Facets of tripartite entanglement
Indian Academy of Sciences (India)
Dipankar Home
2001-02-01
Tripartite entangled states of systems 1, 2 and 3 involving nonorthogonal states are used to reveal two hitherto unexplored quantum effects. The ﬁrst shows that kinematic entanglement between the states of 1 and 2 can affect the result of dynamical interaction between 2 and 3, though 1 and 2 may be spatially separated so that they no longer interact. The second shows that if a residual interaction persists between 1 and 2 while 2 interacts with 3 to form an entangled state, the measurement of observables of 1 can be used to determine whether 2 has interacted with 3. This effect occurs even when the measurement on 1 is made long after the residual interaction between 1 and 2 has ceased to act. Such effects resulting from interplay between unitary dynamics and kinematic entanglement have interesting implications. In particular, we discuss the signiﬁcance as regards what we call the dynamic version of Einstein locality
A Peculiar Tripartite Entangled State
Institute of Scientific and Technical Information of China (English)
黄燕霞; 於亚飞; 詹明生
2003-01-01
We present a scheme to prepare two-atom Einstein-Podolsky-Rosen states and three-atom entangled states via cavity quantum electrodynamics, and it can be realized experimentally. Importantly, we find that in the set of tripartite entangled states prepared by our scheme there is a peculiar tripartite entangled state except the Greenberger-Horne-Zeilinger (GHZ) state. The peculiar tripartite entangled states have double feature of the GHZ state (i.e. T123 ＞ 0) and W state (i.e. the remaining reduce density matrices ρij retain entanglement according to the positive partial transformation (PPT) criterion) simultaneously. However, its entanglement properties are not completely identical either to the GHZ state or to the W state. It is interesting that for peculiar entanglement properties, the remaining reduced density matrices ρij can retain entanglement or disentanglement independently, which can be chosen freely according to our need.
Planat, Michel; Saniga, Metod
2009-01-01
We discuss three important classes of three-qubit entangled states and their encoding into quantum gates, finite groups and Lie algebras. States of the GHZ and W-type correspond to pure tripartite and bipartite entanglement, respectively. We introduce another generic class B of three-qubit states, that have balanced entanglement over two and three parties. We show how to realize the largest cristallographic group $W(E_8)$ in terms of three-qubit gates (with real entries) encoding states of type GHZ or W [M. Planat, {\\it Clifford group dipoles and the enactment of Weyl/Coxeter group $W(E_8)$ by entangling gates}, Preprint 0904.3691 (quant-ph)]. Then, we describe a peculiar "condensation" of $W(E_8)$ into the four-letter alternating group $A_4$, obtained from a chain of maximal subgroups. Group $A_4$ is realized from two B-type generators and found to correspond to the Lie algebra $sl(3,\\mathbb{C})\\oplus u(1)$. Possible applications of our findings to particle physics and the structure of genetic code are also ...
Tripartite Entanglements in Non-inertial Frames
Shamirzai, Mahmoud; Soltani, Morteza
2011-01-01
Entanglement degradation caused by the Unruh effect is discussed for the tripartite GHZ or W states constructed by modes of a non-interacting quantum field viewed by one inertial observer and two uniformly accelerated observers. For fermionic states, the Unruh effect even for infinite accelerations cannot completely remove the entanglement. However, for the bosonic states, the situation is different and the entanglement vanishes asymptotically. Also, the entanglement is studied for the bipartite subsystems. While for the GHZ states all the bipartite subsystems are identically disentangled, for the W states the bipartite subsystems are somewhat entangled, though, this entanglement can be removed for appropriately accelerated observers. Interestingly, logarithmic negativity as a measure for determining the entanglement of one part of the system relative to the other two parts, is not generally the same for different parts. This means that we encounter tripartite systems where each part is differently entangled ...
Tripartite entanglement and quantum relative entropy
Energy Technology Data Exchange (ETDEWEB)
Galvao, E.F. [Centre for Quantum Computation, Clarendon Laboratory, University of Oxford, Oxford (United Kingdom). E-mail: e.galvao@physics.ox.ac.uk; Plenio, M.B. [Optics Section, Blackett Laboratory, Imperial College, London (United Kingdom). E-mail: m.plenio@ic.ac.uk; Virmani, S. [Optics Section, Blackett Laboratory, Imperial College, London (United Kingdom). E-mail: s.virmani@ic.ac.uk
2000-12-08
We establish relations between tripartite pure state entanglement and additivity properties of the bipartite relative entropy of entanglement. Our results pertain to the asymptotic limit of local manipulations on a large number of copies of the state. We show that additivity of the relative entropy would imply that there are at least two inequivalent types of asymptotic tripartite entanglement. The methods used include the application of some useful lemmas that enable us to analytically calculate the relative entropy for some classes of bipartite states. (author)
Tripartite entanglement dynamics of vibrations in triatomic molecules.
Zhai, Liangjun; Zheng, Yujun
2016-06-21
In the present study, the dynamical behaviors of tripartite entanglement of vibrations in triatomic molecules are studied based on the Lie algebraic models of molecules. The dynamical behaviors of tripartite entanglement of the local mode molecule H2O and normal mode molecule NO2 are comparatively studied for different initial states by employing the general concurrence. Our results show that the dynamics of tripartite entanglement are relied on the dynamics of intramolecular energy distribution. The local mode molecule is more suitable to construct the tripartite entangled states. Also, the greater degree of tripartite entanglement can be obtained if the stretching vibration is first excited. These results shed new light on the understanding of quantum multipartite entanglement of vibrations in the polyatomic molecules.
Unsymmetrical Quantum Key Distribution Using Tripartite Entanglement
Institute of Scientific and Technical Information of China (English)
XIONG Jin; ZHANG Zhe-Shen; ZHOU Nan-Run; PENG Jin-Ye; ZENG Gui-Hua
2007-01-01
An unsymmetrical quantum key distribution protocol is proposed,in which Greenberger-Horne-Zeilinger (GHZ) triplet states are used to obtain the secret key.Except the lost qubits due to the unperfectness of the physical devices,the unsymmetrical characteristic makes all transmitted qubits useful.This leads to an excellent efficiency,which reaches 100% in an ideal case.The security is studied from the aspect of information theory.By using the correlation of the GHZ tripartite entanglement state,eavesdropping can be easily checked out,which indicates that the presented protocol is more secure.
Teleportation with Tripartite Entangled State via Thermal Cavity
Institute of Scientific and Technical Information of China (English)
XUE Zheng-Yuan; YI You-Min; CAO Zhuo-Liang
2006-01-01
Teleportation schemes with a tripartite entangled state in cavity QED are investigated. The schemes do not need Bell state measurements and the successful probabilities reach optimality. In addition, the schemes are insensitive to both the cavity decay and the thermal field. We first consider two teleportation schemes via a tripartite GHZ state.The first one is a controlled one for an unknown single-qubit state. The second scheme is teleportation of unknown two-atom entangled state. Then we consider teleporting of single-qubit arbitrary state via a tripartite W state.
Measure of tripartite entanglement in bosonic and fermionic systems
Energy Technology Data Exchange (ETDEWEB)
Buscemi, Fabrizio [Dipartimento di Elettronica, Informatica, e Sistemi, Universita di Bologna, Viale Risorgimento 2, I-40136 Bologna (Italy); ARCES, Alma Mater Studiorum, Universita di Bologna, Via Toffano 2/2, I-40125 Bologna (Italy); Bordone, Paolo [Dipartimento di Fisica, Universita di Modena e Reggio Emilia, I-41125 Modena (Italy); Centro S3, CNR-Istituto di Nanoscienze, Via Campi 213/A, I-41125 Modena (Italy)
2011-08-15
We describe an efficient theoretical criterion suitable for the evaluation of the tripartite entanglement of any mixed three-boson or three-fermion state, based on the notion of the entanglement of particles for bipartite systems of identical particles. Our approach allows one to quantify the accessible number of quantum correlations in the systems without any violation of the local particle number superselection rule. A generalization of the tripartite negativity is here applied to some correlated systems including the continuous-time quantum walks of identical particles (for both bosons and fermions) and compared with other criteria recently proposed in the literature. Our results show the dependence of the entanglement dynamics upon the quantum statistics: The bosonic bunching results in a low number of quantum correlations while Fermi-Dirac statistics allows for higher values of the entanglement.
New Tripartite Nonlinear Entangled State Representation in Quantum Mechanics
Institute of Scientific and Technical Information of China (English)
KUANG Mai-Hua; MA Shan-Jun; LIU Dong-Mei
2008-01-01
Based on the technique of integral within an ordered product of nonlinear bosonic operators, we construct a new kind of tripartite nonlinear entangled state |α,γ>λ in 3-mode Fock space, which can make up a complete set. We also simply discuss its properties and application.
Probabilistic Remote Preparation of a Tripartite High-Dimensional Equatorial Entangled State
Institute of Scientific and Technical Information of China (English)
SHI Jin; ZHAN You-Bang
2009-01-01
We present a scheme for probabilistic remote preparation of a tripartite qutrit entangled state with a partial tripartite qutrit entangled state and a partial bipartite qutrit entangled state as the quantum channel.It is found that a bipartite qutrit orthogonal projective measurement, an auxiliary qutrit particle, and the corresponding unitary transformation are required.A scheme for probabilistic remote preparation of a tripartite qudit equatorial entangled state by using a partial tripartite qudit entangled state and a partial bipartite qudit entangled state as the quantum channel is also proposed.We calculate the successful total probability and the total classical communication cost required in the RSP process, respectively.
Optimal values of bipartite entanglement in a tripartite system
Energy Technology Data Exchange (ETDEWEB)
Sahoo, Shaon, E-mail: shaon.sahoo@gmail.com [Department of Physics, Indian Institute of Science, Bangalore 560012 (India); Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India)
2015-01-23
For a general tripartite system in some pure state, an observer possessing any two parts will see them in a mixed state. By the consequence of Hughston–Jozsa–Wootters theorem, each basis set of local measurement on the third part will correspond to a particular decomposition of the bipartite mixed state into a weighted sum of pure states. It is possible to associate an average bipartite entanglement (S{sup ¯}) with each of these decompositions. The maximum value of S{sup ¯} is called the entanglement of assistance (E{sub A}) while the minimum value is called the entanglement of formation (E{sub F}). An appropriate choice of the basis set of local measurement will correspond to an optimal value of S{sup ¯}; we find here a generic optimality condition for the choice of the basis set. In the present context, we analyze the tripartite states W and GHZ and show how they are fundamentally different. - Highlights: • We study optimal values of bipartite entanglement in a tripartite system. • Using the Hughston–Jozsa–Wootters theorem, an optimality condition is derived. • This condition will help us study mixed bipartite states using ancilla.
Quantum frequency doubling based on tripartite entanglement with cavities
Juan, Guo; Zhi-Feng, Wei; Su-Ying, Zhang
2016-02-01
We analyze the entanglement characteristics of three harmonic modes, which are the output fields from three cavities with an input tripartite entangled state at fundamental frequency. The entanglement properties of the input beams can be maintained after their frequencies have been up-converted by the process of second harmonic generation. We have calculated the parametric dependences of the correlation spectrum on the initial squeezing factor, the pump power, the transmission coefficient, and the normalized analysis frequency of cavity. The numerical results provide references to choose proper experimental parameters for designing the experiment. The frequency conversion of the multipartite entangled state can also be applied to a quantum communication network. Project supported by the National Natural Science Foundation of China (Grant No. 91430109), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111401110004), and the Natural Science Foundation of Shanxi Province, China (Grant No. 2014011005-3).
On the Entangled Fractional Fourier Transform in Tripartite Entangled State Representation
Institute of Scientific and Technical Information of China (English)
FAN Hong-Yi; JIANG Nian-Quan
2003-01-01
Based on the newly constructed two mutually conjugate 3-mode entangled states of continuum variablesin three-mode Fock space we introduce entangled fractional Fourier transform (EFFT) for the tripartite entangled staterepresentations, which are not a direct product of three 1-dimensional FFTs. The eigenmodes of EFFT are obtained,which is different from the usual Hermite polynomials. The EFFT of the three-mode squeezed state is derived.
Entanglement and quantum teleportation via decohered tripartite entangled states
Energy Technology Data Exchange (ETDEWEB)
Metwally, N., E-mail: nmohamed31@gmail.com
2014-12-15
The entanglement behavior of two classes of multi-qubit system, GHZ and GHZ like states passing through a generalized amplitude damping channel is discussed. Despite this channel causes degradation of the entangled properties and consequently their abilities to perform quantum teleportation, one can always improve the lower values of the entanglement and the fidelity of the teleported state by controlling on Bell measurements, analyzer angle and channel’s strength. Using GHZ-like state within a generalized amplitude damping channel is much better than using the normal GHZ-state, where the decay rate of entanglement and the fidelity of the teleported states are smaller than those depicted for GHZ state.
Multisetting Bell-type inequalities for detecting genuine tripartite entanglement
Pal, Karoly F
2011-01-01
In a recent paper, Bancal et al. put forward the concept of device-independent witnesses of genuine multipartite entanglement. These witnesses are capable of verifying genuine multipartite entanglement produced in a lab without resorting to any knowledge of the dimension of the state space or of the specific form of the measurement operators. As a by-product they found a three-party three-setting Bell inequality which enables to detect genuine tripartite entanglement in a noisy 3-qubit Greenberger-Horne-Zeilinger (GHZ) state for visibilities as low as 2/3 in a device-independent way. In this paper, we generalize this inequality to an arbitrary number of settings, demonstrating a threshold visibility of 2/pi~0.6366 for number of settings going to infinity. We also present a pseudo-telepathy Bell inequality achieving the same threshold value. We argue that our device-independent witnesses are optimal in the sense that the above value cannot be beaten with three-party-correlation Bell inequalities.
Bipartite and Tripartite Entanglement in a Three-Qubit Heisenberg Model
Institute of Scientific and Technical Information of China (English)
REN Jie; ZHU Shi-Qun
2006-01-01
The bipartite and tripartite entanglement in a three-qubit Heisenberg XY model with a nonuniformmagnetic field is studied. There are two or four peaks in the concurrence of the bipartite entanglement when the amplitudes of the magnetic fields are differently distributed between the three qubits. It is very interesting to note that there is no tangle of tripartite entanglement between the three qubits when the amplitudes of the magnetic fields are varied. However, the variation of the magnetic field direction can induce the tangle. The tangle is periodic about the angle between the magnetic field and the z axis of the spin.
Experimental generation of tripartite polarization entangled states of bright optical beams
Wu, Liang; Yan, Zhihui; Liu, Yanhong; Deng, Ruijie; Jia, Xiaojun; Xie, Changde; Peng, Kunchi
2016-04-01
The multipartite polarization entangled states of bright optical beams directly associating with the spin states of atomic ensembles are one of the essential resources in the future quantum information networks, which can be conveniently utilized to transfer and convert quantum states across a network composed of many atomic nodes. In this letter, we present the experimental demonstration of tripartite polarization entanglement described by Stokes operators of optical field. The tripartite entangled states of light at the frequency resonant with D1 line of Rubidium atoms are transformed into the continuous variable polarization entanglement among three bright optical beams via an optical beam splitter network. The obtained entanglement is confirmed by the extended criterion for polarization entanglement of multipartite quantized optical modes.
Institute of Scientific and Technical Information of China (English)
YUAN Hong-Chun; QI Kai-Guo
2005-01-01
We mostly investigate two schemes. One is to teleport a multi-mode W-type entangled coherent state using a peculiar bipartite entangled state as the quantum channel different from other proposals. Based on our formalism,teleporting multi-mode coherent state or squeezed state is also possible. Another is that the tripartite entangled state is used as the quantum channel of controlled teleportation of an arbitrary and unknown continuous variable in the case of three participators.
Directory of Open Access Journals (Sweden)
M Soltani
2015-12-01
Full Text Available In this work, we generalize the entanglement of three-qbit Bosonic systems beyond the single-mode approximation when one of the observers is accelerated. For this purpose, we review the effects of acceleration on field modes and quantum states. The single-mode approximation and beyond the single-mode approximation methods are introduced. After this brief introduction, the main problem of this paper, tripartite entanglement of bosonic systems in a noninertial frame beyond the single- mode approximation is investigated. The tripartite entangled states have different classes with GHZ and W states being most important. Here, we choose &pi-tangle as a measure of tripartite entanglement. If the three parties share GHZ state, the corresponding &pi-tangle will increase by increasing acceleration for some Unruh modes. This phenomenon, increasing entanglement, has never been observed in the single-mode approximation for bosonic case. Moreover, the &pi-tangle dose not exhibit a monotonic behavior with increasing acceleration. In the infinite acceleration limit, the &pi-tangle goes to different nonzero values for distinct Unruh modes. Unlike GHZ state, the entanglement of the W state shows only monotonically increasing and decreasing behaviors with increasing acceleration. Also, the entanglement for all possible choices of Unruh modes approaches only 0.176 in the high acceleration limit. Therefore, according to the quantum entanglement, there is no distinction between the single-mode approximation and beyond the single-mode approximation methods in this limit.
Tripartite entanglement dynamics in the presence of Markovian or non-Markovian environment
Park, DaeKil
2016-08-01
We study on the tripartite entanglement dynamics when each party is initially entangled with other parties, but they locally interact with their own Markovian or non-Markovian environment. First we consider three GHZ-type initial states, all of which have GHZ-symmetry provided that the parameters are chosen appropriately. However, this symmetry is broken due to the effect of environment. The corresponding π -tangles, one of the tripartite entanglement measures, are analytically computed at arbitrary time. For Markovian case while the tripartite entanglement for type I exhibits an entanglement sudden death, the dynamics for the remaining cases decays normally in time with the half-life rule. For non-Markovian case the revival phenomenon of entanglement occurs after complete disappearance of entanglement. We also consider two W-type initial states. For both cases the π -tangles are analytically derived. The revival phenomenon also occurs in this case. On the analytical ground the robustness or fragility issue against the effect of environment is examined for both GHZ-type and W-type initial states.
Various notions of positivity for bi-linear maps and applications to tri-partite entanglement
Energy Technology Data Exchange (ETDEWEB)
Han, Kyung Hoon, E-mail: kyunghoon.han@gmail.com [Department of Mathematics, The University of Suwon, Gyeonggi-do 445-743 (Korea, Republic of); Kye, Seung-Hyeok, E-mail: kye@snu.ac.kr [Department of Mathematics and Institute of Mathematics, Seoul National University, Seoul 151-742 (Korea, Republic of)
2016-01-15
We consider bi-linear analogues of s-positivity for linear maps. The dual objects of these notions can be described in terms of Schmidt ranks for tri-tensor products and Schmidt numbers for tri-partite quantum states. These tri-partite versions of Schmidt numbers cover various kinds of bi-separability, and so we may interpret witnesses for those in terms of bi-linear maps. We give concrete examples of witnesses for various kinds of three qubit entanglement.
