We report an efficient mechanism to generate mechanical entanglement in a two-cascaded cavity optomechanical system with optical parametric amplifiers (OPAs) inside the two coupled cavities. We use the especially tuned OPAs to squeeze the hybrid mode composed of two mechanical modes, leading to strong macroscopic entanglement between the two movable mirrors. The squeezing parameter as well as the effective mechanical damping are both modulated by the OPA gains. The optimal degree of mechanical entanglement therefore depends on the balanced process between coherent hybrid mode squeezing and dissipation engineering. The mechanical entanglement is robust to strong cavity decay, going beyond simply resolved sideband regime, and is resistant to reasonable high thermal noise. The scheme provides an alternative way for generating strong macroscopic entanglement in cascaded optomechanical systems.
We report an efficient mechanism to generate mechanical entanglement in a two-cascaded cavity optomechanical system with optical parametric amplifiers (OPAs) inside the two coupled cavities. We use the especially tuned OPAs to squeeze the hybrid mode composed of two mechanical modes, leading to strong macroscopic entanglement between the two movable mirrors. The squeezing parameter as well as the effective mechanical damping are both modulated by the OPA gains. The optimal degree of mechanical entanglement therefore depends on the balanced process between coherent hybrid mode squeezing and dissipation engineering. The mechanical entanglement is robust to strong cavity decay, going beyond simply resolved sideband regime, and is resistant to reasonable high thermal noise. The scheme provides an alternative way for generating strong macroscopic entanglement in cascaded optomechanical systems.
The generation of quantum entanglement in macroscopic systems remains a longstanding challenge. In this paper, we study theoretically the stationary entanglement of the two remote mechanical oscillators in a two-cascaded-cavity optomechanical system with a degenerate optical parametric amplifier (OPA) inside the first cavity. The two cavity modes in each cavity are driven at the red- and blue-sideband frequencies. The logarithmic negativity is used to quantify the amount of the stationary mechanical entanglement. We find that the stationary mechanical entanglement depends on the parametric gain and phase of the OPA, the input laser powers, the cavity decay rates, and the temperature of the environment. We show that it is possible to enhance the stationary mechanical entanglement by the use of the OPA, and the optimal enhancement of the stationary mechanical entanglement happens at the parametric phase 𝜋 / 2 of the OPA. At lower temperatures, the OPA exhibits a more significant improvement effect on the stationary mechanical entanglement.
Abstract The ability to engineer entangled states that involve macroscopic objects is of particular importance for a wide variety of quantum‐enabled technologies, ranging from quantum information processing to quantum sensing. Here how to achieve coherent manipulation and enhancement of quantum entanglement in a hybrid optomechanical system, which consists of a Fabry–Pérot cavity with two movable mirrors, an optical parametric amplifier (OPA), and an injected squeezed vacuum reservoir is proposed. It is shown that the advantages of this system are twofold: 1) one can effectively regulate the light‐mirror interactions by introducing a squeezed intracavity mode via the OPA; 2) when properly matching the squeezing parameters between the squeezed cavity mode and the injected squeezed vacuum reservoir, the optical input noises can be suppressed completely. These peculiar features of this system allow the generation and manipulation of quantum entanglement in a coherent and controllable way. More importantly, it is also found that such controllable entanglement, under some specific squeezing parameters, can be considerably enhanced in comparison with those of the conventional optomechanical system. The work, providing a promising method to regulate and tailor the light‐mirror interaction, is poised to serve as a useful tool for engineering various quantum effects which are based on cavity optomechanics.
We present a theoretical investigation of quantum entanglement enhancement in an electro-optomechanical system comprising a ring cavity with two Coulomb-coupled mechanical resonators and an embedded optical parametric amplifier (OPA). The system dynamics are governed by radiation pressure interactions between the optical field and mechanical modes, modified by both the Coulomb coupling and OPA-induced squeezing. Through a comprehensive quantum Langevin analysis and linearization approach, we demonstrate how these competing interactions can be exploited to generate and control entanglement. Our key finding is that the Coulomb interaction strength is fundamental for generating bipartite entanglement, both between directly coupled mechanical modes and, more remarkably, between optical and mechanical modes, thereby influencing the entire system. The OPA parameters, namely the gain and phase, provide powerful control knobs for entanglement optimization. Notably, the OPA enhances entanglement robustness against thermal noise, resulting in stronger quantum correlations. We quantify these effects through covariance matrix methods and logarithmic negativity measures. The study provides new insights into hybrid optomechanical entanglement generation, showing how combined charge-mediated coupling and optical squeezing can overcome typical limitations of purely optomechanical systems. These results offer practical guidelines for experimental implementations in quantum information processing and macroscopic quantum state engineering, particularly in systems where environmental noise and parameter stability are critical concerns.
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 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.
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.