Symmetry,including the parity-time(PT)-symmetry,is a striking topic,widely discussed and employed in many fields.It is well-known that quantum measurement can destroy or disturb quantum systems.However,can and how doe...Symmetry,including the parity-time(PT)-symmetry,is a striking topic,widely discussed and employed in many fields.It is well-known that quantum measurement can destroy or disturb quantum systems.However,can and how does quantum measurement destroy the symmetry of the measured system?To answer the pertinent question,we establish the correlation between the quan-tum measurement and Floquet PT-symmetry and investigate for the first time how the measurement frequency and measurement strength affect the PT-symmetry of the measured system using the 40Ca+ion.It is already shown that the measurement at high frequencies would break the PT symmetry.Notably,even for an inadequately fast measurement frequency,if the measurement strength is sufficiently strong,the PT symmetry breaking can occur.The current work can enhance our knowledge of quantum measurement and symmetry and may inspire further research on the effect of quantum measurement on symmetry.展开更多
Linewidth narrowing and other quantum coherent effects based on three-photon coherent population trapping （CPT） in Ca＋ ions are investigated. If the propagation directions of the three lasers obey the phase matchin...Linewidth narrowing and other quantum coherent effects based on three-photon coherent population trapping （CPT） in Ca＋ ions are investigated. If the propagation directions of the three lasers obey the phase matching condition, the dark linewidth resulting from the CPT can be very narrow, and it can be controlled by adjusting the parameters of the lasers.展开更多
基金This work was supported by the National Basic Research Program of China(Grant No.2016YFA0301903)the National Natural Science Foundation of China(Grant Nos.12074433,12004430,12174447,12174448,and 11904402).
文摘Symmetry,including the parity-time(PT)-symmetry,is a striking topic,widely discussed and employed in many fields.It is well-known that quantum measurement can destroy or disturb quantum systems.However,can and how does quantum measurement destroy the symmetry of the measured system?To answer the pertinent question,we establish the correlation between the quan-tum measurement and Floquet PT-symmetry and investigate for the first time how the measurement frequency and measurement strength affect the PT-symmetry of the measured system using the 40Ca+ion.It is already shown that the measurement at high frequencies would break the PT symmetry.Notably,even for an inadequately fast measurement frequency,if the measurement strength is sufficiently strong,the PT symmetry breaking can occur.The current work can enhance our knowledge of quantum measurement and symmetry and may inspire further research on the effect of quantum measurement on symmetry.
基金Acknowledgements We thank Prof. Yi-fu Zhu for useful discus- sion. This work was supported by the National Basic Research Pro- gram of China （Grant No. 2005CB724502）, the National Natural Science Foundation of China （Grant Nos. 10874205 and 10774161） and the Chinese Academy of Sciences.
文摘Linewidth narrowing and other quantum coherent effects based on three-photon coherent population trapping （CPT） in Ca＋ ions are investigated. If the propagation directions of the three lasers obey the phase matching condition, the dark linewidth resulting from the CPT can be very narrow, and it can be controlled by adjusting the parameters of the lasers.
