arXiv subjects

E. Collin

Publications and source records attributed to E. Collin.

At least 19 recordsLinked to original sources

arXiv2024

Self-sustained optomechanical state destruction triggered by the Kerr nonlinearity

Cavity optomechanics implements a unique platform where moving objects can be probed by quantum fields, either laser light or microwave signals. With a pump tone driving at a frequency above the cavity resonance, self-sustained oscillations can be triggered at large injected powers. These limit cycle dynamics are particularly rich, presenting hysteretic behaviours, broad comb signals and especially large motion amplitudes. All of these features can be exploited for both fundamental quantum research and engineering. Here we present low temperature microwave experiments performed on a high-Q cavity resonance capacitively coupled to the flexure of a beam resonator. We study the limit cycle dynamics phase space as a function of pump parameters (detuning, power). Unexpectedly, we find that in a region of this phase space the microwave resonance is irremediably destroyed: only a dramatic power-reset can restore the dynamics to its original state. The phenomenon can be understood as an optical instability linked to the Kerr nonlinearity of the cavity. A theory supporting this claim is presented, reproducing almost quantitatively the measurement. This remarkable feature might be further optimized and represents a new resource for quantum microwave circuits.

cond-mat.mes-hall↗

arXiv2022

Mesoscopic Quantum Thermo-mechanics: a new frontier of experimental physics

Within the last decade, experimentalists have demonstrated their impressive ability to control mechanical modes within mesoscopic objects down to the quantum level: it is now possible to create mechanical Fock states, to entangle mechanical modes from distinct objects, store quantum information or transfer it from one quantum bit to another, among the many possibilities found in today's literature. Indeed mechanics is quantum, very much like spins or electromagnetic degrees of freedom. And all of this is in particular referred to as a new engineering resource for quantum technologies. But there is also much more beyond this utilitarian aspect: invoking the original discussions of Braginsky and Caves where a quantum oscillator is thought of as a quantum detector for a classical field, namely a gravitational wave, it is also a unique sensing capability for quantum fields. The subject of study is then the baths to which the mechanical mode is coupled to, let them be known or unknown in nature. This Letter is about this new potentiality, that addresses stochastic thermodynamics, potentially down to its quantum version, the search for a fundamental underlying (random) field postulated in recent theories that can be affiliated to the class of the Wave-function Collapse models, and more generally open questions of Condensed Matter like the actual nature of the elusive (and ubiquitous) Two-Level Systems present within all mechanical objects. But such research turns out to be much more demanding than the usage of a few quantum mechanical modes: all the known baths have to be identified, experiments have to be conducted in-equilibrium, and the word "mechanics" needs to be justified by a real ability to move substantially the centre-of-mass when a proper drive tone is applied to the system.

cond-mat.mes-hall↗

arXiv2021

A macroscopic object passively cooled into its quantum ground state of motion: beyond single-mode cooling

The building blocks of Nature, namely atoms and elementary particles, are described by quantum mechanics. This fundamental theory is the ground on which physicists have built their major mathematical models [1]. Today, the unique features of quantum objects have led to the advent of promising quantum technologies [2, 3]. However, the macroscopic world is manifestly classical, and the nature of the quantum-to-classical crossover remains one of the most challenging open question of Science to date. In this respect, moving objects play a specific role [4, 5]. Pioneering experiments over the last few years have begun exploring quantum behaviour of micron-sized mechanical systems,either by passively cooling single GHz modes, or by adapting laser cooling techniques developed in atomic physics to cool specific modes far below the temperature of their surroundings [6-11]. Here instead we describe a very different approach, passive cooling of a micromechanical system down to 500 microK, reducing the average number of quanta in the fundamental vibrational mode at 15 MHz to just 0.3 (with even lower values expected for higher harmonics); the challenge being to be still able to detect the motion without disturbing the system noticeably. With such an approach higher harmonics and the surrounding environment are also cooled, leading to potentially much longer mechanical coherence times, and enabling experiments questioning mechanical wave-function collapse [12], potentially from the gravitational background [13, 14], and quantum thermodynamics [15]. Beyond the average behaviour, here we also report on the fluctuations of the fundamental vibrational mode of the device in-equilibrium with the cryostat. These reveal a surprisingly complex interplay with the local environment and allow characteristics of two distinct thermodynamic baths to be probed.

