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We report a study of a cavity optomechanical system driven by narrowband electromagnetic fields, which are applied either in the form of uncorrelated noise, or as a more structured spectrum. The bandwidth of the driving spectra is smaller than the mechanical resonant frequency, and thus we can describe the resulting physics using concepts familiar from regular cavity optomechanics in the resolved-sideband limit. With a blue-detuned noise driving, the noise-induced interaction leads to anti-damping of the mechanical oscillator, and a self-oscillation threshold at an average noise power that is comparable to that of a coherent driving tone. This process can be seen as noise-induced dynamical amplification of mechanical motion. However, when the noise bandwidth is reduced down to the order of the mechanical damping, we discover a large shift of the power threshold of self-oscillation. This is due to the oscillator adiabatically following the instantaneous noise profile. In addition to blue-detuned noise driving, we investigate narrowband driving consisting of two coherent drive tones nearby in frequency. Also in these cases, we observe deviations from a naive optomechanical description relying only on the tones' frequencies and powers. [ABSTRACT FROM AUTHOR]

Phonon lasers, as mechanical analogues of optical lasers, are unique tools for not only fundamental studies of the emerging field of phononics but also diverse applications such as deep-ocean monitoring, force sensing, and biomedical ultrasonics. Recently, nonlinear phonon-lasing effects were observed in an opto-levitated micro-sphere, i.e., the spontaneous emerging of weak signals of high-order phonon harmonics in the phonon lasing regime. However, both the strengths and the quality factors of the emerging phonon harmonics are very poor, thus severely hindering their potential applications in making and utilizing nonlinear phonon-laser devices. Here we show that, by applying a single-colour electronic injection to this levitated system, giant enhancement can be achieved for all higher-order phonon harmonics, with more than 3 orders enhanced brightness and 5 orders narrowed linewidth. Such an electronically-enhanced phonon laser is also far more stable, with frequency stability extended from a dozen of minutes to over 1 h. More importantly, higher-order phonon correlations, as an essential lasing feature, are confirmed to be enhanced by the electronic injection as well, which as far as we know, has not been reported in previous works using this technique. This work, providing much stronger and better-quality signals of coherent phonon harmonics, is a key step towards controlling and utilizing nonlinear phonon lasers for applications such as phonon frequency combs, broadband phonon sensors, and ultrasonic bio-medical diagnosis. [ABSTRACT FROM AUTHOR]

The field of levitated optomechanics has experienced significant advancements in manipulating the translational and rotational dynamics of optically levitated particles and exploring their sensing applications. The concept of using optically levitated particles as gyroscopes to measure angular motion has long been explored but has not yet been proven either theoretically or experimentally. In this study, we present the first rotor gyroscope based on optically levitated high-speed rotating particles. The gyroscope is composed of a micrometer-size ellipsoidal vaterite particle that is driven to rotate at MHz frequencies in a vacuum environment. When an external angular velocity is input, the optical axis deviates from its initial position, resulting in changes in the frequency and amplitude of the rotational signal. By analyzing these changes, the angular velocity of the input can be accurately detected, making it the smallest rotor gyroscope in the world. The angular rate bias instability of the gyroscope is measured to be 0.08°/s and can be further improved to as low as 10−9°/h theoretically by cooling the motion and increasing the angular moment of the levitated particle. Our work opens a new application paradigm for levitated optomechanical systems and may pave the way for the development of quantum rotor gyroscopes. [ABSTRACT FROM AUTHOR]

In this study, a method for entangling two spatially separated output laser fields from an optomechanical cavity is proposed. In the existing standard methods, entanglement is created by driving the two-mode squeezing part of the linearized optomechanical interaction;, however our method generates entanglement using the quantum back-action nullifying meter technique. As a result, entanglement can be generated outside the blue sideband frequency in both resolved and unresolved sideband regimes. We further show that the system is stable in the entire region where the Duan criterion for inseparability is fulfilled. The effect of thermal noise on the generated entanglement is examined. Finally, we compare this technique with standard methods for entanglement generation using optomechanics. [ABSTRACT FROM AUTHOR]

Phonon lasers or coherent amplifications of mechanical oscillations are powerful tools for fundamental studies on coherent acoustics and hold potential for diverse applications, ranging from ultrasensitive force sensing to phononic information processing. Here, we propose the use of an optomechanical resonator coupled to a nonlinear optical resonator for directional phonon lasing. We find that by pumping the nonlinear optical resonator, directional optical squeezing can occur along the pump direction. As a result, we can achieve the directional mechanical gain using directional optical squeezing, thereby leading to nonreciprocal phonon lasing with a well-tunable directional power threshold. Our work proposes a feasible way to build nonreciprocal phonon lasers with various nonlinear optical media, which are important for a wide range of applications, such as directional acoustic amplifiers, invisible sound sensing or imaging, and one-way phononic networks. [ABSTRACT FROM AUTHOR]

We theoretically investigate continuous variable entanglement and macroscopic quantum coherence in the hybrid L–G rotational cavity optomechanical system containing two YIG spheres. In this system, a single L–G cavity mode and both magnon modes (which are due to the collective excitation of spins in two YIG spheres) are coupled through the magnetic dipole interaction whereas the L–G cavity mode can also exchange orbital angular momentum (OAM) with the rotating mirror (RM). We study in detail the effects of various physical parameters like cavity and both magnon detunings, environment temperature, optorotational and magnon coupling strengths on the bipartite entanglement and the macroscopic quantum coherence as well. We also explore parameter regimes to achieve maximum values for both of these quantum correlations. We also observed that the parameters regime for achieving maximum bipartite entanglement is completely different from macroscopic quantum coherence. So, our present study shall provide a method to control various nonclassical quantum correlations of macroscopic objects in the hybrid L–G rotational cavity optomechanical system and have potential applications in quantum sensing, quantum meteorology, and quantum information science. [ABSTRACT FROM AUTHOR]

