共查询到20条相似文献,搜索用时 31 毫秒
1.
宏观-微观纠缠最早起源于“薛定谔的猫”思想实验, 是指在宏观体系与微观体系之间建立量子纠缠. 实现宏观-微观纠缠可以利用多种物理体系来完成, 本文重点介绍了在光学体系中制备和检验宏观-微观纠缠的发展过程. 从最初的受激辐射单光子量子克隆到光学参量放大, 再到相空间的位移操作, 实验上制备宏观-微观纠缠的方法取得了长足的进步. 利用非线性光学参量放大过程制备的宏观-微观纠缠的光子数可以达到104量级, 人眼已经可以观察到, 因此使用人眼作为探测器来检验宏观-微观纠缠的实验开始出现. 但随后人们意识到, 粗精度的光子数探测器, 例如人眼, 无法严格判定宏观-微观纠缠的存在. 为了解决这个难题, 提出了一种巧妙的方法, 即在制备宏-微观纠缠后, 利用局域操作过程将宏观态再变为微观态, 通过判定微观纠缠存在的方法来判定宏微观纠缠的存在. 之后相空间的位移操作方法将宏观态的粒子数提高到108, 并且实现了纠缠的严格检验. 利用光机械实现宏观-微观纠缠的方案也被提出. 由于量子密钥分配中纠缠是必要条件, 而宏观-微观纠缠态光子数较多这一优势可能会对量子密钥分配的传输距离有所提高. 本文介绍了利用相位纠缠的相干态来进行量子秘钥分配的方案, 探讨了利用宏观-微观纠缠实现量子密钥分配的可能性. 相似文献
2.
K. Berrada 《Optics Communications》2012,285(8):2227-2235
Quantum discord, a kind of quantum correlation, is defined as the mismatch between two quantum analogues of classically equivalent expressions of the mutual information. Distinguish classical and quantum correlations in quantum systems is therefore of both fundamental and practical importance. We investigate here the dynamics of classical and quantum correlations for two-mode coherent-state superposition in vacuum environment, which are known to be particularly useful for quantum information processing. By analytical and numerical analyzes we find that, contrary to what is usually stated in the literature, quantum discord under decoherence may exhibit sudden death and sudden birth phenomena, and we show also that the classical and quantum correlations vanish at infinite time. Moreover, the quantum discord may be less or more robust than entanglement against environment depending on different strength regimes of the optical fields of the two-mode coherent-state superposition. 相似文献
3.
Arun K. Pati 《Pramana》2009,73(3):485-498
Entanglement is one of the key features of quantum world that has no classical counterpart. This arises due to the linear
superposition principle and the tensor product structure of the Hilbert space when we deal with multiparticle systems. In
this paper, we will introduce the notion of entanglement for quantum systems that are governed by non-Hermitian yet PT-symmetric Hamiltonians. We will show that maximally entangled states in usual quantum theory behave like non-maximally entangled
states in PT-symmetric quantum theory. Furthermore, we will show how to create entanglement between two PT qubits using non-Hermitian Hamiltonians and discuss the entangling capability of such interaction Hamiltonians that are non-Hermitian
in nature. 相似文献
4.
J. L. Cardya 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(3-4):321-326
After a brief introduction to the concept of entanglement in quantum systems, I apply these ideas to many-body systems and show that the von Neumann entropy is an effective way of characterising the entanglement between the degrees of freedom in different regions of space. Close to a quantum phase transition it has universal features which serve as a diagnostic of such phenomena. In the second part I consider the unitary time evolution of such systems following a ‘quantum quench’ in which a parameter in the Hamiltonian is suddenly changed, and argue that finite regions should effectively thermalise at late times, after interesting transient effects. 相似文献
5.
Y. Xiang S. J. Xiong F. Y. Hong 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):257-260
A bipartite quantum state (for two systems in any dimensions) can be
decomposed as a superposition of many components. For a
superposition of more than two components we prove that there is a
bound of the entanglement of the superposition state which can be
expressed according to entanglements of its component states.
Especially, if the component states are mutually bi-orthogonal, the
entanglement of the superposition state can be exactly given in
terms of the entanglements of the states being superposed. 相似文献
6.
We propose a correlation of local observables on many sites in macroscopic quantum systems. By measuring the correlation one can detect, if any, superposition of macroscopically distinct states, which we call macroscopic entanglement, in arbitrary quantum states that are (effectively) homogeneous. Using this property, we also propose an index of macroscopic entanglement. 相似文献
7.
