Sudden birth and sudden death of thermal fidelity in a two-qubit system  

作　　者：秦立国 田立君 姜颖 张宏标 

机构地区：[1]Department of Physics,Shanghai University [2]Institute of Theoretical Physics,Northeast Normal University

出　　处：《Chinese Physics B》2012年第5期487-493,共7页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(Grant No.11075101);the Science & Technology Committee of Shanghai Municipality,China(Grant Nos.08dj1400202 and 09PJ1404700);the Training Fund of NENU's Scientific Innvovation Project,China(Grant No.NENU-STC08018);the Ph.D.Program Foundation of Ministry of Education of China (Grant No.20093108110004)

摘　　要：We study the energy level crossing and the thermal fidelity in a two-qubit system with the presence of a transverse inhomogeneous magnetic field.With the help of contour plots,we clearly identify the ground states of the system in different regions of parameter space,and discuss the corresponding energy level crossing.The fidelity between the ground state of the system and the state of the system at temperature T is calculated.The result shows that the fidelity is very sensitive to the magnetic field anisotropic factor,indicating that this factor may be used as a controller of the fidelity.The influence of the Yangian transition operators on the fidelity of the system is discussed.We find that the Yangian operators can change the fidelity dramatically and give rise to sudden birth and sudden death phenomena of the thermal fidelity.This makes the corresponding Yangian operators possible candidates for switchers to turn the fidelity on and off.We study the energy level crossing and the thermal fidelity in a two-qubit system with the presence of a transverse inhomogeneous magnetic field.With the help of contour plots,we clearly identify the ground states of the system in different regions of parameter space,and discuss the corresponding energy level crossing.The fidelity between the ground state of the system and the state of the system at temperature T is calculated.The result shows that the fidelity is very sensitive to the magnetic field anisotropic factor,indicating that this factor may be used as a controller of the fidelity.The influence of the Yangian transition operators on the fidelity of the system is discussed.We find that the Yangian operators can change the fidelity dramatically and give rise to sudden birth and sudden death phenomena of the thermal fidelity.This makes the corresponding Yangian operators possible candidates for switchers to turn the fidelity on and off.

关 键 词：the ground state energy level crossing FIDELITY YANGIAN 

分 类 号：O413.1[理学—理论物理]