Mechanical Squeezing Research Articles

Biomimetic, Highly Reusable and Hydrophobic Graphene/Polyvinyl Alcohol/Cellulose Nanofiber Aerogels as Oil-Removing Absorbents.

Aerogels have great potential in oil absorption applications; however, many reported aerogels have the drawbacks of a low oil-recovery rate and poor mechanical properties, which limit their application. In this study, highly reusable graphene oxide (GO)/TEMPO-oxidized cellulose nanofiber (TOCN)/polyvinyl alcohol (PVA) aerogels with excellent mechanical properties and with an architecture similar to that of Thalia dealbata stems were fabricated through a three-step process of bidirectional-freezing, freeze-drying, and chemical vapor deposition (CVD) modification. After CVD modification, the modified GTPA (MGTPA) accorded hydrophobicity. The synergistic effects of the three components and the unique biomimetic structure conferred biomimetic-MGTPA (b-MGTPA) with excellent compressible properties. As an adsorbent, b-MGTPA showed a high adsorption capacity (75–151 g/g) for various types of organic solvents. In addition, its high compressibility enables b-MGTPA to have fast and highly efficient recovery of absorbed oil through simple mechanical squeezing and it possesses excellent reusable stability (the oil recovery rate and oil retention rate reached 80% and 91.5%, respectively, after 10 repeated absorption–compression cycles).

Повышение экологической безопасности в свете климатической повестки при производстве цемента

Cement production is associated with the multi-stage mechanical and high-temperature processing of the raw materials. It is characterized by the high energy consumption and, along with the thermal power plants, significant emissions of the main greenhouse gas CO2 into the environment. Cement industry is the basic branch of the construction complex, which significantly effects on the environmental safety and economic development of the country. Environmental safety of the cement industry can be ensured based on the integrated approach which allows organizing the production process in such a way that it becomes possible to prevent or significantly reduce carbon dioxide emissions. This will predetermine high competitiveness of the enterprises in the environmentally sensitive markets. Undoubtedly, the technological modernization of the cement industry is one of the main priorities of its development. Results of the research allowed to identify two main directions for reducing the carbon level of environmental hazard in the cement production: reducing CO2 emissions during decarbonization by reducing the carbonate component in the raw mix; reducing fuel consumption by switching to a dry cement production method. The prospect of transferring cement production technology to the dry method has the number of problems associated mainly with large financial, material and time costs. Considering high natural moisture content of the feedstock, it is possible to switch to a combined production method, in which more than half of the water contained in the sludge is removed by mechanical squeezing. Thus, it is possible to reduce the costs of water removal by 10 times, and the volume of investments, compared with the construction of a dry line, by 5–8 times.

Backaction Evading and Amplification of Weak Force Signal in an Optomechanical System

AbstractA scheme of backaction evading and amplification of weak force signal is presented in an optomechanical system. By introducing the frequency modulation of the cavity field, the system can achieve the quantum nondemolition measurement interaction so that the backaction evading can be reached. With the help of the mechanical squeezing, the weak force signal can be amplified, which equals to amplifying the mechanical response function, reducing additional noise as well as thermal noise of mechanical oscillator. The current scheme opens up an alternative method for simultaneously surpassing the standard quantum limit and enhancing the mechanical response, and also reducing the mechanical thermal noise.

Improving Atom–Mirror Entanglement and Mechanical Squeezing in a Modulated Optomechanical System

AbstractIn this paper, the macroscopic quantum entanglement and squeezing in an unresolved‐sideband atom‐optomechanical system with a modulated optical parametric amplifier (OPA) inside the cavity are studied. Increasing the parametric gain of the OPA, the quantum‐classical correspondence between the atom‐mirror entanglement and classical nonlinear dynamics can be found. The critical point where the system experiences the transition from periodic oscillation to period‐doubling motion can be characterized by the singularity of the atom–mirror entanglement. Furthermore, the dependence of the atom–mirror entanglement and mechanical squeezing on the detuning and the parametric gain of the OPA as well as the environment temperature are investigated in detail. It is found that the atom‐mirror entanglement can be enhanced and the mechanical squeezing can be generated by modulating the OPA.

Dissipative Generation of Two‐Mode Mechanical Squeezing via Frequency Modulation

AbstractDifferent from the general schemes of two‐mode mechanical squeezing, a dissipative scheme to generate strong and robust two‐mode mechanical squeezing via frequency modulation of cavity modes in a cavity optomechanical system consisting of a modulated two‐mode optical cavity and two mechanical oscillators is proposed. It is shown that the strong mechanical squeezing, which is highly robust against the thermal noise, can be engineered by means of cavity dissipation. Moreover, the squeezing mechanism is explored via analytical approach and it is found that the squeezing direction is controlled by modulation amplitude. The scheme provides an alternative pathway to generate strong mechanical–mechanical entanglement.