Robust tripartite-to-bipartite entanglement localization by weak measurements and reversal
Yao, Chunmei; Ma, Zhi-Hao; Chen, Zhi-Hua; Serafini, Alessio
2012-08-01
We propose a robust and efficient approach for tripartite-to-bipartite entanglement localization. By using weak measurements and quantum measurement reversal, an almost maximal entangled state shared by two parties can be generated with the assistance of the third party by local quantum operations and classical communication from a W-like state. We show that this approach works well in the presence of losses and phase diffusion. Our method provides an active way to fight against decoherence, and might help for quantum communication and distributed quantum computation.
Ma, Peng-Cheng; Chen, Gui-Bin; Li, Xiao-Wei; Zhan, You-Bang
2016-10-01
We present two schemes for the joint remote state preparation (JRSP) of an arbitrary tripartite four-qubit entangled state with complex coefficients via four and two three-qubit GHZ states as the quantum channel, respectively. In these schemes, the two senders share the original state which they wish to help the receiver remotely prepare. To complete the JRSP schemes, some novel sets of mutually orthogonal basis vectors are introduced. It is shown that, only if the two senders collaborate with each other, and perform projective measurements under a suitable measuring basis on their own qubits respectively, can the receiver reconstruct the original state by means of some appropriate unitary operations. We demonstrate, in our both schemes, the total success probability of the JRSP can reach 1. Moreover, compared with the first scheme in this paper, the advantage of the second scheme is that the entanglement resource can be reduced.
Directory of Open Access Journals (Sweden)
Gerardo Adesso
2013-05-01
Full Text Available We study a system represented by a Bose-Einstein condensate interacting with a cavity field in presence of a strong off-resonant pumping laser. This system can be described by a three-mode Gaussian state, where two are the atomic modes corresponding to atoms populating upper and lower momentum sidebands and the third mode describes the scattered cavity field light. We show that, as a consequence of the collective atomic recoil instability, these modes possess a genuine tripartite entanglement that increases unboundedly with the evolution time and is larger than the bipartite entanglement in any reduced two-mode bipartition. We further show that the state of the system exhibits genuine tripartite nonlocality, which can be revealed by a robust violation of the Svetlichny inequality when performing displaced parity measurements. Our exact results are obtained by exploiting the powerful machinery of phase-space informational measures for Gaussian states, which we briefly review in the opening sections of the paper.
Kenfack, Lionel Tenemeza; Tchoffo, Martin; Fai, Lukong Cornelius
2017-02-01
We address the dynamics of quantum correlations, including entanglement and quantum discord of a three-qubit system interacting with a classical pure dephasing random telegraph noise (RTN) in three different physical environmental situations (independent, mixed and common environments). Two initial entangled states of the system are examined, namely the Greenberger-Horne-Zeilinger (GHZ)- and Werner (W)-type states. The classical noise is introduced as a stochastic process affecting the energy splitting of the qubits. With the help of suitable measures of tripartite entanglement (entanglement witnesses and lower bound of concurrence) and quantum discord (global quantum discord and quantum dissension), we show that the evolution of quantum correlations is not only affected by the type of the system-environment interaction but also by the input configuration of the qubits and the memory properties of the environmental noise. Indeed, depending on the memory properties of the environmental noise and the initial state considered, we find that independent, common and mixed environments can play opposite roles in preserving quantum correlations, and that the sudden death and revival phenomena or the survival of quantum correlations may occur. On the other hand, we also show that the W-type state has strong dynamics under this noise than the GHZ-type ones.
三体Bell对角态的纠缠%Entanglement of Tripartite Bell Diagonal States
Institute of Scientific and Technical Information of China (English)
赵慧; 张兴华
2011-01-01
给出了三体2(×)2(×)3Bell对角态纠缠判定的一个必要条件和3(×)3(×)3Bell对角态纠缠的充分条件,进一步研究了3(×)3(×)3Bell对角态纠缠与密度矩阵部分转置的关系以及Bell对角态负性的数学表达式.%A necessary condition of entanglement for tripartite 2 (⊕)2 (⊕)3 Bell diagonal states and a sufficient condition of entanglement for 3 (⊕)3 (⊕)3 Bell diagonal states are presented. Moreover, the relation between entanglement of 3(⊕)3(⊕)3 Bell diagonal states and partial transpose of density matrix is investigated. And an analytical expression of negative for Bell diagonal states is presented.Key words: Bell diagonal states; entanglement; density matrix Robust Estimation for Varying Coefficient Model Abstract: This paper considers robust estimation of varying coefficient models with emphasis on resistance against outliers. By combining B-splines method with taut string method, a robust estimation procedure is proposed. Based on local quadratic approximation, an iterative algorithm is introduced. Simulation study indicates that the proposed method is robust.
Olsen, M. K.; Cavalcanti, E. G.
2016-07-01
The fully symmetric Gaussian tripartite entangled pure states will not exhibit two-mode Einstein-Podolsky-Rosen (EPR) steering. This means that any two participants cannot share quantum secrets using the security of one-sided device independent quantum key distribution (1SDI-QKD) without involving the third. They are restricted at most to standard quantum key distribution, which is less secure. Here we demonstrate an asymmetric tripartite system that can exhibit bipartite EPR steering, so that two of the participants can use 1SDI-QKD without involving the other. This is possible because the promiscuity relations of continuous-variable tripartite entanglement are different from those of discrete-variable systems. We analyze these properties for two different systems, showing that the asymmetric system exhibits practical properties not found in the symmetric one.
变系数模型的稳健估计%Entanglement of Tripartite Bell Diagonal States
Institute of Scientific and Technical Information of China (English)
赵培信; 薛留根
2011-01-01
为了研究变系数模型的稳健估计问题,结合B-样条方法和taut string方法得到了一个稳健估计过程;结合局部二次逼近方法,给出了一个迭代算法.数据模拟结果表明所得估计是稳健的.%A necessary condition of entanglement for tripartite 2 (⊕)2 (⊕)3 Bell diagonal states and a sufficient condition of entanglement for 3 (⊕)3 (⊕)3 Bell diagonal states are presented. Moreover, the relation between entanglement of 3(⊕)3(⊕)3 Bell diagonal states and partial transpose of density matrix is investigated. And an analytical expression of negative for Bell diagonal states is presented.Key words: Bell diagonal states; entanglement; density matrix Robust Estimation for Varying Coefficient Model Abstract: This paper considers robust estimation of varying coefficient models with emphasis on resistance against outliers. By combining B-splines method with taut string method, a robust estimation procedure is proposed. Based on local quadratic approximation, an iterative algorithm is introduced. Simulation study indicates that the proposed method is robust.
Transformation of bipartite non-maximally entangled states into a tripartiteWstate in cavity QED
Indian Academy of Sciences (India)
ZANG XUE-PING; YANG MING; DU CHAO-QUN; WANG MIN; FANG SHU-DONG; CAO ZHUO-LIANG
2016-05-01
We present two schemes for transforming bipartite non-maximally entangled states into a W state in cavity QED system, by using highly detuned interactions and the resonant interactions between two-level atoms and a single-mode cavity field. A tri-atom W state can be generated by adjusting the interaction times between atoms and the cavity mode. These schemes demonstrate that two bipartite non-maximally entangled states can be merged into a maximally entangled W state. So the scheme can, in some sense, be regarded as an entanglement concentration process. The experimental feasibility of the schemes is also discussed.
Institute of Scientific and Technical Information of China (English)
刘祥; 陈娟
2016-01-01
The paper indicates that the tripartite continuous-variable entanglement could be realized in the solid-stated circuit through the interconnection between the energy transition of the four-level superconductor qubit system and the three superconducting transmission line resonators. Thus the correlation between the energy level transition of the four-level superconductor qubit system and the driving of classical fields and the coupling of resonators is analyzed. It turns out that an effective tripartite continuous-variable entanglement could be realized in the three solid-stated resonators via the application of the adiabatic eliminated method, besides, the research provides a new way to research the multipartite CV entanglement.%通过三个超导传输线谐振器与四能级超导量子比特相互耦合实现了固态电路 QED 系统中三模连续变量纠缠，并分析了四能级超导量子比特系统的能级跃迁与经典场的驱动和谐振器的耦合之间的关联。结果表明：采用绝热消除的方法可以在三个固态谐振器中实现三模连续变量纠缠，为多模连续变量纠缠研究提供了新途径。
Polygamy of distributed entanglement
Buscemi, Francesco; Gour, Gilad; Kim, Jeong San
2009-07-01
While quantum entanglement is known to be monogamous (i.e., shared entanglement is restricted in multipartite settings), here we show that distributed entanglement (or the potential for entanglement) is by nature polygamous. By establishing the concept of one-way unlocalizable entanglement (UE) and investigating its properties, we provide a polygamy inequality of distributed entanglement in tripartite quantum systems of arbitrary dimension. We also provide a polygamy inequality in multiqubit systems and several trade-offs between UE and other correlation measures.
Quantum Entanglement Swapping between Two Multipartite Entangled States
Su, Xiaolong; Tian, Caixing; Deng, Xiaowei; Li, Qiang; Xie, Changde; Peng, Kunchi
2016-12-01
Quantum entanglement swapping is one of the most promising ways to realize the quantum connection among local quantum nodes. In this Letter, we present an experimental demonstration of the entanglement swapping between two independent multipartite entangled states, each of which involves a tripartite Greenberger-Horne-Zeilinger (GHZ) entangled state of an optical field. The entanglement swapping is implemented deterministically by means of a joint measurement on two optical modes coming from the two multipartite entangled states respectively and the classical feedforward of the measurement results. After entanglement swapping the two independent multipartite entangled states are merged into a large entangled state in which all unmeasured quantum modes are entangled. The entanglement swapping between a tripartite GHZ state and an Einstein-Podolsky-Rosen entangled state is also demonstrated and the dependence of the resultant entanglement on transmission loss is investigated. The presented experiment provides a feasible technical reference for constructing more complicated quantum networks.
Charcterization of multipartite entanglement
Energy Technology Data Exchange (ETDEWEB)
Chong, Bo
2006-06-23
In this thesis, we discuss several aspects of the characterization of entanglement in multipartite quantum systems, including detection, classification and quantification of entanglement. First, we discuss triqubit pure entanglement and propose a special true tripartite entanglement, the mixed entanglement, besides the Greenberger-Horne-Zeilinger (GHZ) entanglement and the W entanglement. Then, based on quantitative complementarity relations, we draw entanglement Venn diagrams for triqubit pure states with different entanglements and introduce the total tangle {tau}{sup (T)} to quantify total entanglement of triqubit pure states by defining the union I that is equivalent to the total tangle {tau}{sup (T)} from the mathematical point of view. The generalizations of entanglement Venn diagrams and the union I to N-qubit pure states are also discussed. Finally, based on the ranks of reduced density matrices, we discuss the separability of multiparticle arbitrary-dimensional pure and mixed states, respectively. (orig.)
Quantum teleportation of entangled squeezed vacuum states
Institute of Scientific and Technical Information of China (English)
蔡新华
2003-01-01
An optical scheme for probabilistic teleporting entangled squeezed vacuum states (SVS) is proposed. In this scheme,the teleported state is a bipartite entangled SVS,and the quantum channel is a tripartite entangled SVS.The process of the teleportation is achieved by using a 50/50 symmetric beamsplitter and photon detectors with the help of classical information.
Entangling gates in even Euclidean lattices such as Leech lattice
Planat, Michel
2010-01-01
We point out a organic relationship between real entangling n-qubit gates of quantum computation and the group of automorphisms of even Euclidean lattices of the corresponding dimension 2n. The type of entanglement that is found in the gates/generators of Aut() depends on the lattice. In particular, we investigate Zn lattices, Barnes-Wall lattices D4, E8, 16 (associated to n = 2, 3 and 4 qubits), and the Leech lattices h24 and 24 (associated to a 3-qubit/qutrit system). Balanced tripartite entanglement is found to be a basic feature of Aut(), a nding that bears out our recent work related to the Weyl group of E8 [1, 2].
Driven optomechanical systems for mechanical entanglement distribution
Paternostro, M; Li, Jie
2012-01-01
We consider the distribution of entanglement from a multi-mode optical driving source to a network of remote and independent optomechanical systems. By focusing on the tripartite case, we analyse the effects that the features of the optical input states have on the degree and sharing-structure of the distributed, fully mechanical, entanglement. This study, which is conducted looking at the mechanical steady-state, highlights the structure of the entanglement distributed among the nodes and determines the relative efficiency between bipartite and tripartite entanglement transfer. We discuss a few open points, some of which directed towards the bypassing of such limitations.
Controlled Probabilistic Teleportation of an Unknown Multi-Particle High-Dimensional Entangled State
Institute of Scientific and Technical Information of China (English)
SHI Jin; ZHAN You-Bang
2009-01-01
We propose a protocol for controlled probabilistic teleportation of an unknown tripartite qutrit entangled state with two partial tripartite qutrit entangled states as the quantum channel. It is found that teleportation associ-ated with the generalized qutrit Bell-basis measurement, the generalized qutrit π-state measurement and the generalized Hadamard operator in three-dimensional Hilbert space. We generalize the protocol for controlled probabilistic telepor-ration of an unknown k-particle qudit entangled state with a multi-particle qudit entangled state and a tripartite qudit entangled state as the quantum channel. We also calculate the classical communication cost required in both cases.
Tripartite composite fermion states
Sreejith, G. J.; Wu, Ying-Hai; Wójs, A.; Jain, J. K.
2013-06-01
The Read-Rezayi wave function is one of the candidates for the fractional quantum Hall effect at filling fraction ν=2+⅗, and thereby also its hole conjugate at 2+⅖. We study a general class of tripartite composite fermion wave functions, which reduce to the Rezayi-Read ground state and quasiholes for appropriate quantum numbers, but also allow a construction of wave functions for quasiparticles and neutral excitations by analogy to the standard composite fermion theory. We present numerical evidence in finite systems that these trial wave functions capture well the low energy physics of a four-body model interaction. We also compare the tripartite composite fermion wave functions with the exact Coulomb eigenstates at 2+⅗, and find reasonably good agreement. The ground state as well as several excited states of the four-body interaction are seen to evolve adiabatically into the corresponding Coulomb states for N=15 particles. These results support the plausibility of the Read-Rezayi proposal for the 2+⅖ and 2+⅗ fractional quantum Hall effect. However, certain other proposals also remain viable, and further study of excitations and edge states will be necessary for a decisive establishment of the physical mechanism of these fractional quantum Hall states.
Killing quantum entanglement by acceleration or a black hole
Dai, Yue; Shi, Yu
2015-01-01
We consider two entangled accelerating qubits coupled with real scalar fields, each described by the Unruh-Wald model. It is demonstrated that because of the Unruh effect, the bipartite entanglement of the two qubits suddenly dies when the acceleration of one or more qubits are large enough. We also consider three entangled accelerating qubits in GHZ state and in W state, with equal acceleration-frequency ratio, and found that in either state, the tripartite entanglement suddenly dies at a certain value of acceleration-frequency ratio. The equivalence between the Rindler metric and the Schwarzchild metric in the vicinity of the horizon of a black hole implies that for the two entangled qubits outside a black hole, the entanglement suddenly dies when one or both of the qubits are close enough to the horizon, while for the three entangled qubits in GHZ or W state, the tripartite entanglement suddenly dies when these qubits are close enough to the horizon.
From entanglement witness to generalized Catalan numbers.
Cohen, E; Hansen, T; Itzhaki, N
2016-07-27
Being extremely important resources in quantum information and computation, it is vital to efficiently detect and properly characterize entangled states. We analyze in this work the problem of entanglement detection for arbitrary spin systems. It is demonstrated how a single measurement of the squared total spin can probabilistically discern separable from entangled many-particle states. For achieving this goal, we construct a tripartite analogy between the degeneracy of entanglement witness eigenstates, tensor products of SO(3) representations and classical lattice walks with special constraints. Within this framework, degeneracies are naturally given by generalized Catalan numbers and determine the fraction of states that are decidedly entangled and also known to be somewhat protected against decoherence. In addition, we introduce the concept of a "sterile entanglement witness", which for large enough systems detects entanglement without affecting much the system's state. We discuss when our proposed entanglement witness can be regarded as a sterile one.
Graphical Classification of Entangled Qutrits
Directory of Open Access Journals (Sweden)
Kentaro Honda
2012-10-01
Full Text Available A multipartite quantum state is entangled if it is not separable. Quantum entanglement plays a fundamental role in many applications of quantum information theory, such as quantum teleportation. Stochastic local quantum operations and classical communication (SLOCC cannot essentially change quantum entanglement without destroying it. Therefore, entanglement can be classified by dividing quantum states into equivalence classes, where two states are equivalent if each can be converted into the other by SLOCC. Properties of this classification, especially in the case of non two-dimensional quantum systems, have not been well studied. Graphical representation is sometimes used to clarify the nature and structural features of entangled states. SLOCC equivalence of quantum bits (qubits has been described graphically via a connection between tripartite entangled qubit states and commutative Frobenius algebras (CFAs in monoidal categories. In this paper, we extend this method to qutrits, i.e., systems that have three basis states. We examine the correspondence between CFAs and tripartite entangled qutrits. Using the symmetry property, which is required by the definition of a CFA, we find that there are only three equivalence classes that correspond to CFAs. We represent qutrits graphically, using the connection to CFAs. We derive equations that characterize the three equivalence classes. Moreover, we show that any qutrit can be represented as a composite of three graphs that correspond to the three classes.
Teleportation of a Kind of Three-Mode Entangled States of Continuous Variables
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
A quantum teleportation scheme to teleport a kind of tripartite entangled states of continuous variables by using a quantum channel composed of three bipartite entangled states is proposed. The joint Bell measurement is feasible because the bipartite entangled states are complete and the squeezed state has a natural representation in the entangled state basis. The calculation is greatly simplified by using the Schmidt decomposition of the entangled states.
