Controllability of Quantum Systems

An overview and synthesis of results and criteria for open-loop controllability of Hamiltonian quantum systems obtained using Lie group and Lie algebra techniques is presented. Negative results for open-loop controllability of dissipative systems are discussed, and the superiority of closed-loop (feedback) control for quantum systems is established.Comment: 6 pages, to appear in Proceedings of Conference on Lagrangian and Hamiltonian Methods in Non-Linear Control (Seville, Spain, 2003

Using Virtual Addresses with Communication Channels

While for single processor and SMP machines, memory is the allocatable quantity, for machines made up of large amounts of parallel computing units, each with its own local memory, the allocatable quantity is a single computing unit. Where virtual address management is used to keep memory coherent and allow allocation of more than physical memory is actually available, virtual communication channel references can be used to make computing units stay connected across allocation and swapping.Comment: 5 pages, 4 figure

Limitations on quantum control

In this note we give an introduction to the topic of quantum control, explaining what its objectives are, and describing some of its limitations.Comment: 6 page

Episodic memory, the cotemporality problem, and common sense

Direct realists about episodic memory claim that a rememberer has direct contact with a past event. But how is it possible to be acquainted with an event that ceased to exist? That’s the so-called cotemporality problem. The standard solution, proposed by Sven Bernecker, is to distinguish between the occurrence of an event and the existence of an event: an event ceases to occur without ceasing to exist. That’s the eternalist solution for the cotemporality problem. Nevertheless, some philosophers of memory claim that the adoption of an eternalist metaphysics of time would be too high a metaphysical price to be paid to hold direct realist intuitions about memory. Although I agree with these critics, I will try to show two things. First, that this kind of “common sense argument” is far from decisive. Second, that Bernecker’s proposal remains the best solution to the cotemporality problem