Zhang-qi Yin 《Contemporary Physics》2017,58(2):119-139
The question whether quantum mechanics is complete and the nature of the transition between quantum mechanics and classical mechanics have intrigued physicists for decades. There have been many experimental breakthroughs in creating larger and larger quantum superposition and entangled states since Erwin Schrödinger proposed his famous thought experiment of putting a cat in a superposition of both alive and dead states in 1935. Remarkably, recent developments in quantum optomechanics and electromechanics may lead to the realisation of quantum superposition of living microbes soon. Recent evidence also suggests that quantum coherence may play an important role in several biological processes. In this review, we first give a brief introduction to basic concepts in quantum mechanics and the Schrödinger’s cat thought experiment. We then review developments in creating quantum superposition and entangled states and the realisation of quantum teleportation. Non-trivial quantum effects in photosynthetic light harvesting and avian magnetoreception are also discussed. At last, we review recent proposals to realise quantum superposition, entanglement and state teleportation of micro-organisms, such as viruses and bacteria. 相似文献
8.
Hari Prakash 《Indian Journal of Physics》2010,84(8):1021-1029
Quantum Teleportation of one qubit of information using entangled state of two qubit is explained. It is shown that if quantum
state of N qubits is to be teleported, the requirement is entangled state of at least 2N qubits. A scheme of teleportation of a superposition of even and odd coherent states was suggested by Van Enk and Hirota
for teleportation of superposed coherent state, success of which is ? according to the authors. It is shown how this scheme
can be modified so as to make the success nearly 1. It is also explained how decoherence can be taken into account and how
such schemas can be applied to similar phenomena of entanglement diversion and entanglement swapping. 相似文献
9.
S. Abdel-Khalek 《Optical and Quantum Electronics》2014,46(8):1055-1064
Realistic quantum systems are the main part of quantum information technology, which causes the rapid destruction of crucial quantum properties. Therefore, the unavoidable interaction between quantum systems, understanding the dynamics of entanglement indicators and finding the correlation between different phenomena may stimulate great interest. In this article the quantum Fisher information and nonlocal correlation between a single qubit and two-mode optical field initially in pair coherent states have investigated. We examine the impact of the qubit motion and intensity dependent function on the flow of quantum Fisher information and quantum entanglement during the time evolution. We discuss the relationship between quantum Fisher information flow and quantum entanglement in the case of moving and unmoving single qubit. 相似文献
10.
E.B. Karlsson 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):393-400
The coherence in quantum superposition states of protons (and chemically similar particles, the positive muons) has been studied
in some condensed matter environments. It is shown that if the proton systems and the experimental techniques used to study
them are carefully selected, it is possible to observe quantum delocalization states of single particles and to understand
the mechanisms for their loss of coherence. Quantum correlated two- and multiparticle states of protons lose coherence very
fast when coupled to condensed matter environments, but new sub-femtosecond techniques have made them accessible to experimental
studies. The degree of decoherence can be measured as function of time and the decoherence mechanisms can, at least in certain
cases, be identified. Although less clean than in corresponding studies of quantum optical systems, these studies can be seen
as a first step towards understanding the conditions for preservation of quantum correlation and entanglement in massive systems.
Some consequences and some suggestions for future work are discussed.
Received 28 August 2002 Published online 7 January 2003 相似文献
11.
Dong Yumin Liu Zhixin Zhang Jinlei 《International Journal of Theoretical Physics》2021,60(8):2723-2732
International Journal of Theoretical Physics - There are some interesting properties in quantum mechanics, such as quantum superposition and entanglement. We can use these features to solve some... 相似文献
12.
We study the time evolution of entanglement in a new quantum version of the Kac ring, where two spin chains become dynamically entangled by quantum gates, which are used instead of the classical markers. The features of the entanglement evolution are best understood by using knowledge about the behavior of an ensemble of classical Kac rings. For instance, the recurrence time of the quantum many-body system is twice the length of the chain and “thermalization” only occurs on time scales much smaller than the dimension of the Hilbert space. The model thus elucidates the relation between the results of measurements in quantum and classical systems: While in classical systems repeated measurements are performed over an ensemble of systems, the corresponding result is obtained by measuring the same quantum system prepared in an appropriate superposition repeatedly. 相似文献
13.