There is a growing interest in the development of transportable optical ground station (TOGS) as an important component of laser communication network. The object of this paper is a TOGS designed for optical LEO satellite downlink as well as for long-distance aircraft downlink. A composite gravity compensation mount is proposed to simplify and efficiently suppress the low-order aberrations of an 800 mm aperture primary mirror with variable orientation of the optical antenna of a TOGS as it changes pointing. In this study, first we describe the composition of the TOGS and the utility of each part. Second, taking the minimization of the primary mirror deformation as the optimization objective, we employ the particle swarm optimization algorithm to find the optima of several key structural parameters by Isight software. Next, the annular Zernike polynomials are adopted to fit the wavefront error over the entire surface of the primary mirror for describing low-order aberrations, proving that the composite mount effectively suppresses the wavefront error to smaller than ⋋ /27, as the elevation angle changes from the horizontal to the vertical one. Finally, the ZYGO interferometer wavefront detections show that, after eliminating fabrication imperfections, the RMS of the wavefront error over the entire surface of the mirrors for horizontal and vertical axes, due to deformation, are 0.04⋋ and 0.035⋋, respectively. Compared to the results of the fitted wavefront error, the relative errors are 9.5% and 8.1%. The results show the validity and feasibility of the optimized composite mount and the wavefront fitting method, which can prove its reference significance for the budget and allocation of the systematic wavefront error in meter-scale optical antenna of the TOGS for satellite downlink. [ABSTRACT FROM AUTHOR]

We showcase the digital quantum simulation of the action of a Hamiltonian that governs the interaction between a quantum mechanical oscillator and an optical field, generating quantum entanglement between them via gravitational effects. This is achieved by making use of a boson-qubit mapping protocol and a digital gate decomposition that allow us to run the simulations in the quantum computers available in the IBM Quantum platform. We present the obtained results for the fidelity of the experiment in two different quantum computers, after applying error mitigation and post-selection techniques. The achieved results correspond to fidelities over 90%, which indicates that we were able to perform a faithful digital quantum simulation of the interaction and therefore of the generation of quantum entanglement by gravitational means in optomechanical systems. [ABSTRACT FROM AUTHOR]

Observation of molecular optomechanical effects is complicated by the need to localize electromagnetic energy in metal gaps about 1 nm in size. We propose to use a nanocavity with an epsilon-near-zero medium so that the conditions required for optomechanical coupling are less stringent. In this work, we simulate the enhancement of Raman scattering depending on the permittivity of the material and the polarization of the near field of the nanoparticle. It is shown that when the real part of dielectric permittivity close to zero, Raman scattering demonstrates an additional enhancement. [ABSTRACT FROM AUTHOR]

We have analyzed the photon blockade effect in a double-cavity optomechanical system. We have explained the conventional and unconventional photon blockade effects in both weak and strong Kerr-nonlinear regimes. Through the analytical solution of the non-Hermitian Hamiltonian and the numerical solution of the master equation, the second-order correlation function of the cavity field has been calculated. We can control photon blockade effects under a small value of external pump amplitude. In this theoretical simulation, both numerical and analytical results are agreed well. The photon blockade effect is visualized by using a different contour plot. In this study, we achieve the optimal conditions for red detuning and blue detuning. We can control the rate of transmission and minimal points to locate g 2 0 . This proposal may be used to generate a single photon source with sub-Poissonian distribution and can also be useful for quantum information processing in quantum communication technology. [ABSTRACT FROM AUTHOR]

The fragile nature of quantum circuits is a major bottleneck to scalable quantum applications. Operating at cryogenic temperatures, quantum circuits are highly vulnerable to amplifier backaction and external noise. Non-reciprocal microwave devices such as circulators and isolators are used for this purpose. These devices have a considerable footprint in cryostats, limiting the scalability of quantum circuits. As a proof-of-concept, here we report a compact microwave diode architecture, which exploits the non-linearity of a superconducting flux qubit. At the qubit degeneracy point we experimentally demonstrate a significant difference between the power levels transmitted in opposite directions. The observations align with the proposed theoretical model. At − 99 dBm input power, and near the qubit-resonator avoided crossing region, we report the transmission rectification ratio exceeding 90% for a 50 MHz wide frequency range from 6.81 GHz to 6.86 GHz, and over 60% for the 250 MHz range from 6.67 GHz to 6.91 GHz. The presented architecture is compact, and easily scalable towards multiple readout channels, potentially opening up diverse opportunities in quantum information, microwave read-out and optomechanics. Quantum devices exhibiting non-reciprocal behaviour have been attracting attention for fundamental studies and applications. Here the authors report a microwave quantum diode based on a superconducting flux qubit coupled to two resonators, which has the advantage of compactness and scalability. [ABSTRACT FROM AUTHOR]

Phase transition from the over-damping to under-damping states is a ubiquitous phenomenon in physical systems. However, what kind of symmetry is broken associated with this phase transition remains unclear. Here, we discover that this phase transition is determined by an anti-parity-time (anti- P T ) symmetry hidden in a single damping linear resonator, which is significantly different from the conventional anti- P T -symmetric systems with two or more modes. We show that the breaking of the anti- P T symmetry yields the phase transition from the over-damping to under-damping states, with an exceptional point (EP) corresponding to the critical-damping state. Moreover, we propose an optomechanical scheme to show this anti- P T symmetry breaking by using the optical spring effect in a quadratic optomechanical system. We also suggest an optomechanical sensor with the sensitivity enhanced significantly around the EPs for the anti- P T symmetry breaking. Our work unveils the anti- P T symmetry hidden in damping oscillations and hence opens up new possibilities for exploiting wide anti- P T symmetry applications in single damping linear resonators. [ABSTRACT FROM AUTHOR]

The coherent transduction of information between microwave and optical domains is a fundamental building block for future quantum networks. A promising way to bridge these widely different frequencies is using high-frequency nanomechanical resonators interacting with low-loss optical modes. State-of-the-art optomechanical devices rely on purely dispersive interactions that are enhanced by a large photon population in the cavity. Additionally, one could use dissipative optomechanics, where photons can be scattered directly from a waveguide into a resonator hence increasing the degree of control of the acousto-optic interplay. Hitherto, such dissipative optomechanical interaction was only demonstrated at low mechanical frequencies, precluding prominent applications such as the quantum state transfer between photonic and phononic domains. Here, we show the first dissipative optomechanical system operating in the sideband-resolved regime, where the mechanical frequency is larger than the optical linewidth. Exploring this unprecedented regime, we demonstrate the impact of dissipative optomechanical coupling in reshaping both mechanical and optical spectra. Our figures represent a two-order-of-magnitude leap in the mechanical frequency and a tenfold increase in the dissipative optomechanical coupling rate compared to previous works. Further advances could enable the individual addressing of mechanical modes and help mitigate optical nonlinearities and absorption in optomechanical devices. Dissipative optomechanics, once limited to low frequencies, now operates in a sideband-resolved regime, reshaping optical and mechanical spectra and paving the way for the individual addressing of different mechanical modes in a single device. [ABSTRACT FROM AUTHOR]

