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arXiv:2604.12050

Bell Nonlocality Test on Two-Mode Squeezed Output Generated in Double-Cavity Optomechanical

Souvik Agasti

quant-phSubmitted Apr 13, 2026• Announced Apr 15, 2026• 0 citations
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Abstract

We explore here how to generate a two-mode squeezed output using reservoir engineering in a double-cavity optomechanical system coupled to a common mechanical resonator. Such hybrid platforms are experimentally accessible in electro-optomechanical interfaces and are relevant for high-fidelity state transfer, quantum communication, and metrological applications. By examining violations of the CHSH Bell inequality, we demonstrate that maximal squeezing does not necessarily imply nonlocality; instead, nonlocal correlations can emerge in states with lower squeezing. Furthermore, by analyzing the CHSH inequality across different cavity finesse values, we find that the parameter region supporting nonlocality can broaden even as the squeezing region shrinks. Across all regimes considered, our results emphasize the crucial influence of the mixedness of the state in determining the relationship between squeezing and nonlocality.

Comments
8 pages, 6 figures

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We explore here how to generate a two-mode squeezed output using reservoir engineering in a double-cavity optomechanical system coupled to a common mechanical resonator. Such hybrid platforms are experimentally accessible in electro-optomechanical interfaces and are relevant for high-fidelity state transfer, quantum communication, and metrological applications. By examining violations of the CHSH Bell inequality, we demonstrate that maximal squeezing does not necessarily imply nonlocality; instead, nonlocal correlations can emerge in states with lower squeezing. Furthermore, by analyzing the CHSH inequality across different cavity finesse values, we find that the parameter region supporting nonlocality can broaden even as the squeezing region shrinks. Across all regimes considered, our results emphasize the crucial influence of the mixedness of the state in determining the relationship between squeezing and nonlocality.
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This study presents a detailed proposal for an optomechanical system consisting of two mechanical oscillators coupled to a common cavity, aimed at generating pure and entangled two-mode squeezed mechanical steady states. We found that the violation of Bell's measurement may not occur where the entanglement is maximum; rather, nonlocality can be observed for lower entangled states. A central result is that optomechanical coupling imperfections can enhance mechanical entanglement while simultaneously suppressing Bell nonlocality by reducing the purity of the mechanical state. To mitigate this trade-off, we introduce phase-dependent phonon hopping between the mechanical oscillators and show that Bell nonlocality can be selectively enhanced in specific dark-mode configurations, even when the overall entanglement is reduced. We trace this contrasting behaviorto changes in state purity associated with the imbalance of the Bogoliubov-mode occupations. Compatible with existing microwave cavity optomechanical platforms, the proposed architecture provides an experimentally accessible route for controlling nonlocal quantum correlations in multimode mechanical systems. Our proposed scheme serves as an attractive platform for the deployment of continuous-variable teleportation and high-fidelity quantum communication.
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We investigate under which conditions quantum nonlocal manifestations such as Einstein-Podolsky-Rosen steering or Bell nonlocality can manifest themselves even at the macroscopic level of two mechanical resonators in optomechanical systems. We adopt the powerful scheme of reservoir engineering, implemented by driving a cavity mode with a properly chosen two-tone field, to prepare two mechanical oscillators in an entangled state. We show that large and robust (both one-way and two-way) steering could be achieved in the steady state with realistic parameters. We analyze the mechanism of the asymmetric nature of steering in our system of a two-mode Gaussian state. However, unlike steering, a Bell nonlocality is present under much more stringent conditions. We consider two types of measurements, displaced parity and on-off detection, respectively. We show that for both the measurements the Bell violation requires very low environmental temperature. For the parity detection, a large Bell violation is observed only in the transient state when the mechanical modes decouple from the optical mode and with extremely small cavity losses and mechanical damping. However, for the on-off detection, a moderate Bell violation is found in the steady state and is robust against cavity losses and mechanical damping. Although a Bell violation with parity detection seems extremely challenging to demonstrate experimentally, the conditions required for violating Bell inequalities with the on-off detection are much less demanding.
We propose here a scheme based on the measurement of quadrature phase coherence that is aimed at testing the Clauser-Horne-Shimony-Holt Bell inequality in an optomechanical setting. Our setup is constituted by two optical cavities dispersively coupled to a common mechanical resonator. We show that it is possible to generate Einstein-Podolsky-Rosen--like correlations between the quadratures of the output fields of the two cavities and, depending on the system parameters, to observe the violation of the Clauser-Horne-Shimony-Holt inequality.
A nonlocal circulator protocol is proposed in a hybrid optomechanical system. By analogy with quantum communication, using the input–output relationship, we establish the quantum channel between two optical modes with long-range. The three-body nonlocal interaction between the cavity and the two oscillators is obtained by eliminating the optomechanical cavity mode and verifying the Bell-CHSH inequality of continuous variables. By introducing the phase accumulation between cyclic interactions, the unidirectional transmission of quantum state between the optical mode and two mechanical modes is achieved. The results show that nonreciprocal transmissions are achieved as long as the accumulated phase reaches a certain value. In addition, the effective interaction parameters in our system are amplified, which reduces the difficulty of the implementation of our protocol. Our research can provide potential applications for nonlocal manipulation and transmission control of quantum platforms.