Quantum noise interference and backaction cooling in cavity nanomechanics

Quantum nonlinear effect in a dissipatively coupled optomechanical system

A full-quantum approach is used to study the quantum nonlinear properties of a compound Michelson-Sagnac interferometer optomechanical system. By deriving the effective Hamiltonian, we find that the reduced system exhibits a Kerr nonlinear term with a complex coefficient, entirely induced by the dissipative and dispersive couplings. Unexpectedly, the nonlinearities resulting from the dissipative coupling possess non-Hermitian Hamiltonian-like properties preserving the quantum nature of the dispersive coupling beyond the traditional system dissipation. This protective mechanism allows the system to exhibit strong quantum nonlinear effects when the detuning (the compound cavity detuning Δc and the auxiliary cavity detuning Δe) and the tunneling coupling strength (J) of two cavities satisfy the relation J2 = ΔcΔe. Moreover, the additive effects of dispersive and dissipative couplings can produce strong anti-bunching effects, which exist in both strong and weak coupling conditions. Our work may provide a new way to study and produce strong quantum nonlinear effects in dissipatively coupled optomechanical systems.

Dissipative optomechanics in high-frequency nanomechanical resonators

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.

Integrated microcavity optomechanics with a suspended photonic crystal mirror above a distributed Bragg reflector

Increasing the interaction between light and mechanical resonators is an ongoing endeavor in the field of cavity optomechanics. Optical microcavities allow for boosting the interaction strength through their strong spatial confinement of the optical field. In this work, we follow this approach by realizing a sub-wavelength-long, free-space optomechanical microcavity on-chip fabricated from an (Al,Ga)As heterostructure. A suspended GaAs photonic crystal mirror is acting as a highly reflective mechanical resonator, which together with a distributed Bragg (DBR) reflector forms an optomechanical microcavity. We demonstrate precise control over the microcavity resonance by change of the photonic crystal parameters. We find that the microcavity mode can strongly couple to the transmissive modes of the DBR. The interplay between the microcavity mode and a guided resonance of the photonic crystal modifies the cavity response and results in a stronger dynamical backaction on the mechanical resonator compared to conventional optomechanical dynamics.

A path towards single molecule vibrational strong coupling in a Fabry-Pérot microcavity

Interaction between light and molecular vibrations leads to hybrid light-matter states called vibrational polaritons. Even though many intriguing phenomena have been predicted for single-molecule vibrational strong coupling (VSC), several studies suggest that these effects tend to be diminished in the many-molecule regime due to the presence of dark states. Achieving single or few-molecule vibrational polaritons has been constrained by the need for fabricating extremely small mode volume infrared cavities. In this theoretical work, we propose an alternative strategy to achieve single-molecule VSC in a cavity-enhanced Raman spectroscopy (CERS) setup, based on the physics of cavity optomechanics. We then present a scheme harnessing few-molecule VSC to thermodynamically couple two reactions, such that a spontaneous electron transfer can now fuel a thermodynamically uphill reaction that was non-spontaneous outside the cavity.

Negative-mass exciton polaritons induced by dissipative light-matter coupling in an atomically thin semiconductor

Dispersion engineering is a powerful and versatile tool that can vary the speed of light signals and induce negative-mass effects in the dynamics of particles and quasiparticles. Here, we show that dissipative coupling between bound electron-hole pairs (excitons) and photons in an optical microcavity can lead to the formation of exciton polaritons with an inverted dispersion of the lower polariton branch and hence, a negative mass. We perform direct measurements of the anomalous dispersion in atomically thin (monolayer) WS₂ crystals embedded in planar microcavities and demonstrate that the propagation direction of the negative-mass polaritons is opposite to their momentum. Our study introduces the concept of non-Hermitian dispersion engineering for exciton polaritons and opens a pathway for realising new phases of quantum matter in a solid state.

