Abstract Based on a scheme proposed to experience the dynamical Casimir effect in optomechanical systems, we show how to squeeze mechanical motion and entangle the optical field with mechanical motion in an optomechanical system containing a parametric amplification. The scheme is based on optical bistability which emerges in the system for a strong enough driving field. By considering the steady state’s lower branch of the bistability, the system shows weak entanglement and almost no mechanical squeezing. When the steady state is on the upper branch of the bistable shape, both squeezing and entanglement are greatly enhanced. Specifically, the entanglement shows three degrees of magnitude enhancement. However, this giant entanglement is fragile against decoherence and thermal fluctuation. Regarding the mechanical squeezing, it reaches the standard quantum limit (SQL) in the upper branch of the bistability. Our proposal provides a way to improve quantum effects in optomechanical systems by taking advantage of nonlinearities. This scheme can be realized in similar systems such as superconducting microwave, and hybrid optomechanical systems.
Abstract Based on a scheme proposed to experience the dynamical Casimir effect in optomechanical systems, we show how to squeeze mechanical motion and entangle the optical field with mechanical motion in an optomechanical system containing a parametric amplification. The scheme is based on optical bistability which emerges in the system for a strong enough driving field. By considering the steady state’s lower branch of the bistability, the system shows weak entanglement and almost no mechanical squeezing. When the steady state is on the upper branch of the bistable shape, both squeezing and entanglement are greatly enhanced. Specifically, the entanglement shows three degrees of magnitude enhancement. However, this giant entanglement is fragile against decoherence and thermal fluctuation. Regarding the mechanical squeezing, it reaches the standard quantum limit (SQL) in the upper branch of the bistability. Our proposal provides a way to improve quantum effects in optomechanical systems by taking advantage of nonlinearities. This scheme can be realized in similar systems such as superconducting microwave, and hybrid optomechanical systems.
Quantum entanglement and squeezing associated with the motions of massive mechanical oscillators play an essential role in both fundamental science and emerging quantum technologies, yet realizing such macroscopic nonclassical states remains a formidable challenge. In this paper, we investigate how to achieve strong optomechanical entanglement and mechanical squeezing in a membrane-embedded cavity optomechanical system incorporating a coherent feedback loop, where the membrane interacts with the cavity mode through both linear and quadratic optomechanical couplings. This hybrid optomechanical architecture offers a flexible tunability of intrinsic system parameters, thereby enabling controlled stiffening or softening of the mechanical mode through adjusting quadratic optomechanical coupling, as well as effective modulation of the cavity decay rate via feedback control. More importantly, the synergistic interplay effect allows for a strategic reconfiguration of the system's stability regime, which in turn permits the presence of significantly enhanced effective optomechanical coupling strengths before entering the unstable regime. Exploiting these unique features, we demonstrate that optomechanical entanglement can be substantially enhanced with positive coupling sign and suitable feedback parameters, while strong mechanical squeezing beyond the 3dB limit is simultaneously achieved over a broad parameter range with negative coupling sign, reaching squeezing degree above 10dB under optimized conditions. Our proposal, establishing an all-optical method for generating highly entangled or squeezed states in cavity optomechanical systems, opens up a new route to explore macroscopic quantum effects and to advance quantum information processing.
ABSTRACT Previous investigations of mechanical squeezing have primarily been concentrated on a single manipulation method. We propose an innovative scheme to address the research gap by leveraging the synergy of an optical Kerr media and mechanical parametric amplification (MPA) in an optomechanical system to efficiently generate strong mechanical squeezing. By reasonably choosing the system parameters, this scheme has the following outstanding advantages: the squeezing effect of the cavity field induced by the optical Kerr medium can be transferred to the mechanical oscillator, which has been squeezed by the mechanical parametric amplifiers. The squeezing of the mechanical oscillator is higher than that of either state alone, and through this joint effect the squeezing can be significantly increased, ultimately realizing a strong mechanical squeezing. The scheme also exhibits notable robustness against both thermal noise and decay of the mechanical oscillator. The presented scheme provides an efficient and experimentally feasible platform for achieving strong mechanical squeezing, paving the way for generating other quantum effects.
