Evolutions of Quantum States in a Laser Channel

Xiang-Guo Meng, Bao-Long Liang, Jian-Ming Liu +1 more

Using the integration within ordered products, we obtain the analytical density-operator evolution of the general quadratic state ρ 0 in a laser channel, which always maintains the same form as the initial density operator ρ 0. Introducing the differential representation of the von-Neumann entropy and two important resemble formulas, we analytically and numerically investigate the entropy evolution of the state ρ 0 in a laser channel, which is determined by not only the competition of the gain and loss of the laser channel, but also the coefficients α, β of the initial quadratic state ρ 0.

Lampros A. A. Nikolopoulos

Chuan-Xun Du, Xiang‐Gao Meng, Ran Zhang +1 more

We investigate how displaced thermal states (DTSs) evolve in a laser channel. Remarkably, the initial DTS, an example of a mixed state, still remains mixed and thermal. At long times, they finally decay to a highly classical thermal field only related to the laser parameters κ and g . The normal ordering product of density operator of the DTS in the laser channel leads to obtaining the analytical time-evolution expressions of the photon number, Wigner function, and von Neumann entropy. Also, some interesting results are presented via numerically investigating these explicit time-dependent expressions.

Ke Zhang, Lan-Lan Li, Hong-Yi Fan

In this paper, by using the method of integration within the ordered product of operators and entangled state representation, the degree of second-order coherence of coherent state evolving in a laser channel is derived for the first time, which exhibits its anti-bunching property. The master equation of the laser channel is solved by entangled state representation, and the cumulant for deriving mean and mean-square photon numbers is evaluated.

Daniel F. Walls, Gerard J Milburn