Kerr Enhanced Backaction Cooling in Magnetomechanics

Optomechanics is a prime example of light matter interaction, where photons directly couple to phonons, allowing the precise control and measurement of the state of a mechanical object. This makes it a very appealing platform for testing fundamental physics or for sensing applications. Usually, such mechanical oscillators are in highly excited thermal states and require cooling to the mechanical ground state for quantum applications, which is often accomplished by using optomechanical backaction. However, while massive mechanical oscillators are desirable for many tasks, their frequency usually decreases below the cavity linewidth, significantly limiting the methods that can be used to efficiently cool. Here, we demonstrate a novel approach relying on an intrinsically nonlinear cavity to backaction-cool a low frequency mechanical oscillator. We experimentally demonstrate outperforming an identical, but linear, system by more than 1 order of magnitude. Furthermore, our theory predicts that with this approach we can also surpass the standard cooling limit of a linear system. By exploiting a nonlinear cavity, our approach enables efficient cooling of a wider range of optomechanical systems, opening new opportunities for fundamental tests and sensing.

Cooling of mechanical resonator in a hybrid intracavity squeezing optomechanical system

A hybrid intracavity squeezing optomechanical cooling system, in which an auxiliary cavity couples to an optomechanical cavity with a nonlinear medium inside it, is proposed to realize the ground state cooling of the mechanical resonator in the highly unresolved sideband regime. We demonstrate that the quantum backaction heating can be suppressed perfectly by the intracavity squeezing, and the cooling process can be further promoted by adjusting the tunnel coupling between the coupled cavities. The scheme has good performance in resisting the environmental thermal noise and better tolerance for the auxiliary cavity quality factor and provides the possibility for the quantum manipulation of the mechanical resonator with large mass and low frequency.

Asymmetry-Based Quantum Backaction Suppression in Quadratic Optomechanics

As the field of optomechanics advances, quadratic dispersive coupling (QDC) represents an increasingly feasible path toward qualitatively new functionality. However, the leading QDC geometries generate linear dissipative coupling and an associated quantum radiation force noise that is detrimental to QDC applications. Here, we propose a simple geometry that dramatically reduces this noise without altering the QDC strength. We identify optimal regimes of operation, and discuss advantages within the examples of optical levitation and nondestructive phonon measurement.

Hybrid coupling optomechanical assisted nonreciprocal photon blockade

The properties of the open quantum system in quantum information is a science now extensively investigated more generally as a fundamental issue for a variety of applications. Usually, the states of the open quantum system might be disturbed by decoherence which will reduce the fidelity in the quantum information processing. So it is better to eliminate the influence of the environment. However, as part of the composite system, rational use of the environment system could be beneficial to quantum information processing. Here we theoretically studied the environment induced quantum nonlinearity and energy spectrum tuning method in the optomechanical system. And we found that the dissipation coupling of the hybrid dissipation and dispersion optomechanical system can induce the coupling between the environment and system in the cross-Kerr interaction form. When the symmetry is broken with a directional auxiliary field, the system exhibits the non-reciprocal behavior during the photon excitation and photon blockade for the clockwise and counterclockwise modes of the whispering gallery mode microcavity. Furthermore, we believe that the cross-Kerr coupling can be more widely used in quantum information processing and quantum simulation.

Full three-dimensional wavelength-scale plasmomechanical resonator

Plasmomechanical systems have received considerable interest in mediating the strong interaction between the optical field and mechanical motion. However, typical plasmomechanical systems based on mechanical oscillators that are significantly larger than the wavelength of light do not take full advantage of the optical field concentration beyond the optical diffraction limit of the employed plasmonic resonators. Here we present a full three-dimensional wavelength-scale plasmomechanical resonator consisting of a plasmonic nano-antenna and a hydrogen silsesquioxane nano-wall. The experimental results demonstrated the precise detection of longitudinal mechanical oscillation on a picometer scale, and we investigated the tunability and thermoelastic effect of the mechanical resonance.

Optomechanical atomic force microscope

In the scanning probe microscope system, the weak signal detection of cantilever vibration is one of the important factors affecting the sensor sensitivity. In our current work, we present a novel design concept for an atomic force microscope (AFM) combined with optomechanics with an ultra-high quality factor and a low thermal noise. The detection system consists of a fixed mirror placed on the cantilever of the AFM and pump-probe beams that is equivalent to a Fabry-Perot cavity. We realize that the AFM combined with an optical cavity can achieve ultra-sensitive detection of force gradients of 10^-12 N m^-1 in the case of high-vacuum and low effective temperature of 1 mK, which may open up new avenues for super-high resolution imaging and super-high precision force spectroscopy.

