State transfer in dissipative and dephasing environments

By diagonalization of a generalized superoperator for solving the master equation, we investigated effects of dissipative and dephasing environments on quantum state transfer, as well as entanglement distribution and creation in spin networks. Our results revealed that under the condition of the same decoherence rate $\gamma$, the detrimental effects of the dissipative environment are more severe than that of the dephasing environment. Beside this, the critical time $t_c$ at which the transfer fidelity and the concurrence attain their maxima arrives at the asymptotic value $t_0=\pi/2\lambda$ quickly as the spin chain length $N$ increases. The transfer fidelity of an excitation at time $t_0$ is independent of $N$ when the system subjects to dissipative environment, while it decreases as $N$ increases when the system subjects to dephasing environment. The average fidelity displays three different patterns corresponding to $N=4r+1$, $N=4r-1$ and $N=2r$. For each pattern, the average fidelity at time $t_0$ is independent of $r$ when the system subjects to dissipative environment, and decreases as $r$ increases when the system subjects to dephasing environment. The maximum concurrence also decreases as $N$ increases, and when $N\rightarrow\infty$, it arrives at an asymptotic value determined by the decoherence rate $\gamma$ and the structure of the spin network.Comment: 12 pages, 6 figure

State transfer in intrinsic decoherence spin channels

By analytically solving the master equation, we investigate quantum state transfer, creation and distribution of entanglement in the model of Milburn's intrinsic decoherence. Our results reveal that the ideal spin channels will be destroyed by the intrinsic decoherence environment, and the detrimental effects become severe as the decoherence rate $\gamma$ and the spin chain length $N$ increase. For infinite evolution time, both the state transfer fidelity and the concurrence of the created and distributed entanglement approach steady state values, which are independent of the decoherence rate $\gamma$ and decrease as the spin chain length $N$ increases. Finally, we present two modified spin chains which may serve as near perfect spin channels for long distance state transfer even in the presence of intrinsic decoherence environments $\mathcal {F}{[\rho(t)]}$.Comment: 11 pages, 11 figure

Lipase immobilization in a silics gel matrix

Badano proces immobilizacji lipazy z Candida rugosa w sieci silikażelu, otrzymywanego z tetrametoksysilanu na drodze procesu zol-żel. Żelowanie przeprowadzono przy trzech stężeniach fluorku sodu, który pełnił rolę katalizatora procesu. Stwierdzono spowolnienie procesu żelowania ze zmniejszeniem stężenia katalizatora. Wykazano także niewielki wpływ wymiaru ziaren biokatalizatorów na ich aktywność oraz istotny wpływ temperatury na stabilność podczas przechowywania.The immobilization of lipase from Candida rugosa in a matrix of silica gel obtained from tetramethoxysilane by means of a sol-gel process was investigated. Gelation was effected at three concentrations of sodium fluoride which was used as the process catalyst. It was found that the gelation process was slower for lower concentrations of the catalyst. It also was demonstrated that the grain size of the biocatalysts had a minor effect on their activity while temperature had a significant effect on their stability during storage