Parity-time (PT) symmetry/anti-parity-time (APT) symmetry in non-Hermitian systems reveal profound physics andspawn intriguing effects. Recently, it has been introduced into diffusive systems together with the concept...Parity-time (PT) symmetry/anti-parity-time (APT) symmetry in non-Hermitian systems reveal profound physics andspawn intriguing effects. Recently, it has been introduced into diffusive systems together with the concept of exceptionalpoints (EPs) from quantum mechanics and the wave systems. With the aid of convection, we can generate complex thermalconductivity and imitate various wavelike dynamics in heat transfer, where heat flow can be “stopped” or moving against thebackground motion. Non-Hermitian diffusive systems offer us a new platform to investigate the heat wave manipulation.In this review, we first introduce the construction of APT symmetry in a simple double-channel toy model. Then we showthe phase transition around the EP. Finally, we extend the double-channel model to the four-channel one for showing thehigh-order EP and the associated phase transition. In a general conclusion, the phase difference of adjacent channels isalways static in the APT symmetric phase, while it dynamically evolves or oscillates when the APT symmetry is broken.展开更多
Phase transition from the over-damping to under-damping states is a ubiquitous phenomenon in physical systems. However, what kind of symmetry is broken associated with this phase transition remains unclear. Here, we d...Phase transition from the over-damping to under-damping states is a ubiquitous phenomenon in physical systems. However, what kind of symmetry is broken associated with this phase transition remains unclear. Here, we discover that this phase transition is determined by an anti-parity-time(anti-PT) symmetry hidden in a single damping linear resonator, which is significantly different from the conventional anti-PT-symmetric systems with two or more modes. We show that the breaking of the anti-PT symmetry yields the phase transition from the over-damping to under-damping states, with an exceptional point(EP) corresponding to the critical-damping state. Moreover, we propose an optomechanical scheme to show this anti-PT symmetry breaking by using the optical spring effect in a quadratic optomechanical system. We also suggest an optomechanical sensor with the sensitivity enhanced significantly around the EPs for the anti-PT symmetry breaking. Our work unveils the anti-PT symmetry hidden in damping oscillations and hence opens up new possibilities for exploiting wide anti-PT symmetry applications in single damping linear resonators.展开更多
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...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(PT)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 compared to that of the conventional device without EPs.Remarkably,the PT symmetry can be broken when including the Kerr nonlinearity of the materials and,as a 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 PT gyroscopes in practice to achieve ultrasensitive rotation measurement.展开更多
Non-Hermitian systems satisfying parity-time(PT)symmetry have aroused considerable interest owing to their exotic features.Anti-PT symmetry is an important counterpart of the symmetry,and has been studied in various c...Non-Hermitian systems satisfying parity-time(PT)symmetry have aroused considerable interest owing to their exotic features.Anti-PT symmetry is an important counterpart of the symmetry,and has been studied in various classical systems.Although a Hamiltonian with anti-PT symmetry only differs from its PT-symmetric counterpart in a global phase,the information and energy exchange between systems and environment are different under them.It is also suggested theoretically that anti-PT symmetry is a useful concept in the context of quantum information storage with qubits coupled to a bosonic bath.So far,the observation of anti-PT symmetry in individual quantum systems remains elusive.Here,we implement an anti-PT-symmetric Hamiltonian of a single qubit in a single trapped ion by a designed microwave and optical control-pulse sequence.We characterize the anti-PT phase transition by mapping out the eigenvalues at different ratios between coupling strengths and dissipation rates.The full information of the quantum state is also obtained by quantum state tomography.Our work allows quantum simulation of genuine open-system feature of an anti-PT-symmetric system,which paves the way for utilizing non-Hermitian properties for quantum information processing.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674119 and 11690032)the Fundamental Research Funds for the Central Universities,China(HUST:2019JYCXJJ038)X.F.Z.and P.C.C.acknowledge the financial support from the Bird Nest Plan of HUST.