Mechanical squeezing induced by Duffing nonlinearity and two driving tones in an optomechanical system

We propose a scheme to engineer strong steady-state mechanical squeezing via the joint effect between Duffing nonlinearity and two driving tones in an optomechanical system. It is found that the joint effect can achieve strong squeezing exceeding 3 dB when the amplitude ratio of two driving tones is large enough. Moreover, the generated squeezing can be flexibly manipulated by increasing the red-detuned laser power and selecting the amplitude ratio of two driving lasers. The robustness of mechanical squeezing set up by the joint effect to the thermal noise can be improved benefiting from the enhancement of red-detuned laser power. Furthermore, we present that the mechanical squeezing can be directly detected by homodyning the cavity output field under an appropriate phase.

Strong mechanical squeezing and optomechanical entanglement in a dissipative double-cavity system via pump modulation

We consider a dissipative cavity optomechanical system which couples to an auxiliary cavity with a high-quality factor and is driven by an amplitude-modulated laser field. Due to the introduction of the auxiliary cavity, we find that the steady-state mechanical squeezing can be enhanced compared to the case without an auxiliary cavity and the so-called 3 dB limit can also be broken in the resolved-sideband regime. Moreover, the squeezing can also be achieved even in the unresolved-sideband regime. We study the optomechanical entanglement in the presented system. It is found that the enhanced entanglement can be obtained by introducing the auxiliary cavity, and the entanglement can also be generated in the unresolved-sideband regime for appropriate system parameters. Numerical results show that the presented schemes have strong robustness against the thermal noise acting on the mechanical mode.

An Electro-Optical Method for Differential Diagnosis of Pathologies of Blood Supply to the Brain

This work is devoted to the development of a new simplified method for express diagnostics of cerebral blood supply disorders of a vertebrogenic and non-vertebral nature based on electrocardiogram and photoplethysmogram data. The research was conducted using the example of vertebral artery syndrome in osteochondrosis of the cervical spine and somatoform dysfunction of the autonomic nervous system, respectively. Several experimental studies into the dynamics of heart rate variability and differential indicators of the coordinated work of the heart and blood vessels were carried out according to the data of electrocardiography and photoplethysmography. Three experimental groups included healthy volunteers and volunteers with cerebral blood supply disorders connected with either the loss of plasticity and narrowing of brain blood vessels or their mechanical squeezing. According to the research results, statistically significant (with a significance level of less than 0.05) differences by a number of indicators were revealed between the experimental groups. A conventional discriminant analysis of the indicators of the coordinated work of the heart and blood vessels was carried out for all experimental groups in order to determine criteria for differentiating people with vertebrogenic disorders, non-vertebral disorders and healthy volunteers. It is concluded that three variables can be used for such differentiation, each of which describes the coordinated work of the heart and blood vessels in a specific way.

Signatures of the quantum nature of gravity in the differential motion of two masses

We show that a signature of the quantum nature of gravity is the quantum mechanical squeezing of the differential motion of two identical masses with respect to their common mode. This is because the gravitational interaction depends solely on the relative position of the two masses. In principle, this squeezing is equivalent to quantum entanglement between the masses. In practice, detecting the squeezing is more feasible than detecting the entanglement. To that end, we propose an optical interferometric scheme to falsify hypothetical models of gravity.

Fabrication of chitin nanofiber-PDMS composite aerogels from Pickering emulsion templates with potential application in hydrophobic organic contaminant removal

Natural polymers have aroused increasing attention in water treatment but their application in removing hydrophobic organic contaminants (HOCs) was limited due to their hydrophilicity. Herein, hydrophobic aerogels were successfully fabricated from Pickering emulsions stabilized by chitin nanofibers (ChNF) with polydimethylsiloxane (PDMS) as dispersed phase and glutaraldehyde as a crosslinking agent, and their performance in HOCs removal were evaluated. The Pickering emulsions with PDMS ratios of 2.5–20% v/v showed high stability, demonstrating great potential as aerogel templates. The solidified PDMS droplets were evenly distributed within the matrix, contributing to homogeneous and permanent hydrophobicity. The composite aerogels with water contact angles of over 130° could selectively remove non-aqueous phase HOCs from water. The CCl4 adsorption capacity was 521–2820 wt%, depending on PDMS contents. Meanwhile, the mechanical resilience of the composite aerogels was significantly improved, facilitating the adsorbent regeneration by simple mechanical squeezing. The adsorption capacity remained above 85% for 24 cycles. Moreover, the aerogels could also remove dissolved HOCs from water with a maximum adsorption capacity of 1.34 mg/g for 10 mg/L TCE. This work reveals the potential of Pickering emulsions in the fabrication of composite hydrophobic materials from natural biopolymers with promising application in HOCs related water treatment.

