Abstract By introducing the von Neumann entropy as a measure of the extent of noise, this paper discusses the entropy evolution in a two-level quantum feedback controlled system. The results show that the feedback control can induce the reduction of the degree of noise, and different control schemes exhibit different noise controlling ability, the extent of the reduction also related with the position of the target state on the Bloch sphere. It is shown that the evolution of entropy can provide a real time noise observation and a systematic guideline to make reasonable choice of control strategy.
Received: 27 May 2006
Revised: 05 July 2006
Accepted manuscript online:
(Quantum fluctuations, quantum noise, and quantum jumps)
Fund: Project supported by the
National Natural Science
Foundation of China (Grant No 10374025).
Cite this article:
Wang Tao-Bo(王涛波), Fang Mao-Fa(方卯发), and Hu Yao-Hua(胡要花) Entropy as a measure of the noise extent in a two-level quantum feedback controlled system 2007 Chinese Physics 16 111
Altmetric calculates a score based on the online attention an article receives. Each coloured thread in the circle represents a different type of online attention. The number in the centre is the Altmetric score. Social media and mainstream news media are the main sources that calculate the score. Reference managers such as Mendeley are also tracked but do not contribute to the score. Older articles often score higher because they have had more time to get noticed. To account for this, Altmetric has included the context data for other articles of a similar age.