quant-ph↗

arXiv2020

Beyond linear coupling in microwave optomechanics

We explore the nonlinear dynamics of a cavity optomechanical system. Our realization consisting of a drumhead nano-electro-mechanical resonator (NEMS) coupled to a microwave cavity, allows for a nearly ideal platform to study the nonlinearities arising purely due to radiation-pressure physics. Experiments are performed under a strong microwave Stokes pumping which triggers mechanical self-sustained oscillations. We analyze the results in the framework of an extended nonlinear optomechanical theory, and demonstrate that quadratic and cubic coupling terms in the opto-mechanical Hamiltonian have to be considered. Quantitative agreement with the measurements is obtained considering only genuine geometrical nonlinearities: no thermo-optical instabilities are observed, in contrast with laser-driven systems. Based on these results, we describe a method to quantify nonlinear properties of microwave optomechanical devices. Such a technique, available now in the quantum electro-mechanics toolbox, but completely generic, is mandatory for the development of new schemes where higher-order coupling terms are proposed as a new resource, like Quantum Non-Demolition measurements, or in the search for new fundamental quantum signatures, like Quantum Gravity. We also find that the motion imprints a wide comb of extremely narrow peaks in the microwave output field, which could also be exploited in specific microwave-based measurements, potentially limited only by the quantum noise of the optical and the mechanical fields for a ground-state cooled NEMS device.

cond-mat.mes-hall↗

arXiv2019

Design Evaluation of Serial and Parallel sub-mK Continuous Nuclear Demagnetization Refrigerators

We present the evaluation of two different design configurations of a two-stage PrNi$_5$ continuous nuclear demagnetization refrigerator. Serial and parallel configurations of the two stages are considered, with emphasis on the attainable cooling power at sub-mK temperatures and the impact of the design choices on the operation of the refrigerator. Numerical simulations of heat transfer in the setup are used to evaluate the performance of the refrigerator as well as the technological requirements for the essential thermal links. In accord with similar findings for adiabatic demagnetization refrigerators [Shirron, \emph{Cryogenics} \textbf{62}, 2014], our simulations show that the performance of both configurations improves as the thermal links improve, and that the parallel configuration yields a higher cooling power than the series design for a given thermal link resistance and sample temperature.

physics.ins-det↗

arXiv2019

Geometrical Nonlinearity of Circular Plates and Membranes: an Alternative Method

We apply the well-established theoretical method developed for geometrical nonlinearities of micro/nano-mechanical clamped beams to circular drums. The calculation is performed under the same hypotheses, the extra difficulty being to analytically describe the (coordinate-dependent) additional stress generated in the structure by the motion. Specifically, the model applies to non-axisymmetric mode shapes. An analytic expression is produced for the Duffing (hardening) nonlinear coefficient, which requires only the knowledge of the mode shape functions to be evaluated. This formulation is simple to handle, and does not rely on complex numerical methods. Moreover, no hypotheses are made on the drive scheme and the nature of the in-plane stress: it is not required to be of electrostatic origin. We confront our predictions with both typical experimental devices and relevant theoretical results from the literature. Generalization of the presented method to Duffing-type mode-coupling should be a straightforward extension of this work. We believe that the presented modeling will contribute to the development of nonlinear physics implemented in 2D micro/nano-mechanical structures.

cond-mat.mes-hall↗

arXiv2019

Probing superfluid $^4\mathrm{He}$ with high-frequency nanomechanical resonators down to $\mathrm{mK}$ temperatures

Superfluids, such as superfluid $^3\mathrm{He}$ and $^4\mathrm{He}$, exhibit a broad range of quantum phenomena and excitations which are unique to these systems. Nanoscale mechanical resonators are sensitive and versatile force detectors with the ability to operate over many orders of magnitude in damping. Using nanomechanical-doubly clamped beams of extremely high quality factors ($Q>10^6$), we probe superfluid $^4\mathrm{He}$ from the superfluid transition temperature down to $\mathrm{mK}$ temperatures at frequencies up to $11.6 \, \mathrm{MHz}$. Our studies show that nanobeam damping is dominated by hydrodynamic viscosity of the normal component of $^4\mathrm{He}$ above $1\,\mathrm{K}$. In the temperature range $0.3-0.8\,\mathrm{K}$, the ballistic quasiparticles (phonons and rotons) determine the beams' behavior. At lower temperatures, damping saturates and is determined either by magnetomotive losses or acoustic emission into helium. It is remarkable that all these distinct regimes can be extracted with just a single device, despite damping changing over six orders of magnitude.

cond-mat.mes-hall↗

arXiv2019

Detecting the "phonon wind" in superfluid $\mathrm{^4He}$ by a nanomechanical resonator

Nanoscale mechanical resonators are widely utilized to provide high sensitivity force detectors. Here we demonstrate that such high quality factor resonators immersed in superfluid $^4\mathrm{He}$ can be excited by a modulated flux of phonons. A nanosized heater immersed in superfluid $^4\mathrm{He}$ acts as a source of ballistic phonons in the liquid -- "phonon wind". When the modulation frequency of the phonon flux matches the resonance frequency of the mechanical resonator, the motion of the latter can be excited. This ballistic thermomechanical effect can potentially open up new types of experiments in quantum fluids.