Two-photon blockade generated and enhanced by mechanical squeezing

Photon blockade is an important quantum nonlinear phenomenon in cavity optomechanics. Here, we investigate the two-photon blockade effect by exploiting the mechanical squeezing. This squeezing can enhance the optomechanical-coupling strength into the single-photon strong-coupling regime. With strong coupling, we find the photon blockade effects can be generated and enhanced, and the region where the two-photon blockade occurs can be widened. Finally, we study the transition between photon-induced tunneling and blockade.

Generation and transfer of squeezed states in a cavity magnomechanical system by two-tone microwave fields.

We propose a scheme to generate squeezed states of magnon and phonon modes and verify squeezing transfer between different modes of distinct frequencies in a cavity magnomechanical system which is composed of a microwave cavity and a yttrium iron garnet sphere. We present that by activating the magnetostrictive force in the ferrimagnet, realized by driving the magnon mode with red-detuned and blue-detuned microwave fields, the driven magnon mode can be prepared in a squeezed state. Moreover, the squeezing can be transferred to the cavity mode via the cavity-magnon beamsplitter interaction with strong magnomechanical coupling. We show that under the weak coupling regime, large mechanical squeezing of phonon mode can be achieved, which verifies that our scheme can find the existence of quantum effects at macroscopic scales. Furthermore, distinct parameter regimes for obtaining large squeezing of the magnons and phonons are given, which is the principal feature of our scheme. The considered scheme can be extended to hybrid optical systems, and can facilitate the advancement for realization of strong mechanical squeezing in cavity magnomechanical systems.

Micro-cellular polymer foam supported silica aerogel: Eco-friendly tool for petroleum oil spill cleanup

Flexible micro-cellular open porous 3D polymer foam silica aerogel composites with exceptional oil sorption characteristics were prepared by implanting silica aerogel in the interstices of foam substrates. Silica aerogels were engineered from silane precursors namely tetraethoxysilane (TEOS) and methyltrimethoxysilane (MTMS) adopting economical, energy efficient and scalable ambient pressure drying technique. These flexible composites exhibited outstanding structural ruggedness. The foam-aerogel composites deliver superior hydrophobic characteristics in terms of contact angle data. The aerogel composites recorded an oil uptake of 31.3 g per g of the composite for engine oil and the uptake was very swift. Mechanical squeezing enables near complete oil removal from the composites. The foam aerogel composites displayed superior recyclability features, as first time absorption is retained even after 10 cycles of repeated squeezing and re-absorption operations.

Unconditional mechanical squeezing via backaction-evading measurements and nonoptimal feedback control

Backaction-evading (BAE) measurements of a mechanical resonator, by continuously monitoring a single quadrature of motion, can achieve precision below the zero-point uncertainty. When this happens, the measurement leaves the resonator in a quantum squeezed state. The squeezed state so generated is however conditional on the measurement outcomes, while for most applications it is desirable to have a deterministic, i.e., unconditional, squeezed state with the desired properties. In this work we apply feedback control to achieve deterministic manipulation of mechanical squeezing in an optomechanical system subject to a continuous BAE measurement. We study in details two strategies, direct (Markovian) and state-based (Bayesian) feedback. We show that both are capable to achieve optimal performances, i.e., a vanishing noise added by the feedback loop. Moreover, even when the feedback is restricted to be a time-varying mechanical force (experimentally friendly scenario) and an imperfect BAE regime is considered, the ensuing nonoptimal feedback may still obtain significant amount of squeezing. In particular, we show that Bayesian feedback control is nearly optimal for a wide range of sideband resolution. Our analysis is of direct relevance for ultrasensitive measurements and quantum state engineering in state-of-the-art optomechanical devices.

Cavity optomechanics assisted by optical coherent feedback

We consider a wide family of optical coherent feedback loops acting on an optomechanical system operating in the linearized regime. We assess the efficacy of such loops in improving key operations, such as cooling, steady-state squeezing and entanglement, as well as optical to mechanical state transfer. We find that mechanical sideband cooling can be enhanced through passive, interferometric coherent feedback, achieving lower steady-state occupancies and considerably speeding up the cooling process; we also quantify the detrimental effect of non-zero delay times on the cooling performance. Steady state entanglement generation in the blue sideband can also be assisted by passive interferometric feedback, which allows one to stabilise otherwise unstable systems, though active feedback (including squeezing elements) does not help to this aim. We show that active feedback loops only allow for the generation of optical, but not mechanical squeezing. Finally, we prove that passive feedback can assist state transfer at transient times for red-sideband driven systems in the strong coupling regime.

