Frontiers of Physics分享


分享:Frontiers of Physics 2010,5(1) (SCIE收录)

已有 3813 次阅读 2010-1-19 13:44 |个人分类:Frontiers of Physics|系统分类:科研笔记

Cover illustration
Volume 5, Number 1

Over the last decades, digital information processing progressed at an enormous speed. It already becomes an indispensable resource both in science and in society. However, for some computational problems, no efficient algorithms are known yet. If quantum mechanical systems are used for information process, an exponential speedup will be obtained for some of these problems instead of today's classical computers. Among the many different physical systems that have been proposed as carriers of quantum information, nuclear and electronic spins have so far been the most successful candidates. The main challenge remains to be the combination of the spins into scalable quantum registers with hundreds or thousands of spins. The picture shows a particularly interesting candidate: the information would be stored in the nuclear spin of nitrogen or phosphorus atoms (blue spheres), which are stored in the center of C60 molecules. The molecules form nanometer-sized traps for the neutral atoms and thus make it possible to arrange them in predefined patterns, e.g. as rows on a silicon surface. More details could be found in the article “Spin qubits for quantum simulations” by Xin-hua PENG (彭新华) and Dieter SUTER, pp 125. [Photo credits: Prof. Dieter SUTER (Fakultät Physik, Technische Universität Dortmund, Germany)]

Xin-hua PENG (彭新华), Dieter SUTER

This review discusses a specific type of quantum simulator, based on nuclear spin qubits, and using nuclear magnetic resonance for processing. The authors review the basics of quantum information processing by nuclear magnetic resonance (NMR) as well as the fundamentals of quantum simulation and describe some simple applications that can readily be realized by today’s quantum computers. In particular, the authors discuss the simulation of quantum phase transitions: the qualitative changes that the ground states of some quantum mechanical systems exhibit when some parameters in their Hamiltonians change through some critical points. As specific examples, the authors consider quantum phase transitions where the relevant ground states are entangled. Chains of spins coupled by Heisenberg interactions represent an ideal system for studying these effects: depending on the type and strength of interactions, the ground states can be product states or they can be maximally entangled states representing different types of entanglement.

This article reviews recent progress on quantum entanglement and disentanglement of multi-atom systems. New aspects of entanglement behavior, such as entanglement sudden birth, entanglement sudden death, and revival of entanglement, are presented and discussed in details. The author discussed several important issues including the role of spontaneous emission in creation of an entanglement from separable states, the controlled and steered evolution of entanglement between different pairs of qubits, and how to deterministically prepare hot and cold atomic ensembles, trapped inside a ring cavity, in desired multi-mode entangled and cluster states.

Da-he LIU (刘大禾), Jin-wei SHI (石锦卫), Xu-dong CHEN (陈旭东), Min OUYANG (欧阳敏), Wen-ping GONG (弓文平)

This paper proposed a method for remote sensing of the ocean. Through this method, some oceanographic parameters can be measured in real time and a submerged object can be detected easily. Several physical problems related to Brillouin lidar and Brillouin scattering are also investigated.

Giancarlo CAVALLERI, Francesco BARBERO, Gianfranco BERTAZZI, Eros CESARONI, Ernesto TONNI, Leonardo BOSI, Gianfranco SPAVIERI, George T. GILLIES

The article discusses the history of attempts to interpret and explain some of the foundational features of quantum mechanics via appeals to the effects of nonrenormalized, electromagnetic stochastic zero-point fields. The shortcomings and the amelioration of the method are also described within the context of the relevant theoretical developments and proposed experimental tests thereof. In particular, possible methods of discriminating between the predictions of the principle theories are proffered, with a particular focus on what might be learned from new examinations of double-slit diffraction and interference patterns.

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