Nonlinear interactions between modes with eigenfrequencies that differ by orders of magnitude are ubiquitous in various fields of physics, ranging from cavity optomechanics to aeroelastic systems. Simplifying their description to a minimal model and grasping the essential physics is typically a system-specific challenge. We show that the complex dynamics of these interactions can be distilled into a single generic form, namely, the Stuart-Landau oscillator. With our model, we study the injection locking and frequency pulling of a low-frequency mode interacting with a blue-detuned high-frequency mode, which generate frequency combs. Such combs are tunable around both the high and low carrier frequencies. By discussing the analogy with a simple mechanical system model, we offer a minimalistic conceptual view of these complex interactions originating the frequency combs, together with showcasing their frequency tunability. Nonlinear interactions between modes with eigenfrequencies that differ by orders of magnitude occur in several physical systems. This article provides a simple conceptual model of these interactions, and uses this model to design tunable frequency combs. [ABSTRACT FROM AUTHOR]

Measurement-based feedback has been adopted as an efficient cooling scheme capable of suppressing the thermal fluctuation of a mechanical resonator to a level limited by measurement imprecision. We present a scheme of squeezed cooling in which the limit of feedback cooling imposed by the measurement imprecision is surpassed by parametrically squeezing the mechanical resonator in a periodically oscillating optical trap. To stabilize the parametrically amplified quadrature and simultaneously optimize the cooling for the squeezed quadrature, a measurement-based vector feedback capable of independently controlling the orthogonal motional quadrature is implemented. Our experiment demonstrates that the optimal condition for the squeezed cooling closely depends on the strength of squeezing. With the ability to keep the orthogonal quadrature well decoupled, optimal squeezed cooling of the mechanical resonator under strong squeezing is achieved with the squeezed variance becoming 8.1 dB below the limit of feedback cooling and the creation of a 31.7 dB thermomechanical squeezed cooling. Although this research is conducted in the classical regime, the scheme of squeezed cooling can be naturally extended to quantum systems with the prospects of creating quantum squeezing of a room-temperature mechanical resonator and enabling displacement measurement beyond the standard quantum limit. [ABSTRACT FROM AUTHOR]

The momentum carried by structured light fields exhibits a rich array of surprising features. In this work, we generate transverse orbital angular momentum (TOAM) in the interference field of two parallel and counter-propagating linearly-polarised focused beams, synthesising an array of identical handedness vortices carrying intrinsic TOAM. We explore this structured light field using an optomechanical sensor, consisting of an optically levitated silicon nanorod, whose rotation is a probe of the optical angular momentum, which generates an exceptionally large torque. This simple creation and direct observation of TOAM will have applications in studies of fundamental physics, the optical manipulation of matter and quantum optomechanics. A new polarization structure of light is synthesized in a straightforward and robust way. The light field is probed using a levitated nanoparticle as a sensor. Optical angular momentum is used to control the particle in a novel way, with applications in sensing and quantum optomechanics. [ABSTRACT FROM AUTHOR]

Optomechanics deals with the control and applications of mechanical effects of light that stems from the redistribution of photon momenta in light scattering. As an example, light-induced levitation of an infinitesimally small dipolar particle is expected in front of epsilon-near-zero (ENZ) metamaterials. However, a theoretical understanding of these effects on single-material and multi-material larger particles is still lacking. Here, we investigate, analytically and numerically, optical forces on polarizable particles with size ranging from 20 nm to a 1 μm in proximity of ENZ metamaterials. We look at the general features of the repulsive-attractive optomechanics from the nano to the microscale exploiting different theoretical methods (dipole approximation, finite elements calculations, transition (T-)matrix). We discuss the role of realistic layered materials, as our ENZ substrate, on optical forces and analyze the influence of composition and shape by studying a range of complex particles (dielectric, core-shell, plasmonic ellipsoids). Physical insights into the results are discussed and future research directions are forecasted. Our results provide possibilities in exploiting engineered materials and surfaces for the manipulation and tailoring of light-induced forces in optomechanics. Optomechanics deals with the control and applications of mechanical effects of light on matter. Here, these effects on single-material and multimaterial larger particles with size ranging from 20 nm to a 1 μm are investigated in proximity of epsilon-near-zero metamaterials exploiting different theoretical methods. [ABSTRACT FROM AUTHOR]

The nonlinear component of the optomechanical interaction between light and mechanical vibration promises many exciting classical and quantum mechanical applications, but is generally weak. Here we demonstrate enhancement of nonlinear optomechanical measurement of mechanical motion by using pairs of coupled optical and mechanical modes in a photonic crystal device. In the same device we show linear optomechanical measurement with a strongly reduced input power and reveal how both enhancements are related. Our design exploits anisotropic mechanical elasticity to create strong coupling between mechanical modes while not changing optical properties. Additional thermo-optic tuning of the optical modes is performed with an auxiliary laser and a thermally-optimised device design. We envision broad use of this enhancement scheme in multimode phonon lasing, two-phonon heralding and eventually nonlinear quantum optomechanics. The authors demonstrate the enhancement of nonlinear optomechanical measurement of mechanical motion by using pairs of coupled optical and mechanical modes in a 1D photonic crystal. The design harnesses the anisotropic mechanical elasticity to create strong coupling between mechanical modes. [ABSTRACT FROM AUTHOR]

