Iterative quantum state transfer along a chain of nuclear spin qubits

Transferring quantum information between two qubits is a basic requirement for many applications in quantum communication and quantum information processing. In the iterative quantum state transfer (IQST) proposed by D. Burgarth et al. [Phys. Rev. A 75, 062327 (2007)], this is achieved by a static spin chain and a sequence of gate operations applied only to the receiving end of the chain. The only requirement on the spin chain is that it transfers a finite part of the input amplitude to the end of the chain, where the gate operations accumulate the information. For an appropriate sequence of evolutions and gate operations, the fidelity of the transfer can asymptotically approach unity. We demonstrate the principle of operation of this transfer scheme by implementing it in a nuclear magnetic resonance quantum information processor.Comment: Version for submission. Comments are welcom

Effect of system level structure and spectral distribution of the environment on the decoherence rate

Minimizing the effect of decoherence on a quantum register must be a central part of any strategy to realize scalable quantum information processing. Apart from the strength of the coupling to the environment, the decoherence rate is determined by the the system level structure and by the spectral composition of the noise trace that the environment generates. Here, we discuss a relatively simple model that allows us to study these different effects quantitatively in detail. We evaluate the effect that the perturbation has on an NMR system while it performs a Grover search algorithm.Comment: Generalizations are added. Comments are welcom

Factors Regulating Neurogenesis in the Adult Dentate Gyrus

The dentate gyrus (DG), an important part of the hippocampus, plays a critical role in consolidation of information from short-term to long-term memory, and also in spatial navigation. Neural stem/progenitor cells (NSPCs) exist throughout life in the subgranular zone (SGZ) of the DG, where they develop into granular cells and establish synaptic connections with nearby cells. Granular cells of the DG sprout axons targeting neurons in the cornu ammonis 3 (CA3) area of the hippocampus, forming a neural trisynaptic circuit, an important part of the neural network in the hippocampus. Thus, the DG and the neurogenic cells it contains are of importance in controlling formation of memories, learned behaviors, and also in the maintenance and restoration of functions of the hippocampus. According to reports, both in vivo and in vitro neurogenesis in the DG are regulated by a variety of endogenous and exogenous factors at different stages. Therefore, a better understanding of the factors in NSPC niches and the intracellular molecules regulating/directing adult DG neurogenesis is needed to fully realize the potential of NSPCs in the treatment of hippocampal-related disorders. This chapter systematically summarizes the factors reported in regulating adult DG neurogenesis in mammals. Specifically, neurotransmitters, hormones, trophic factors, and others will be discussed