Mechanical squeezing in a dissipative optomechanical system with two driving tones

The squeezed state of a macroscopic mechanical oscillator can be exploited to enhance the sensitivity of precision measurements. Here, we theoretically demonstrate that the displacement squeezing of a mechanical oscillator in a dissipative optomechanical system can be generated by the use of two driving tones tuned to the first upper and lower mechanical sidebands. We find that the displacement squeezing of the mechanical oscillator is determined by the powers of the two driving tones and the temperature of the environment. Even when the temperature of the environment is as high as 20 mK, the mechanical squeezing beyond 3 dB can be achieved. Moreover, we show that the mechanical squeezing can be detected by directly measuring the cavity output spectrum.

Preparation and verification of two-mode mechanical entanglement through pulsed optomechanical measurements

We propose a protocol how to generate and verify bipartite Gaussian entanglement between two mechanical modes coupled to a single optical cavity, by means of short optical pulses and measurement. Our protocol requires neither the resolved sideband regime, nor low thermal phonon occupancy, and allows the generation and verification of quantum entanglement in less than a mechanical period of motion. Entanglement is generated via effective two-mode mechanical squeezing through conditioning position measurements. We study the robustness of entanglement to experimental deviations in mechanical frequencies and optomechanical coupling rates.

Shish-Kebab-Structured UHMWPE Coating for Efficient and Cost-Effective Oil-Water Separation.

High-performance low-cost superhydrophobic sponges are desired for selective recycling of leaking oils from open water. Herein, an ingenious method is proposed to fabricate an ultrathin superhydrophobic coating layer on a commercial sponge. The coating layer is composed of a shish-kebab-structured porous ultrahigh molecular weight polyethylene (UHMWPE) film that is fabricated from a UHMWPE/xylene solution by shear flow-induced crystallization. A strong relationship between the shish-kebab crystallite morphology and the superwetting performance is confirmed. The UHMWPE coating layer fabricated at a 900 rpm rotation rate possesses a lamellae size of 95.1 nm and a lamellae distance of 27.4 nm, which lead to a high water contact angle of 157° and a low contact angle hysteresis of 4.5°. The UHMWPE layer prepared in 4 min of treatment is thick enough to prevent the intrusion of water even under vacuum and remain superoleophilic. The developed UHMWPE-coated sponge (UCS) exhibited a high absorption capability of 70-191 g/g toward various oils and solvents, which is comparable with the neat melamine sponge. Its excellent compressibility and durability enabled fast recovery of absorbed oil with a high recovery rate (over 85%) by mechanical squeezing. The UCS could be assembled into small devices to selectively collect oil from open water and a water/oil mixture using a pump, which manifests its promising practical applicability. Apart from these extraordinary properties, the approach developed has the lowest material cost and the shortest processing time hitherto.

Nonstationary force sensing under dissipative mechanical quantum squeezing

We study the stationary and nonstationary measurement of a classical force driving a mechanical oscillator coupled to an electromagnetic cavity under two-tone driving. For this purpose, we develop a theoretical framework based on the signal-to-noise ratio to quantify the sensitivity of linear spectral measurements. Then, we consider stationary force sensing and study the necessary conditions to minimise the added force noise. We find that imprecision noise and back-action noise can be arbitrarily suppressed by manipulating the amplitudes of the input coherent fields, however, the force noise power spectral density cannot be reduced below the level of thermal fluctuations. Therefore, we consider a nonstationary protocol that involves non-thermal dissipative state preparation followed by a finite time measurement, which allows one to perform measurements with a signal-to-noise much greater than the maximum possible in a stationary measurement scenario. We analyse two different measurement schemes in the nonstationary transient regime, a back-action evading measurement, which implies modifying the drive asymmetry configuration upon arrival of the force, and a nonstationary measurement that leaves the drive asymmetry configuration unchanged. Conditions for optimal force noise sensitivity are determined, and the corresponding force noise power spectral densities are calculated.

Large and robust mechanical squeezing of optomechanical systems in a highly unresolved sideband regime via Duffing nonlinearity and intracavity squeezed light.

We propose a scheme to generate strong and robust mechanical squeezing in an optomechanical system in the highly unresolved sideband (HURSB) regime with the help of the Duffing nonlinearity and intracavity squeezed light. The system is formed by a standard optomechanical system with the Duffing nonlinearity (mechanical nonlinearity) and a second-order nonlinear medium (optical nonlinearity). In the resolved sideband regime, the second-order nonlinear medium may play a destructive role in the generation of mechanical squeezing. However, it can significantly increase the mechanical squeezing (larger than 3dB) in the HURSB regime when the parameters are chosen appropriately. Finally, we show the mechanical squeezing is robust against the thermal fluctuations of the mechanical resonator. The generation of large and robust mechanical squeezing in the HURSB regime is a combined effect of the mechanical and optical nonlinearities.