Quasinormal-Mode Perturbation Theory for Dissipative and Dispersive Optomechanics

Despite the several novel features arising from the dissipative optomechanical coupling, such effect remains vastly unexplored due to the lack of a simple formalism that captures non-Hermiticity in the engineering of optomechanical systems. In this Letter, we show that quasinormal-mode-based perturbation theory is capable of correctly predicting both dispersive and dissipative optomechanical couplings. We validate our model through simulations and also by comparison with experimental results reported in the literature. Finally, we apply this formalism to plasmonic systems, used for molecular optomechanics, where strong dissipative coupling signatures in the amplification of vibrational modes could be observed.

Ground-State Cooling and High-Fidelity Quantum Transduction via Parametrically Driven Bad-Cavity Optomechanics

Optomechanical couplings involve both beam splitter and two-mode-squeezing types of interactions. While the former underlies the utility of many applications, the latter creates unwanted excitations and is usually detrimental. In this Letter, we propose a simple but powerful method based on cavity parametric driving to suppress the unwanted excitation that does not require working with a deeply sideband-resolved cavity. Our approach is based on a simple observation: as both the optomechanical two-mode-squeezing interaction and the cavity parametric drive induce squeezing transformations of the relevant photonic bath modes, they can be made to cancel one another. We illustrate how our method can cool a mechanical oscillator below the quantum backaction limit, and significantly suppress the output noise of a sideband-unresolved optomechanical transducer.

Controlling Excitons in an Atomically Thin Membrane with a Mirror

We demonstrate a new approach for dynamically manipulating the optical response of an atomically thin semiconductor, a monolayer of MoSe_{2}, by suspending it over a metallic mirror. First, we show that suspended van der Waals heterostructures incorporating a MoSe_{2} monolayer host spatially homogeneous, lifetime-broadened excitons. Then, we interface this nearly ideal excitonic system with a metallic mirror and demonstrate control over the exciton-photon coupling. Specifically, by electromechanically changing the distance between the heterostructure and the mirror, thereby changing the local photonic density of states in a controllable and reversible fashion, we show that both the absorption and emission properties of the excitons can be dynamically modulated. This electromechanical control over exciton dynamics in a mechanically flexible, atomically thin semiconductor opens up new avenues in cavity quantum optomechanics, nonlinear quantum optics, and topological photonics.

Flexure-tuned membrane-at-the-edge optomechanical system

We introduce a passively-aligned, flexure-tuned cavity optomechanical system in which a membrane is positioned microns from one end mirror of a Fabry-Perot optical cavity. By displacing the membrane through gentle flexure of its silicon supporting frame (i.e., to ∼80 m radius of curvature (ROC)), we gain access to the full range of available optomechanical couplings, finding also that the optical spectrum exhibits none of the abrupt discontinuities normally found in "membrane-in-the-middle" (MIM) systems. More aggressive flexure (3 m ROC) enables >15 μm membrane travel, milliradian tilt tuning, and a wavelength-scale (1.64 ± 0.78 μm) membrane-mirror separation. We also provide a complete set of analytical expressions for this system's leading-order dispersive and dissipative optomechanical couplings. Notably, this system can potentially generate orders of magnitude larger linear dissipative or quadratic dispersive strong coupling parameters than is possible with a MIM system. Additionally, it can generate the same purely quadratic dispersive coupling as a MIM system, but with significantly suppressed linear dissipative back-action (and force noise).

Ground-state cooling of mechanical oscillator via quadratic optomechanical coupling with two coupled optical cavities

We present a scheme for the electromagnetically induced transparency (EIT)-like nonlinear ground-state cooling in a double-cavity optomechanical system in which an optical cavity mode is coupled parametrically to the square of the position of a mechanical oscillator, an additional auxiliary cavity is coupled to the optomechanical cavity. The optimum cooling conditions is derived, based on which the heating process can be well suppressed and the mechanical resonator can be cooled with an optimal effect to near its ground state through EIT-like cooling mechanism even in unresolved sideband regime. It is demonstrated by numerical simulations that not only the average phonon number of steady state is lower than that of single-cavity optomechanical system, but also the cooling rate is greatly faster than that of the linear optomechanical coupling due to the two-phonon cooling process in the quadratic coupling. Also, the ground-state cooling is achievable even with a relatively weak quadratic coupling strengthby tunning the coupling between two cavities to reach the optimum cooling conditions, thus provides an solution for overcoming the limitations of weak quadratic coupling rate in experiments. The proposed approach provides a platform for quantum manipulation of macroscopic mechanical devices beyond the resolved sideband limit and linear coupling regime.

