Cavity optomechanics

Cavity optomechanics, a fast-developing research frontier related to quantum physics, optics, and nano-science, addresses the radiation-pressure couplings between the electromagnetic fields in cavities and the mechanical oscillation of micro- and nano-scale mechanical resonators, and explores the fundamental physical phenomena and effects induced by the optomechanical interactions, as well as the applications of optomechanical effects to modern quantum technologies. Cavity optomechanical systems not only provide a convincing platform for studying the fundamental quantum theories, such as the macroscopic quantum coherence and quantum-classical boundary, but also bear wide potential applications in modern quantum science and technology, especially in quantum precision measurement and gravitational wave physics. In this sense, the study of cavity optomechanics will deepen the understanding of light-matter interactions and extend the optomechanical applications.

With the merits of universality and conciseness, the cavity optomechanical models can be implemented on various physical platforms, such as the Fabry-Perot cavity with suspended mirrors, the cavity with a “membrane-in-the-middle” configuration, various microscale resonators with oscillating boundaries, microwave electromechanical systems, photonic crystal nano beams, coupled cavity-cold-atoms systems, cavity magnomechanical systems, and levitated optomechanical systems. Typically, the involved electromagnetic fields work in the optical and microwave frequency ranges. Meanwhile, the mechanical modes in devices span a huge range of parameters: the mass of these mechanical degrees of freedom may change from kilogram to zepto gram, the mechanical scale may vary from meter to dozens of nanometers, and the mechanical frequency may jump from a few Hertz to giga Hertz.

In principle, the two elements of an optomechanical system, i.e., the optical field and mechanical resonator, have their respective advantages. The optical modes have their inherent advantages, including high-speed transmission, thermal-noise-free environments, and natural techniques for manipulation and state preparation and measurement. The mechanical degree of freedom is an ideal sensor for transducing a variety of physical signals, such as force, displacement, spin, charge, magnetism, and mass. In particular, the optomechanical interaction between the optical and mechanical degrees of freedom is the core of cavity optomechanics. It not only provides a versatile means to realize the quantum control of mechanical motion, but also lays a physical foundation for implementing the quantum manipulation of electromagnetic fields by controlling the moving boundary.

The last fifteen years have witnessed great advances in the field of cavity optomechanics, especially the ground-state cooling of the mechanical degree of freedom and the demonstration of different quantum effects associated with linearized optomechanical interactions, such as optomechanical entanglement, optomechanical normal-mode splitting, optical or mechanical squeezing, optomechanical state transfer, and optical-microwave frequency conversion. Of note, research interest on optomechanics has recently extended to multimode optomechanical systems involving multiple optical modes or multiple mechanical modes associated with a single or many mechanical resonators, which provide a new platform for studying mechanical entanglement, quantum synchronization of mechanical oscillation, many-body physics, and quantum simulation of various coupled boson models. In parallel to the study of quantum effects, cavity optomechanical systems are considered ideal candidates for studying nonlinear dynamics, optomechanical chaos, and multi-stability, and great progress has been achieved in its application to quantum precision measurements, which approach the fundamental limit imposed by quantum mechanics. Nevertheless, there still remain challenges in the field of cavity optomechanics. For example, the observation of optomechanical effects at the single-quanta level has long been a problem owing to the coupling strength that is too weak to enter the single-photon strong-coupling regime.

Today, the field of cavity optomechanics is experiencing a high-speed development both theoretically and experimentally. New analytical methods have been proposed to solve the dynamics of the driven optomechanical cavity. A great number of new physical models, different parameter regimes, and ingenious physical mechanisms have been exploited to unveil the novel optomechanical effects and new applications. Moreover, several new physical setups have been established to implement optomechanical interactions. All these call for a special issue to showcase the latest research achievements and envision the future cavity optomechanics. This special issue on the theme of cavity optomechanics collects thirteen papers: two review articles, two perspectives, and nine original research articles. The two review articles are on nonequilibrium thermodynamics in cavity optomechanics and cavity optomechanical chaos, which have been systematically studied recently. The two perspectives report on the levitated optomechanics and dynamical approach for solving quantum optomechanical models, introducing new analytical methods for solving the optomechanical system. The nine original research articles following span a wide range of topics: ringing spectroscopy in the magnomechanical system, magnonic frequency combs based on the resonantly enhanced magnetostrictive effect, phonon and photon lasing dynamics, generation of optomechanical Schrӧdinger cat states in a cavity Bose-Einstein condensate system, realization of the yoctonewton force detection based on an optically levitated oscillator, magnon squeezing enhanced ground-state cooling in cavity magnomechanics, parity-dependent unidirectional and chiral photon transfer in reversed-dissipation cavity optomechanics, phase-controlled photon blockade in optomechanical systems, and simulation of the optomechanical system with cavity-QED setup. We wish this special issue an academic feast for the audience of Fundamental Research, and expect it may initiate and promote more active scientific communication and greater advances in cavity optomechanics as well as in its relevant frontier research areas, including nano science, quantum information science, and gravitational wave physics.

Finally, as guest editors of this special issue, we cordially thank all the Authors for their outstanding contributions to this issue, Associate Editor Prof. Gui-Lu Long and Editorial Board Member Prof. Yun-Feng Xiao for their constructive guidance and instruction regarding the organization of this issue, science Editors Can Liu and Yawen Yao for their perfect organization of this issue, and all the Referees for their thoughtful and helpful advice on these papers.

Biographies

Jie-Qiao Liao received his BS and PhD degrees from Hunan Normal University in 2003 and 2008, respectively. He is a professor of physics at Hunan Normal University, where he is the Vice Dean of School of Physics and Electronics. His main research is focused on cavity optomechanics, quantum optics, quantum information, and open quantum systems.

Chun-Hua Dong received his BS and PhD degrees from the University of Science and Technology of China (USTC) in 2006 and 2011, respectively. He is currently a professor in the CAS Key Laboratory of Quantum Information at USTC, where his research is focused on whispering-gallery-mode resonators for cavity optomechanics, cavity magnomechanics, and frequency comb.

Min Wang received her BS degree from Fudan University in 2013, and PhD degree from Tsinghua University in 2019. She is an assistant research scientist at Beijing Academy of Quantum Information Sciences. Her research is focused on whispering-gallery-mode microresonators for cavity optome- chanics, quantum communication, and quantum information.