Three qubit entanglement within graphical Z/X-calculus
Directory of Open Access Journals (Sweden)
Bob Coecke
2011-03-01
Full Text Available The compositional techniques of categorical quantum mechanics are applied to analyse 3-qubit quantum entanglement. In particular the graphical calculus of complementary observables and corresponding phases due to Duncan and one of the authors is used to construct representative members of the two genuinely tripartite SLOCC classes of 3-qubit entangled states, GHZ and W. This nicely illustrates the respectively pairwise and global tripartite entanglement found in the W- and GHZ-class states. A new concept of supplementarity allows us to characterise inhabitants of the W class within the abstract diagrammatic calculus; these method extends to more general multipartite qubit states.
Two Theorems on Calculating the Relative Entropy of Entanglement
Institute of Scientific and Technical Information of China (English)
WU Sheng-Jun; ZHANG Yong-De; WU Qiang
2001-01-01
We present two theorems on calculating the relative entropy of entanglement. Theorem 1 is an extension of Vedral and Plenio's theorem (Phys. Rev. A 57 (1998) 1619) for pure states, which is useful for calculating the relative entropy of entanglement for all pure states as well as for a class of mixed states. Theorem 2 gives the relative entropy of entanglement for any bipartite state whose tripartite purification has two separable reduced bipartite states.
From Entanglement Witness to Generalized Catalan Numbers
Cohen, Eliahu; Itzhaki, Nissan
2015-01-01
The problem of entanglement detection for arbitrary spin systems is analyzed. We demonstrate how a single measurement of the squared total spin can probabilistically discern separable from entangled many-particle states. For achieving this goal, we construct a tripartite analogy between the degeneracy of entanglement witness eigenstates, tensor products of SO(3) representations and classical lattice walks with special constraints. Within this framework, degeneracies are naturally given by generalized Catalan numbers and determine the fraction of states that are decidedly entangled. In addition, we introduce the concept of a "sterile entanglement witness", which detects entanglement without affecting much the system's dynamics. We show that our proposed witness is sterile when the system becomes large enough.
Multipartite Entanglement in Stabilizer Tensor Networks
Nezami, Sepehr
2016-01-01
Tensor network models reproduce important structural features of holography, including the Ryu-Takayanagi formula for the entanglement entropy and quantum error correction in the entanglement wedge. In contrast, only little is known about their multipartite entanglement structure, which has been of considerable recent interest. In this work, we study random stabilizer tensor networks and show that here the tripartite entanglement question has a sharp answer: The average number of GHZ triples that can be extracted from a stabilizer tensor network is small, implying that the entanglement is predominantly bipartite. As a consequence, we obtain a new operational interpretation of the monogamy of the Ryu-Takayanagi mutual information and an entropic diagnostic for higher-partite entanglement. Our technical contributions include a spin model for evaluating the average GHZ content of stabilizer tensor networks and a novel formula for the third moment of random stabilizer states.
Monogamy, polygamy, and other properties of entanglement of purification
Bagchi, Shrobona; Pati, Arun Kumar
2015-04-01
For bipartite pure and mixed quantum states, in addition to the quantum mutual information, there is another measure of total correlation, namely, the entanglement of purification. We study the monogamy, polygamy, and additivity properties of the entanglement of purification for pure and mixed states. In this paper, we show that, in contrast to the quantum mutual information which is strictly monogamous for any tripartite pure states, the entanglement of purification is polygamous for the same. This shows that there can be genuinely two types of total correlation across any bipartite cross in a pure tripartite state. Furthermore, we find the lower bound and actual values of the entanglement of purification for different classes of tripartite and higher-dimensional bipartite mixed states. Thereafter, we show that if entanglement of purification is not additive on tensor product states, it is actually subadditive. Using these results, we identify some states which are additive on tensor products for entanglement of purification. The implications of these findings on the quantum advantage of dense coding are briefly discussed, whereby we show that for tripartite pure states, it is strictly monogamous and if it is nonadditive, then it is superadditive on tensor product states.
$E_{6}$ and the bipartite entanglement of three qutrits
Duff, M J
2007-01-01
Recent investigations have established an analogy between the entropy of four-dimensional supersymmetric black holes in string theory and entanglement in quantum information theory. Examples include: (1) N=2 STU black holes and the tripartite entanglement of three qubits (2-state systems), where the common symmetry is [SL(2)]^3 and (2) N=8 black holes and the tripartite entanglement of seven qubits where the common symmetry is E_7 which contains [SL(2)]^7. Here we present another example: N=8 black holes (or black strings) in five dimensions and the bipartite entanglement of three qutrits (3-state systems), where the common symmetry is E_6 which contains [SL(3)]^3. Both the black hole (or black string) entropy and the entanglement measure are provided by the Cartan cubic E_6 invariant. Similar analogies exist for ``magic'' N=2 supergravity black holes in both four and five dimensions.
Entanglement distillation for three-particle W class states
Cao, Z L; Cao, Zhuo-Liang; Yang, Ming
2003-01-01
In this paper, we propose two general entanglement distillation protocols, which can concentrate the non-maximally entangled pure W class state. The general protocols are mainly based on the unitary transformation on the auxiliary particle and one of the three entangled particles, and in the second protocol, the entanglement distillation includes two meanings, namely, extracting the concentrated tripartite entangled W state and obtaining the maximally entangled bipartite state from the garbage state, which gives no contribution to the distillation of non-maximally entangled pure W class state. We can make use of the garbage in the distillation process, and make the entanglement waste in quantum communication as small as possible. A feasible physical scheme is suggested based on the cavity QED.
Avoiding disentanglement of multipartite entangled optical beams with a correlated noisy channel
Deng, Xiaowei; Tian, Caixing; Su, Xiaolong; Xie, Changde
2017-01-01
A quantum communication network can be constructed by distributing a multipartite entangled state to space-separated nodes. Entangled optical beams with highest flying speed and measurable brightness can be used as carriers to convey information in quantum communication networks. Losses and noises existing in real communication channels will reduce or even totally destroy entanglement. The phenomenon of disentanglement will result in the complete failure of quantum communication. Here, we present the experimental demonstrations on the disentanglement and the entanglement revival of tripartite entangled optical beams used in a quantum network. We experimentally demonstrate that symmetric tripartite entangled optical beams are robust in pure lossy but noiseless channels. In a noisy channel, the excess noise will lead to the disentanglement and the destroyed entanglement can be revived by the use of a correlated noisy channel (non-Markovian environment). The presented results provide useful technical references for establishing quantum networks. PMID:28295024
Avoiding disentanglement of multipartite entangled optical beams with a correlated noisy channel
Deng, Xiaowei; Tian, Caixing; Su, Xiaolong; Xie, Changde
2017-03-01
A quantum communication network can be constructed by distributing a multipartite entangled state to space-separated nodes. Entangled optical beams with highest flying speed and measurable brightness can be used as carriers to convey information in quantum communication networks. Losses and noises existing in real communication channels will reduce or even totally destroy entanglement. The phenomenon of disentanglement will result in the complete failure of quantum communication. Here, we present the experimental demonstrations on the disentanglement and the entanglement revival of tripartite entangled optical beams used in a quantum network. We experimentally demonstrate that symmetric tripartite entangled optical beams are robust in pure lossy but noiseless channels. In a noisy channel, the excess noise will lead to the disentanglement and the destroyed entanglement can be revived by the use of a correlated noisy channel (non-Markovian environment). The presented results provide useful technical references for establishing quantum networks.
Entanglement dynamics in quantum information theory
Energy Technology Data Exchange (ETDEWEB)
Cubitt, T.S.
2007-03-29
This thesis contributes to the theory of entanglement dynamics, that is, the behaviour of entanglement in systems that are evolving with time. Progressively more complex multipartite systems are considered, starting with low-dimensional tripartite systems, whose entanglement dynamics can nonetheless display surprising properties, progressing through larger networks of interacting particles, and finishing with infinitely large lattice models. Firstly, what is perhaps the most basic question in entanglement dynamics is considered: what resources are necessary in order to create entanglement between distant particles? The answer is surprising: sending separable states between the parties is sufficient; entanglement can be created without it being carried by a ''messenger'' particle. The analogous result also holds in the continuous-time case: two particles interacting indirectly via a common ancilla particle can be entangled without the ancilla ever itself becoming entangled. The latter result appears to discount any notion of entanglement flow. However, for pure states, this intuitive idea can be recovered, and even made quantitative. A ''bottleneck'' inequality is derived that relates the entanglement rate of the end particles in a tripartite chain to the entanglement of the middle one. In particular, no entanglement can be created if the middle particle is not entangled. However, although this result can be applied to general interaction networks, it does not capture the full entanglement dynamics of these more complex systems. This is remedied by the derivation of entanglement rate equations, loosely analogous to the rate equations describing a chemical reaction. A complete set of rate equations for a system reflects the full structure of its interaction network, and can be used to prove a lower bound on the scaling with chain length of the time required to entangle the ends of a chain. Finally, in contrast with these more
Equivalence between entanglement and the optimal fidelity of continuous variable teleportation.
Adesso, Gerardo; Illuminati, Fabrizio
2005-10-07
We devise the optimal form of Gaussian resource states enabling continuous-variable teleportation with maximal fidelity. We show that a nonclassical optimal fidelity of N-user teleportation networks is necessary and sufficient for N-party entangled Gaussian resources, yielding an estimator of multipartite entanglement. The entanglement of teleportation is equivalent to the entanglement of formation in a two-user protocol, and to the localizable entanglement in a multiuser one. Finally, we show that the continuous-variable tangle, quantifying entanglement sharing in three-mode Gaussian states, is defined operationally in terms of the optimal fidelity of a tripartite teleportation network.
Three-qubit topological phase on entangled photon pairs
Johansson, Markus; Singh, Kuldip; Sjöqvist, Erik
2013-01-01
We propose an experiment to observe the topological phases associated with cyclic evolutions, generated by local SU(2) operations, on three-qubit entangled states prepared on different degrees of freedom of entangled photon pairs. The topological phases reveal the nontrivial topological structure of the local SU(2) orbits. We describe how to prepare states showing different topological phases, and discuss their relation to entanglement. In particular, the presence of a $\\pi/2$ phase shift is a signature of genuine tripartite entanglement in the sense that it does not exist for two-qubit systems.
Institute of Scientific and Technical Information of China (English)
范洪义; 姜年权
2002-01-01
By extending the Einstein-Podolsky-Rosen bipartite entanglement to the tripartite case, we construct the com-mon eigenvector of the tripartite centre-of-mass coordinate and two mass-weighted relative momenta, which is anew entangled state of continuum variables. The classical dilation transform of variables in such a state inducesa new three-mode squeezing operator related to a three-mode bosonic operator realization of S U(1,1 ) Lie algebra.
Enhancement of multipartite entanglement in an open system under non-inertial frames
Sun, Wen-Yang; Wang, Dong; Yang, Jie; Ye, Liu
2017-04-01
In this paper, multipartite entanglement enhancement in an open system under non-inertial frames via local non-unitary operations is explored. Explicitly, we investigate an available methodology to enhance tripartite entanglement of X-state, when the systems suffer from amplitude damping (AD) noise and one subsystem is under non-inertial frames. As an illustration, we consider three cases (one subsystem or multi-subsystem suffers from decoherence) by using local non-unitary operations, and the corresponding entanglement behaviors are revealed. It turns out that the local non-unitary operation can enhance entanglement to some degree. The Unruh effect and decoherence will influence the tripartite entanglement. However, the impact of Unruh effect on tripartite entanglement is weaker than that of decoherence. In addition, we obtain an interesting result: One can estimate and probe the decoherence strength (AD noise) in accordance with the change of local non-unitary operation strength and genuinely multipartite entanglement variation. Therefore, our work may be beneficial to explore the dynamic behavior of tripartite entanglement in open systems under relativity frame.
Structure and operation of bacterial tripartite pumps.
Hinchliffe, Philip; Symmons, Martyn F; Hughes, Colin; Koronakis, Vassilis
2013-01-01
In bacteria such as Pseudomonas aeruginosa and Escherichia coli, tripartite membrane machineries, or pumps, determine the efflux of small noxious molecules, such as detergents, heavy metals, and antibiotics, and the export of large proteins including toxins. They are therefore influential in bacterial survival, particularly during infections caused by multidrug-resistant pathogens. In these tripartite pumps an inner membrane transporter, typically an ATPase or proton antiporter, binds and translocates export or efflux substrates. In cooperation with a periplasmic adaptor protein it recruits and opens a TolC family cell exit duct, which is anchored in the outer membrane and projects across the periplasmic space between inner and outer membranes. Assembled tripartite pumps thus span the entire bacterial cell envelope. We review the atomic structures of each of the three pump components and discuss how these have allowed high-resolution views of tripartite pump assembly, operation, and possible inhibition.
Brachistochrone of entanglement for spin chains
Carlini, Alberto; Koike, Tatsuhiko
2017-03-01
We analytically investigate the role of entanglement in time-optimal state evolution as an application of the quantum brachistochrone, a general method for obtaining the optimal time-dependent Hamiltonian for reaching a target quantum state. As a model, we treat two qubits indirectly coupled through an intermediate qubit that is directly controllable, which represents a typical situation in quantum information processing. We find the time-optimal unitary evolution law and quantify residual entanglement by the two-tangle between the indirectly coupled qubits, for all possible sets of initial pure quantum states of a tripartite system. The integrals of the motion of the brachistochrone are determined by fixing the minimal time at which the residual entanglement is maximized. Entanglement plays a role for W and Greenberger–Horne–Zeilinger (GHz) initial quantum states, and for the bi-separable initial state in which the indirectly coupled qubits have a nonzero value of the 2-tangle.
Multipartite entanglement arising from dense Euclidean lattices in dimensions 4-24
Planat, Michel
2012-02-01
The group of automorphisms of Euclidean (embedded in {R}^n ) dense lattices such as the root lattices D4 and E8, the Barnes-Wall lattice BW16, the unimodular lattice D12+ and the Leech lattice Λ24 may be generated by entangled quantum gates of the corresponding dimension. These (real) gates/lattices are useful for quantum error correction: for instance, the two- and four-qubit real Clifford groups are the automorphism groups of the lattices D4 and BW16, respectively, and the three-qubit real Clifford group is maximal in the Weyl group W(E8). Technically, the automorphism group Aut(Λ) of the lattice Λ is the set of orthogonal matrices B such that, following the conjugation action by the generating matrix of the lattice, the output matrix is unimodular (of determinant ±1, with integer entries). When the degree n is equal to the number of basis elements of Λ, Aut(Λ) also acts on basis vectors and is generated with matrices B such that the sum of squared entries in a row is 1, i.e. B may be seen as a quantum gate. For the dense lattices listed above, maximal multipartite entanglement arises. In particular, one finds a balanced tripartite entanglement in E8 (the two- and three-tangles have the same magnitude 1/4) and a Greenberger-Horne-Zeilinger-type entanglement in BW16. In this paper, we also investigate the entangled gates from D12+ and Λ24, by seeing them as systems coupling a qutrit to two- and three-qubits, respectively. In addition to quantum computing, the work may be related to particle physics in the spirit of Planat et al (2011 Rep. Math. Phys. 66 39-51).
Bound entanglement and entanglement bounds
Energy Technology Data Exchange (ETDEWEB)
Sauer, Simeon [Physikalisch-Astronomische Fakultaet, Friedrich-Schiller-Univesitaet Jena (Germany)]|[Physikalisches Institut, Albert-Ludwigs-Universitaet Freiburg, Hermann-Herder-Strasse 3, D-79104 Freiburg (Germany); Melo, Fernando de; Mintert, Florian; Buchleitner, Andreas [Physikalisches Institut, Albert-Ludwigs-Universitaet Freiburg, Hermann-Herder-Strasse 3, D-79104 Freiburg (Germany)]|[Max-Planck-Institut fuer Physik komplexer Systeme, Noethnitzer Str.38, D-01187 Dresden (Germany); Bae, Joonwoo [School of Computational Sciences, Korea Institute for Advanced Study, Seoul 130-012 (Korea); Hiesmayr, Beatrix [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria)
2008-07-01
We investigate the separability of Bell-diagonal states of two qutrits. By using lower bounds to algebraically estimate concurrence, we find convex regions of bound entangled states. Some of these regions exactly coincide with the obtained results when employing optimal entanglement witnesses, what shows that the lower bound can serve as a precise detector of entanglement. Some hitherto unknown regions of bound entangled states were discovered with this approach, and delimited efficiently.
Gualdi, Giulia; Giampaolo, Salvatore M; Illuminati, Fabrizio
2011-02-04
We introduce and discuss the concept of modular entanglement. This is the entanglement that is established between the end points of modular systems composed by sets of interacting moduli of arbitrarily fixed size. We show that end-to-end modular entanglement scales in the thermodynamic limit and rapidly saturates with the number of constituent moduli. We clarify the mechanisms underlying the onset of entanglement between distant and noninteracting quantum systems and its optimization for applications to quantum repeaters and entanglement distribution and sharing.
Gualdi, Giulia; Illuminati, Fabrizio
2010-01-01
We introduce and discuss the concept of modular entanglement. This is the entanglement that is established between the end points of modular systems composed by sets of interacting blocks of arbitrarily fixed size. We show that end-to-end modular entanglement scales in the thermodynamic limit and rapidly saturates with the number of constituent blocks. We clarify the mechanisms underlying the onset of entanglement between distant and non-interacting quantum systems and its optimization for applications to quantum repeaters and entanglement distribution and sharing.
Topological entanglement negativity in Chern-Simons theories
Wen, Xueda; Ryu, Shinsei
2016-01-01
We study the topological entanglement negativity between two spatial regions in (2+1)-dimensional Chern-Simons gauge theories by using the replica trick and the surgery method. For a bipartitioned or tripartitioned spatial manifold, we show how the topological entanglement negativity depends on the presence of quasiparticles and the choice of ground states. In particular, for two adjacent non-contractible regions on a tripartitioned torus, the entanglement negativity provides a simple way to distinguish Abelian and non-Abelian theories. Our method applies to a Chern-Simons gauge theory defined on an arbitrary oriented (2+1)-dimensional spacetime manifold. Our results agree with the edge theory approach in a recent work (X. Wen, S. Matsuura and S. Ryu, arXiv:1603.08534).
Topological entanglement negativity in Chern-Simons theories
Wen, Xueda; Chang, Po-Yao; Ryu, Shinsei
2016-09-01
We study the topological entanglement negativity between two spatial regions in (2+1)-dimensional Chern-Simons gauge theories by using the replica trick and the surgery method. For a bipartitioned or tripartitioned spatial manifold, we show how the topological entanglement negativity depends on the presence of quasiparticles and the choice of ground states. In particular, for two adjacent non-contractible regions on a tripartitioned torus, the entanglement negativity provides a simple way to distinguish Abelian and non-Abelian theories. Our method applies to a Chern-Simons gauge theory defined on an arbitrary oriented (2+1)-dimensional spacetime manifold. Our results agree with the edge theory approach in a recent work [35].