Quantum-Limited Measurements Using an Optical Cavity with Modulated Intrinsic Loss

We analyze a cavity optomechanical setup, in which the position of an oscillator modulates the internal optical loss. We show that, in contrast to systems with a fixed internal loss, in such a setup, quantum-limited position measurements can be performed and formulate conditions under which it is possible. Additionally, under these conditions the setup exhibits a number of potential benefits for practical operation, including the complete absence of dynamical backaction and optomechanical instability, rejection of classical laser noise, and thermal fluctuations of cavity frequency from the measurement record. We address a few potential experimental implementations of this setup.

Double-passage ground-state cooling induced by quantum interference in the hybrid optomechanical system

We propose a quantum interference cooling scheme for a nano-mechanical resonator (NAMR) in a hybrid optomechanical system. In our scheme, atoms are trapped in an optomechanical cavity, and this optomechanical cavity interacts both atoms and an optical cavity. Therefore, the absorption of the optomechanical resonator can be modified by quantum interference effects induced by the atom-cavity and cavity-cavity couplings. With the modification of the quantum interference, the desired transition for cooling is enhanced, while the undesired transition for heating can be suppressed. As a result, the NAMR vibration can be cooled down to its ground state. Particularly, with the assistance of the atoms, the experimental difficulty can be reduced since the effective decay rate of the cavity can be decreased via the quantum interference for the atom-cavity coupling.

Parametric Excitation of Optomechanical Resonators by Periodical Modulation

Optical excitation of mechanical resonators has long been a research interest, since it has great applications in the physical and engineering field. Previous optomechanical methods rely on the wavelength-dependent, optical anti-damping effects, with the working range limited to the blue-detuning range. In this study, we experimentally demonstrated the excitation of optomechanical resonators by periodical modulation. The wavelength working range was extended from the blue-detuning to red-detuning range. This demonstration will provide a new way to excite mechanical resonators and benefit practical applications, such as optical mass sensors and gyroscopes with an extended working range.

Nano-opto-electro-mechanical systems

A new class of hybrid systems that couple optical, electrical and mechanical degrees of freedom in nanoscale devices is under development in laboratories worldwide. These nano-opto-electro-mechanical systems (NOEMS) offer unprecedented opportunities to control the flow of light in nanophotonic structures, at high speed and low power consumption. Drawing on conceptual and technological advances from the field of optomechanics, they also bear the potential for highly efficient, low-noise transducers between microwave and optical signals, in both the classical and the quantum domains. This Perspective discusses the fundamental physical limits of NOEMS, reviews the recent progress in their implementation and suggests potential avenues for further developments in this field.

Ground-state cooling of a mechanical oscillator in a hybrid optomechanical system including an atomic ensemble

We investigate dynamical properties and the ground-state cooling of a mechanical oscillator in an optomechanical system coupling with an atomic ensemble. In this hybrid optomechanical system, an atomic ensemble which consists of two-level atoms couples with the cavity field. Here we consider the case where the atomic ensemble is in higher excitation. Studies show that the atom-field coupling strength can obviously influence the cooling process, and we can achieve the ground-state cooling of the mechanical oscillator by choosing the appropriate physical parameters of the system. Our cooling mechanism has potential applications in quantum information processing and procession measurement.

Ground-State Cooling of a Mechanical Oscillator by Interference in Andreev Reflection

We study the ground-state cooling of a mechanical oscillator linearly coupled to the charge of a quantum dot inserted between a normal metal and a superconducting contact. Such a system can be realized, e.g., by a suspended carbon nanotube quantum dot with a capacitive coupling to a gate contact. Focusing on the subgap transport regime, we analyze the inelastic Andreev reflections which drive the resonator to a nonequilibrium state. For small coupling, we obtain that vibration-assisted reflections can occur through two distinct interference paths. The interference determines the ratio between the rates of absorption and emission of vibrational energy quanta. We show that ground-state cooling of the mechanical oscillator can be achieved for many of the oscillator's modes simultaneously or for single modes selectively, depending on the experimentally tunable coupling to the superconductor.

