量子游走是量子计算的重要模型,而多硬币量子游走模型由于在量子通讯协议中表现突出也越来越受到人们的关注.量子相干不仅可以刻画量子态的特点,也可以反映量子演化过程的性质.主要对一维圆上两硬币量子游走模型的量子相干性进行了分析.一方面,讨论了初始量子态和硬币算子的选取对量子相干的影响.当硬币算子为Hadamard算子且初态只要在位置子空间上是均衡叠加态,整个量子游走演化过程是具有周期性的,且量子相干仅依赖于步数和圆上顶点的个数;当初始态是均衡叠加态而对硬币算子没有任何限制时,量子相干的演化也极具规律性.另一方面,发现在利用量子游走实现完美状态转移(perfect state transfer)的过程中,硬币算子的选取直接影响量子相干的值.最后,探讨了2种量子游走模型之间的等价性,并基于此指出了其在量子隐形传输(quantum teleportation)中的应用和改进的可能性.
The paper discusses a class of generalized multiprocessor scheduling problems which is to arrange some independent jobs on almost identical processors. Different from the classical multiprocessor scheduling, each job ...
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The paper discusses a class of generalized multiprocessor scheduling problems which is to arrange some independent jobs on almost identical processors. Different from the classical multiprocessor scheduling, each job may only be processed by some processors, not all. In this paper, we first prove that the problems of minimization makespan and minimization total weighted completion time can be solved by the polynomial algorithms if all processing time are unit time. Then for arbitrary processing time, we try to analyze the worst performance of list schedule (LS) method and longest processing time(LPT) method when there are only two machines involved. We show that the bounds for LS and LPT are exactly two.
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