Optomechanical systems are known to exhibit self-sustained limit cycles once driven above the parametric instability point. By increasing the driving in the unresolved sideband limit, they reach chaotic regime through the cascaded period doubling process. Here, we study classical nonlinear dynamics of optomechanical systems operating in the resolved sideband regime ( ω m / κ ≫ 1 ) having a high mechanical Q - factor. We combine numerical simulations and analytical calculations to predict new nonlinear phenomena, so far unexplored in optomechanics. In the regime of single optical mode in the cavity, we connect the dynamical multistability to the hidden attractors, i.e., stable periodic state whose basin of attraction does not overlap with the neighbourhood of an unstable equilibrium point. In the regime where more than one optical modes are involved, we show that complex dynamics like metamorphoses of basin boundaries take place. These metamorphoses, which are revealed through the creation (or disappearance) of some new (or old) basin sets, are induced via the increase of the input driving field. Interestingly, we point out also the frequency locking effect which prevents all routes to chaos in the system. However, the locking range shrinks rapidly as the optical linewidth increases. The concept of hidden attractors introduced here provides new opportunities to generate nonclassical states. Moreover, the frequency locking effect can be useful for stable clock oscillations, for metrological applications and to control oscillations in optomechanics. [ABSTRACT FROM AUTHOR]

Quantum entanglement plays a key role in both understanding the fundamental aspects of quantum physics and realizing various quantum devices for practical applications. Here we propose how to achieve a coherent switch of optomechanical entanglement in an optical whispering-gallery-mode resonator, by tuning the phase difference of the driving lasers. We find that the optomechanical entanglement and the associated two-mode quantum squeezing can be well tuned in a highly asymmetric way, providing an efficient way to protect and enhance quantum entanglement against optical backscattering, in comparison with conventional symmetric devices. Our findings shed a new light on improving the performance of various quantum devices in the practical noisy environment, which is crucial in such a wide range of applications as noise-tolerant quantum processing and the backscattering-immune quantum metrology. [ABSTRACT FROM AUTHOR]

Based on the f-oscillator formalism, we introduce a nonlinear optomechanical framework which is constructed from the standard optomechanical system by deforming the single-mode photonic-field operators. Such a generalized optomechanical system describes an intensity-dependent interaction of a mechanical oscillator with a single-mode electromagnetic field. To gain insight into the effectiveness of the non-linearization processes, we investigate the role of the involving parameters especially the nonlinearity function that controls the entanglement and statistical properties of the photon-phonon state was considered. Thus, we apply the linear entropy measure and the Wigner function to quantify the entanglement and non-classical properties of this composite system and the condition in which quantum entanglement and negativity of the Wigner function can be enhanced and maximized has been identified. Thus, depending on an election of the nonlinearity function, one can observe different non-classical effects. These trends are compared with those obtained for the standard optomechanical system including photon-phonon interaction, too. [ABSTRACT FROM AUTHOR]

We report the quantum memory efficiency and optical transistor action in a two-sided hybrid optomechanical cavity with a medium composed of three-level atoms inside it. We show that the hybrid system has higher controllable memory efficiency to store and retrieve information as a function of optomechanical coupling parameter. We control the efficiency of this system for different values of optomechanical parameters. Moreover, this system acts as an optical transistor that works on the principle of optomechanically induced transparency (OMIT). We achieve the control over transmission profile, simultaneously turning on and off the different coupling parameters involved in this system. We also present the contrast for transmission of light when control field turns on and off as an evidence of optical transistor action. The numerical results obtained are in complete agreement with analytical results based on presently available technology. [ABSTRACT FROM AUTHOR]

We present a novel cavity opto-magno-mechanical hybrid system to generate entanglements among multiple quantum carriers, such as magnons, mechanical resonators, and cavity photons in both the optical and microwave domains. Two Yttrium iron garnet (YIG) spheres are embedded in two separate microwave cavities which are joined by a communal mechanical resonator. Because the microwave cavities are separate, the ferromagnetic resonate frequencies of two YIG spheres can be tuned independently, as well as the cavity frequencies. We show that entanglement can be achieved with experimentally reachable parameters. The entanglement is robust against environmental thermal noise, owing to the mechanical cooling process achieved by the optical cavity. The maximum entanglement among different carriers is achieved by optimizing the parameters of the system. The individual tunability of the separated cavities allows us to independently control the entanglement properties of different subsystems and establish quantum channels with different entanglement properties in one system. This work could provide promising applications in quantum metrology and quantum information tasks. [ABSTRACT FROM AUTHOR]

We investigate theoretically, the optical response for a cavity optomechanical system containing a Kerr non-linear substrate. The optomechanical cavity's moving membrane interacts linearly and quadratically with the radiation pressure of the photons. We found that the quadratic non-linear coupling and Kerr non-linearity strongly influence the system's optical multistability. Further, the transmission spectrum is observed under the influence of both non-linearities. Our theoretical results show that the width of the spectrum alters significantly by tuning the non-linearities present in the system. In addition, our results show that a peculiar positive value of quadratic optomechanical coupling is instrumental in generating Normal Mode splitting while the absence and negative value of quadratic optomechanical coupling inhibit the Normal-Mode splitting. [ABSTRACT FROM AUTHOR]

This paper theoretically studies a hybrid optomechanical system embedded with two coupled quantum dots and a third-order Kerr nonlinear medium inside the cavity. The optical bistability and absorption spectrum are analyzed for the proposed system. From the Hamiltonian which describes the proposed system, a set of quantum Langevin equations are derived. Using these equations of motion, the steady-state mean field analysis is done which gives the phenomena of optical bistability. The performance of the optical switch is also analyzed in terms of gain and switching ratio. Further, the absorption spectrum of the system is derived and analyzed from the fluctuation dynamics. The optical bistability has the potential to design tunable all-optical switches. The absorption spectra display peculiar characteristics of negative absorption (transparency dip). The transparency dips are found to be strongly dependent on the frequency of the mechanical resonator. The results of our investigation reveal that the proposed system can be used as an optical switch and has numerous other applications in quantum communication systems. [ABSTRACT FROM AUTHOR]