Laser Cooling of a Micromechanical Membrane to the Quantum Backaction Limit

The radiation pressure of light can act to damp and cool the vibrational motion of a mechanical resonator, but even if the light field has no thermal component, shot noise still sets a limit on the minimum phonon occupation. In optomechanical sideband cooling in a cavity, the finite off-resonant Stokes scattering defined by the cavity linewidth combined with shot noise fluctuations dictates a quantum backaction limit, analogous to the Doppler limit of atomic laser cooling. In our work, we sideband cool a micromechanical membrane resonator to the quantum backaction limit. Monitoring the optical sidebands allows us to directly observe the mechanical object come to thermal equilibrium with the optical bath. This level of optomechanical coupling that overwhelms the intrinsic thermal decoherence was not reached in previous ground-state cooling demonstrations.

Simultaneous cooling of coupled mechanical oscillators using whispering gallery mode resonances

We demonstrate simultaneous center-of-mass cooling of two coupled oscillators, consisting of a microsphere-cantilever and a tapered optical fiber. Excitation of a whispering gallery mode (WGM) of the microsphere, via the evanescent field of the taper, provides a transduction signal that continuously monitors the relative motion between these two microgram objects with a sensitivity of 3 pm. The cavity enhanced optical dipole force is used to provide feedback damping on the motion of the micron-diameter taper, whereas a piezo stack is used to damp the motion of the much larger (up to 180 μm in diameter), heavier (up to 1.5 × 10(-7) kg) and stiffer microsphere-cantilever. In each feedback scheme multiple mechanical modes of each oscillator can be cooled, and mode temperatures below 10 K are reached for the dominant mode, consistent with limits determined by the measurement noise of our system. This represents stabilization on the picometer level and is the first demonstration of using WGM resonances to cool the mechanical modes of both the WGM resonator and its coupling waveguide.

Electromechanical control of nitrogen-vacancy defect emission using graphene NEMS

Despite recent progress in nano-optomechanics, active control of optical fields at the nanoscale has not been achieved with an on-chip nano-electromechanical system (NEMS) thus far. Here we present a new type of hybrid system, consisting of an on-chip graphene NEMS suspended a few tens of nanometres above nitrogen-vacancy centres (NVCs), which are stable single-photon emitters embedded in nanodiamonds. Electromechanical control of the photons emitted by the NVC is provided by electrostatic tuning of the graphene NEMS position, which is transduced to a modulation of NVC emission intensity. The optomechanical coupling between the graphene displacement and the NVC emission is based on near-field dipole–dipole interaction. This class of optomechanical coupling increases strongly for smaller distances, making it suitable for nanoscale devices. These achievements hold promise for selective control of emitter arrays on-chip, optical spectroscopy of individual nano-objects, integrated optomechanical information processing and open new avenues towards quantum optomechanics.

Active control of optical fields at the nanoscale is difficult to achieve. Here, the authors fabricate an on-chip graphene NEMS suspended a few tens of nanometres above nitrogen vacancy centres and demonstrate electromechanical control of the photons emitted by electrostatic tuning of the graphene NEMS position.

Intracavity Squeezing Can Enhance Quantum-Limited Optomechanical Position Detection through Deamplification

It has been predicted and experimentally demonstrated that by injecting squeezed light into an optomechanical device, it is possible to enhance the precision of a position measurement. Here, we present a fundamentally different approach where the squeezing is created directly inside the cavity by a nonlinear medium. Counterintuitively, the enhancement of the signal-to-noise ratio works by deamplifying precisely the quadrature that is sensitive to the mechanical motion without losing quantum information. This enhancement works for systems with a weak optomechanical coupling and/or strong mechanical damping. This can allow for larger mechanical bandwidth of quantum-limited detectors based on optomechanical devices. Our approach can be straightforwardly extended to quantum nondemolition qubit detection.

