We present the squeezing and entanglement features of the vibrational phonon modes in a double-cavity optomechanical system with input squeezed light. The non-classical features of the vibrational phonon modes arise from the transfer of quantum coherence from the optical to the phonon modes. The phonon modes exhibit squeezing, and the degree of squeezing increases with the increase in the input squeezed light. To quantify the entanglement between the phonon modes, we apply the Hillery and Zubairy criterion. We demonstrate that the entanglement between the phonon modes increases with an increase in optomechanical cooperativity. Moreover, the input squeezed light has a substantial effect on the entanglement between the phonon modes.
We present the squeezing and entanglement features of the vibrational phonon modes in a double-cavity optomechanical system with input squeezed light. The non-classical features of the vibrational phonon modes arise from the transfer of quantum coherence from the optical to the phonon modes. The phonon modes exhibit squeezing, and the degree of squeezing increases with the increase in the input squeezed light. To quantify the entanglement between the phonon modes, we apply the Hillery and Zubairy criterion. We demonstrate that the entanglement between the phonon modes increases with an increase in optomechanical cooperativity. Moreover, the input squeezed light has a substantial effect on the entanglement between the phonon modes.
Quantum entanglement is pivotal in modern quantum technologies, spanning applications from quantum networks to quantum metrology. Controllable quantum entanglement in cavity optomechanical systems has been an enduring pursuit. We propose a unique method for flexible manipulation and switching of optomechanical entanglement in a squeezed-cavity-assisted optomechanical system consisting of a χ (2) -nonlinear optical cavity and an optomechanical cavity. Squeezing the nonlinear optical cavity through parametric pumping allows effective control of light-light and light-vibration interactions within the system. This capability of the squeezed system plays a key role in manipulating quantum entanglement. We find that quantum entanglement between the unsqueezed cavity mode and the mechanical mode can be effectively regulated by adjusting the pump laser parameters. Furthermore, by turning the phase of the pump, we can achieve highly flexible quantum switching between entanglement and separability. Additionally, we demonstrate increased entanglement between the squeezed cavity mode and the mechanical mode when completely suppressing the pump-induced optical input noise. Our findings pave the way not only towards the manipulation and protection of fragile quantum entanglement but also to achieve photon-phonon quantum control by exploiting quantum squeezing.
We investigate the generation of quantum correlations between mechanical modes and optical modes in an optomechanical system, using the rotating wave approximation. The system is composed of two Fabry–Pérot cavities separated in space; each of the two cavities has a movable end-mirror. Our aim is the evaluation of entanglement between mechanical modes and optical modes, generated by correlations transfer from the squeezed light to the system, using Gaussian intrinsic entanglement as a witness of entanglement in continuous variables Gaussian states, and the quantification of the degree of mixedness of the Gaussian states using the purity. Then, we quantify nonclassical correlations between mechanical modes and optical modes even beyond entanglement by considering Gaussian geometric discord via the Hellinger distance. Indeed, entanglement, mixdness, and quantum discord are analyzed as a function of the parameters characterizing the system (thermal bath temperature, squeezing parameter, and optomechanical cooperativity). We find that, under thermal effect, when entanglement vanishes, purity and quantum discord remain nonzero. Remarkably, the Gaussian Hellinger discord is more robust than entanglement. The effects of the other parameters are discussed in detail.
We consider a two-mode light generated by nondegenerate three-level laser with parametric oscillator in optomechanical cavity coupled to two-mode squeezed vacuum reservoir. Effects of pump mode, optomechanical coupling strength and squeezed vacuum reservoir on squeezing and entanglement properties of the cavity modes have been analyzed using the expectation values of cavity mode variables at steady state. The results show that the two-mode light produced by the system under consideration exhibits quadrature squeezing and entanglement. The presence of parametric oscillator in the cavity and squeezed vacuum reservoir enhance the degree of squeezing, entanglement and mean photon number of the cavity mode lights. The optomechanical cavity has no effect on the mean photon number and entanglement of the cavity mode but increases the degree of quadrature squeezing.
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.
We experimentally demonstrate a source of squeezed light featuring simultaneous ponderomotive squeezing from two mechanical modes of an optomechanical system. We use ultra-coherent vibrational modes (Q factors on the order of 108) of a soft-clamped membrane placed in a Fabry–Pérot optical cavity at cryogenic conditions (T=11K) to create correlations between amplitude and phase quadratures of the light field. As a result of the interaction between the membrane position and the light, we generated ponderomotive squeezing of 4.8dB for the first localized mechanical mode at 1.32MHz and 4.2dB for the second localized mode at 2.43MHz, as observed in direct detection when correcting for the detection inefficiency. Thus, we have demonstrated that by leveraging more than one quantum-limited mechanical mode, optomechanical squeezed light generation can be extended to dual-band operation with an ample band separation of about an octave. Utilizing homodyne detection to detect squeezing in an optimal quadrature would lead to squeezing levels at the output of the cavity of 7.3 dB and 6.8 dB, in the two modes, respectively. Squeezing of light demonstrated here for near-infrared light can be achieved in a broad range of wavelengths due to the relative insensitivity of optomechanical interaction with SiN membranes to the wavelength. The demonstrated dual-band squeezing can be linked to the generation of two photon–phonon entangled mode pairs, suggesting that our system, viewed as an entanglement source, is more resource-efficient than single-mode optomechanics.