Quantum entanglement and squeezing associated with the motions of massive mechanical oscillators play an essential role in both fundamental science and emerging quantum technologies, yet realizing such macroscopic nonclassical states remains a formidable challenge. In this paper, we investigate how to achieve strong optomechanical entanglement and mechanical squeezing in a membrane-embedded cavity optomechanical system incorporating a coherent feedback loop, where the membrane interacts with the cavity mode through both linear and quadratic optomechanical couplings. This hybrid optomechanical architecture offers a flexible tunability of intrinsic system parameters, thereby enabling controlled stiffening or softening of the mechanical mode through adjusting quadratic optomechanical coupling, as well as effective modulation of the cavity decay rate via feedback control. More importantly, the synergistic interplay effect allows for a strategic reconfiguration of the system's stability regime, which in turn permits the presence of significantly enhanced effective optomechanical coupling strengths before entering the unstable regime. Exploiting these unique features, we demonstrate that optomechanical entanglement can be substantially enhanced with positive coupling sign and suitable feedback parameters, while strong mechanical squeezing beyond the 3dB limit is simultaneously achieved over a broad parameter range with negative coupling sign, reaching squeezing degree above 10dB under optimized conditions. Our proposal, establishing an all-optical method for generating highly entangled or squeezed states in cavity optomechanical systems, opens up a new route to explore macroscopic quantum effects and to advance quantum information processing.
We propose a scheme of an optomechanical system that optimizes entanglement in nanomechanical resonators through quantum state transfer of intracavity squeezing and squeezed reservoir field sources assisted by radiation pressure. The system is driven by red-detuned laser fields, which enable simultaneous cooling of the mechanical resonators and facilitate the quantum state transfer in a weak coupling and good cavity limit. Specifically, the mechanical entanglement is quantified using logarithmic negativity within the bipartite Gaussian states of the two mechanical modes. The results show that several key parameters, including the parametric phase and nonlinear gain of the non-degenerate optical parametric amplifier, the strength of the squeezing reservoir, optomechanical cooperativity, thermal excitation of phonons, and the temperature of mechanical baths, strongly influence the degree of mechanical entanglement. Hence, the findings indicate that careful tuning of the parameters can enable control over the enhancement of entanglement robustness, suggesting that this optomechanical scheme provides a viable pathway for applications in quantum sensing and information processing
Abstract We present a double-cavity optomechanical system with a mechanical oscillator, which is jointly driven by an amplitude-modulated laser field and a weak squeezed vacuum field, aiming to explore quantum entanglement effects under the unresolved-sideband regime. Within our proposed scheme, it is possible not only to surpass the limit of maximum steady-state entanglement ln2 for bipartite entanglement, achieving strong entanglement, but also to significantly enhance tripartite entanglement and improve the system’s robustness against thermal noise. Meanwhile, the introduction of the squeezed vacuum field plays a crucial role in entanglement control, enabling not only a several-fold enhancement of entanglement but also continuous and precise manipulation of its strength within specific ranges. The suggested method demonstrates exceptional flexibility and adaptability under a wide range of operating conditions, offering a new pathway for theoretical and experimental investigations of strong bipartite entanglement and tripartite entanglement.
Quantum entanglement is a crucial resource in quantum technologies, enabling advancements in quantum computing, quantum communication, and quantum precision measurement. Here, we propose a method to enhance optomechanical entanglement by introducing an optical Kerr nonlinear medium and a squeezed vacuum reservoir of the optomechanical cavity. By performing the displacement and squeezing transformations, the system can be reduced to a standard linearized optomechanical system with normalized driving detuning and linearized-coupling strength, in which the optical and mechanical modes are, respectively, coupled to an optical vacuum bath and a mechanical heat bath. We focus on the entanglement generation in the single stable regime of the system. By evaluating the steady-state logarithm negativity, we find that the optomechanical entanglement can be enhanced within a wide range of the Kerr constant. In addition, the Kerr nonlinearity can extend the stable region, enabling considerable entanglement generation in the blue-sideband parameter region. We also investigate the dependence of the entanglement generation on the average thermal phonon occupation of the mechanical bath and the optical driving amplitude. It is found that the presence of the Kerr nonlinearity allows the generation of optomechanical entanglement even when the thermal phonon occupation of the mechanical bath is as high as 3000. Our findings will provide valuable insights into enhancing fragile quantum resources in quantum systems.