论文标题
量子反馈控制的宏观量子非局部性
Quantum-feedback-controlled macroscopic quantum nonlocality in cavity optomechanics
论文作者
论文摘要
在本文中，我们提出了一种连续的测量和反馈方案，以实现强大的爱因斯坦 - 波多尔斯基 - 罗森（EPR）转向和贝尔的转向和钟形非局部性，对腔磁力力学中的两个宏观机械振荡器。我们的系统由两个光学机械腔组成，其中两个腔场通过非等级参数下调相互耦合。两个空腔输出场受到连续的钟形同伴检测，并且检测电流被向后馈入以驱动腔场。已经发现，当没有反馈时，两个机械振荡器只能在稳定的弱纠缠状态下制备，但是由于所谓的3 dB限制，这并不显示EPR转向和贝尔非局部性。但是，当存在反馈时，发现机械纠缠会大大增强，因此可以在稳态状态下获得强大的机械转向和贝尔非局部性。我们在分析上揭示这是因为反馈将机械振荡器驱动到稳定的近似于两模式的挤压真空状态，并原则上有任意挤压。结果表明，反馈也可以显然可以提高非经典机械状态的纯度。研究了机械量子非局部性对反馈强度和热波动的依赖性，并且发现贝尔非局部性比EPR的非局部性更容易受到热噪声的影响。
In this paper, we propose a continuous measurement and feedback scheme to achieve strong Einstein-Podolsky-Rosen (EPR) steering and Bell nonlocality of two macroscopic mechanical oscillators in cavity optomechanics. Our system consists of two optomechanical cavities in which two cavity fields are coupled to each other via a nondegenerate parametric downconversion. The two cavity output fields are subject to continuous Bell-like homodyne detection and the detection currents are fed back to drive the cavity fields. It is found that when the feedback is absent, the two mechanical oscillators can only be prepared in steady weakly entangled states which however do not display EPR steering and Bell nonlocality, due to the so-called 3 dB limit. But when the feedback is present, it is found that the mechanical entanglement is considerably enhanced such that strong mechanical steering and Bell nonlocality can be obtained in the steady-state regime. We analytically reveal that this is because the feedback drives the mechanical oscillators into a steady approximate two-mode squeezed vacuum state, with arbitrary squeezing in principle. It is shown that the feedback can also obviously improve the purity of the nonclassical mechanical states. The dependences of the mechanical quantum nonlocality on the feedback strength and thermal fluctuations are studied, and it is found that Bell nonlocality is much more vulnerable to thermal noise than EPR steerable nonlocality.
