a Shandong Provincial Key Laboratory of Laser Polarization and Information Technology, Department of Physics, Qufu Normal University, Qufu 273165, China; b Department of Physics, Engineering University of CAPF, Xi'an 710086, China; c Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Abstract The lower bounds of the evolution time between two distinguishable states of a system, defined as quantum speed limit time, can characterize the maximal speed of quantum computers and communication channels. We study the quantum speed limit time between the composite quantum states and their target states in the presence of nondissipative decoherence. For the initial states with maximally mixed marginals, we obtain the exact expressions of the quantum speed limit time which mainly depend on the parameters of the initial states and the decoherence channels. Furthermore, by calculating the quantum speed limit time for the time-dependent states started from a class of initial states, we discover that the quantum speed limit time gradually decreases in time, and the decay rate of the quantum speed limit time would show a sudden change at a certain critical time. Interestingly, at the same critical time, the composite system dynamics would exhibit a sudden transition from classical decoherence to quantum decoherence.
Fund: Project supported by the National Natural Science Foundation of China (Grant Nos. 61178012 and 11304179), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20123705120002 and 20133705110001), the Natural Science Foundation of Shandong Province of China (Grant No. ZR2014AP009), and the Scientific Research Foundation of Qufu Normal University.
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