Optical forces are known to arise in a universal fashion in many and diverse physical settings. As such, they are successfully employed over a wide range of applications in areas like biophotonics, optomechanics and integrated optics. While inter-elemental optical forces in few-mode photonic networks have been so far systematically analyzed, little is known, if any, as to how they manifest themselves in highly multimoded optical environments. In this work, by means of statistical mechanics, we formally address this open problem in optically thermalized weakly nonlinear heavily multimode tight-binding networks. The outlined thermodynamic formulation allows one to obtain in an elegant manner analytical results for the exerted thermodynamic pressures in utterly complex arrangements-results that are either computationally intensive or impossible to obtain otherwise. Thus, we derive simple closed-form expressions for the thermodynamic optical pressures displayed among elements, which depend only on the internal energy as well as the coupling coefficients involved. In all cases, our theoretical results are in excellent agreement with numerical computations. Our study may pave the way towards a deeper understanding of these complex processes and could open up avenues in harnessing radiation forces in multimode optomechanical systems. Optical radiation forces have many applications in various fields, from biophonic, to soft matter and atomic physics. The authors theoretically investigate thermodynamic optical pressure in tight-binding nonlinear multimode photonic systems. [ABSTRACT FROM AUTHOR]

A nanomechanical oscillator can be used as a sensitive probe of a small linearized mechanical force. We propose a simple quantum optomechanical scheme using a coherent light mode in the cavity and weak short-pulsed light-matter interactions. Our main result is that if we transfer some displacement to the mechanical mode in an initialization phase, then a much weaker optomechanical interaction is enough to obtain a high-precision multiparameter estimation of the unknown force. This approach includes not only estimating the displacement caused by the force but also simultaneously observing the phase shift and squeezing of the mechanical mode. We show that the proposed scheme is robust against typical experimental imperfections and demonstrate the feasibility of our scheme using orders of magnitude weaker optomechanical interactions than in previous related works. Thus, we present a simple, robust estimation scheme requiring only very weak light-matter interactions, which could open the way to new nanomechanical sensors. [ABSTRACT FROM AUTHOR]

This study focuses on the Optomechanical bichromatic wavelength switching system as an indirect two-color up-conversion process that relies on optical force and nanorod scattering effects. This system is used to control light coupling between four parallel optical waveguides made of silicon nitride (Si3N4) which form two identical parts. The parallel waveguides with 0.5 µm × 0.5 µm cross-section and 220 µm lengths are suspended on a silica (SiO2) substrate embedded with the array of square silicon (Si) nanorods. By mid-IR plane wave illumination, as control light, with different intensities and different wavelengths on nanorods, scattering would increase and result in an improvement in attractive gradient optical force exerted on waveguides. Via bending waveguides toward each other, caused by optical gradient force, two different visible lights, as probe signals, propagating in the first waveguide of each section would couple to the adjacent waveguide. Simulation results reveal that when the distance between the parallel waveguides in the equilibrium position is 100 nm and the intensity of mid-IR light is 1.28 mW/µm2 total coupling would occur in two situations: 1- when the control light is 4.5 µm, the probe light with 713 nm wavelength is transmitted to the output, 2- when the control light is 3 µm, the probe light with 609 nm wavelength is transmitted to the output. In the first case 1.92 pN/µm optical force is needed to bend each waveguide by 9 nm and in the second one, 1.28 pN/µm optical force is needed to bend each waveguide by 6 nm for total coupling. The efficiency of the coupled waveguides system is %88.6 for 609 nm probe light injection and %96.5 for 713 nm probe light injection. [ABSTRACT FROM AUTHOR]

Light is a powerful tool for controlling mechanical motion, as shown by numerous applications in the field of cavity optomechanics. Recently, small scale optomechanical circuits, connecting a few optical and mechanical modes, have been demonstrated in an ongoing push towards multi-mode on-chip optomechanical systems. An ambitious goal driving this trend is to produce topologically protected phonon transport. Once realized, this will unlock the full toolbox of optomechanics for investigations of topological phononics. Here, we report the realization of topological phonon transport in an optomechanical device. Our experiment is based on an innovative multiscale optomechanical crystal design and allows for site-resolved measurements in an array of more than 800 cavities. The sensitivity inherent in our optomechanical read-out allowed us to detect thermal fluctuations traveling along topological edge channels. This represents a major step forward in an ongoing effort to downscale mechanical topological systems. To realize the full promise of topological mechanical vibrations, they have to be controlled successfully at the nanoscale. Here the authors report topological phonon transport in an optomechanical array. This unlocks the full toolbox of cavity optomechanics, coupling light to motion, for the area of topological phononics. [ABSTRACT FROM AUTHOR]

We present an efficient and experimentally feasible scheme for the generation of entanglement among photon, magnon and phonon by exploiting magnetoelastic interaction between magnonic and phononic modes. Our scheme is based on direct coupling between magnon and phonon modes whereas magnon and optical modes are indirectly coupled. Our numerical results show that the magnetoelastic coupling between magnon and phonon is significantly larger than the optomechanical coupling between photon and phonon. In addition to directly coupled modes entanglements, indirectly coupled bipartition also shows a strong correlation when we consider the magnon frequency to be much larger than the phonon frequency and magnon decay rate to be less than the cavity decay rate. Furthermore, we also obtained the robustness of entanglement, among all bipartitions, against thermal and environmental fluctuations. Moreover, we have characterized tripartite entanglement which shows the existence of a strong correlation among magnon, phonon, and photon. [ABSTRACT FROM AUTHOR]

Mechanical quantum systems embedded in an external nonlinear potential currently offer the first deep excursion into quantum non-Gaussian motion. The Gaussian statistics of the motion of a linear mechanical quantum system, characterised by its mass and a linear-and-quadratic potential, possess a limited capacity to reduce noise in nonlinear variables. This limitation induces thresholds for noise reduction in nonlinear variables beyond which linear mechanical oscillators cannot pass. Squeezing below the thresholds for such variables is relevant for the implementation of nonlinear mechanical devices, such as sensors, processors or engines. First however, quantum non-Gaussian conservative motion must be identified in experiments with diverse nonlinear potentials. For this purpose, we provide sufficient criteria for quantum non-Gaussian motional states in conservative systems based on the observation of squeezing in nonlinear variables. We further extend these criteria to a hierarchy able to recognise the quantum non-Gaussian motion induced via diverse nonlinear potentials through their various capacities to produce nonlinear squeezing. Gaussian systems are useful for many quantum technologies but new applications will require control over nonlinear systems generating quantum non-Gaussian states. The authors present a method for the detection of quantum non-Gaussian states of mechanical particles which may be applied for future experiments in optomechanics and levitated nanoparticles in the quantum regime. [ABSTRACT FROM AUTHOR]