We study frustrated quantum systems from a quantum information perspective. Within this approach, we find that highly frustrated systems do not follow any general "area law" of block entanglement, while weakly frustrated ones have area laws similar to those of nonfrustrated systems away from criticality. To calculate the block entanglement in systems with degenerate ground states, typical in frustrated systems, we define a "cooling" procedure of the ground state manifold and propose a frustration degree and a method to quantify constructive and destructive interference effects of entanglement. 相似文献
14.
Given a bipartite quantum state (in arbitrary dimension) and a decomposition of it as a superposition of two others, we find bounds on the entanglement of the superposition state in terms of the entanglement of the states being superposed. In the case that the two states being superposed are biorthogonal, the answer is simple, and, for example, the entanglement of the superposition cannot be more than one ebit more than the average of the entanglement of the two states being superposed. However, for more general states, the situation is very different. 相似文献
15.
Aspects of Generic Entanglement 总被引:4,自引:4,他引:0
Patrick Hayden Debbie W. Leung Andreas Winter 《Communications in Mathematical Physics》2006,265(1):95-117
We study entanglement and other correlation properties of random states in high-dimensional bipartite systems. These correlations
are quantified by parameters that are subject to the ``concentration of measure' phenomenon, meaning that on a large-probability
set these parameters are close to their expectation. For the entropy of entanglement, this has the counterintuitive consequence
that there exist large subspaces in which all pure states are close to maximally entangled. This, in turn, implies the existence
of mixed states with entanglement of formation near that of a maximally entangled state, but with negligible quantum mutual
information and, therefore, negligible distillable entanglement, secret key, and common randomness. It also implies a very
strong locking effect for the entanglement of formation: its value can jump from maximal to near zero by tracing over a number
of qubits negligible compared to the size of the total system. Furthermore, such properties are generic. Similar phenomena
are observed for random multiparty states, leading us to speculate on the possibility that the theory of entanglement is much
simplified when restricted to asymptotically generic states. Further consequences of our results include a complete derandomization
of the protocol for universal superdense coding of quantum states. 相似文献
16.
REN XueZao CONG HongLu WANG XuWen & XIA JianPing School of Science Southwest University of Science Technology Mianyang China Physics Group Beijing Jiaotong University Hai Bin College Huanghua 《中国科学:物理学 力学 天文学(英文版)》2011,(9)
In this paper, the quantum entanglement between a single mode binomial field and a cascade three-level atom is calculated mechanically without the rotating wave approximation. The numerical results indicate that the quantum entanglement at the first few periods is reduced notably due to the fact that the atom is initially in the superposition state. With increasing field parameter , the period of the entanglement evolution becomes obvious and the quantum decoherence phenomenon emerges in a short time. 相似文献
17.
O. D. Timofeevskaya 《Moscow University Physics Bulletin》2010,65(2):145-149
The application of the conditional density matrix in the Heisenberg representation to the processes caused by entanglement
allows elimination of any misunderstanding of these phenomena. We consider quantum entanglement of two- and four-particle
systems, quantum correlations different from entanglement, and their causes. 相似文献
18.
研究了热平衡温度,自旋交换相互作用,Dzyaloshinskii-Moriya(DM)相互作用及外加非一致性磁场对两比特海森堡XYZ自旋链量子系统的热纠缠与局域量子不确定度的影响,对比分析了并发度量子纠缠与局域量子不确定度描述自旋链系统量子关联的差别.结果表明自旋链系统的量子纠缠在热平衡温度,DM相互作用及外加磁场的非一致性参数的变化情况下均会出现纠缠突然死亡的再生现象,而自旋链系统的局域量子不确定度随着这些参数呈连续变化现象.并且,自旋交换相互作用,DM相互作用及外加横向磁场作用强度较小时,他们的变化对自旋链系统的量子纠缠与局域量子不确定度的影响有着明显的差别. 相似文献
19.
The dynamics of a mixed spin system governed by XXZ model in additional to an intrinsic decoherence is investigated. The behavior of quantum correlation and the degree of entanglement between the two subsystems is quantified by using measurement-induced disturbance and the negativity, respectively. It is shown that, the phenomena of long-lived entanglement appears for larger values of intrinsic decoherence parameters. The degree of entanglement and quantum correlation depend on the dimensions of subsystems which are pass through the external field and the initial states setting. We show that the negativity for some initial classes is more robust than the measurement-induced disturbance, while for some other initial classes the quantum correlations are more robust than entanglement. 相似文献