Tripartitions do not always discriminate phylogenetic networks.
Cardona, Gabriel; Rosselló, Francesc; Valiente, Gabriel
2008-02-01
Phylogenetic networks are a generalization of phylogenetic trees that allow for the representation of non-treelike evolutionary events, like recombination, hybridization, or lateral gene transfer. In a recent series of papers devoted to the study of reconstructibility of phylogenetic networks, Moret, Nakhleh, Warnow and collaborators introduced the so-called tripartition metric for phylogenetic networks. In this paper we show that, in fact, this tripartition metric does not satisfy the separation axiom of distances (zero distance means isomorphism, or, in a more relaxed version, zero distance means indistinguishability in some specific sense) in any of the subclasses of phylogenetic networks where it is claimed to do so. We also present a subclass of phylogenetic networks whose members can be singled out by means of their sets of tripartitions (or even clusters), and hence where the latter can be used to define a meaningful metric.
Institute of Scientific and Technical Information of China (English)
董世永; 张丁文
2014-01-01
本文在对我国保障性住房空间布局的问题和建设模式综合分析的基础上，从三方博弈的角度，探讨了低收入居民的社会需求、开发商的经济诉求和政府对综合效益的平衡，指出我国保障性住房边缘化集中布局、职住分离、公共服务设施缺乏等问题根本上是源于因为政府主导、开发商偏向和低收入居民话语权缺失而失衡的三方选址博弈机制。最后通过借鉴美国保障性住房建设中角色激励的经验，提出了拓宽社会投资渠道、对开发商采用制度激励、强化公众参与和城市规划引导和控制能力等重构策略。%This article first makes a comprehensive analysis about the spatial layout problems and the construction patterns of affordable housing in our country. Then, from the perspective of the tripartite game, discusses the social demands of low-income residents, the economic demands of developers and the balance of the comprehensive beneifts kept by the government. After that, this paper points out that the marginal centralized layout, the phenomena of separation of workplace and residence and the lack of public service facilities of the affordable housing in our country are rooted in the imbalance of the tripartite game mechanism. At last, by reference to the role of motivation in the affordable housing strategy in the USA, this article puts forward strategies such as widening the channel of social investment, adopting incentives for developers and strengthening public participation and the ability of guidance and control of urban planning.
Samblowski, Aiko; Grosse, Nicolai; Lam, Ping Koy; Schnabel, Roman
2010-01-01
We report on the generation of entangled states of light between the wavelengths 810 and 1550 nm in the continuous variable regime. The fields were produced by type I optical parametric oscillation in a standing-wave cavity build around a periodically poled potassium titanyl phosphate crystal, operated above threshold. Balanced homodyne detection was used to detect the non-classical noise properties, while filter cavities provided the local oscillators by separating carrier fields from the entangled sidebands. We were able to obtain an inseparability of I=0.82, corresponding to about -0.86 dB of non-classical quadrature correlation.
Carmichael, H.
1953-01-01
A torsional-type analytical balance designed to arrive at its equilibrium point more quickly than previous balances is described. In order to prevent external heat sources creating air currents inside the balance casing that would reiard the attainment of equilibrium conditions, a relatively thick casing shaped as an inverted U is placed over the load support arms and the balance beam. This casing is of a metal of good thernnal conductivity characteristics, such as copper or aluminum, in order that heat applied to one portion of the balance is quickly conducted to all other sensitive areas, thus effectively preventing the fornnation of air currents caused by unequal heating of the balance.
Dechoum, K; Khoury, A Z; 10.1103/PhysRevA.83.063843
2011-01-01
We analyze the three-mode correlation properties of the electromagnetic field in a optical parametric oscillator below threshold. We employ a perturbative expansion of the It\\^o equations derived from the positive-P representation of the density matrix. Using the generalized Cauchy-Schwarz inequality, we investigate the genuine quantum nature of the triple correlations between the interacting fields, since in this case continuous variable entanglement is not detected by the van Loock-Furusawa criterion [Phys. Rev. A {\\bf 67}, 052315 (2003)]. Although not being a necessary condition, these triple correlations are a sufficient evidence of tripartite entanglement. Of course, our characterization of the quantum correlations is applicable to non-Gaussian states, which we show to be the case of the optical parametric oscillator below threshold, provided nonlinear quantum fluctuations are properly taken into account.
Popp, M; Martín-Delgado, M A; Cirac, J I
2004-01-01
We consider systems of interacting spins and study the entanglement that can be localized, on average, between two separated spins by performing local measurements on the remaining spins. This concept of Localizable Entanglement (LE) leads naturally to notions like entanglement length and entanglement fluctuations. For both spin-1/2 and spin-1 systems we prove that the LE of a pure quantum state can be lower bounded by connected correlation functions. We further propose a scheme, based on matrix-product states and the Monte Carlo method, to efficiently calculate the LE for quantum states of a large number of spins. The virtues of LE are illustrated for various spin models. In particular, characteristic features of a quantum phase transition such as a diverging entanglement length can be observed. We also give examples for pure quantum states exhibiting a diverging entanglement length but finite correlation length. We have numerical evidence that the ground state of the antiferromagnetic spin-1 Heisenberg chai...
Entanglement sharing: from qubits to Gaussian states
Adesso, G; Adesso, Gerardo; Illuminati, Fabrizio
2005-01-01
It is a central trait of quantum information theory that there exist limitations to the free sharing of quantum correlations among multiple parties. Such {\\em monogamy constraints} have been introduced in a landmark paper by Coffman, Kundu and Wootters, who derived a quantitative inequality expressing a trade-off between the couplewise and the genuine tripartite entanglement for states of three qubits. Since then, a lot of efforts have been devoted to the investigation of distributed entanglement in multipartite quantum systems. In these proceedings we report, in a unifying framework, a bird's eye view of the most relevant results that have been established so far on entanglement sharing in quantum systems. We will take off from the domain of $N$ qubits, graze qudits, and finally land in the almost unexplored territory of multimode Gaussian states of continuous variable systems.
Almost-quantum correlations and their refinements in a tripartite Bell scenario
Vallins, James; Sainz, Ana Belén; Liang, Yeong-Cherng
2017-02-01
We study the set of almost-quantum correlations and their refinements in the simplest tripartite Bell scenario where each party is allowed to perform two dichotomic measurements. In contrast to its bipartite counterpart, we find that there already exist facet Bell inequalities that witness almost-quantum correlations beyond quantum theory in this simplest tripartite Bell scenario. Furthermore, we study the relation between the almost-quantum set and the hierarchy of supersets to the quantum set due to Navascués-Pironio-Acín (NPA) [Phys. Rev. Lett. 98, 010401 (2007), 10.1103/PhysRevLett.98.010401]. While the former lies between the first and the third level of the NPA hierarchy, we find that its second level does not contain and is not contained within the almost-quantum set. Finally, we investigate the hierarchy of refinements to the almost-quantum set due to Moroder et al. [Phys. Rev. Lett. 111, 030501 (2013), 10.1103/PhysRevLett.111.030501], which converges to the set of quantum correlations producible by quantum states having positive partial transposition. This allows us to consider (approximations of) the "biseparable" subsets of the almost-quantum set as well as of the quantum set of correlations, and thereby gain further insights into the subtle similarities and differences between the two sets. In addition, they allow us to identify candidate Bell-like inequalities that can serve as device-independent witnesses for genuine tripartite entanglement.
Energy Technology Data Exchange (ETDEWEB)
Hu, Ming-Liang, E-mail: mingliang0301@163.com
2012-09-15
Dynamics of disentanglement as measured by the tripartite negativity and Bell nonlocality as measured by the extent of violation of the multipartite Bell-type inequalities are investigated in this work. It is shown definitively that for the initial three-qubit Greenberger-Horne-Zeilinger (GHZ) or W class state preparation, the Bell nonlocality suffers sudden death under the influence of thermal reservoirs. Moreover, all the Bell-nonlocal states are useful for nonclassical teleportation, while there are entangled states that do not violate any Bell-type inequalities, but still yield nonclassical teleportation fidelity. - Highlights: Black-Right-Pointing-Pointer Comparison of different aspects of quantum correlations. Black-Right-Pointing-Pointer Robustness of the initial tripartite GHZ and W class states against decoherence. Black-Right-Pointing-Pointer Bell-nonlocality sudden death under the influence of thermal reservoir. Black-Right-Pointing-Pointer A nonzero minimum tripartite negativity is needed for nonclassical teleportation. Black-Right-Pointing-Pointer All the Bell-nonlocal states yield nonclassical teleportation fidelity.
Quantum correlations and entanglement in a model comprised of a short chain of nonlinear oscillators
Kalaga, J. K.; Kowalewska-Kudłaszyk, A.; Leoński, W.; Barasiński, A.
2016-09-01
We discuss a model comprised of a chain of three Kerr-like nonlinear oscillators pumped by two modes of external coherent field. We show that the system can be treated as nonlinear quantum scissors and behave as a three-qubit model. For such situation, different types of tripartite entangled states can be generated, even when damping effects are present in the system. Some amount of such entanglement can survive even in a long-time limit. The flow of bipartite entanglement between subsystems of the model and relations among first-order correlations, second-order correlations, and the entanglement are discussed.
Remote Preparation of Multipartite Equatorial Entangled States in High Dimensions with Three Parties
Institute of Scientific and Technical Information of China (English)
HOU Kui; WANG Jing; SHI Shou-Hua
2009-01-01
A scheme for probabilistic remotely preparing N-particle d-dimensional equatorial entangled states via entangled swapping with three parties is presented. The quantum channel is composed of N - 1 pairs of bipartite d-dimensional non-maximally entangled states and a tripartite d-dimension non-maximally entangled state. It is shown that the sender can help either of the two receivers to remotely prepare the original state, and the N-particle projective measurement and the genera//zed Hadamard transformation are needed in this scheme. The total success probability and classical communication cost are calculated.
Dahlsten, Oscar C. O.; Lupo, Cosmo; Mancini, Stefano; Serafini, Alessio
2014-09-01
We provide a summary of both seminal and recent results on typical entanglement. By ‘typical’ values of entanglement, we refer here to values of entanglement quantifiers that (given a reasonable measure on the manifold of states) appear with arbitrarily high probability for quantum systems of sufficiently high dimensionality. We shall focus on pure states and work within the Haar measure framework for discrete quantum variables, where we report on results concerning the average von Neumann and linear entropies as well as arguments implying the typicality of such values in the asymptotic limit. We then proceed to discuss the generation of typical quantum states with random circuitry. Different phases of entanglement, and the connection between typical entanglement and thermodynamics are discussed. We also cover approaches to measures on the non-compact set of Gaussian states of continuous variable quantum systems.
Deterministically Entangling Two Remote Atomic Ensembles via Light-Atom Mixed Entanglement Swapping.
Liu, Yanhong; Yan, Zhihui; Jia, Xiaojun; Xie, Changde
2016-05-11
Entanglement of two distant macroscopic objects is a key element for implementing large-scale quantum networks consisting of quantum channels and quantum nodes. Entanglement swapping can entangle two spatially separated quantum systems without direct interaction. Here we propose a scheme of deterministically entangling two remote atomic ensembles via continuous-variable entanglement swapping between two independent quantum systems involving light and atoms. Each of two stationary atomic ensembles placed at two remote nodes in a quantum network is prepared to a mixed entangled state of light and atoms respectively. Then, the entanglement swapping is unconditionally implemented between the two prepared quantum systems by means of the balanced homodyne detection of light and the feedback of the measured results. Finally, the established entanglement between two macroscopic atomic ensembles is verified by the inseparability criterion of correlation variances between two anti-Stokes optical beams respectively coming from the two atomic ensembles.
Toward a tripartite model of intrinsic motivation.
Carbonneau, Noémie; Vallerand, Robert J; Lafrenière, Marc-André K
2012-10-01
Intrinsic motivation (IM) refers to engaging in an activity for the pleasure inherent in the activity. The present article presents a tripartite model of IM consisting of IM to know (i.e., engaging in an activity to experience pleasure while learning and trying to understand something new), IM toward accomplishment (i.e., engaging in an activity for the pleasure experienced when attempting task mastery), and IM to experience stimulation (i.e., engaging in an activity for feelings of sensory pleasure). The tripartite model of IM posits that each type of IM can result from task, situational, and personality determinants and can lead to specific types of cognitive, affective, and behavioral outcomes. The purpose of this research was to test some predictions derived from this model. Across 4 studies (Study 1: N = 331; Study 2: N = 113; Study 3: N = 58; Study 4: N = 135), the 3 types of IM as well as potential determinants and consequences were assessed. Results revealed that experiencing one type of IM over the others depends in part on people's personality styles. Also, each type of IM was found to predict specific outcomes (i.e., affective states and behavioral choices). The implications of the tripartite model of IM for motivation research are discussed.
Tripartite assembly of RND multidrug efflux pumps
Daury, Laetitia; Orange, François; Taveau, Jean-Christophe; Verchère, Alice; Monlezun, Laura; Gounou, Céline; Marreddy, Ravi K. R.; Picard, Martin; Broutin, Isabelle; Pos, Klaas M.; Lambert, Olivier
2016-02-01
Tripartite multidrug efflux systems of Gram-negative bacteria are composed of an inner membrane transporter, an outer membrane channel and a periplasmic adaptor protein. They are assumed to form ducts inside the periplasm facilitating drug exit across the outer membrane. Here we present the reconstitution of native Pseudomonas aeruginosa MexAB-OprM and Escherichia coli AcrAB-TolC tripartite Resistance Nodulation and cell Division (RND) efflux systems in a lipid nanodisc system. Single-particle analysis by electron microscopy reveals the inner and outer membrane protein components linked together via the periplasmic adaptor protein. This intrinsic ability of the native components to self-assemble also leads to the formation of a stable interspecies AcrA-MexB-TolC complex suggesting a common mechanism of tripartite assembly. Projection structures of all three complexes emphasize the role of the periplasmic adaptor protein as part of the exit duct with no physical interaction between the inner and outer membrane components.
Entanglement of mixed quantum states for qubits and qudit in double photoionization of atoms
Energy Technology Data Exchange (ETDEWEB)
Chakraborty, M., E-mail: bminakshi@yahoo.com [Department of Physics, Asansol Girls’ College, Asansol 713304 (India); Sen, S. [Department of Physics, Triveni Devi Bhalotia College, Raniganj 713347 (India)
2015-08-15
Highlights: • We study tripartite entanglement between two electronic qubits and an ionic qudit. • We study bipartite entanglement between any two subsystems of a tripartite system. • We have presented a quantitative application of entangled properties in Neon atom. - Abstract: Quantum entanglement and its paradoxical properties are genuine physical resources for various quantum information tasks like quantum teleportation, quantum cryptography, and quantum computer technology. The physical characteristic of the entanglement of quantum-mechanical states, both for pure and mixed, has been recognized as a central resource in various aspects of quantum information processing. In this article, we study the bipartite entanglement of one electronic qubit along with the ionic qudit and also entanglement between two electronic qubits. The tripartite entanglement properties also have been investigated between two electronic qubits and an ionic qudit. All these studies have been done for the single-step double photoionization from an atom following the absorption of a single photon without observing spin orbit interaction. The dimension of the Hilbert space of the qudit depends upon the electronic state of the residual photoion A{sup 2+}. In absence of SOI, when Russell–Saunders coupling (L–S coupling) is applicable, dimension of the qudit is equal to the spin multiplicity of A{sup 2+}. For estimations of entanglement and mixedness, we consider the Peres–Horodecki condition, concurrence, entanglement of formation, negativity, linear and von Neumann entropies. In case of L–S coupling, all the properties of a qubit–qudit system can be predicted merely with the knowledge of the spins of the target atom and the residual photoion.
Generation of Entangled State and Entanglement Swapping
Institute of Scientific and Technical Information of China (English)
YE Liu; GUO Guangcan
2002-01-01
A scheme is proposed for the generation of entangled atomic states and a method is presented to produce entangled photon states. It is shown that entanglement can be swapped from atoms to cavities via atom-cavity interaction.
Entanglement and Coherence in Quantum State Merging.
Streltsov, A; Chitambar, E; Rana, S; Bera, M N; Winter, A; Lewenstein, M
2016-06-17
Understanding the resource consumption in distributed scenarios is one of the main goals of quantum information theory. A prominent example for such a scenario is the task of quantum state merging, where two parties aim to merge their tripartite quantum state parts. In standard quantum state merging, entanglement is considered to be an expensive resource, while local quantum operations can be performed at no additional cost. However, recent developments show that some local operations could be more expensive than others: it is reasonable to distinguish between local incoherent operations and local operations which can create coherence. This idea leads us to the task of incoherent quantum state merging, where one of the parties has free access to local incoherent operations only. In this case the resources of the process are quantified by pairs of entanglement and coherence. Here, we develop tools for studying this process and apply them to several relevant scenarios. While quantum state merging can lead to a gain of entanglement, our results imply that no merging procedure can gain entanglement and coherence at the same time. We also provide a general lower bound on the entanglement-coherence sum and show that the bound is tight for all pure states. Our results also lead to an incoherent version of Schumacher compression: in this case the compression rate is equal to the von Neumann entropy of the diagonal elements of the corresponding quantum state.
Energy Technology Data Exchange (ETDEWEB)
Adesso, Gerardo; Illuminati, Fabrizio [Dipartimento di Fisica ' E R Caianiello' , Universita degli Studi di Salerno (Italy); CNISM and CNR-Coherentia, Gruppo di Salerno (Italy); and INFN Sezione di Napoli-Gruppo Collegato di Salerno (Italy); Via S Allende, 84081 Baronissi, SA (Italy)
2006-01-15
For continuous-variable (CV) systems, we introduce a measure of entanglement, the CV tangle (contangle), with the purpose of quantifying the distributed (shared) entanglement in multimode, multipartite Gaussian states. This is achieved by a proper convex-roof extension of the squared logarithmic negativity. We prove that the contangle satisfies the Coffman-Kundu-Wootters monogamy inequality in all three-mode Gaussian states, and in all fully symmetric N-mode Gaussian states, for arbitrary N. For three-mode pure states, we prove that the residual entanglement is a genuine tripartite entanglement monotone under Gaussian local operations and classical communication. We show that pure, symmetric three-mode Gaussian states allow a promiscuous entanglement sharing, having both maximum tripartite residual entanglement and maximum couplewise entanglement between any pair of modes. These states are thus simultaneous CV analogues of both the GHZ and the W states of three qubits: in CV systems monogamy does not prevent promiscuity, and the inequivalence between different classes of maximally entangled states, holding for systems of three or more qubits, is removed.