Guided by recent progress in ground state cooling and ultraweak force sensing in the optomechanical systems with optically levitated particles, we propose a novel quantum sensing protocol that can detect the gradient of a force field directly with extremely high sensitivity. The system consists of a pair of nanospheres levitated in the high vacuum environment with optical tweezers and an optical resonator. By positioning the two spheres suitably relative to the cavity, only the collective breathing mode of the sphere pair couples to the cavity field. This optomechanical coupling will transfer the information of force difference acting on the two sensors to cavity photons, which can then be detected directly at the output of the cavity. Given the optimal control of various technical noise sources, the sensitivity could reach 10 − 15 N m − 1 / Hz with a high spatial resolution of micron scale on a state-of-the-art experimental setup. The potential application of this protocol in searching for short range "new force" is analyzed. Compared with conventional searching protocols with a single levitated sphere, the method proposed here can increase the signal-to-noise ratio by more than one magnitude in a large searching parameter space. [ABSTRACT FROM AUTHOR]

Experimentally certifying the nonclassicality of quantum states in a reliable and efficient way is a challenge that remains both fundamental and daunting. Despite decades of topical research, techniques that can exploit optimally the information available in a given experimental setup are lacking. Here, we introduce a different paradigm to tackle these challenges, that is both directly applicable to experimental realities, and extendible to a wide variety of circumstances. We demonstrate that Klyshko's criteria, which remained a primary approach to tackle nonclassicality for the past 20 years, is a special case of a much more general class of nonclassicality criteria. We provide both analytical results and numerical evidence for the optimality of our approach in several different scenarios of interest for trapped-ion, superconducting circuits, optical and optomechanical experiments with photon-number resolving detectors. This work represents a significant milestone towards a complete characterisation of the nonclassicality detectable from the limited knowledge scenarios faced in experimental implementations. [ABSTRACT FROM AUTHOR]

Cavity optomechanics explores the coupling between optical and mechanical modes mediated by the radiation pressure force. Unlike the passive scheme, the active optomechanics with optical gain directly imposes the mechanical motion upon the lasing dynamics, unveiling the intrinsic properties determined by the system itself. Here we numerically explore the general characteristics of the active optomechanics. The effects of the mechanical oscillation on the macroscopic laser include introducing multiple unstable regimes in the lasing phase, shifting the laser central frequency, broadening the laser spectrum, and degrading the laser frequency stability. Reducing the optical gain down to one active atom highlights the quantum nature of atom–cavity and photon–phonon interactions. The one-atom optomechanical microlaser does not only emit nonclassical photons but also generate nonclassical photon–phonon pairs. Our work extends the cavity optomechanics to the active fashion, paving the way towards optomechanical light sources for photonic integrated circuits, on-chip quantum communication, and biosensing. Active optomechanics offers a route to precise microscopic sensing by measuring the intrinsic laser dynamics. Here, the principles of active optomechanics are studied numerically at the limit of a single active atom, opening a path to quantum applications. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) has been consistently supporting nanosciences and nanotechnologies for over 30 years and is used in many fields from condensed matter physics to biology. It enables the measurement of very weak forces at the nanoscale, thus elucidating the interactions at play in fundamental processes. Here, we leverage the combined benefits of micro/nanoelectromechanical systems and cavity optomechanics to fabricate a sensor for dynamic mode AFM at a frequency above 100 MHz. This frequency is two decades above the fastest commercial AFM probes, suggesting an opportunity for measuring forces at timescales unexplored thus far. The fabrication is achieved using very-large-scale integration technologies derived from photonic silicon circuits. The probe's optomechanical ring cavity is coupled to a 1.55 μm laser light and features a 130 MHz mechanical resonance mode with a quality factor of 900 in air. A limit of detection in the displacement of 3 × 10−16 m/√Hz is obtained, enabling the detection of the Brownian motion of the probe and paving the way for force sensing experiments in the dynamic mode with a working vibration amplitude in the picometer range. When inserted in a custom AFM instrument embodiment, this optomechanical sensor demonstrates the capacity to perform force-distance measurements and to maintain a constant interaction strength between the tip and sample, an essential requirement for AFM applications. Experiments indeed show a stable closed-loop operation with a setpoint of 4 nN/nm for an unprecedented subpicometer vibration amplitude, where the tip–sample interaction is mediated by a stretched water meniscus. [ABSTRACT FROM AUTHOR]

Brillouin scattering has been widely exploited for advanced photonics functionalities such as microwave photonics, signal processing, sensing, lasing, and more recently in micro- and nano-photonic waveguides. Most of the works have focused on the opto-acoustic interaction driven from the core region of micro- and nano-waveguides. Here we observe, for the first time, an efficient Brillouin scattering generated by an evanescent field nearby a single-pass sub-wavelength waveguide embedded in a pressurised gas cell, with a maximum gain coefficient of 18.90 ± 0.17 m−1W−1. This gain is 11 times larger than the highest Brillouin gain obtained in a hollow-core fibre and 79 times larger than in a standard single-mode fibre. The realisation of strong free-space Brillouin scattering from a waveguide benefits from the flexibility of confined light while providing a direct access to the opto-acoustic interaction, as required in free-space optoacoustics such as Brillouin spectroscopy and microscopy. Therefore, our work creates an important bridge between Brillouin scattering in waveguides, Brillouin spectroscopy and microscopy, and opens new avenues in light-sound interactions, optomechanics, sensing, lasing and imaging. The authors observe efficient Brillouin scattering generated by an evanescent field nearby a single pass sub-wavelength waveguide. This work creates an important bridge between Brillouin scattering in waveguides, Brillouin spectroscopy and microscopy. [ABSTRACT FROM AUTHOR]

In this paper, we consider a hybrid fiber-atom-optomechanical system consisting of two optomechanical cavities where they are connected together with an optical fiber. Moreover, each cavity interacts separately with a two-level atom. Obtaining the effective Hamiltonian of the whole system, we find the state vector of the system numerically. Afterward, we study the degree of entanglement (DEM) between two atoms with the benefit of concurrence. We show that the DEM between the atoms can be appropriately controlled by adopting cavity-fiber and optomechanical couplings. Furthermore, we observe from the numerical results that the so-called phenomena of entanglement sudden death and birth (ESD and ESB) happen in the considered system. [ABSTRACT FROM AUTHOR]

