Recent interest in aspects common to quantum information and condensed matter has prompted a flurry of activity at the border these disciplines that were far distant until few years ago. Numerous interesting questions have been addressed so far. Here an important part this field, properties entanglement many-body systems, are reviewed. The zero finite temperature interacting spin, fermion, boson model systems discussed. Both bipartite multipartite will be considered. In equilibrium is shown...

We discuss the problem of separating consistently total correlations in a bipartite quantum state into and purely classical part. A measure is proposed its properties are explored.

We present conditions every measure of entanglement has to satisfy, and construct a whole class ``good'' measures. The generalization our measures more than two particles is straightforward. which statistical operational basis that might enable experimental determination the quantitative degree entanglement.

One of the best signatures nonclassicality in a quantum system is existence correlations that have no classical counterpart. Different methods for quantifying and parts are among more actively studied topics quantum-information theory over past decade. Entanglement most prominent these correlations, but many cases unentangled states exhibit nonclassical behavior too. Thus distinguishing other than entanglement provides better division between worlds, especially when considering mixed states....

We improve previously proposed conditions each measure of entanglement has to satisfy. present a class measures that satisfy these and show the quantum relative entropy Bures metric generate two this class. calculate for number mixed spin-1/2 systems using entropy, provide an efficient numerical method obtain in case. In addition, we prove properties our have important physical implications. briefly explain statistical basis case entropy. then argue determines upper bound singlets can be...

Quantum discord characterizes ``nonclassicality'' of correlations in quantum mechanics. It has been proposed as the key resource present certain communication tasks and computational models without containing much entanglement. We obtain a necessary sufficient condition for existence nonzero any dimensional bipartite states. This is easily experimentally implementable. Based on this, we propose geometrical way quantifying discord. For two qubits this results closed form expression apply our...

We show how stationary entanglement between an optical cavity field mode and a macroscopic vibrating mirror can be generated by means of radiation pressure. also the optomechanical quantified, we suggest experimental readout scheme to fully characterize entangled state. Surprisingly, such is shown persist for environment temperatures above 20 K using state-of-the-art parameters.

Quantum mechanics and information theory are among the most important scientific discoveries of last century. Although these two areas initially developed separately, it has emerged that they in fact intimately related. In this review author shows how quantum extends traditional by exploring limits imposed quantum, rather than classical, on storage transmission. The derivation many key results differentiates from usual presentation shown to follow logically one crucial property relative...

Quantum computers require quantum arithmetic. We provide an explicit construction of networks effecting basic arithmetic operations: from addition to modular exponentiation. exponentiation seems be the most difficult (time and space consuming) part Shor's factorizing algorithm. show that auxiliary memory required perform this operation in a reversible way grows linearly with size number factorized. \textcopyright{} 1996 The American Physical Society.

We discuss the problem of separation total correlations in a given quantum state into entanglement, dissonance, and classical using concept relative entropy as distance measure correlations. This allows us to put all on an equal footing. Entanglement whose definition is introduced here, jointly belong what known discord. Our methods are completely applicable for multipartite systems arbitrary dimensions. investigate additivity relations between different show that dissonance may be present...

We investigate the entanglement between any two spins in a one dimensional Heisenberg chain as function of temperature and external magnetic field. find that an antiferromagnetic can be increased by increasing or Increasing field also create otherwise disentangled spins. This confirmed testing Bell's inequalities involving solid.

We generalize the procedure of entanglement swapping to obtain a scheme for manipulating in multiparticle systems. describe how this allows one establish between particles belonging distant users communication network through prior distribution singlets followed by only local measurements. show that can be regarded as method generating entangled states many and compare it with existing schemes using simple quantum computational networks. highlight practical advantages series swappings during...

Maxwell's demon was born in 1867 and still thrives modern physics. He plays important roles clarifying the connections between two theories: thermodynamics information. Here history of a variety interesting consequences second law are presented, mainly quantum mechanics, but also theory gravity. Also highlighted some recent work that explores role information, illuminated by demon, arena quantum-information theory.

All existing quantum-gravity proposals are extremely hard to test in practice. Quantum effects the gravitational field exceptionally small, unlike those electromagnetic field. The fundamental reason is that coupling constant about 43 orders of magnitude smaller than fine structure constant, which governs light-matter interactions. For example, detecting gravitons—the hypothetical quanta predicted by certain proposals—is deemed be practically impossible. Here we adopt a radically different,...

A quantum telecloning process combining teleportation and optimal cloning from one input to M outputs is presented. The scheme relies on the establishment of particular multiparticle entangled states, which function as multiuser information channels. entanglement structure these states analyzed shown be crucial for this type processing.

We provide a physical prescription based on interferometry for introducing the total phase of mixed state undergoing unitary evolution, which has been an elusive concept in past. define parallel transport condition that provides connection form obtaining geometric states. The expression reduces to well known formulas pure case when system undergoes noncyclic and quantum evolution.

Recently some authors have pointed out that there exist nonclassical correlations which are more general, and possibly fundamental, than entanglement. For these general quantum their classical counterparts, under the action of decoherence, we identify three types dynamics include a peculiar sudden change in decay rates. We show that, suitable conditions, correlation is unaffected by decoherence. Such dynamic behavior suggests an operational measure both can be computed without any...

We show how the state of an atom trapped in a cavity can be teleported to second distant simply by detecting photon decays from cavities. This is rare example decay mechanism playing constructive role quantum information processing. The scheme comparatively easy implement, requiring only ability trap single three level cavity.

We consider one copy of a quantum system prepared in two orthogonal pure states, entangled or otherwise, and distributed between any number parties. demonstrate that it is possible to identify which these states the by means local operations classical communication alone. The protocol we outline both completely reliable general; will correctly distinguish 100% time.

Recent results in quantum information theory characterize coherence the context of resource theories. Here, we study relation between and discord, a kind correlation which appears even nonentangled states. We prove that creation discord with multipartite incoherent operations is bounded by amount consumed its subsystems during process. show how interplay consumption works preparation correlated states model deterministic computation one qubit.

In artificial systems, quantum superposition and entanglement typically decay rapidly unless cryogenic temperatures are used. Could life have evolved to exploit such delicate phenomena? Certain migratory birds the ability sense very subtle variations in Earth's magnetic field. Here we apply information theory widely accepted "radical pair" model analyze recent experimental observations of avian compass. We find that sustained this living system for at least tens microseconds, exceeding...