Entanglement and coherence in quantum state merging
Streltsov, A; Rana, S; Bera, M N; Winter, A; Lewenstein, M
2016-01-01
Understanding the resource consumption in distributed scenarios is one of the main goals of quantum information theory. A prominent example for such a scenario is the task of quantum state merging where two parties aim to merge their parts of a tripartite quantum state. In standard quantum state merging, entanglement is considered as an expensive resource, while local quantum operations can be performed at no additional cost. However, recent developments show that some local operations could be more expensive than others: it is reasonable to distinguish between local incoherent operations and local operations which can create coherence. This idea leads us to the task of incoherent quantum state merging, where one of the parties has free access to local incoherent operations only. In this case the resources of the process are quantified by pairs of entanglement and coherence. Here, we develop tools for studying this process, and apply them to several relevant scenarios. While quantum state merging can lead to ...
Astaneh, Amin Faraji
2015-01-01
We use the Heat Kernel method to calculate the Entanglement Entropy for a given entangling region on a fractal. The leading divergent term of the entropy is obtained as a function of the fractal dimension as well as the walk dimension. The power of the UV cut-off parameter is (generally) a fractional number which indeed is a certain combination of these two indices. This exponent is known as the spectral dimension. We show that there is a novel log periodic oscillatory behavior in the entropy which has root in the complex dimension of a fractal. We finally indicate that the Holographic calculation in a certain Hyper-scaling violating bulk geometry yields the same leading term for the entanglement entropy, if one identifies the effective dimension of the hyper-scaling violating theory with the spectral dimension of the fractal. We provide more supports with comparing the behavior of the thermal entropy in terms of the temperature in these two cases.
Horodecki, R; Horodecki, M; Horodecki, K; Horodecki, Ryszard; Horodecki, Pawel; Horodecki, Michal; Horodecki, Karol
2007-01-01
All our former experience with application of quantum theory seems to say: {\\it what is predicted by quantum formalism must occur in laboratory}. But the essence of quantum formalism - entanglement, recognized by Einstein, Podolsky, Rosen and Schr\\"odinger - waited over 70 years to enter to laboratories as a new resource as real as energy. This holistic property of compound quantum systems, which involves nonclassical correlations between subsystems, is a potential for many quantum processes, including ``canonical'' ones: quantum cryptography, quantum teleportation and dense coding. However, it appeared that this new resource is very complex and difficult to detect. Being usually fragile to environment, it is robust against conceptual and mathematical tools, the task of which is to decipher its rich structure. This article reviews basic aspects of entanglement including its characterization, detection, distillation and quantifying. In particular, the authors discuss various manifestations of entanglement via ...
Tripartite states Bell-nonlocality sudden death in a spin environment with multisite interaction
Institute of Scientific and Technical Information of China (English)
Xie Li-Jun; Zhang Deng-Yu; Wang Xin-wen; Zhan Xiao-Gui; Tang Shi-Qing; Gao Feng
2011-01-01
Tis paper demonstrates that multipartite Bell-inequality violations can be fully destroyed in a finite time in three-qubit states coupled to a general XY spin-chain with a three-site interaction environment.The Mermin-Ardehali-Belinksii-Klyshko inequality is used to detect the degree of nonlocality,as measured by the extent of their violations.The effects of system-environment couplings,the size of degrees of freedom of the environment and the strength of the three-site interaction on the Bell-inequality violations are given.The results indicate that the Bell-inequality violations of the tripartite states will be completely destroyed by decoherence under certain conditions for the GHZ state.The decoherence-free subspaces of our model are identified and the entanglement of quantum states is also discussed.
Mutual Contextualization in Tripartite Graphs of Folksonomies
Yeung, Ching-Man Au; Gibbins, Nicholas; Shadbolt, Nigel
The use of tags to describe Web resources in a collaborative manner has experienced rising popularity among Web users in recent years. The product of such activity is given the name folksonomy, which can be considered as a scheme of organizing information in the users' own way. This research work attempts to analyze tripartite graphs - graphs involving users, tags and resources - of folksonomies and discuss how these elements acquire their semantics through their associations with other elements, a process we call mutual contextualization. By studying such process, we try to identify solutions to problems such as tag disambiguation, retrieving documents of similar topics and discovering communities of users. This paper describes the basis of the research work, mentions work done so far and outlines future plans.
Authenticating Tripartite Key Agreement Protocol with Pairings
Institute of Scientific and Technical Information of China (English)
Sheng-Li Liu; Fang-Guo Zhang; Ke-Fei Chen
2004-01-01
In this paper, an authenticated tripartite key agreement protocol is proposed, which is an ID-based one with pairings. This protocol involves only one round. The authenticity of the protocol is assured by a special signature scheme, so that messages carrying the information of two ephemeral keys can be broadcasted authentically by an entity. Consequently, one instance of the protocol results in eight session keys for three entities. In other word, one instance of the protocol generates a session key, which is eight times longer than those obtained from traditional key agreement protocols. Security attributes of the protocol are presented, and the computational overhead and bandwidth of the broadcast messages are analyzed as well.
Hadjiivanov, Ludmil
2015-01-01
Expository paper providing a historical survey of the gradual transformation of the "philosophical discussions" between Bohr, Einstein and Schr\\"odinger on foundational issues in quantum mechanics into a quantitative prediction of a new quantum effect, its experimental verification and its proposed (and loudly advertised) applications. The basic idea of the 1935 paper of Einstein-Podolsky-Rosen (EPR) was reformulated by David Bohm for a finite dimensional spin system. This allowed John Bell to derive his inequalities that separate the prediction of quantum entanglement from its possible classical interpretation. We reproduce here their later (1971) version, reviewing on the way the generalization (and mathematical derivation) of Heisenberg's uncertainty relations (due to Weyl and Schr\\"odinger) needed for the passage from EPR to Bell. We also provide an improved derivation of the quantum theoretic violation of Bell's inequalities. Soon after the experimental confirmation of the quantum entanglement (culminati...
The entanglement evolution between two entangled atoms
Indian Academy of Sciences (India)
Zong-Cheng Xu; Mai-Lin Liang; Ya-Ting Zhang; Jian-Quan Yao
2016-03-01
The entanglement properties of two entangled atoms interacting with the field under intensity-dependent coupling are studied in detail. It is found that the degree of entanglement between the two atoms changes periodically and undergoes the entanglement sudden death (ESD) and sudden birth at some time. The entanglement properties between the field and the atom insidethe cavity are dependent on the photon number. Most interestingly, the entanglement between the field and the atom in the field is influenced significantly by manipulating the atom outside the field.
Preparation and measurement of three-qubit entanglement in a superconducting circuit.
Dicarlo, L; Reed, M D; Sun, L; Johnson, B R; Chow, J M; Gambetta, J M; Frunzio, L; Girvin, S M; Devoret, M H; Schoelkopf, R J
2010-09-30
Traditionally, quantum entanglement has been central to foundational discussions of quantum mechanics. The measurement of correlations between entangled particles can have results at odds with classical behaviour. These discrepancies grow exponentially with the number of entangled particles. With the ample experimental confirmation of quantum mechanical predictions, entanglement has evolved from a philosophical conundrum into a key resource for technologies such as quantum communication and computation. Although entanglement in superconducting circuits has been limited so far to two qubits, the extension of entanglement to three, eight and ten qubits has been achieved among spins, ions and photons, respectively. A key question for solid-state quantum information processing is whether an engineered system could display the multi-qubit entanglement necessary for quantum error correction, which starts with tripartite entanglement. Here, using a circuit quantum electrodynamics architecture, we demonstrate deterministic production of three-qubit Greenberger-Horne-Zeilinger (GHZ) states with fidelity of 88 per cent, measured with quantum state tomography. Several entanglement witnesses detect genuine three-qubit entanglement by violating biseparable bounds by 830 ± 80 per cent. We demonstrate the first step of basic quantum error correction, namely the encoding of a logical qubit into a manifold of GHZ-like states using a repetition code. The integration of this encoding with decoding and error-correcting steps in a feedback loop will be the next step for quantum computing with integrated circuits.
Measurement of Creativity: The tripartite approach for creative thinking
Takahashi,Kiyoshi; Hirikami, Akira
2014-01-01
The purpose of this paper is to propose a new measurement method of creativity. Based on the tripartite thinking model (TTM), this paper developed the tripartite creativity test (TCT). The TCT was generated by considering creative process in problem solving. The TCT defines creativity as the interaction of three modes of thinking: logical thinking, critical thinking, and lateral thinking. This model is apart from traditional definition of creativity that prescribes it as the skill for produci...
Exact entanglement bases and general bound entanglement
Zhong, Z Z
2004-01-01
In this paper, we give the more general bound entangled states associated with the unextendible product bases (UPB), i.e. by using of the exact entanglement bases (EEB) and the complete basis with unextendible product bases (CBUPB), we prove that the arbitrary convex sums of the uniform mixtures (bound entangled states) associated with UPBs are still bound entangled states. Further, we discuss the equivalent transformation group and classification of the CBUPBs, and by using this classification, we prove that in the meaning of indistinguishability, the set of the above all possible bound entangled states can be reduced to the set of all possible mixtures of some fixed basic bound entangled states. At last, we prove that every operating of the partial transposition (PT) map acting upon a density matrix under any bipartite partitioning induces a mapping from the above reduced set of bound entangled states to oneself, which corresponds to a non-identical permutation of the basic bound entangled states.
Barzanjeh, Sh; Soltanolkotabi, M
2011-01-01
In this paper, we study theoretically the bipartite and tripartite continuous variable entanglement as well as the normal-mode splitting in a single-atom cavity optomechanical system with intensity-dependent coupling. The system under consideration is formed by a Fabry-Perot cavity with a thin vibrating end mirror and a two-level atom in the Gaussian standing-wave of the cavity mode. We first derive the general form of Hamiltonian describing the tripartite intensity-dependent atom-field-mirror coupling due to the presence of cavity mode structure. We then restrict our treatment to the first vibrational sideband of the mechanical resonator and derive a novel form of tripartite atom-field-mirror Hamiltonian. We show that when the optical cavity is intensely driven one can generate bipartite entanglement between any pair of the tripartite system, and that, due to entanglement sharing, the atom-mirror entanglement is efficiently generated at the expense of optical-mechanical and optical-atom entanglement. We also...
Entanglement in continuous-variable systems: recent advances and current perspectives
Energy Technology Data Exchange (ETDEWEB)
Adesso, Gerardo [Dipartimento di Fisica, Universita degli Studi di Roma ' La Sapienza' , Piazzale Aldo Moro 5, I-00185 Rome (Italy); Illuminati, Fabrizio [Dipartimento di Matematica e Informatica, Universita degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy)
2007-07-13
We review the theory of continuous-variable entanglement with special emphasis on foundational aspects, conceptual structures and mathematical methods. Much attention is devoted to the discussion of separability criteria and entanglement properties of Gaussian states, for their great practical relevance in applications to quantum optics and quantum information, as well as for the very clean framework that they allow for the study of the structure of nonlocal correlations. We give a self-contained introduction to phase-space and symplectic methods in the study of Gaussian states of infinite-dimensional bosonic systems. We review the most important results on the separability and distillability of Gaussian states and discuss the main properties of bipartite entanglement. These include the extremal entanglement, minimal and maximal, of two-mode mixed Gaussian states, the ordering of two-mode Gaussian states according to different measures of entanglement, the unitary (reversible) localization and the scaling of bipartite entanglement in multimode Gaussian states. We then discuss recent advances in the understanding of entanglement sharing in multimode Gaussian states, including the proof of the monogamy inequality of distributed entanglement for all Gaussian states. Multipartite entanglement of Gaussian states is reviewed by discussing its qualification by different classes of separability, and the main consequences of the monogamy inequality, such as the quantification of genuine tripartite entanglement in three-mode Gaussian states, the promiscuous nature of entanglement sharing in symmetric Gaussian states and the possible coexistence of unlimited bipartite and multipartite entanglement. We finally review recent advances and discuss possible perspectives on the qualification and quantification of entanglement in non-Gaussian states, a field of research that is to a large extent yet to be explored.
Renormalizing Entanglement Distillation.
Waeldchen, Stephan; Gertis, Janina; Campbell, Earl T; Eisert, Jens
2016-01-15
Entanglement distillation refers to the task of transforming a collection of weakly entangled pairs into fewer highly entangled ones. It is a core ingredient in quantum repeater protocols, which are needed to transmit entanglement over arbitrary distances in order to realize quantum key distribution schemes. Usually, it is assumed that the initial entangled pairs are identically and independently distributed and are uncorrelated with each other, an assumption that might not be reasonable at all in any entanglement generation process involving memory channels. Here, we introduce a framework that captures entanglement distillation in the presence of natural correlations arising from memory channels. Conceptually, we bring together ideas from condensed-matter physics-ideas from renormalization and matrix-product states and operators-with those of local entanglement manipulation, Markov chain mixing, and quantum error correction. We identify meaningful parameter regions for which we prove convergence to maximally entangled states, arising as the fixed points of a matrix-product operator renormalization flow.
Distillation of bi-partite entanglement from W state with cavity QED
Institute of Scientific and Technical Information of China (English)
Deng Li; Chen Ai-Xi; Chen De-Hai; Huang Ke-Lin
2008-01-01
Following the theoretical protocol described by Fortescue and Lo [Fortescue B and Lo H K 2007 Phys. Rev. Lett. 98 260501], we present a scheme in which one can distill maximally entangled bi-partite states from a tri-partite W state with cavity QED. Our scheme enables the concrete physical system to realize its protocol. In our scheme, the rate distillation also asymptotically approaches one. Based on the present cavity QED techniques, we discuss the experimental feasibility.
Multi-particle entanglement under asymptotic positive partial transpose preserving operations
Ishizaka, S; Plenio, M. B.
2005-01-01
We demonstrate that even under positive partial transpose preserving operations in an asymptotic setting GHZ and W states are not reversibly interconvertible. We investigate the structure of minimal reversible entanglement generating set (MREGS) for tri-partite states under positive partial transpose (ppt) preserving operations. We demonstrate that the set consisting of W and EPR states alone cannot be an MREGS. In this context we prove the surprising result that the relative entropy of entan...
Completely mixed state is a critical point for three-qubit entanglement
Energy Technology Data Exchange (ETDEWEB)
Tamaryan, Sayatnova, E-mail: sayat@mail.yerphi.am [Department of Theoretical Physics, A. Alikhanyan National Laboratory, Yerevan (Armenia)
2011-06-06
Pure three-qubit states have five algebraically independent and one algebraically dependent polynomial invariants under local unitary transformations and an arbitrary entanglement measure is a function of these six invariants. It is shown that if the reduced density operator of a some qubit is a multiple of the unit operator, than the geometric entanglement measure of the pure three-qubit state is absolutely independent of the polynomial invariants and is a constant for such tripartite states. Hence a one-particle completely mixed state is a critical point for the geometric measure of entanglement. -- Highlights: → Geometric measure of pure three-qubits is expressed in terms of polynomial invariants. → When one Bloch vector is zero the measure is independent of the remaining invariants. → Hence a one-particle completely mixed state is a critical point for the geometric measure. → The existence of the critical points is an inherent feature of the entanglement.
Quantum entanglement and quantum operation
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
It is a simple introduction to quantum entanglement and quantum operations. The authors focus on some applications of quantum entanglement and relations between two-qubit entangled states and unitary operations. It includes remote state preparation by using any pure entangled states, nonlocal operation implementation using entangled states, entanglement capacity of two-qubit gates and two-qubit gates construction.
The emergence of typical entanglement in two-party random processes
Energy Technology Data Exchange (ETDEWEB)
Dahlsten, O C O [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, South Kensington London, SW7 2PG (United Kingdom); Oliveira, R [Instituto Nacional de Matematica Pura e Aplicada-IMPA Estrada Dona Castorina, 110 Jardim Botanico 22460-320, Rio de Janeiro, RJ (Brazil); Plenio, M B [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, South Kensington London, SW7 2PG (United Kingdom)
2007-07-13
We investigate the entanglement within a system undergoing a random, local process. We find that there is initially a phase of very fast generation and spread of entanglement. At the end of this phase the entanglement is typically maximal. In Oliveira et al (2007 Phys. Rev. Lett. 98 130502) we proved that the maximal entanglement is reached to a fixed arbitrary accuracy within O(N{sup 3}) steps, where N is the total number of qubits. Here we provide a detailed and more pedagogical proof. We demonstrate that one can use the so-called stabilizer gates to simulate this process efficiently on a classical computer. Furthermore, we discuss three ways of identifying the transition from the phase of rapid spread of entanglement to the stationary phase: (i) the time when saturation of the maximal entanglement is achieved, (ii) the cutoff moment, when the entanglement probability distribution is practically stationary, and (iii) the moment block entanglement exhibits volume scaling. We furthermore investigate the mixed state and multipartite setting. Numerically, we find that the mutual information appears to behave similarly to the quantum correlations and that there is a well-behaved phase-space flow of entanglement properties towards an equilibrium. We describe how the emergence of typical entanglement can be used to create a much simpler tripartite entanglement description. The results form a bridge between certain abstract results concerning typical (also known as generic) entanglement relative to an unbiased distribution on pure states and the more physical picture of distributions emerging from random local interactions.
Ma, Chen-Te
2015-01-01
Entanglement is a physical phenomenon that each state cannot be described individually. Entanglement entropy gives quantitative understanding to the entanglement. We use decomposition of the Hilbert space to discuss properties of the entanglement. Therefore, partial trace operator becomes important to define the reduced density matrix from different centers, which commutes with all elements in the Hilbert space, corresponding to different entanglement choices or different observations on entangling surface. Entanglement entropy is expected to satisfy the strong subadditivity. We discuss decomposition of the Hilbert space for the strong subadditivity and other related inequalities. The entanglement entropy with centers can be computed from the Hamitonian formulations systematically, provided that we know wavefunctional. In the Hamitonian formulation, it is easier to obtain symmetry structure. We consider massless $p$-form theory as an example. The massless $p$-form theory in ($2p+2)$-dimensions has global symm...
