Table of Contents
Advances in Optics
Volume 2014, Article ID 141076, 6 pages
Research Article

Analyzing Density Operator in Thermal State for Complicated Time-Dependent Optical Systems

1Department of Radiologic Technology, Daegu Health College, Yeongsong-ro 15, Buk-gu, Daegu 702-722, Republic of Korea
2Division of Mathematical Modeling, National Institute for Mathematical Sciences, KT Daeduk 2 Research Center, 463-1 Jeonmin-dong, Yuseong-gu, Daejeon 305-390, Republic of Korea

Received 18 April 2014; Accepted 9 July 2014; Published 24 July 2014

Academic Editor: Kim Fook Lee

Copyright © 2014 Jeong Ryeol Choi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Density operator of oscillatory optical systems with time-dependent parameters is analyzed. In this case, a system is described by a time-dependent Hamiltonian. Invariant operator theory is introduced in order to describe time-varying behavior of the system. Due to the time dependence of parameters, the frequency of oscillation, so-called a modified frequency of the system, is somewhat different from the natural frequency. In general, density operator of a time-dependent optical system is represented in terms of the modified frequency. We showed how to determine density operator of complicated time-dependent optical systems in thermal state. Usually, density operator description of quantum states is more general than the one described in terms of the state vector.