Integrated III-V Photonic Crystal--Si waveguide platform with tailored optomechanical coupling

Optomechanical systems, in which the vibrations of a mechanical resonator are coupled to an electromagnetic radiation, have permitted the investigation of a wealth of novel physical effects. To fully exploit these phenomena in realistic circuits and to achieve different functionalities on a single chip, the integration of optomechanical resonators is mandatory. Here, we propose a novel approach to heterogeneously integrate arrays of two-dimensional photonic crystal defect cavities on top of silicon-on-insulator waveguides. The optomechanical response of these devices is investigated and evidences an optomechanical coupling involving both dispersive and dissipative mechanisms. By controlling the optical coupling between the waveguide and the photonic crystal, we were able to vary and understand the relative strength of these couplings. This scalable platform allows for an unprecedented control on the optomechanical coupling mechanisms, with a potential benefit in cooling experiments, and for the development of multi-element optomechanical circuits in the framework of optomechanically-driven signal-processing applications.

Observation of generalized optomechanical coupling and cooling on cavity resonance

Optomechanical coupling between a light field and the motion of a cavity mirror via radiation pressure plays an important role for the exploration of macroscopic quantum physics and for the detection of gravitational waves (GWs). It has been used to cool mechanical oscillators into their quantum ground states and has been considered to boost the sensitivity of GW detectors, e.g., via the optical spring effect. Here, we present the experimental characterization of generalized, that is, dispersive and dissipative, optomechanical coupling, with a macroscopic (1.5  mm)2-size silicon nitride membrane in a cavity-enhanced Michelson-type interferometer. We report for the first time strong optomechanical cooling based on dissipative coupling, even on cavity resonance, in excellent agreement with theory. Our result will allow for new experimental regimes in macroscopic quantum physics and GW detection.

Fast cooling in dispersively and dissipatively coupled optomechanics

The cooling performance of an optomechanical system comprising both dispersive and dissipative coupling is studied. Here, we present a scheme to cool a mechanical resonator to its ground state in finite time using a chirped pulse. We show that there is distinct advantage in using the chirp-pulse scheme to cool a resonator rapidly. The cooling behaviors of dispersively and dissipatively coupled system is also explored with different types of incident pulses and different coupling strengths. Our scheme is feasible in cooling the resonator for a wide range of the parameter region.

Optomechanical coupling between a multilayer graphene mechanical resonator and a superconducting microwave cavity

The combination of low mass density, high frequency and high quality factor, Q, of mechanical resonators made of two-dimensional crystals such as graphene make them attractive for applications in force/mass sensing and exploring the quantum regime of mechanical motion. Microwave optomechanics with superconducting cavities offers exquisite position sensitivity and enables the preparation and detection of mechanical systems in the quantum ground state. Here, we demonstrate coupling between a multilayer graphene resonator with quality factors up to 220,000 and a high-Q superconducting cavity. Using thermomechanical noise as calibration, we achieve a displacement sensitivity of 17 fm Hz(-1/2). Optomechanical coupling is demonstrated by optomechanically induced reflection and absorption of microwave photons. We observe 17 dB of mechanical microwave amplification and signatures of strong optomechanical backaction. We quantitatively extract the cooperativity C, a characterization of coupling strength, from the measurement with no free parameters and find C = 8, which is promising for the quantum regime of graphene motion.

Optomechanics with cavity polaritons: dissipative coupling and unconventional bistability

We study a hybrid system formed from an optomechanical resonator and a cavity mode strongly coupled to an excitonic transition inside a quantum well. We show that due to the mixing of cavity photon and exciton states, the emergent quasiparticles-polaritons-possess coupling to the mechanical mode of both a dispersive and dissipative nature. We calculate the occupancies of polariton modes and reveal bistable behavior, which deviates from conventional Kerr nonlinearity or dispersive coupling cases due to the dissipative coupling. The described system serves as a good candidate for future polaritonic devices.

Optomechanically induced transparency in the nonlinear quantum regime

Optomechanical systems have been shown both theoretically and experimentally to exhibit an analogon to atomic electromagnetically induced transparency, with sharp transmission features that are controlled by a second laser beam. Here we investigate these effects in the regime where the fundamental nonlinear nature of the optomechanical interaction becomes important. We demonstrate that pulsed transistorlike switching of transmission still works even in this regime. We also show that optomechanically induced transparency at the second mechanical sideband could be a sensitive tool to see first indications of the nonlinear quantum nature of the optomechanical interaction even for single-photon coupling strengths significantly smaller than the cavity linewidth.