Faithful Squashed Entanglement
Brandao, Fernando G S L; Yard, Jon
2010-01-01
Squashed entanglement is a measure for the entanglement of bipartite quantum states. In this paper we present a lower bound for squashed entanglement in terms of the LOCC distance to the set of separable states. This implies that squashed entanglement is faithful, that is, it is strictly positive if and only if the state is entangled. We derive the lower bound on squashed entanglement from a lower bound on the quantum conditional mutual information which is used to define squashed entanglement. The quantum conditional mutual information corresponds to the amount by which strong subadditivity of von Neumann entropy fails to be saturated. Our result therefore sheds light on the structure of states that almost satisfy strong subadditivity with equality. The proof is based on two recent results from quantum information theory: the operational interpretation of the quantum mutual information as the optimal rate for state redistribution and the interpretation of the regularised relative entropy of entanglement as a...
Higher-curvature Corrections to Holographic Entanglement with Momentum Relaxation
Tanhayi, M Reza
2016-01-01
We study the effects of Gauss-Bonnet corrections on entanglement entropy and mutual information in the holographic model with momentum relaxation. There are in fact two kinds of deformation in the states of conformal field theory in this model: the higher-curvature terms, which could address the low-energy quantum excitation corrections, and the deformation due to scalar fields, which are responsible for the momentum conservation breaking. We use holographic methods to obtain the corresponding changes due to these deformations in the finite and universal parts of entanglement entropy for strip geometry. Holographic calculation indicates that mutual and tripartite information undergo a transition beyond which they identically change their values. We find that the behavior of transition curves depends on the sign of the Gauss-Bonnet coupling $\\lambda$. The transition for $\\lambda>0$ takes place in larger separation of subsystems than that of $\\lambda<0$.
Properties of entanglement molecules
Energy Technology Data Exchange (ETDEWEB)
Huang Yanxia [Department of Physics, Hubei Normal University, Huangshi 435002 (China); Zhan Mingsheng [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China)
2004-09-14
We propose a scheme to prepare a certain kind of N-atom entangled state that allows us to construct some possible types of entanglement molecules via cavity QED. The entanglement properties of entanglement molecules vertical bar {psi}{sub N}){sub {alpha}} are studied with respect to bipartite entanglement that is robust against the disposal of particles and are compared with entanglement molecules {rho}{sub I} introduced in Dur (2001 Phys. Rev. A 63 020303). We also give the maximal amount of entanglement achievable for two particular situations in two possible configurations. Meanwhile, we investigate the entanglement properties of entanglement molecules vertical bar {psi}{sub N}){sub {alpha}} in terms of local measurement using the maximum connectedness and persistency and compare them with other kinds of N-atom entangled states such as |GHZ), vertical bar W{sub N}) and vertical bar {phi}{sub N}). We show that the maximal value N - 1 of the persistency of the state vertical bar {psi}{sub N}){sub {alpha}} corresponds to the case that all atoms are pairwise entangled. If any pair of atoms {rho}{sub ij} is disentangled, the entanglement of the state vertical bar {psi}{sub N}){sub {alpha}} is very easy to destroy by a single local measurement.
Properties of entanglement molecules
Huang, Yan-Xia; Zhan, Ming-Sheng
2004-09-01
We propose a scheme to prepare a certain kind of N-atom entangled state that allows us to construct some possible types of entanglement molecules via cavity QED. The entanglement properties of entanglement molecules |psgrNrangagr are studied with respect to bipartite entanglement that is robust against the disposal of particles and are compared with entanglement molecules rgrI introduced in Dur (2001 Phys. Rev. A 63 020303). We also give the maximal amount of entanglement achievable for two particular situations in two possible configurations. Meanwhile, we investigate the entanglement properties of entanglement molecules |psgrNrangagr in terms of local measurement using the maximum connectedness and persistency and compare them with other kinds of N-atom entangled states such as |GHZrang, |WNrang and |phgrNrang. We show that the maximal value N - 1 of the persistency of the state |psgrNrangagr corresponds to the case that all atoms are pairwise entangled. If any pair of atoms rgrij is disentangled, the entanglement of the state |psgrNrangagr is very easy to destroy by a single local measurement.
Limitations to sharing entanglement
Kim, Jeong San; Sanders, Barry C
2011-01-01
We discuss limitations to sharing entanglement known as monogamy of entanglement. Our pedagogical approach commences with simple examples of limited entanglement sharing for pure three-qubit states and progresses to the more general case of mixed-state monogamy relations with multiple qudits.
On Clark-Watson's tripartite model of anxiety and depression.
Bedford, A
1997-02-01
Clark and Watson's tripartite model of anxiety and depression symptoms is reinterpreted using their data. It is suggested that a parsimonious view of the factor loadings is a three-factor structure of "general psychological distress," "high positive affect," and "somatic anxiety."
Policy modes for climate change: the role of tripartite partnerships
Kolk, A.; Pinkse, J.
2010-01-01
This position paper provides an initial overview of the role of tripartite partnerships for climate change in the broader framework of policy options available to address the issue. First, we will position partnerships in relation to other policy modes for climate change, including emissions trading
Quantum Teleportation of Tripartite Arbitrary State via W State
Institute of Scientific and Technical Information of China (English)
XUE Zheng-Yuan; YI You-Min; CAO Zhuo-Liang
2005-01-01
A scheme of teleportation of a tripartite state via W state is suggested. The W state serves as quantum channels. Standard Bell-state measurements and Von Neumann measurements are performed. After the sender operates the measurements and informs the receiver her results, he can reconstruct the original state by the corresponding unitary transformation. The probability of the successful teleportation is also obtained.
Towards an Urbanism of Entanglement
DEFF Research Database (Denmark)
Tietjen, Anne
2009-01-01
both with regard to an academic research context and with regard to the context of urban development practice is stressed. Based on actor-network-theory (ANT), it is outlined how site knowledge and site knowledge production can be understood and further articulated with regard to a transdisciplinary...... of spatial equality throughout Denmark to an ideal of balanced development. This shift dates back to the 1980s but has gained new topicality in light of increased spatial inequality. Current Danish spatial policy targets the two large city regions around Copenhagen and in East Jutland as the engines...... than being an autonomous field of work urban design is a transdisciplinary field that connects multiple practice and knowledge forms. Finally, an urbanism of entanglement brings about design interventions which stress performativity and connectivity. An urbanism of entanglement proposes new...
Spectral conditions for entanglement witnesses versus bound entanglement
Chruściński, Dariusz; Kossakowski, Andrzej; Sarbicki, Gniewomir
2009-10-01
It is shown that entanglement witnesses constructed via the family of spectral conditions are decomposable, i.e., cannot be used to detect bound entanglement. It supports several observations that bound entanglement reveals highly nonspectral features.
Spectral conditions for entanglement witnesses vs. bound entanglement
Chruscinski, Dariusz; Sarbicki, Gniewomir
2009-01-01
It is shown that entanglement witnesses constructed via the family of spectral conditions are decomposable, i.e. cannot be used to detect bound entanglement. It supports several observations that bound entanglement reveals highly non-spectral features.
Creation of Multipartite Entanglement and Entanglement Transfer via Heisenberg Interaction
Institute of Scientific and Technical Information of China (English)
ZHANG Yong; CAO Wan-Cang; LONG Gui-Lu
2005-01-01
@@ We discuss how to create multipartite entanglement. By coupling a new particle with entangled particles via Heisenberg interaction between two particles, we can prepare three-particle entangled states. For some special coupling strength, entanglement transfer can be achieved from entangled pair AB to particles A and C that never interact by coupling particle C with particle B, which can be used to create entanglement between two separated particles.
Theory of entanglement and entanglement-assisted communication
Bennett, Charles H.
2011-03-01
Protocols such as quantum teleportation and measurement-based quantum computation highlight the importance of entanglement as a resource to be quantified and husbanded. Unlike classical shared randomness, entanglement has a profound effect on the capacity of quantum channels: a channel's entanglement-assisted capacity can be much greater than its unassisted capacity, and in any case is given by much a simpler formula, paralleling Shannon's original formula for the capacity of a classical channel. We review the differences between entanglement and weaker forms of correlation, and the theory of entanglement distillation and entanglement-assisted communication, including the role of strong forms of entanglement such as entanglement-embezzling states.
Krenn, Mario; Lahiri, Mayukh; Zeilinger, Anton
2016-01-01
Quantum entanglement is one of the most prominent features of quantum mechanics and forms the basis of quantum information technologies. Here we present a novel method for the creation of quantum entanglement in multipartite and high-dimensional photonic systems, exploiting an idea introduced by the group of Leonard Mandel 25 years ago. The two ingredients are 1) superposition of photon pairs with different origins and 2) aligning photon paths such that they emerge from the same output mode. We explain examples for the creation of various classes of multiphoton entanglement encoded in polarization as well as in high-dimensional Hilbert spaces -- starting only from separable (non-entangled) photon pairs. For two photons, we show how arbitrary high-dimensional entanglement can be created. Interestingly, a common source for two-photon polarization entanglement is found as a special case. We discovered the technique by analyzing the output of a computer algorithm designing quantum experiments, and generalized it ...
Thermalization of entanglement.
Zhang, Liangsheng; Kim, Hyungwon; Huse, David A
2015-06-01
We explore the dynamics of the entanglement entropy near equilibrium in highly entangled pure states of two quantum-chaotic spin chains undergoing unitary time evolution. We examine the relaxation to equilibrium from initial states with either less or more entanglement entropy than the equilibrium value, as well as the dynamics of the spontaneous fluctuations of the entanglement that occur in equilibrium. For the spin chain with a time-independent Hamiltonian and thus an extensive conserved energy, we find slow relaxation of the entanglement entropy near equilibration. Such slow relaxation is absent in a Floquet spin chain with a Hamiltonian that is periodic in time and thus has no local conservation law. Therefore, we argue that slow diffusive energy transport is responsible for the slow relaxation of the entanglement entropy in the Hamiltonian system.
Entanglement of two hybrid optomechanical cavities composed of BEC atoms under Bell detection
Eghbali-Arani, M.; Ameri, V.
2017-02-01
In this paper, firstly, we consider bipartite entanglement between each part of an optomechanical cavity composed of one-dimensional Bose-Einstein condensate (BEC). We investigate atomic collision on the behaviour of the BEC in the week photon-atom coupling constant and use Bogoliubov approximation for the BEC. Secondly under above condition, we propose a scheme for entanglement swapping protocol which involves tripartite systems. In our investigation, we consider a scenario where BECs, moving mirrors, and optical cavity modes are given in a Gaussian state with a covariance matrix. By applying the Bell measurement to the output optical field modes, we show how the remote entanglement between two BECs, two moving mirrors, and BEC-mirror modes in different optomechanical cavity can be generated.
Quantum entanglement and quantum operation
Institute of Scientific and Technical Information of China (English)
2008-01-01
It is a simple introduction to quantum entanglement and quantum operations.The authors focus on some applications of quantum entanglement and relations between two-qubit entangled states and unitary operations.It includes remote state preparation by using any pure entangled states,nonlocal operation implementation using entangled states,entanglement capacity of two-qubit gates and two-qubit gates construction.
Xiao, Yunlong; Jing, Naihuan; Li-Jost, Xianqing; Fei, Shao-Ming
2016-08-01
We present several criteria for genuine multipartite entanglement from universal uncertainty relations based on majorization theory. Under non-negative Schur-concave functions, the vector-type uncertainty relation generates a family of infinitely many detectors to check genuine multipartite entanglement. We also introduce the concept of k-separable circles via geometric distance for probability vectors, which include at most ( k-1)-separable states. The entanglement witness is also generalized to a universal entanglement witness which is able to detect the k-separable states more accurately.
Collective Uncertainty Entanglement Test
Rudnicki, Łukasz; Życzkowski, Karol
2011-01-01
For a given pure state of a composite quantum system we analyze the product of its projections onto a set of locally orthogonal separable pure states. We derive a bound for this product analogous to the entropic uncertainty relations. For bipartite systems the bound is saturated for maximally entangled states and it allows us to construct a family of entanglement measures, we shall call collectibility. As these quantities are experimentally accessible, the approach advocated contributes to the task of experimental quantification of quantum entanglement, while for a three-qubit system it is capable to identify the genuine three-party entanglement.
Holographic Quantum Entanglement Negativity
Chaturvedi, Pankaj; Sengupta, Gautam
2016-01-01
We propose a holographic prescription to compute the entanglement negativity for conformal field theories at finite temperatures which exactly reproduces the entanglement negativity for (1+1)- dimensional conformal field theories at finite temperatures dual to (2+1)- dimensional bulk Euclidean BTZ black holes. We observe that the holographic entanglement negativity captures the distillable pure quantum entanglement and is related to the holographic mutual information. The application of our prescription to higher dimensional conformal field theories at finite temperatures within a $AdS_{d+1}/CFT_{d}$ scenario involving dual bulk $AdS$-Schwarzschild black holes is discussed to elucidate the universality of our conjecture.
An examination of the tripartite model of anxiety and depression and its application to youth.
Laurent, J; Ettelson, R
2001-09-01
The ability to differentiate anxiety and depression has been a topic of discussion in the adult and youth literatures for several decades. The tripartite model of anxiety and depression proposed by L. A. Clark and D. Watson (1991) has helped focus the discussion. In the tripartite model, anxiety is characterized by elevated levels of physiological hyperarousal (PH), depression is characterized by low levels of positive affect (PA), and negative affect (NA) or generalized emotional distress is common to both. The advent of the model led to the development of measures of tripartite constructs and subsequent validity studies. The tripartite model and resultant activity concerning the model was largely devoted to adult samples. However. those interested in anxiety and depression among youth are now incorporating the tripartite model in their work. This paper examines the current influence of the tripartite model in the youth literature, especially with regard to measuring anxiety and depression.
Entanglement and nonextensive statistics
1999-01-01
It is presented a generalization of the von Neumann mutual information in the context of Tsallis' nonextensive statistics. As an example, entanglement between two (two-level) quantum subsystems is discussed. Important changes occur in the generalized mutual information, which measures the degree of entanglement, depending on the entropic index q.
Quantum Entanglement and Teleportation
2011-01-01
Even Einstein has to be wrong sometimes. However, when Einstein was wrong he created a 70 year debate about the strange behavior of quantum mechanics. His debate helped prove topics such as the indeterminacy of particle states, quantum entanglement, and a rather clever use of quantum entanglement known as quantum teleportation.
On Fermionic Entangled State Representation and Fermionic Entangled Wigner Operator
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
By analogy with the bosonic bipartite entangled state we construct fermionic entangled state with the Grassmann numbers. The Wigner operator in the fermionic entangled state representation is introduced, whose marginal distributions are understood in an entangled way. The technique of integration within an ordered product (IWOP) of Fermi operators is used in our discussion.
Continuous variable quantum communication with bright entangled optical beams
Institute of Scientific and Technical Information of China (English)
XIE Chang-de; ZHANG Jing; PAN Qing; JIA Xiao-jun; PENG Kun-chi
2006-01-01
In this paper,we briefly introduce the basic concepts and protocols of continuous variable quantum communication,and then summarize the experimental researches accomplished by our group in this field.The main features of quantum communication systems used in our experiments are:(1) The bright entangled optical beams with the anticorrelated amplitude quadratures and the correlated phase quadratures that serve as the entanglement resources and (2) The Bell-state direct detection systems are utilized in the measurements of quantum entanglement and transmitted signals instead of the usually balanced homodyne detectors.
Dynamics of quantum entanglement
Zyczkowski, K; Horodecki, M; Horodecki, R; Zyczkowski, Karol; Horodecki, Pawel; Horodecki, Michal; Horodecki, Ryszard
2002-01-01
A model of discrete dynamics of entanglement of bipartite quantum state is considered. It involves a global unitary dynamics of the system and periodic actions of local bistochastic or decaying channel. For initially pure states the decay of entanglement is accompanied with an increase of von Neumann entropy of the system. We observe and discuss revivals of entanglement due to unitary interaction of both subsystems. For some mixed states having different marginal entropies of both subsystems (one larger than the global entropy and one smaller) we find an asymmetry in speed of entanglement decay. The entanglement of these states decreases faster, if the depolarizing channel acts on the "classical" subsystem, characterized by smaller marginal entropy.
Locality of quantum entanglement
Guowen, W
2005-01-01
This article presents a local realistic interpretation of quantum entanglement. The entanglement is explained as innate interference between the non-empty state associated with the peaked piece of one particle and the empty states associated with the non-peaked pieces of the others of entangled particles, which inseparably join together. The correlation of the results of measurements on the ensemble of composite entangled systems is related to this kind of interference. Consequently, there is no nonlocal influence between entangled particles in measurements. Particularly, this explanation thus rules out the possibility of quantum teleportation which is nowadays considered as one of cornerstones of quantum information processing. Besides, likewise, communication and computation schemes based on alleged spooky action at a distance are unlikely to be promising.
Quantum entanglement percolation
Siomau, Michael
2016-09-01
Quantum communication demands efficient distribution of quantum entanglement across a network of connected partners. The search for efficient strategies for the entanglement distribution may be based on percolation theory, which describes evolution of network connectivity with respect to some network parameters. In this framework, the probability to establish perfect entanglement between two remote partners decays exponentially with the distance between them before the percolation transition point, which unambiguously defines percolation properties of any classical network or lattice. Here we introduce quantum networks created with local operations and classical communication, which exhibit non-classical percolation transition points leading to striking communication advantages over those offered by the corresponding classical networks. We show, in particular, how to establish perfect entanglement between any two nodes in the simplest possible network—the 1D chain—using imperfectly entangled pairs of qubits.
Entanglement generated by dissipation
Krauter, Hanna; Jensen, Kasper; Wasilewski, Wojciech; Petersen, Jonas M; Cirac, J Ignacio; Polzik, Eugene S
2010-01-01
Entanglement is not only one of the most striking features of Quantum Mechanics but also an essential ingredient in most applications in the field of Quantum Information. Unfortunately, this property is very fragile. In experiments conducted so far, coupling of the system to a quantum mechanical environment, commonly referred to as dissipation, either inhibits entanglement or prevents its generation. In this Letter, we report on an experiment in which dissipation induces entanglement between two atomic objects rather than impairing it. This counter-intuitive effect is achieved by engineering the dissipation by means of laser- and magnetic fields, and leads to entanglement which is very robust and therefore long-lived. Our system consists of two distant macroscopic ensembles containing about 10^{12} atoms coupled to the environment composed of the vacuum modes of the electromagnetic field. The two atomic objects are kept entangled by dissipation at room temperature for about 0.015s. The prospects of using this...