We describe an optomechanical ratchet scheme to realize nonreciprocal transmission of a light field, which is based on the bias of the optical cavity's frequency spectrum caused by mechanical ratchet interactions. This approach to break the time-reversal symmetry of light propagation is universally valid in various optomechanical systems with ratchet-oscillator structures. We discuss specifically the implementation of an on-chip Casimir-ratchet optomechanical protocol and demonstrate the optical nonreciprocity with an extremely high isolation ratio and flexible controllability, which does not require external additional optical engineering. Our study opens a door for manipulating flexibly light propagation by using mechanical ratchet resonators, and has potential applications in the on-chip integration of nonreciprocal devices and harness of lateral Casimir forces. [ABSTRACT FROM AUTHOR]

Cavity optomechanics has achieved groundbreaking control and detection of mechanical oscillators, based on their coupling to linear electromagnetic modes. Recently, however, there is increasing interest in cavity nonlinearities as resource in radiation-pressure interacting systems. Here, we present a flux-mediated optomechanical device combining a nonlinear superconducting quantum interference cavity with a mechanical nanobeam. We demonstrate how the Kerr nonlinearity of the circuit can be used to enhance the device performance by suppressing cavity frequency noise, and for a counter-intuitive sideband-cooling scheme based on intracavity four-wave-mixing. With a large single-photon coupling rate of up to g0 = 2π ⋅ 3.6 kHz and a high mechanical quality factor Qm ≈ 4 ⋅ 105, we achieve an effective four-wave cooperativity of C fw > 100 and demonstrate four-wave cooling of the mechanical oscillator close to its quantum groundstate. Our results advance the recently developed platform of flux-mediated optomechanics and demonstrate how cavity Kerr nonlinearities can be utilized in cavity optomechanics. Cavity optomechanics studies interactions between mechanical oscillators and the radiation pressure induced by intracavity photons. The authors embedded a nonlinear Josephson junction in their microwave cavity to make the cavity response highly nonlinear and observed a counter-intuitive optomechanical process, blue-tone mechanical cooling. [ABSTRACT FROM AUTHOR]

Ground-state cooling of multiple mechanical resonators is an important goal in the study of quantum optomechanics. Here, we propose a dynamic dissipative synchronous cooling method for the simultaneous cooling of the two mechanical resonators in the strong optomechanical coupling regime. The synchronized modulation of the cavity dissipation can significantly accelerate the cooling process, with both of the resonators reaching the ground state. We derive the analytical cooling limits, which agree with the numerical simulations. The present scheme opens a new prospect for the research of multiple-mode ground-state cooling of mechanical resonators. [ABSTRACT FROM AUTHOR]

We theoretically investigate the second-order sideband generation (SSG) in a photonic-molecule optomechanics with phonon pump under the condition of resonance and off-resonance. We find that the efficiency of SSG presents four sideband peaks in resonance with controlling the different parametric regimes including the cavity-cavity coupling J, the ratio parameter δ of the two cavities, and the amplitude f and the phase ϕm of the phonon pump. Combining the two cavities coupling and phonon pump, the efficiency of SSG can be significantly enhanced. Furthermore, the SSG is also sensitive to the condition of off-resonance, which presents mode splitting behavior under different parametric regimes, and our work offer a promising route towards achieving tunable optical nonlinearity. [ABSTRACT FROM AUTHOR]

Schemes of gravitationally induced decoherence are being actively investigated as possible mechanisms for the quantum-to-classical transition. Here, we introduce a decoherence process due to quantum gravity effects. We assume a foamy quantum spacetime with a fluctuating minimal length coinciding on average with the Planck scale. Considering deformed canonical commutation relations with a fluctuating deformation parameter, we derive a Lindblad master equation that yields localization in energy space and decoherence times consistent with the currently available observational evidence. Compared to other schemes of gravitational decoherence, we find that the decoherence rate predicted by our model is extremal, being minimal in the deep quantum regime below the Planck scale and maximal in the mesoscopic regime beyond it. We discuss possible experimental tests of our model based on cavity optomechanics setups with ultracold massive molecular oscillators and we provide preliminary estimates on the values of the physical parameters needed for actual laboratory implementations. Current hypotheses towards quantisation of gravity imply the presence of a minimal length scale, which may have a role in explaining quantum-to-classical transition. Here, the authors show how assuming the minimal length scale to be a fluctuating quantity leads to a possible universal decoherence mechanism. [ABSTRACT FROM AUTHOR]

We have designed and implemented a compact, cost-efficient miniaturised light-sheet microscopy system based on optical microelectromechanical systems scanners and tunable lenses. The system occupies a footprint of 20 × 28 × 13 cm3 and combines off-the-shelf optics and optomechanics with 3D-printed structural and optical elements, and an economically costed objective lens, excitation laser and camera. All-optical volume scanning enables imaging of 435 × 232 × 60 µm3 volumes with 0.25 vps (volumes per second) and minimum lateral and axial resolution of 1.0 µm and 3.8 µm respectively. An open-top geometry allows imaging of samples on flat bottomed holders, allowing integration with microfluidic devices, multi-well plates and slide mounted samples, with applications envisaged in biomedical research and pre-clinical settings. [ABSTRACT FROM AUTHOR]

Microlasers, relying on the strong coupling between active particles and optical microcavity, exhibit fundamental differences from conventional lasers, such as multi-threshold/thresholdless behavior and nonclassical photon emission. As light sources, microlasers possess extensive applications in precision measurement, quantum information processing, and biochemical sensing. Here we propose a whispering-gallery-mode microlaser scheme, where ultracold alkaline-earth metal atoms, i.e., gain medium, are tightly confined in a two-color evanescent lattice that is in the ring shape and formed around a microsphere. To suppress the influence of the lattice-induced ac Stark shift on the moderately-narrow-linewidth laser transition, the red-detuned trapping beams operate at a magic wavelength while the wavelength of the blue-detuned trapping beam is set close to the other magic wavelength. The tiny mode volume and high quality factor of the microsphere ensure the strong atom-microcavity coupling in the bad-cavity regime. As a result, both saturation photon and critical atom numbers, which characterize the laser performance, are substantially reduced below unity. We explore the lasing action of the coupled system by using the Monte Carlo approach. Our scheme may be potentially generalized to the microlasers based on the forbidden clock transitions, holding the prospect for microscale active optical clocks in precision measurement and frequency metrology. [ABSTRACT FROM AUTHOR]

