Entanglement and squeezing are two useful resources in quantum technologies. Recent studies have increasingly focused on generating these nonclassical features in macroscopic objects. However, establishing entanglement and squeezing in the degrees of freedom of mechanical motion of macroscopic objects is generally hindered by thermal fluctuations of their environments. Here, we propose a scheme to generate steady-state squeezing and entanglement between two rotating mirrors of a Laguerre-Gaussian cavity by quantum squeezed-reservoir engineering. It is revealed that, by injecting a broadband squeezed light into the cavity, stable squeezing in the relative momentum and entanglement between the two rotating mirrors are created. Compared to the previous work where only the entanglement between the two rotating mirrors appears under the condition of different angular frequencies, our result highlights the stable entanglement of the two mirrors with identical frequency and the simultaneous presence of the entanglement and squeezing of the two mirrors. Our finding deepens our understanding of macroscopic quantum phenomena of Laguerre-Gaussian cavity optomechanical system.
Entanglement and squeezing are two useful resources in quantum technologies. Recent studies have increasingly focused on generating these nonclassical features in macroscopic objects. However, establishing entanglement and squeezing in the degrees of freedom of mechanical motion of macroscopic objects is generally hindered by thermal fluctuations of their environments. Here, we propose a scheme to generate steady-state squeezing and entanglement between two rotating mirrors of a Laguerre-Gaussian cavity by quantum squeezed-reservoir engineering. It is revealed that, by injecting a broadband squeezed light into the cavity, stable squeezing in the relative momentum and entanglement between the two rotating mirrors are created. Compared to the previous work where only the entanglement between the two rotating mirrors appears under the condition of different angular frequencies, our result highlights the stable entanglement of the two mirrors with identical frequency and the simultaneous presence of the entanglement and squeezing of the two mirrors. Our finding deepens our understanding of macroscopic quantum phenomena of Laguerre-Gaussian cavity optomechanical system.
Quantum entanglement will play an important role in future quantum technologies. Here, we theoretically study the steady-state entanglement between a cavity field and a macroscopic rotating mirror in a Laguerre–Gaussian-(LG)-cavity optomechanical system with cross-Kerr nonlinearity. Logarithmic negativity is used to quantify the steady-state entanglement between the cavity and mechanical modes. We analyze the impacts of the cross-Kerr coupling strength, the cavity detuning, the input laser power, the topological charge of the LG-cavity mode, and the temperature of the environment on the steady-state optomechanical entanglement. We find that cross-Kerr nonlinearity can significantly enhance steady-state optomechanical entanglement and make steady-state optomechanical entanglement more robust against the temperature of the thermal environment.
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.
Abstract We propose a new scheme to prepare macroscopic entanglement between two rotating mirrors using dissipative atomic reservoir in a double-Laguerre–Gaussian-cavity system. The two-level atomic system driven by a strong field, acts as a single pathway of Bogoliubov dissipation to push the two original cavity modes into the desirable entangled state under the near-resonant conditions. Successively, the photon–photon entanglement can be transferred to mirror–mirror entanglement through the exchange of orbital angular momentum. In essence, the macroscopic entanglement is originated from the dissipative atomic reservoir rather than the radiation torque, thereby it is usually robust against environmental noises. The present scheme provides a feasible way to realize stable entanglement between spatially separated mirrors with high capacity, which may find potential applications in remote quantum communications.
Quantum entanglement in macroscopic systems plays an important role in quantum information processing. Here, we show that the steady-state entanglement between the two cavity modes in the macroscopic Laguerre–Gaussian (L–G) cavity optorotating system can be enhanced by placing a degenerate optical parametric amplifier (OPA) inside the cavity. The two L–G cavity modes are coupled to the same rotating mirror and are respectively driven at the red and blue mechanical sidebands. We use the logarithmic negativity to quantify the steady-state entanglement between the two cavity modes. We study the influences of the nonlinear gain and phase of the OPA, the temperature of the environment, and the angular momentums of the two cavity modes on the entanglement between the two cavity modes. In the cryogenic environment temperatures, when the angular momentums of the two cavity modes are identical, the enhancement of the entanglement between the two cavity modes by the OPA is the most significant.
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.
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.