Entanglement and decoherence: fragile and robust entanglement
Novotný, Jaroslav; Jex, Igor
2011-01-01
The destruction of entanglement of open quantum systems by decoherence is investigated in the asymptotic long-time limit. Starting from a general and analytically solvable decoherence model which does not involve any weak-coupling or Markovian assumption it is shown that two fundamentally different classes of entangled states can be distinguished. Quantum states of the first class are fragile against decoherence so that they can be disentangled asymptotically even if coherences between pointer states are still present. Quantum states of the second type are robust against decoherence. Asymptotically they can be disentangled only if also decoherence is perfect. A simple criterion for identifying these two classes on the basis of two-qubit entanglement is presented.
Experimental activation of bound entanglement.
Kaneda, Fumihiro; Shimizu, Ryosuke; Ishizaka, Satoshi; Mitsumori, Yasuyoshi; Kosaka, Hideo; Edamatsu, Keiichi
2012-07-27
Entanglement is one of the essential resources in quantum information and communication technology (QICT). The entanglement thus far explored and applied to QICT has been pure and distillable entanglement. Yet, there is another type of entanglement, called "bound entanglement," which is not distillable by local operations and classical communication. We demonstrate the experimental "activation" of the bound entanglement held in the four-qubit Smolin state, unleashing its immanent entanglement in distillable form, with the help of auxiliary two-qubit entanglement and local operations and classical communication. We anticipate that it opens the way to a new class of QICT applications that utilize more general classes of entanglement than ever, including bound entanglement.
Entanglement negativity in the multiverse
Energy Technology Data Exchange (ETDEWEB)
Kanno, Sugumi [Department of Theoretical Physics and History of Science, University of the Basque Country UPV/EHU, 48080 Bilbao (Spain); IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013, Bilbao (Spain); Laboratory for Quantum Gravity & Strings and Astrophysics, Cosmology & Gravity Center, Department of Mathematics & Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7701 (South Africa); Shock, Jonathan P. [Laboratory for Quantum Gravity & Strings and Astrophysics, Cosmology & Gravity Center, Department of Mathematics & Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7701 (South Africa); National Institute for Theoretical Physics, Private Bag X1, Matieland, 7602 (South Africa); Soda, Jiro [Department of Physics, Kobe University, Kobe 657-8501 (Japan)
2015-03-10
We explore quantum entanglement between two causally disconnected regions in the multiverse. We first consider a free massive scalar field, and compute the entanglement negativity between two causally separated open charts in de Sitter space. The qualitative feature of it turns out to be in agreement with that of the entanglement entropy. We then introduce two observers who determine the entanglement between two causally disconnected de Sitter spaces. When one of the observers remains constrained to a region of the open chart in a de Sitter space, we find that the scale dependence enters into the entanglement. We show that a state which is initially maximally entangled becomes more entangled or less entangled on large scales depending on the mass of the scalar field and recovers the initial entanglement in the small scale limit. We argue that quantum entanglement may provide some evidence for the existence of the multiverse.
Entanglement negativity in the multiverse
Kanno, Sugumi; Soda, Jiro
2014-01-01
We explore quantum entanglement between two causally disconnected regions in the multiverse. We first consider a free massive scalar field, and compute the entanglement negativity between two causally separated open charts in de Sitter space. The qualitative feature of it turns out to be in agreement with that of the entanglement entropy. We then introduce two observers who determine the entanglement between two causally disconnected de Sitter spaces. When one of the observers remains constrained to a region of the open chart in a de Sitter space, we find that the scale dependence enters into the entanglement. We show that a state which is initially maximally entangled becomes more entangled or less entangled on large scales depending on the mass of the scalar field and recovers the initial entanglement in the small scale limit. We argue that quantum entanglement may provide some evidence for the existence of the multiverse.
Entanglement negativity in the multiverse
Kanno, Sugumi; Shock, Jonathan P.; Soda, Jiro
2015-03-01
We explore quantum entanglement between two causally disconnected regions in the multiverse. We first consider a free massive scalar field, and compute the entanglement negativity between two causally separated open charts in de Sitter space. The qualitative feature of it turns out to be in agreement with that of the entanglement entropy. We then introduce two observers who determine the entanglement between two causally disconnected de Sitter spaces. When one of the observers remains constrained to a region of the open chart in a de Sitter space, we find that the scale dependence enters into the entanglement. We show that a state which is initially maximally entangled becomes more entangled or less entangled on large scales depending on the mass of the scalar field and recovers the initial entanglement in the small scale limit. We argue that quantum entanglement may provide some evidence for the existence of the multiverse.
Constructing optimal entanglement witnesses
Chruściński, Dariusz; Pytel, Justyna; Sarbicki, Gniewomir
2009-12-01
We provide a class of indecomposable entanglement witnesses. In 4×4 case, it reproduces the well-known Breuer-Hall witness. We prove that these witnesses are optimal and atomic, i.e., they are able to detect the “weakest” quantum entanglement encoded into states with positive partial transposition. Equivalently, we provide a construction of indecomposable atomic maps in the algebra of 2k×2k complex matrices. It is shown that their structural physical approximations give rise to entanglement breaking channels. This result supports recent conjecture by Korbicz [Phys. Rev. A 78, 062105 (2008)].
Entanglement in Anderson Nanoclusters
Samuelsson, Peter
2007-01-01
We investigate the two-particle spin entanglement in magnetic nanoclusters described by the periodic Anderson model. An entanglement phase diagram is obtained, providing a novel perspective on a central property of magnetic nanoclusters, namely the temperature dependent competition between local Kondo screening and nonlocal Ruderman-Kittel-Kasuya-Yoshida spin ordering. We find that multiparticle entangled states are present for finite magnetic field as well as in the mixed valence regime and away from half filling. Our results emphasize the role of charge fluctuations.
Tripartite Therapy with Older Children: Mutuality in the Relationship of a Parent-Child Attachment
Berlin, Nancy
2008-01-01
This is the last of a series of three papers exploring the use with older children of tripartite psychotherapy--a technique of psychoanalytic psychotherapy of the parent-child relationship with both parent and child in the room together with the therapist. Tripartite psychotherapy merits more attention than it has received. It is a flexible,…
An Evaluation of the Applicability of the Tripartite Constructs to Social Anxiety in Adolescents
Anderson, Emily R.; Veed, Glen J.; Inderbitzen-Nolan, Heidi M.; Hansen, David J.
2010-01-01
The current study examined the tripartite model of anxiety and depression in relation to social phobia in a nonclinical sample of adolescents (ages 13-17). Adolescent/parent dyads participated in a semistructured interview and completed self-report measures of the tripartite constructs and social anxiety. Adolescents gave an impromptu speech, and…
Chin, Eu Gene; Ebesutani, Chad; Young, John
2013-01-01
The tripartite model of anxiety and depression has received strong support among child and adolescent populations. Clinical samples of children and adolescents in these studies, however, have usually been referred for treatment of anxiety and depression. This study investigated the fit of the tripartite model with a complicated sample of…
Institute of Scientific and Technical Information of China (English)
Xi Xiao-Qiang; Liu Wu-Ming
2007-01-01
Based on the calculation of all the pairwise entanglements in the n(n≤6)-qubit Heisenberg ⅩⅩ open chain with system impurity, we find an important result: pairwise entanglement can only be transferred by an entangled pair. The non-nearest pairwise entanglements will have the possibility to exist as long as there has been even number of qubits in their middle. This point indicates that we can obtain longer distance entanglement in a solid system.
Converting Nonclassicality into Entanglement
Killoran, N.; Steinhoff, F. E. S.; Plenio, M. B.
2016-02-01
Quantum mechanics exhibits a wide range of nonclassical features, of which entanglement in multipartite systems takes a central place. In several specific settings, it is well known that nonclassicality (e.g., squeezing, spin squeezing, coherence) can be converted into entanglement. In this work, we present a general framework, based on superposition, for structurally connecting and converting nonclassicality to entanglement. In addition to capturing the previously known results, this framework also allows us to uncover new entanglement convertibility theorems in two broad scenarios, one which is discrete and one which is continuous. In the discrete setting, the classical states can be any finite linearly independent set. For the continuous setting, the pertinent classical states are "symmetric coherent states," connected with symmetric representations of the group S U (K ). These results generalize and link convertibility properties from the resource theory of coherence, spin coherent states, and optical coherent states, while also revealing important connections between local and nonlocal pictures of nonclassicality.
D'Ambrosio, Vincenzo; Carvacho, Gonzalo; Graffitti, Francesco; Vitelli, Chiara; Piccirillo, Bruno; Marrucci, Lorenzo; Sciarrino, Fabio
2016-09-01
Light beams having a vectorial field structure, or polarization, that varies over the transverse profile and a central optical singularity are called vector vortex (VV) beams and may exhibit specific properties such as focusing into "light needles" or rotation invariance. VV beams have already found applications in areas ranging from microscopy to metrology, optical trapping, nano-optics, and quantum communication. Individual photons in such beams exhibit a form of single-particle quantum entanglement between different degrees of freedom. On the other hand, the quantum states of two photons can be also entangled with each other. Here, we combine these two concepts and demonstrate the generation of quantum entanglement between two photons that are both in VV states: a form of entanglement between two complex vectorial fields. This result may lead to quantum-enhanced applications of VV beams as well as to quantum information protocols fully exploiting the vectorial features of light.
Converting Nonclassicality into Entanglement.
Killoran, N; Steinhoff, F E S; Plenio, M B
2016-02-26
Quantum mechanics exhibits a wide range of nonclassical features, of which entanglement in multipartite systems takes a central place. In several specific settings, it is well known that nonclassicality (e.g., squeezing, spin squeezing, coherence) can be converted into entanglement. In this work, we present a general framework, based on superposition, for structurally connecting and converting nonclassicality to entanglement. In addition to capturing the previously known results, this framework also allows us to uncover new entanglement convertibility theorems in two broad scenarios, one which is discrete and one which is continuous. In the discrete setting, the classical states can be any finite linearly independent set. For the continuous setting, the pertinent classical states are "symmetric coherent states," connected with symmetric representations of the group SU(K). These results generalize and link convertibility properties from the resource theory of coherence, spin coherent states, and optical coherent states, while also revealing important connections between local and nonlocal pictures of nonclassicality.
Kus, M; Kus, Marek; Zyczkowski, Karol
2001-01-01
Geometric properties of the set of quantum entangled states are investigated. We propose an explicit method to compute the dimension of local orbits for any mixed state of the general K x M problem. In particular we analyze the simplest case of 2 x 2 problem finding a stratification of the 6-D set of N=4 pure states. The set of effectively different states (which cannot be related by local transformations) is one dimensional. It starts at a 3-D manifold of maximally entangled states, cuts generic 5-D manifolds of entangled states (labeled by non-zero values of the entropy of entanglement), and ends at a single 4-D manifold of separable states.
Entanglement in neutrino oscillations
Energy Technology Data Exchange (ETDEWEB)
Blasone, M.; Dell' Anno, F.; De Siena, S.; Illuminati, F. [Universita degli Studi di Salerno Via Ponte don Melillon, Dipt. di Matematica e Informatica, Fisciano SA (Italy); INFN Sezione di Napoli, Gruppo collegato di Salerno - Baronissi SA (Italy); Dell' Anno, F.; De Siena, S.; Illuminati, F. [CNR-INFM Coherentia - Napoli (Italy); Blasone, M. [ISI Foundation for Scientific Interchange, Torino (Italy)
2009-03-15
Flavor oscillations in elementary particle physics are related to multimode entanglement of single-particle states. We show that mode entanglement can be expressed in terms of flavor transition probabilities, and therefore that single-particle entangled states acquire a precise operational characterization in the context of particle mixing. We treat in detail the physically relevant cases of two- and three-flavor neutrino oscillations, including the effective measure of CP violation. We discuss experimental schemes for the transfer of the quantum information encoded in single-neutrino states to spatially delocalized two-flavor charged-lepton states, thus showing, at least in principle, that single-particle entangled states of neutrino mixing are legitimate physical resources for quantum information tasks. (authors)
Covariant holographic entanglement negativity
Chaturvedi, Pankaj; Sengupta, Gautam
2016-01-01
We conjecture a holographic prescription for the covariant entanglement negativity of $d$-dimensional conformal field theories dual to non static bulk $AdS_{d+1}$ gravitational configurations in the framework of the $AdS/CFT$ correspondence. Application of our conjecture to a $AdS_3/CFT_2$ scenario involving bulk rotating BTZ black holes exactly reproduces the entanglement negativity of the corresponding $(1+1)$ dimensional conformal field theories and precisely captures the distillable quantum entanglement. Interestingly our conjecture for the scenario involving dual bulk extremal rotating BTZ black holes also accurately leads to the entanglement negativity for the chiral half of the corresponding $(1+1)$ dimensional conformal field theory at zero temperature.
DEFF Research Database (Denmark)
Ateniese, Giuseppe; Dagdelen, Özgür; Damgård, Ivan Bjerre
2012-01-01
Entangled cloud storage enables a set of clients {P_i} to “entangle” their files {f_i} into a single clew c to be stored by a (potentially malicious) cloud provider S. The entanglement makes it impossible to modify or delete significant part of the clew without affecting all files in c. A clew...... recover their files. We provide theoretical foundations for entangled cloud storage, introducing the notion of an entangled encoding scheme that guarantees strong security requirements capturing the properties above. We also give a concrete construction based on privacy-preserving polynomial interpolation......, along with protocols for using the encoding scheme in practice. Protocols for cloud storage find application in the cloud setting, where clients store their files on a remote server and need to be ensured that the cloud provider will not delete their data illegitimately. Current solutions, e.g., based...
Cosmological quantum entanglement
Martin-Martinez, Eduardo
2012-01-01
We review recent literature on the connection between quantum entanglement and cosmology, with an emphasis on the context of expanding universes. We discuss recent theoretical results reporting on the production of entanglement in quantum fields due to the expansion of the underlying spacetime. We explore how these results are affected by the statistics of the field (bosonic or fermionic), the type of expansion (de Sitter or asymptotically stationary), and the coupling to spacetime curvature (conformal or minimal). We then consider the extraction of entanglement from a quantum field by coupling to local detectors and how this procedure can be used to distinguish curvature from heating by their entanglement signature. We review the role played by quantum fluctuations in the early universe in nucleating the formation of galaxies and other cosmic structures through their conversion into classical density anisotropies during and after inflation. We report on current literature attempting to account for this trans...
Holographic Entanglement Entropy
Rangamani, Mukund
2016-01-01
We review the developments in the past decade on holographic entanglement entropy, a subject that has garnered much attention owing to its potential to teach us about the emergence of spacetime in holography. We provide an introduction to the concept of entanglement entropy in quantum field theories, review the holographic proposals for computing the same, providing some justification for where these proposals arise from in the first two parts. The final part addresses recent developments linking entanglement and geometry. We provide an overview of the various arguments and technical developments that teach us how to use field theory entanglement to detect geometry. Our discussion is by design eclectic; we have chosen to focus on developments that appear to us most promising for further insights into the holographic map. This is a preliminary draft of a few chapters of a book which will appear sometime in the near future, to be published by Springer. The book in addition contains a discussion of application o...
Gaussian Intrinsic Entanglement
Mišta, Ladislav; Tatham, Richard
2016-12-01
We introduce a cryptographically motivated quantifier of entanglement in bipartite Gaussian systems called Gaussian intrinsic entanglement (GIE). The GIE is defined as the optimized mutual information of a Gaussian distribution of outcomes of measurements on parts of a system, conditioned on the outcomes of a measurement on a purifying subsystem. We show that GIE vanishes only on separable states and exhibits monotonicity under Gaussian local trace-preserving operations and classical communication. In the two-mode case, we compute GIE for all pure states as well as for several important classes of symmetric and asymmetric mixed states. Surprisingly, in all of these cases, GIE is equal to Gaussian Rényi-2 entanglement. As GIE is operationally associated with the secret-key agreement protocol and can be computed for several important classes of states, it offers a compromise between computable and physically meaningful entanglement quantifiers.
Multipartite Entanglement and Firewalls
Luo, Shengqiao; Albrecht, Andreas
2016-01-01
Black holes offer an exciting area to explore the nature of quantum gravity. The classic work on Hawking radiation indicates that black holes should decay via quantum effects, but our ideas about how this might work at a technical level are incomplete. Recently Almheiri-Marolf-Polchinski-Sully (AMPS) have noted an apparent paradox in reconciling fundamental properties of quantum mechanics with standard beliefs about black holes. One way to resolve the paradox is to postulate the existence of a "firewall" inside the black hole horizon which prevents objects from falling smoothly toward the singularity. A fundamental limitation on the behavior of quantum entanglement known as "monogamy" plays a key role in the AMPS argument. Our goal is to study and apply many-body entanglement theory to consider the entanglement among different parts of Hawking radiation and black holes. Using the multipartite entanglement measure called negativity, we identify an example which could change the AMPS accounting of quantum entan...
Preparation of entangled squeezed states and quantification of their entanglement
Institute of Scientific and Technical Information of China (English)
蔡新华; 匡乐满
2002-01-01
We propose a scheme for generating bipartite and multipartite entangled squeezed states via the Jaynes-Cummingsmodel with large detuning. Bipartite entanglement of these entangled states is quantified by the concurrence. We alsouse the N-tangle to compute multipartite entanglement of these multipartite entangled squeezed states. Finally wediscuss two limiting cases which arise from r → oo and r → 0, in which the multipartite entangled squeezed statereduces correspondingly into an N-qubit Greenberger-Horne-Zeilinger state and an N-qubit W state.
Entanglement is Sometimes Enough
Qian, X -F
2013-01-01
For many decades the word "entanglement" has been firmly attached to the world of quantum mechanics. So is the phrase "Bell violation". Here we show, without contradicting quantum mechanics, that classical non-deterministic fields also provide a natural basis for entanglement and Bell analyses. Surprisingly, such fields are not eliminated by the Clauser-Horne-Shimony-Holt Bell violation test as viable alternatives to quantum theory. An experimental setup for verification is proposed.
Institute of Scientific and Technical Information of China (English)
Shun-long Luo; You-feng Luo
2003-01-01
In quantum mechanics, it is long recognized that there exist correlations between observables which are much stronger than the classical ones. These correlations are usually called entanglement, and cannot be accounted for by classical theory. In this paper, we will study correlations between observables in terms of covariance and the Wigner-Yanase correlation, and compare their merits in characterizing entanglement. We will show that the Wigner-Yanase correlation has some advantages over the conventional covariance.