文摘Parity-time (PT) symmetry/anti-parity-time (APT) symmetry in non-Hermitian systems reveal profound physics andspawn intriguing effects. Recently, it has been introduced into diffusive systems together with the concept of exceptionalpoints (EPs) from quantum mechanics and the wave systems. With the aid of convection, we can generate complex thermalconductivity and imitate various wavelike dynamics in heat transfer, where heat flow can be “stopped” or moving against thebackground motion. Non-Hermitian diffusive systems offer us a new platform to investigate the heat wave manipulation.In this review, we first introduce the construction of APT symmetry in a simple double-channel toy model. Then we showthe phase transition around the EP. Finally, we extend the double-channel model to the four-channel one for showing thehigh-order EP and the associated phase transition. In a general conclusion, the phase difference of adjacent channels isalways static in the APT symmetric phase, while it dynamically evolves or oscillates when the APT symmetry is broken.
基金supported by the National Natural Science Foundation of China(Grant Nos.12064010,12247105,12175061,11935006,11774086,1217050862,and 11775075)the Natural Science Foundation of Hunan Province(Grant No.2021JJ20036)the Science and Technology Innovation Program of Hunan Province(Grant Nos.2022RC1203,2020RC4047,and 2021RC4029)。
文摘Phase transition from the over-damping to under-damping states is a ubiquitous phenomenon in physical systems. However, what kind of symmetry is broken associated with this phase transition remains unclear. Here, we discover that this phase transition is determined by an anti-parity-time(anti-PT) symmetry hidden in a single damping linear resonator, which is significantly different from the conventional anti-PT-symmetric systems with two or more modes. We show that the breaking of the anti-PT symmetry yields the phase transition from the over-damping to under-damping states, with an exceptional point(EP) corresponding to the critical-damping state. Moreover, we propose an optomechanical scheme to show this anti-PT symmetry breaking by using the optical spring effect in a quadratic optomechanical system. We also suggest an optomechanical sensor with the sensitivity enhanced significantly around the EPs for the anti-PT symmetry breaking. Our work unveils the anti-PT symmetry hidden in damping oscillations and hence opens up new possibilities for exploiting wide anti-PT symmetry applications in single damping linear resonators.
基金the National Natural Science Foundation of China(Grant Nos.11935006,11774086,and 12064010)Science and Technology Innovation Program of Hunan Province,China(Grant No.2020RC4047)+1 种基金Natural Science Foundation of Hunan Province of China(Grant No.2021JJ20036)Natural Science Foundation of Jiangxi Province of China(Grant No.20192ACB21002)。
文摘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(PT)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 compared to that of the conventional device without EPs.Remarkably,the PT symmetry can be broken when including the Kerr nonlinearity of the materials and,as a 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 PT gyroscopes in practice to achieve ultrasensitive rotation measurement.
基金the Key-Area Research and Development Program of Guangdong Province(2019B030330001)the National Natural Science Foundation of China(11774436,11974434 and 12074439)+3 种基金the fundamental research funds for the Central Universities(Sun Yat-sen University,2021qntd28)Le Luo receives support from Guangdong Province Youth Talent Program(2017GC010656)Sun Yat-Sen University Core Technology Development Fund.Yang Liu receives support from Natural Science Foundation of Guangdong Province(2020A1515011159)Ji Bian receives support from China Postdoctoral Science Foundation(2021M703768).
文摘Non-Hermitian systems satisfying parity-time(PT)symmetry have aroused considerable interest owing to their exotic features.Anti-PT symmetry is an important counterpart of the symmetry,and has been studied in various classical systems.Although a Hamiltonian with anti-PT symmetry only differs from its PT-symmetric counterpart in a global phase,the information and energy exchange between systems and environment are different under them.It is also suggested theoretically that anti-PT symmetry is a useful concept in the context of quantum information storage with qubits coupled to a bosonic bath.So far,the observation of anti-PT symmetry in individual quantum systems remains elusive.Here,we implement an anti-PT-symmetric Hamiltonian of a single qubit in a single trapped ion by a designed microwave and optical control-pulse sequence.We characterize the anti-PT phase transition by mapping out the eigenvalues at different ratios between coupling strengths and dissipation rates.The full information of the quantum state is also obtained by quantum state tomography.Our work allows quantum simulation of genuine open-system feature of an anti-PT-symmetric system,which paves the way for utilizing non-Hermitian properties for quantum information processing.