%A Peng,Tao
%A Zhao,Xingchen
%A Shih,Yanhua
%A Scully,Marlan O.
%D 2021
%J Frontiers in Physics
%C
%F
%G English
%K High order coherence,quantum theory of the laser,spectral line distribution,density matrix,Heterodyne detection
%Q
%R 10.3389/fphy.2021.657333
%W
%L
%M
%P
%7
%8 2021-April-21
%9 Original Research
%#
%! High order coherence by the QTL
%*
%<
%T High Order Coherence Functions and Spectral Distributions as Given by the Scully-Lamb Quantum Theory of the Laser
%U https://www.frontiersin.org/articles/10.3389/fphy.2021.657333
%V 9
%0 JOURNAL ARTICLE
%@ 2296-424X
%X We propose and demonstrate a method for measuring the time evolution of the off-diagonal elements ρ_{n,n+k}(t) of the reduced density matrix obtained from the quantum theory of the laser. The decay rates of the off-diagonal matrix element ρ_{n,n+k}(t) (k = 2,3) are measured for the first time and compared with that of ρ_{n,n+1}(t), which corresponds to the linewidth of the laser. The experimental results agree with the Scully-Lamb quantum theory of the laser.