分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Non-Hermitian systems can exhibit unconventional spectral singularities called exceptional points (EPs). Various EP sensors have been fabricated in recent years, showing strong spectral responses to external signals. Here we propose how to achieve a nonlinear anti-parity-time ($\mathcal{APT}$) gyroscope by spinning an optical resonator. We show that, in the absence of any nonlinearity, the sensitivity or optical mode splitting of the linear device can be magnified up to 3 orders than that of the conventional device without EPs. Remarkably, the $\mathcal{APT}$ symmetry can be broken when including the Kerr nonlinearity of the materials and, as the result, the detection threshold can be significantly lowered, i.e., much weaker rotations which are well beyond the ability of a linear gyroscope can now be detected with the nonlinear device. Our work shows the powerful ability of $\mathcal{APT}$ gyroscopes in practice to achieve ultrasensitive rotation measurement.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Non-Hermitian systems with anti-parity-time ($\mathcal{APT}$) symmetry have revealed rich physics beyond conventional systems. Here, we study optomechanics in an $\mathcal{APT}$-symmetric spinning resonator and show that, by tuning the rotating speed to approach the exceptional point (EP) or the non-Hermitian spectral degeneracy, nonreciprocal light transmission with a high isolation ratio can be realized. Accompanying this process, nonreciprocal group delay or advance is also identified in the vicinity of EP. Our work sheds new light on manipulating laser propagation with optomechanical EP devices and, in a broader view, can be extended to explore a wide range of $\mathcal{APT}$-symmetric effects, such as $\mathcal{APT}$-symmetric phonon lasers, $\mathcal{APT}$-symmetric topological effects, and $\mathcal{APT}$-symmetric force sensing or accelerator.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Quantum entanglement plays a key role in both understanding the fundamental aspects of quantum physics and realizing various quantum devices for practical applications. Here we propose how to achieve coherent switch of optomechanical entanglement in an optical whispering-gallery-mode resonator, by tuning the phase difference of the driving lasers. We find that the optomechanical entanglement and the associated two-mode quantum squeezing can be well tuned in a highly asymmetric way, providing an efficient way to protect and enhance quantum entanglement against optical backscattering, in comparison with conventional symmetric devices. Our findings shed a new light on improving the performance of various quantum devices in practical noisy environment, which is crucial in such a wide range of applications as noise-tolerant quantum processing and the backscattering-immune quantum metrology.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Jian-Qi Zhang
Jing-Xin Liu
Hui-Lai Zhang
Zhi-Rui Gong
Shuo Zhang
Lei-Lei Yan
Shi-Lei Su
Hui Jing
Mang Feng
摘要： We propose how to achieve synthetic $\mathcal{PT}$ symmetry in optomechanics without using any active medium. We find that harnessing the Stokes process in such a system can lead to the emergence of exceptional point (EP), i.e., the coalescing of both the eigenvalues and the eigenvectors of the system. By encircling the EP, both non-reciprocal optical amplification and chiral mode switching can be achieved. As a result, our synthetic $\mathcal{PT}$-symmetric optomechanics works as a topological optomechanical amplifier. This provides a surprisingly simplified route to realize $\mathcal{PT}$-symmetric optomechanics, indicating that a wide range of EP devices can be created and utilized for various applications such as topological optical engineering and nanomechanical processing or sensing.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Entanglement between distant massive mechanical oscillators is of particular interest in quantum-enabled devices due to its potential applications in distributed quantum information processing. Here we propose how to achieve nonreciprocal remote entanglement between two spatially separated mechanical oscillators within a cascaded optomechanical configuration, where the two optomechanical resonators are indirectly coupled through a telecommunication fiber. We show that by selectively spinning the optomechanical resonators, one can break the time reversal symmetry of this compound system via Sagnac effect, and more excitingly, enhance the indirect couplings between the mechanical oscillators via the individual optimizations of light-motion interaction in each optomechanical resonator. This ability allows us to generate and manipulate nonreciprocal entanglement between distant mechanical oscillators, that is, the entanglement could be achieved only through driving the system from one specific input direction but not the other. Moreover, in the case of two frequency-mismatched mechanical oscillators, it is also found that the degree of the generated nonreciprocal entanglement is counterintuitively enhanced in comparison with its reciprocal counterparts, which are otherwise unattainable in static cascaded systems with a single-tone driving laser. Our work, which is well within the feasibility of current experimental capabilities, provides an enticing new opportunity to explore the nonclassical correlations between distant massive objects and facilitates a variety of emerging quantum technologies ranging from quantum information processing to quantum sensing.
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