Spontaneous symmetry breaking has revolutionized the understanding in numerous fields of modern physics. Here, we theoretically demonstrate the spontaneous time-reversal symmetry breaking in a cavity quantum electrody...Spontaneous symmetry breaking has revolutionized the understanding in numerous fields of modern physics. Here, we theoretically demonstrate the spontaneous time-reversal symmetry breaking in a cavity quantum electrodynamics system in which an atomic ensemble interacts coherently with a single resonant cavity mode. The interacting system can be effectively described by two coupled oscillators with positive and negative mass, when the two-level atoms are prepared in their excited states. The occurrence of symmetry breaking is controlled by the atomic detuning and the coupling to the cavity mode,which naturally divides the parameter space into the symmetry broken and symmetry unbroken phases.The two phases are separated by a spectral singularity, a so-called exceptional point, where the eigenstates of the Hamiltonian coalesce. When encircling the singularity in the parameter space, the quasiadiabatic dynamics shows chiral mode switching which enables topological manipulation of quantum states.展开更多
This paper investigates the distributed finite-time consensus tracking problem for higher- order nonlinear multi-agent systems （MASs）. The distributed finite-time consensus protocol is based on full order sliding su...This paper investigates the distributed finite-time consensus tracking problem for higher- order nonlinear multi-agent systems （MASs）. The distributed finite-time consensus protocol is based on full order sliding surface and super twisting algorithm. The nominal consensus control for the MASs is designed based on the geometric homogeneous finite time control technique. The chattering is avoided by designing a full order sliding surface. The switching control is constructed by integrating super twisting algorithm, hence a chattering alleviation protocol is obtained to maintain a smooth control input. The finite time convergence analysis for the leader follower network is presented by using strict Lyapunov function. Finally, the numerical simulations validate the proposed homogeneous full-order sliding mode control for higher-order MASs.展开更多
基金supported by the National Key R&D Program of China(2016YFA0301302)the National Natural Science Foundation of China(61435001,11654003,11474011)High-performance Computing Platform of Peking University
文摘Spontaneous symmetry breaking has revolutionized the understanding in numerous fields of modern physics. Here, we theoretically demonstrate the spontaneous time-reversal symmetry breaking in a cavity quantum electrodynamics system in which an atomic ensemble interacts coherently with a single resonant cavity mode. The interacting system can be effectively described by two coupled oscillators with positive and negative mass, when the two-level atoms are prepared in their excited states. The occurrence of symmetry breaking is controlled by the atomic detuning and the coupling to the cavity mode,which naturally divides the parameter space into the symmetry broken and symmetry unbroken phases.The two phases are separated by a spectral singularity, a so-called exceptional point, where the eigenstates of the Hamiltonian coalesce. When encircling the singularity in the parameter space, the quasiadiabatic dynamics shows chiral mode switching which enables topological manipulation of quantum states.
文摘This paper investigates the distributed finite-time consensus tracking problem for higher- order nonlinear multi-agent systems （MASs）. The distributed finite-time consensus protocol is based on full order sliding surface and super twisting algorithm. The nominal consensus control for the MASs is designed based on the geometric homogeneous finite time control technique. The chattering is avoided by designing a full order sliding surface. The switching control is constructed by integrating super twisting algorithm, hence a chattering alleviation protocol is obtained to maintain a smooth control input. The finite time convergence analysis for the leader follower network is presented by using strict Lyapunov function. Finally, the numerical simulations validate the proposed homogeneous full-order sliding mode control for higher-order MASs.
