9 mK.

cond-mat.mes-hall↗

arXiv2014

Ultrasonic Interferometer for First-Sound Measurements of Confined Liquid 4He

We present a new technique for probing the properties of quantum fluids in restricted geometries. We have confined liquid 4He within microfluidic devices formed from glass wafers, in which one dimension is on the micro scale. Using an ultrasonic analog to Fabry-Perot interferometry, we have measured the first-sound of the confined liquid 4He, which can be a probe of critical behavior near the lambda point ($T_λ$). All thermodynamic properties of liquid $^4$He can be derived from first-sound and heat capacity measurements, and although quite a bit of experimental work has been done on the latter, no measurement of first-sound has been reported for a precisely confined geometry smaller than a few tens of micrometers. In this work, we report measurements of isobaric first sound in liquid $^4$He confined in cavities as small as ~ 5 $μ$m. Our experimental set-up allows us to pressurize the liquid up to ~ 25 bar without causing deformation of the confined geometry, a pressure which is about 4 times larger than previously reported with similar microfluidic devices. Our preliminary results indicate that one can possibly observe finite-size effects and verify scaling laws, by using similar devices with smaller confinement.

cond-mat.supr-con↗

arXiv2014

Nonlinear optomechanics in the stationary regime

We have observed nonlinear transduction of the thermomechanical motion of a nanomechanical resonator when detected as laser transmission through a sideband unresolved optomechanical cavity. Nonlinear detection mechanisms are of considerable interest as special cases allow for quantum nondemolition measurements of the mechanical resonator's energy. We investigate the origin of the nonlinearity in the optomechanical detection apparatus and derive a theoretical framework for the nonlinear signal transduction, and the optical spring effect, from both nonlinearities in the optical transfer function and second order optomechanical coupling. By measuring the dependence of the linear and nonlinear signal transduction -- as well as the mechanical frequency shift -- on laser detuning from optical resonance, we provide estimates of the contributions from the linear and quadratic optomechanical couplings.

cond-mat.mes-hall↗

arXiv2013

Multidimensional optomechanical cantilevers for high frequency atomic force microscopy

High-frequency atomic force microscopy has enabled extraordinary new science through large bandwidth, high speed measurements of atomic and molecular structures. However, traditional optical detection schemes restrict the dimensions, and therefore the frequency, of the cantilever - ultimately setting a limit to the time resolution of experiments. Here we demonstrate optomechanical detection of low-mass, high-frequency nanomechanical cantilevers (up to 20 MHz) that surpass these limits, anticipating their use for single-molecule force measurements. These cantilevers achieve 2 fm / sqrt(Hz) displacement noise floors, and force sensitivity down to 132 aN / sqrt(Hz). Furthermore, the ability to resolve both in-plane and out-of-plane motion of our cantilevers opens the door for ultrasensitive multidimensional force spectroscopy, and optomechanical interactions, such as tuning of the cantilever frequency in situ, provide new opportunities in high-speed, high-resolution experiments.

cond-mat.mes-hall↗

arXiv2013

A general procedure for thermomechanical calibration of nano/micro-mechanical resonators

We provide a detailed description of a general procedure by which a nano/micro-mechanical resonator can be calibrated using its thermal motion. A brief introduction to the equations of motion for such a resonator is presented, followed by a detailed derivation of the corresponding power spectral density (PSD) function. The effective masses for a number of different resonator geometries are determined using both finite element method (FEM) modeling and analytical calculations.

cond-mat.mes-hall↗

arXiv2012

Nanoscale Torsional Optomechanics

Optomechanical transduction is demonstrated for nanoscale torsional resonators evanescently coupled to optical microdisk whispering gallery mode resonators. The on-chip, integrated devices are measured using a fully fiber-based system, including a tapered and dimpled optical fiber probe. With a thermomechanically calibrated optomechanical noise floor down to 7 fm/sqrt(Hz), these devices open the door for a wide range of physical measurements involving extremely small torques, as little as 4x10^-20 N*m.

cond-mat.mes-hall↗

arXiv2012

High-Q Gold and Silicon Nitride Bilayer Nanostrings

Low-mass, high-Q, silicon nitride nanostrings are at the cutting edge of nanomechanical devices for sensing applications. Here we show that the addition of a chemically functionalizable gold overlayer does not adversely affect the Q of the fundamental out-of-plane mode. Instead the device retains its mechanical responsiveness while gaining sensitivity to molecular bonding. Furthermore, differences in thermal expansion within the bilayer give rise to internal stresses that can be electrically controlled. In particular, an alternating current excites resonant motion of the nanostring. This AC thermoelastic actuation is simple, robust, and provides an integrated approach to sensor actuation.

cond-mat.mes-hall↗

arXiv2012

Dissipation Mechanisms in Thermomechanically Driven Silicon Nitride Nanostrings

High-stress silicon nitride nanostrings are a promising system for sensing applications because of their ultra-high mechanical quality factors (Qs). By performing thermomechanical calibration across multiple vibrational modes, we are able to assess the roles of the various dissipation mechanisms in these devices. Specifically, we possess a set of nanostrings in which all measured modes fall upon a single curve of peak displacement versus frequency. This allows us to rule out bulk bending and intrinsic loss mechanisms as dominant sources of dissipation and to conclude that the most significant contribution to dissipation in high-stress nanostrings occurs at the anchor points.

cond-mat.mes-hall↗