开放量子系统的理论及其在量子信息中的应用

Based on the subdynamics of the open quantum system,we have expounded the realization of quantum computer in projected subspace. The generalized formalism for the decoherence -free subspace, which is caused by the interaction of evironment with quantum system, has been constructed. To eliminate possible phase or unitary errors ,a cancellation technique is proposed,using the adjustment of the coupling time,and applied in a two-qubit computing system. An approach is presented for directly construction multi-qubit logic gates using quantum dots .The error-avoiding codes in the projected sub-space are discussed ,offering a potentially robust scheme for protecting against decoherence. A method for quantum control of coherence in an open quantum computing system in silicon based nuclear spin quantum computing system subjected to Bose-type environment noise has been discussed. A description is formulated for decoherence in quantum registers in weak-coupling limit for non-Markovain dynamical evolution and a general criteria for decoherence-free states is proposed. In addition, the code communication in sub-space is discused. The research of quantum computing based on the theory of sub-dynamical kinetics is first discussed in our works, which have been published in Phys.Rev.A, J.App. Phys, et al. Some additional achievements,which were not mentioned in the application,have been obtained as well.Based on the sub-dynamics theory,we give some description of the transportation in a mesoscopic system by presenting the extended Kubo formular with higher-order correction,and apply it in analytic study on the giant- magnetoresistance of multi-layer sandwich structure and spin-valve structure.In addition,we report a study on the collision dynamics of Na clusters by means of distance dependent tight-binding molecular dynamics (DDTB－MD). We study the non-symmetric collision and the collision between two Nan clusters with different temperatures. Different reaction mechanisms have been observed at the different incident energies and different impact parameters, which are likely similar to the nuclear heavy-ion collisions (HIC).

本项目研究开放量子系统的理论及其在信息系统中的应用。将构造能克服环境对量子计算机的解相干和耗散干扰的开放量子计算机理论。在此理论基础上将研究这类系统的计算机仿真技术和相应的数值计算方法，并将这些理论和方法应用于开放量子计算机的设计。本项目的完成无疑将对下一代的信息系统的研制起重要作用。