cond-mat.mes-hall↗

arXiv2019

On-chip thermometry for microwave optomechanics implemented in a nuclear demagnetization cryostat

We report on microwave optomechanics measurements performed on a nuclear adiabatic demagnetization cryostat, whose temperature is determined by accurate thermometry from below 500$~\mu$K to about 1$~$Kelvin. We describe a method for accessing the on-chip temperature, building on the blue-detuned parametric instability and a standard microwave setup. The capabilities and sensitivity of both the experimental arrangement and the developed technique are demonstrated with a very weakly coupled silicon-nitride doubly-clamped beam mode of about 4$~$MHz and a niobium on-chip cavity resonating around 6$~$GHz. We report on an unstable intrinsic driving force in the coupled microwave-mechanical system acting on the mechanics that appears below typically 100$~$mK. The origin of this phenomenon remains unknown, and deserves theoretical input. It prevents us from performing reliable experiments below typically 10-30$~$mK; however no evidence of thermal decoupling is observed, and we propose that the same features should be present in all devices sharing the microwave technology, at different levels of strengths. We further demonstrate empirically how most of the unstable feature can be annihilated, and speculate how the mechanism could be linked to atomic-scale two level systems. The described microwave/microkelvin facility is part of the EMP platform, and shall be used for further experiments within and below the millikelvin range.

cond-mat.mes-hall↗

arXiv2018

Cryogenic broadband vibration measurement on a cryogen-free dilution refrigerator

This manuscript reports a set of acceleration measurements in the frequency range from 0 to 50 kHz performed at the mixing chamber plate (2 axes) and the top flange (3 axes) of a cryogen-free dilution refrigerator. Various configurations of the support frame and coupling to the pulse tube compressor and motor have been tested, and the dominant contribution in the spectrum of vibrations is located, surprisingly, near 20 kHz. Finally, the efficiency of various precautions in suppressing the observed vibration levels is illustrated.

physics.app-ph↗

arXiv2018

Driving nanomechanical resonators by phonon flux in superfluid $\mathbf{^4He}$

We report on nanomechanical resonators with very high-quality factors operated as mechanical probes in liquid helium $^4\mathrm{He}$, with special attention to the superfluid regime down to millikelvin temperatures. Such resonators have been used to map out the full range of damping mechanisms in the liquid on the nanometer scale from $10\,\mathrm{mK}$ up to $\sim3\,\mathrm{K}$. The high sensitivity of these doubly-clamped beams to thermal excitations in the superfluid $^4\mathrm{He}$ makes it possible to drive them using the momentum transfer from phonons generated by a nearby heater. This so-called "\textit{phonon wind}" is an inverse thermomechanical effect that until now has never been demonstrated, and provides the possibility to perform a new type of optomechanical experiments in quantum fluids.

cond-mat.mes-hall↗

arXiv2017

Surface-induced near-field scaling in the Knudsen layer of a rarefied gas

We report on experiments performed within the Knudsen boundary layer of a low-pressure gas. The non-invasive probe we use is a suspended nano-electro-mechanical string (NEMS), which interacts with $^4$He gas at cryogenic temperatures. When the pressure $P$ is decreased, a reduction of the damping force below molecular friction $\propto P$ had been first reported in Phys. Rev. Lett. Vol 113, 136101 (2014) and never reproduced since. We demonstrate that this effect is independent of geometry, but dependent on temperature. Within the framework of kinetic theory, this reduction is interpreted as a rarefaction phenomenon, carried through the boundary layer by a deviation from the usual Maxwell-Boltzmann equilibrium distribution induced by surface scattering. Adsorbed atoms are shown to play a key role in the process, which explains why room temperature data fail to reproduce it.

cond-mat.mes-hall↗

arXiv2017

Temperature Dependent Energy Levels of Electrons on Liquid Helium

We present measurements of the resonant microwave absorption by the Rydberg energy levels of surface state electrons on the surface of superfluid liquid helium, in the frequency range 165 - 220 GHz. The resonant frequency was strongly temperature dependent from 0.1 to 2 K. The experiments are in agreement with recent theoretical calculations of the renormalisation of the electron energy levels due to zero-point and thermal ripplons, analogous to a condensed matter Lamb shift. The temperature-dependent contribution to the linewidth for excitation to the first excited state at 189.6 GHz is compared with other measurements and theoretical predictions.

