Nature Physics online published an article entitled "Anti-Parity-Time Symmetry with Flying Atoms" by Xiao Yanhong's group at Physics Department of Fudan University. It reported that for the first time in this group, Sex (Anti-PT Symmetry) Optical Hamiltonian Related Results. The work is the result of cooperation with Professor Liang Jiang and Dr. Wen Jianming's theoretical team from Yale University in the United States. PT Symmetry and PT Antisymmetry In traditional quantum mechanics, the Hamiltonian describing a quantum mechanics system must be mathematically mathematically guaranteed, so as to ensure the real observables and the system probability conservation. This means that the system is a standalone system that does not exchange energy with the outside world. Non-Hermitian Hamiltonian is only used as a theoretical approximation tool for equivalently describing the interaction of a physical system with the external environment. However, Bender and Boettcher pointed out in 1998 that the Hermitianity is not a necessary condition for the eigenvalues ​​to be real numbers. For non-Hermitian Hamiltonian quantities that satisfy the parity-time symmetry (PT symmetry), symmetry breaks down Before its eigenvalues ​​are all real numbers, the eigenvalues ​​will appear after the occurrence of symmetry breaking an imaginary number. The process of symmetry from non-breaking to breaking is phase change, similar to the process of changing from water to ice. The state of water changes from liquid to solid. The so-called PT symmetry means that the Hamiltonian remains the same after one time inversion (T) and spatial reflection (P) operation. It can be understood that supposing there is a world and a huge mirror, the world is PT symmetrical if the situation we see is exactly the same as the mirror outside the world reflected in the mirror. This theory is likely to widen the current framework of quantum mechanics, thus stimulating the study of many frontier issues such as non-Hermitian quantum mechanics and quantum field theory, non-Hermits model, open quantum system. At the same time, through the simulation of optical potential field, we can experimentally realize the equivalent PT non-Hamiltonian Hamiltonian which can not be achieved in the quantum mechanics framework and apply it to single-mode laser with large cross section, perfect laser absorber, In the visual structure and so on. Previous experiments on PT symmetry have focused on solid systems. To produce PT-symmetric Hamiltonian requires complex artificial material techniques. In general, atomic systems have much longer quantum states than solid systems and can produce precise spectra with high frequency resolution. Moreover, the optical potential field of weak light in an atom can be constructed and regulated by another intense light. There is no need to use micro / nano processing to achieve a specific optical potential as in the case of solid systems. In addition, the coherent control of light and atoms developed over the past decade, represented by electromagnetic induced transparency (EIT) In the case of strong coupling still maintain a good coherence. If PT symmetry can be achieved in the atomic system, it will greatly increase the research scope of non-Hermitian optics, reveal more interesting optical properties and generate new light regulation methods. Anything has its front, there must be the opposite, just as material and antimatter. As a concept that is dual to PT symmetry, the time-parity antisymmetric (PT antisymmetric) Hamiltonian means that after the P and T operations, the Hamiltonian has the opposite form of the negative one. In optical terms, PT antisymmetry will also exhibit perfect duality with PT symmetry, such as lossless propagation in a PT symmetry system, which corresponds to a non-refractive propagation in the PT antisymmetric system, which provides a new light control The concept and technical means, greatly expanded the scope of the study of non-Hermitian optics. Prior to this, the PT antisymmetric Hamiltonian has not been experimentally implemented. It is worth mentioning that although these concepts of symmetry are not necessary to explain the corresponding physical phenomena, they can macroscopically deepen people's understanding of the physical essence and help people design new optical systems and even practical devices. The use of atomic thermal motion to achieve the coupling between light modes The key to achieve a PT or anti-PT optical system is to achieve the coupling between different optical modes. Before the work of Xiao Yanhong's research group, there is no international experiment to achieve PT or anti-PT symmetry in the atomic system. The main difficulty is that achieving the coupling between two light modes in an atomic system is not as straightforward as in solids. In solid, the two modes of light are coupled directly by the evanescent wave of the waveguide, but similar coupling is difficult to achieve in an atomic system. Many research groups at home and abroad have tried to imitate the characteristics of solid systems in the atomic system to achieve PT symmetry, but none of these attempts succeeded. Under such circumstances, Xiao Yanhong's research group has taken another approach to give up the waveguide coupling mode in the solid system, and directly uses the atomic system's thermal motion to construct the coupling between the two light modes. The basic idea is that when an atom interacts with light in a channel, its quantum state will change, and the atom moves into another light channel by thermal motion and interacts with this beam of light, Information is transmitted to this beam of light, thereby achieving an indirect coupling between the two light modes and constructing an antisymmetric Hamiltonian of PT. Solar Panel Bracket,Aluminum Frame Bracket,Solar Aluminum Frame Accessories,Solar Panel Aluminum Frame Bracket Jiangsu Yuma Solar Co., Ltd. , https://www.yumaaluminum.com