Using photoemission spectroscopy (PES), we have systematically investigated the behavior of polar organic molecule, chloroaluminum phthalocyanine (ClAlPc), adsorbed in the Cl-down configuration on the Ag(111) substrate at low temperature − 195 °C under UV irradiation with a range of different photon fluxes. Judging from the evolution of photoemission spectral line shapes of molecular energy states, we discovered that the Cl atoms are so robustly anchored at Ag(111) that the impinging photons cannot flip the ClAlPc molecules, but instead they crouch them down due to radiation pressure; we observe that the phthalocyanine (Pc) lobes bend down to interact with Ag atoms on the substrate and induce charge transfer from them. As photon flux is increased, radiation pressure on the Pc plane initiates tunneling of the Cl atom through the molecular plane to turn the adsorption configuration of ClAlPc from Cl-down to an upheld Cl-up configuration, elucidating an optomechanical way of manipulating the dipole direction of polar molecules. Finally, work function measurements provide a distinct signature of the resulting upheld Cl-up configuration as it leads to a large increase in vacuum level (VL), ~ 0.4 eV higher than that of a typical flat-on Cl-up configuration driven by thermal annealing. [ABSTRACT FROM AUTHOR]

Measuring the orbital angular momentum (OAM) of vortex beams, including the magnitude and the sign, has great application prospects due to its theoretically unbounded and orthogonal modes. Here, the sign-distinguishable OAM measurement in optomechanics is proposed, which is achieved by monitoring the shift of the transmission spectrum of the probe field in a double Laguerre-Gaussian (LG) rotational-cavity system. Compared with the traditional single LG rotational cavity, an asymmetric optomechanically induced transparency window can occur in our system. Meanwhile, the position of the resonance valley has a strong correlation with the magnitude and sign of OAM. This originally comes from the fact that the effective detuning of the cavity mode from the driving field can vary with the magnitude and sign of OAM, which causes the spectral shift to be directional for different signs of OAM. Our scheme solves the shortcoming of the inability to distinguish the sign of OAM in optomechanics, and works well for high-order vortex beams with topological charge value ±45, which is a significant improvement for measuring OAM based on the cavity optomechanical system. [ABSTRACT FROM AUTHOR]

Optomechanical crystal cavities (OMC) have rich perspectives for detecting and indirectly analysing biological particles, such as proteins, bacteria and viruses. In this work we demonstrate the working principle of OMCs operating under ambient conditions as a sensor of submicrometer particles by optically monitoring the frequency shift of thermally activated mechanical modes. The resonator has been specifically designed so that the cavity region supports a particular family of low modal-volume mechanical modes, commonly known as -pinch modes-. These involve the oscillation of only a couple of adjacent cavity cells that are relatively insensitive to perturbations in other parts of the resonator. The eigenfrequency of these modes decreases as the deformation is localized closer to the centre of the resonator. Thus, by identifying specific modes that undergo a frequency shift that amply exceeds the mechanical linewidth, it is possible to infer if there are particles deposited on the resonator, how many are there and their approximate position within the cavity region. OMCs have rich perspectives for detecting and indirectly analysing biological particles, such as proteins, viruses and bacteria. [ABSTRACT FROM AUTHOR]

We systematically study the influence of simultaneously modulating the input laser intensity and quantum-dot (QD) resonance frequency on the mean-field dynamics, fluctuation energy transfer and entanglement in a optomechanical semiconductor resonator embedded with a QD. We show that the modulation and the hybrid system can be engineered to attain the desired mean-field values and control the fluctuation energy transfer and the entanglement among the various degrees of freedom. A remarkably high degree of entanglement can be generated by modulating only the QD frequency. The interplay between the two modulations leads to a decrease in the entanglement. Switching on the modulation leads to a transition from low stationary to large dynamical entanglement. This investigation provides novel strategies to coherently control data signal transfer and storage in quantum information processing networks. [ABSTRACT FROM AUTHOR]

The radiation force calculated in the Rayleigh regime is investigated by comparison with the generalized Lorenz Mie Theory (GLMT). The basic concepts behind the Rayleigh regime and GLMT are introduced, and a numerical simulation is conducted to analyze the difference between these two methods. Several physical parameters are considered to evaluate their effect on the calculation accuracy of the Rayleigh regime, including the particle size, optical wavelength, and beam waist. The numerical results show that the valid region of the Rayleigh regime depends primarily on the ratio of the wavelength and particle size, whereas the Gaussian beam size has a lesser impact on the calculation results for both methods. Our study provides critical conditions under which the Rayleigh regime is applicable. The calculation accuracy of the Rayleigh regime is also theoretically analyzed. [ABSTRACT FROM AUTHOR]

The piezoelectric optomechanical devices supply a promising experimental platform to realize the coherent and effective control and measurement of optical circuits working in Terahertz (THz) frequencies via superconducting electron devices typically working in Radio (MHz) frequencies. However, quantum fluctuations are unavoidable when the size of mechanical oscillators enter into the nanoscale. The consequences of the noisy environment are still challenging due to the lack of analytical tools. In this paper, a semi-classical and full-quantum model of piezoelectric optomechanical systems coupled to a noisy bosonic quantum environment are introduced and solved in terms of quantum-state diffusion (QSD) trajectories in the non-Markovian regime. We show that the noisy environment, particularly the central frequency of the environment, can enhance the entanglement generation between optical cavities and LC circuits in some parameter regimes. Moreover, we observe the critical points in the coefficient functions, which can lead the different behaviors in the system. Besides, we also witness the entanglement transfers between macroscopic objects due to the memory effect of the environment. Our work can be applied in the fields of electric/ optical switches, and long-distance distribution in a large-scale quantum network. [ABSTRACT FROM AUTHOR]