cond-mat.mes-hall↗

arXiv2015

Slippage and boundary layer probed in an almost-ideal gas by a nano-mechanical oscillator

We have measured the interaction between $^4$He gas at 4.2$~$K and a high-quality nano-electro-mechanical string device for its first 3 symmetric modes (resonating at 2.2$~$MHz, 6.7$~$MHz and 11$~$MHz with quality factor $Q > 0.1$ million) over almost 6 orders of magnitude in pressure. This fluid can be viewed as the best experimental implementation of an almost-ideal monoatomic and inert gas which properties are tabulated. The experiment ranges from high pressure where the flow is of laminar Stokes-type presenting slippage, down to very low pressures where the flow is molecular. In the molecular regime, when the mean-free-path is of the order of the distance between the suspended nano-mechanical probe and the bottom of the trench we resolve for the first time the signature of the boundary (Knudsen) layer onto the measured dissipation. Our results are discussed in the framework of the most recent theories investigating boundary effects in fluids (both analytic approaches and Monte-Carlo DSMC simulations).

cond-mat.mes-hall↗

arXiv2015

Probing Bogoliubov quasiparticles in superfluid $^3$He with a 'vibrating-wire like' MEMS device

We have measured the interaction between superfluid $^3$He-B and a micro-machined goalpost-shaped device at temperatures below $0.2\,T_c$. The measured damping follows well the theory developed for vibrating wires, in which the Andreev reflection of quasiparticles in the flow field around the moving structure leads to a nonlinear frictional force. At low velocities the damping force is proportional to velocity while it tends to saturate for larger excitations. Above a velocity of 2.6$\,$mms$^{-1}$ the damping abruptly increases, which is interpreted in terms of Cooper-pair breaking. Interestingly, this critical velocity is significantly lower than reported with other mechanical probes immersed in superfluid $^3$He. Furthermore, we report on a nonlinear resonance shape for large motion amplitudes that we interpret as an inertial effect due to quasiparticle friction, but other mechanisms could possibly be invoked as well.

cond-mat.mes-hall↗

arXiv2015

Evidence for the role of normal-state electrons in nanoelectromechanical damping mechanisms at very low temperatures

We report on experiments performed at low temperatures on aluminum covered silicon nanoelectromechanical resonators. The substantial difference observed between the mechanical dissipation in the normal and superconducting states measured within the same device unambiguously demonstrates the importance of normal-state electrons in the damping mechanism. The dissipative component becomes vanishingly small at very low temperatures in the superconducting state, leading to exceptional values for the quality factor of such small silicon structures. A critical discussion is given within the framework of the standard tunneling model.

cond-mat.mes-hall↗

arXiv2015

In-situ comprehensive calibration of a tri-port nano-electro-mechanical device

We report on experiments performed in vacuum and at cryogenic temperatures on a tri-port nano-electro-mechanical (NEMS) device. One port is a very non-linear capacitive actuation, while the two others implement the magnetomotive scheme with a linear input force port and a (quasi-linear) output velocity port. We present an experimental method enabling a full characterization of the nanomechanical device harmonic response: the non-linear capacitance function $C(x)$ is derived, and the normal parameters $k$ and $m$ (spring constant and mass) of the mode under study are measured through a careful definition of the motion (in meters) and of the applied forces (in Newtons). These results are obtained with a series of purely electric measurements performed without disconnecting/reconnecting the device, and rely only on known DC properties of the circuit, making use of a thermometric property of the oscillator itself: we use the Young modulus of the coating metal as a thermometer, and the resistivity for Joule heating. The setup requires only three connecting lines without any particular matching, enabling the preservation of a high impedance NEMS environment even at MHz frequencies. The experimental data are fit to a detailed electrical and thermal model of the NEMS device, demonstrating a complete understanding of its dynamics. These methods are quite general and can be adapted (as a whole, or in parts) to a large variety of elecromechanical devices.

cond-mat.mes-hall↗

arXiv2015

Modal "self-coupling" as a sensitive probe for nanomechanical detection

We present a high-sensitivity measurement technique for mechanical nanoresonators. Due to intrinsic nonlinear effects, different flexural modes of a nanobeam can be coupled while driving each of them on resonance. This mode-coupling scheme is dispersive and one mode resonance shifts with respect to the motional amplitude of the other. The same idea can be implemented on a {\it single} mode, exciting it with two slightly detuned signals. This two-tone scheme is used here to measure the resonance lineshape of one mode through a frequency shift in the response of the device. The method acts as an amplitude-to-frequency transduction which ultimately suffers only from phase noise of the local oscillator used and of the nanomechanical device itself. We also present a theory which reproduces the data without free parameters.

cond-mat.mes-hall↗