Squeezing of the mirror motion via periodic modulations in a dissipative optomechanical system

We investigate the generation of squeezed state of the mirror motion in a dissipative optomechanical system driven with a strong laser field accompanied with two periodically-modulated lights. Using the density operator approach we calculate the variances of quantum fluctuations around the classical orbits. Both the numerical and analytical results predict that the squeezed state of the mirror motion around its ground state is achievable. Moreover, the obtained squeezed state is robust against the thermal noise because of the strong cooling effect outside the resolved-sideband regime, which arises from the destructive interference of quantum noise.

Dynamic dissipative cooling of a mechanical resonator in strong coupling optomechanics

Cooling of mesoscopic mechanical resonators represents a primary concern in cavity optomechanics. In this Letter, in the strong optomechanical coupling regime, we propose to dynamically control the cavity dissipation, which is able to significantly accelerate the cooling process while strongly suppressing the heating noise. Furthermore, the dynamic control is capable of overcoming quantum backaction and reducing the cooling limit by several orders of magnitude. The dynamic dissipation control provides new insights for tailoring the optomechanical interaction and offers the prospect of exploring mesoscopic quantum physics.

Dissipative optomechanics in a Michelson-Sagnac interferometer

Dissipative optomechanics studies the coupling of the motion of an optical element to the decay rate of a cavity. We propose and theoretically explore a realization of this system in the optical domain, using a combined Michelson-Sagnac interferometer, which enables a strong and tunable dissipative coupling. Quantum interference in such a setup results in the suppression of the lower motional sideband, leading to strongly enhanced cooling in the non-sideband-resolved regime. With state-of-the-art parameters, ground-state cooling and low-power quantum-limited position transduction are both possible. The possibility of a strong, tunable dissipative coupling opens up a new route towards observation of such fundamental optomechanical effects as nonlinear dynamics. Beyond optomechanics, the suggested method can be readily transferred to other setups involving nonlinear media, atomic ensembles, or single atoms.

Scattering approach to backaction in coherent nanoelectromechanical systems

We present theoretical results for the backaction force noise and damping of a mechanical oscillator whose position is measured by a mesoscopic conductor. Our scattering approach is applicable to a wide class of systems; in particular, it may be used to describe point contact position detectors far from the weak tunneling limit. We find that the backaction depends not only on the mechanical modulation of transmission probabilities, but also on the modulation of scattering phases, even in the absence of a magnetic field. We illustrate our general approach with several simple examples, and use it to calculate the backaction for a movable, Au atomic point contact modeled by ab initio density functional theory.

Theoretical analysis of mechanical displacement measurement using a multiple cavity mode transducer

We present an optomechanical displacement transducer that relies on three cavity modes parametrically coupled to a mechanical oscillator and whose frequency spacing matches the mechanical resonance frequency. The additional resonances allow reaching the standard quantum limit at a substantially lower input power (compared to the case of a single cavity mode), as both sensitivity and quantum backaction are enhanced. Furthermore, it is shown that in the case of multiple cavity modes, coupling between the modes is induced via reservoir interaction, e.g., enabling quantum backaction noise cancellation. Experimental implementation of the schemes is discussed in both the optical and microwave domain.

Reactive cavity optical force on microdisk-coupled nanomechanical beam waveguides

We demonstrate spectrally tuned dispersive and reactive optical force in a cavity optomechanics system that comprises a microdisk and a vibrating nanomechanical beam waveguide. The waveguide coupled to the microdisk acts as a bosonic dissipation channel and its motion modulates the cavity's damping rate. As a result a reactive optical force arises in addition to the normal dispersive force. The cavity enhanced force is not observed at zero detuning but shows asymmetric behavior with a maximum at red-detuned offset. Such reactive cavity backaction force points to new avenues in cavity optomechanics.

Standard quantum limit for probing mechanical energy quantization

We derive a standard quantum limit for probing mechanical energy quantization in a class of systems with mechanical modes parametrically coupled to external degrees of freedom. To resolve a single mechanical quantum, it requires a strong-coupling regime-the decay rate of external degrees of freedom is smaller than the parametric coupling rate. In the case for cavity-assisted optomechanical systems, e.g., the one proposed by Thompson et al. [Nature (London) 452, 72 (2008)], zero-point motion of the mechanical oscillator needs to be comparable to the linear dynamical range of the optical system which is characterized by the optical wavelength divided by the cavity finesse.