Tensor Rank and Stochastic Entanglement Catalysis for Multipartite Pure States
Chen, Lin; Duan, Runyao; Ji, Zhengfeng; Winter, Andreas
2010-01-01
The tensor rank (aka generalized Schmidt rank) of multipartite pure states plays an important role in the study of entanglement classifications and transformations. We employ powerful tools from the theory of homogeneous polynomials to investigate the tensor rank of symmetric states such as the tripartite state $\\ket{W_3}=\\tfrac{1}{\\sqrt{3}}(\\ket{100}+\\ket{010}+\\ket{001})$ and its $N$-partite generalization $\\ket{W_N}$. Previous tensor rank estimates are dramatically improved and we show that (i) three copies of $\\ket{W_3}$ has rank either 15 or 16, (ii) two copies of $\\ket{W_N}$ has rank $3N-2$, and (iii) $n$ copies of $\\ket{W_N}$ has rank O(N). A remarkable consequence of these results is that certain multipartite transformations, impossible even probabilistically, can become possible when performed in multiple copy bunches or when assisted by some catalyzing state. This novel effect is impossible for bipartite pure states.
Multipartite entanglement and firewalls
Luo, Shengqiao; Stoltenberg, Henry; Albrecht, Andreas
2017-03-01
Black holes offer an exciting area to explore the nature of quantum gravity. The classic work on Hawking radiation indicates that black holes should decay via quantum effects, but our ideas about how this might work at a technical level are incomplete. Recently Almheiri-Marolf-Polchinski-Sully (AMPS) have noted an apparent paradox in reconciling fundamental properties of quantum mechanics with standard beliefs about black holes. One way to resolve the paradox is to postulate the existence of a "firewall" inside the black hole horizon which prevents objects from falling smoothly toward the singularity. A fundamental limitation on the behavior of quantum entanglement known as "monogamy" plays a key role in the AMPS argument. Our goal is to study and apply many-body entanglement theory to consider the entanglement among different parts of Hawking radiation and black holes. Using the multipartite entanglement measure called negativity, we identify an example which could change the AMPS accounting of quantum entanglement and perhaps eliminate the need for a firewall. Specifically, we constructed a toy model for black hole decay which has different entanglement behavior than that assumed by AMPS. We discuss the additional steps that would be needed to bring lessons from our toy model to our understanding of realistic black holes.
Adesso, G; Serafini, A; Adesso, Gerardo; Illuminati, Fabrizio; Serafini, Alessio
2005-01-01
We present a complete analysis of multipartite entanglement of three-mode Gaussian states of continuous variable systems. We derive standard forms which characterize the covariance matrix of pure and mixed three-mode Gaussian states up to local unitary operations, showing that the local entropies of pure Gaussian states are bound to fulfill a relationship which is stricter than the general Araki-Lieb inequality. Quantum correlations will be quantified by a proper convex roof extension of the squared logarithmic negativity (the contangle), satisfying a monogamy relation for multimode Gaussian states, whose proof will be reviewed and elucidated. The residual contangle, emerging from the monogamy inequality, is an entanglement monotone under Gaussian local operations and classical communication and defines a measure of genuine tripartite entanglement. We analytically determine the residual contangle for arbitrary pure three-mode Gaussian states and study the distribution of quantum correlations for such states. ...
Entanglement Swapping: Entangling Atoms That Never Interacted
Guerra, E S
2005-01-01
In this paper we discuss four different proposals of entangling atomic states of particles which have never interacted. The experimental realization proposed makes use of the interaction of Rydberg atoms with a micromaser cavity prepared in either a coherent state or in a superposition of the zero and one field Fock states. We consider atoms in either a three-level cascade or lambda configuration
Entanglement properties in a system of a pairwise entangled state
Institute of Scientific and Technical Information of China (English)
Liu Tang-Kun; Cheng Wei-Wen; Shan Chuan-Jia; Gao Yun-Feng; Wang Ji-Suo
2007-01-01
Based on the quantum information theory, this paper has investigated the entanglement properties of a system which is composed of the two entangled two-level atoms interacting with the two-mode entangled coherent fields. The influences of the strength of light field and the two parameters of entanglement between the two-mode fields on the field entropy and on the negative eigenvalues of partial transposition of density matrix are discussed by using numerical calculations. The result shows that the entanglement properties in a system of a pairwise entangled states can be controlled by appropriately choosing the two parameters of entanglement between the two-mode entangled coherent fields and the strength of two light fields respectively.
Entanglement entropy and entanglement spectrum of the Kitaev model.
Yao, Hong; Qi, Xiao-Liang
2010-08-20
In this letter, we obtain an exact formula for the entanglement entropy of the ground state and all excited states of the Kitaev model. Remarkably, the entanglement entropy can be expressed in a simple separable form S = SG+SF, with SF the entanglement entropy of a free Majorana fermion system and SG that of a Z2 gauge field. The Z2 gauge field part contributes to the universal "topological entanglement entropy" of the ground state while the fermion part is responsible for the nonlocal entanglement carried by the Z2 vortices (visons) in the non-Abelian phase. Our result also enables the calculation of the entire entanglement spectrum and the more general Renyi entropy of the Kitaev model. Based on our results we propose a new quantity to characterize topologically ordered states--the capacity of entanglement, which can distinguish the st ates with and without topologically protected gapless entanglement spectrum.
Entanglement swapping of two arbitrarily degraded entangled states
Kirby, Brian T.; Santra, Siddhartha; Malinovsky, Vladimir S.; Brodsky, Michael
2016-07-01
We consider entanglement swapping, a key component of quantum network operations and entanglement distribution. Pure entangled states, which are the desired input to the swapping protocol, are typically mixed by environmental interactions, causing a reduction in their degree of entanglement. Thus an understanding of entanglement swapping with partially mixed states is of importance. Here we present a general analytical solution for entanglement swapping of arbitrary two-qubit states. Our result provides a comprehensive method for analyzing entanglement swapping in quantum networks. First, we show that the concurrence of a partially mixed state is conserved when this state is swapped with a Bell state. Then, we find upper and lower bounds on the concurrence of the state resulting from entanglement swapping for various classes of input states. Finally, we determine a general relationship between the ranks of the initial states and the rank of the final state after swapping.
Entanglement required in achieving entanglement-assisted channel capacities
Bowen, G
2002-01-01
Entanglement shared between the two ends of a quantum communication channel has been shown to be a useful resource in increasing both the quantum and classical capacities for these channels. The entanglement-assisted capacities were derived assuming an unlimited amount of shared entanglement per channel use. In this paper, bounds are derived on the minimum amount of entanglement required per use of a channel, in order to asymptotically achieve the capacity. This is achieved by introducing a class of entanglement-assisted quantum codes. Codes for classes of qubit channels are shown to achieve the quantum entanglement-assisted channel capacity when an amount of shared entanglement per channel given by, E = 1 - Q_E, is provided. It is also shown that for very noisy channels, as the capacities become small, the amount of required entanglement converges for the classical and quantum capacities.
Nuclear shell effect and collinear tripartition of nuclei
Nasirov, A K; Tashkhodjaev, R B
2014-01-01
A possibility of formation of the three reaction products having comparable masses at the spontaneous fission of $^{252}$Cf is theoretically explored. This work is aimed to study the mechanism leading to observation of the reaction products with masses $M_1=$136---140 and $M_2=$68---72 in coincidence by the FOBOS group in JINR. The same type of ternary fission decay has been observed in the reaction $^{235}$U(n$_{\\rm th}$,fff). The potential energy surface for the ternary system forming a collinear nuclear chain is calculated for the wide range of mass and charge numbers of constituent nuclei. The results of the PES for the tripartition of $^{252}$Cf(sf,fff) shows, that we have favorable dynamical conditions for the formation of fragments with mass combinations of clusters $^{68-70}$Ni with $^{130-132}$Sn and with missing cluster $^{48-52}$Ca.
Nuclear shell effect and collinear tripartition of nuclei
Indian Academy of Sciences (India)
Avazbek K Nasirov; Wolfram von Oertzen; Rustam B Tashkhodjaev
2015-08-01
A possibility for the formation of three reaction products having comparable masses at the spontaneous fission of 252Cf is theoretically explored. This work is aimed to study the mechanism leading to the observation of the reaction products with masses $M_{1}$ = 136–140 and $M_{2}$ = 68–72 in coincidence with the FOBOS group in JINR. The same type of ternary fission decay has been observed in the 235U(nth, fff) reaction. The potential energy surface (PES) for the ternary system forming a collinear nuclear chain is calculated for a wide range of masses and charge numbers of the constituent nuclei. The results of the PES for the tripartition of 252Cf(sf, fff) allows us to establish dynamical conditions leading to the formation of fragments with mass combinations of clusters 68−70Ni with 130−132Sn and with the missing cluster 48−52Ca.
Literature, Society And The Writer In Tripartite Unity
Directory of Open Access Journals (Sweden)
George Nworah Anaso
2014-08-01
Full Text Available The proactive unity of purpose between Literature, society and the writer is the main focus of this paper. Writers use Literature to address various important themes or the goings on in the society, with the purpose of edifying its virtues and condemning the vices so as to adulate the good deeds or correct the society where it goes wrong. However, this role often exposes the writer to danger and risks from vested interests. The paper nevertheless recommends both local and international actions that could be explored to enhance Literature, society and the writer’s works. It concludes with the submission that with proper political education, the society would be better placed to choose more responsible leaders so that the lots of the society would be better enhanced. In this way the tripartite unity and the full potentials of Literature and writers in society would be realized.
Entanglement diversion and quantum teleportation of entangled coherent states
Institute of Scientific and Technical Information of China (English)
Cai Xin-Hua; Guo Jie-Rong; Nie Jian-Jun; Jia Jin-Ping
2006-01-01
The proposals on entanglement diversion and quantum teleportation of entangled coherent states are presented.In these proposals,the entanglement between two coherent states,|α〉and |-α〉,with the same amplitude but a phase difference of π is utilized as a quantum channel.The processes of the entanglement diversion and the teleportation are achieved by using the 5050 symmetric beam splitters,the phase shifters and the photodetectors with the help of classical information.
A review of the tripartite model for understanding the link between anxiety and depression in youth.
Anderson, Emily R; Hope, Debra A
2008-02-01
Although research from numerous investigations indicates that there is substantial overlap in anxiety and depressive symptoms and comorbid diagnoses in youth, these constructs can be adequately differentiated. Clark and Watson [Clark, L. A. & Watson, D., (1991). Tripartite model of anxiety and depression: Psychometric evidence and taxonomic implications. Journal of Abnormal Psychology, 100, 316-336] proposed a tripartite model to account for the symptom overlap and diagnostic comorbidity between anxiety and depression. This tripartite model posits that anxiety and depression share a common component of negative affect, but can be differentiated by low positive affect associated with depression and high physiological hyperarousal associated with anxiety. The present article reviews initial research which has supported the utility of the tripartite model for explaining the association between anxiety and depression in adult and youth samples. Following that review, more recent investigations which have called into question the applicability of the tripartite constructs for youth are presented. Finally, the paper reviews evidence suggesting that the tripartite factors may not function similarly across all anxiety and depressive disorders. This article concludes by suggesting that more research is necessary with children and adolescents in order to determine the functioning of tripartite constructs across anxiety disorders in youth.
On-chip continuous-variable quantum entanglement
Masada, Genta; Furusawa, Akira
2016-09-01
Entanglement is an essential feature of quantum theory and the core of the majority of quantum information science and technologies. Quantum computing is one of the most important fruits of quantum entanglement and requires not only a bipartite entangled state but also more complicated multipartite entanglement. In previous experimental works to demonstrate various entanglement-based quantum information processing, light has been extensively used. Experiments utilizing such a complicated state need highly complex optical circuits to propagate optical beams and a high level of spatial interference between different light beams to generate quantum entanglement or to efficiently perform balanced homodyne measurement. Current experiments have been performed in conventional free-space optics with large numbers of optical components and a relatively large-sized optical setup. Therefore, they are limited in stability and scalability. Integrated photonics offer new tools and additional capabilities for manipulating light in quantum information technology. Owing to integrated waveguide circuits, it is possible to stabilize and miniaturize complex optical circuits and achieve high interference of light beams. The integrated circuits have been firstly developed for discrete-variable systems and then applied to continuous-variable systems. In this article, we review the currently developed scheme for generation and verification of continuous-variable quantum entanglement such as Einstein-Podolsky-Rosen beams using a photonic chip where waveguide circuits are integrated. This includes balanced homodyne measurement of a squeezed state of light. As a simple example, we also review an experiment for generating discrete-variable quantum entanglement using integrated waveguide circuits.
Adesso, Gerardo; Serafini, Alessio; Illuminati, Fabrizio
2006-03-01
We present a complete analysis of the multipartite entanglement of three-mode Gaussian states of continuous-variable systems. We derive standard forms which characterize the covariance matrix of pure and mixed three-mode Gaussian states up to local unitary operations, showing that the local entropies of pure Gaussian states are bound to fulfill a relationship which is stricter than the general Araki-Lieb inequality. Quantum correlations can be quantified by a proper convex roof extension of the squared logarithmic negativity, the continuous-variable tangle, or contangle. We review and elucidate in detail the proof that in multimode Gaussian states the contangle satisfies a monogamy inequality constraint [G. Adesso and F. Illuminati, New J. Phys8, 15 (2006)]. The residual contangle, emerging from the monogamy inequality, is an entanglement monotone under Gaussian local operations and classical communications and defines a measure of genuine tripartite entanglements. We determine the analytical expression of the residual contangle for arbitrary pure three-mode Gaussian states and study in detail the distribution of quantum correlations in such states. This analysis yields that pure, symmetric states allow for a promiscuous entanglement sharing, having both maximum tripartite entanglement and maximum couplewise entanglement between any pair of modes. We thus name these states GHZ/W states of continuous-variable systems because they are simultaneous continuous-variable counterparts of both the GHZ and the W states of three qubits. We finally consider the effect of decoherence on three-mode Gaussian states, studying the decay of the residual contangle. The GHZ/W states are shown to be maximally robust against losses and thermal noise.
On Relativistic Quantum Information Properties of Entangled Wave Vectors of Massive Fermions
Cafaro, Carlo; Capozziello, Salvatore; Mancini, Stefano
2012-08-01
We study special relativistic effects on the entanglement between either spins or momenta of composite quantum systems of two spin-1/2 massive particles, either indistinguishable or distinguishable, in inertial reference frames in relative motion. For the case of indistinguishable particles, we consider a balanced scenario where the momenta of the pair are well-defined but not maximally entangled in the rest frame while the spins of the pair are described by a one-parameter ( η) family of entangled bipartite states. For the case of distinguishable particles, we consider an unbalanced scenario where the momenta of the pair are well-defined and maximally entangled in the rest frame while the spins of the pair are described by a one-parameter ( ξ) family of non-maximally entangled bipartite states. In both cases, we show that neither the spin-spin ( ss) nor the momentum-momentum ( mm) entanglements quantified by means of Wootters' concurrence are Lorentz invariant quantities: the total amount of entanglement regarded as the sum of these entanglements is not the same in different inertial moving frames. In particular, for any value of the entangling parameters, both ss and mm-entanglements are attenuated by Lorentz transformations and their parametric rates of change with respect to the entanglements observed in a rest frame have the same monotonic behavior. However, for indistinguishable (distinguishable) particles, the change in entanglement for the momenta is (is not) the same as the change in entanglement for spins. As a consequence, in both cases, no entanglement compensation between spin and momentum degrees of freedom occurs.
Entanglement of Superpositions of Orthogonal Maximally Entangled States
Institute of Scientific and Technical Information of China (English)
ZHANG Dao-Hua; ZHOU Duan-Lu; FAN Heng
2010-01-01
@@ We study the entanglement properties of the superposed state of orthogonal maximally entangled states.It is shown that the superposed state is maximally entangled and the superposed state is separable.The relation between the superposed state and the mutually unbiased state is discussed.
Hessian geometry and entanglement thermodynamics
Matsueda, Hiroaki
2015-01-01
We reconstruct entanglement thermodynamics by means of Hessian geometry, since this method exactly generalizes thermodynamics into much wider exponential family cases including quantum entanglement. Starting with the correct first law of entanglement thermodynamics, we derive that a proper choice of the Hessian potential leads to both of the entanglement entropy scaling for quantum critical systems and hyperbolic metric (or AdS space with imaginary time). We also derive geometric representation of the entanglement entropy in which the entropy is described as integration of local conserved current of information flowing across an entangling surface. We find that the entangling surface is equivalent to the domain boundary of the Hessian potential. This feature originates in a special property of critical systems in which we can identify the entanglement entropy with the Hessian potential after the second derivative by the canonical parameters, and this identification guarantees violation of extensive nature of ...
Electromagnetically Induced Entanglement.
Yang, Xihua; Xiao, Min
2015-08-28
Quantum entanglement provides an essential resource for quantum computation, quantum communication, and quantum network. How to conveniently and efficiently produce entanglement between bright light beams presents a challenging task to build realistic quantum information processing networks. Here, we present an efficient and convenient way to realize a novel quantum phenomenon, named electromagnetically induced entanglement, in the conventional Λ-type three-level atomic system driven by a strong pump field and a relatively weak probe field. Nearly perfect entanglement between the two fields can be achieved with a low coherence decay rate between the two lower levels, high pump-field intensity, and large optical depth of the atomic ensemble. The physical origin is quantum coherence between the lower doublet produced by the pump and probe fields, similar to the well-known electromagnetically induced transparency. This method would greatly facilitate the generation of nondegenerate narrow-band continuous-variable entanglement between bright light beams by using only coherent laser fields, and may find potential and broad applications in realistic quantum information processing.
Entanglement in the Bogoliubov vacuum
DEFF Research Database (Denmark)
Poulsen, Uffe Vestergaard; Meyer, T.; Lewenstein, M.
2005-01-01
We analyze the entanglement properties of the Bogoliubov vacuum, which is obtained as a second-order approximation to the ground state of an interacting Bose-Einstein condensate. We work in one- and two-dimensional lattices and study the entanglement between two groups of sites as a function...... and to be favoured by strong interactions. Conversely, long-range entanglement is favoured by relatively weak interactions. No examples of bound entanglement are found....
Generic entangling through quantum indistinguishability
Indian Academy of Sciences (India)
Sougato Bose; Dipankar Home
2002-08-01
We present a general scheme for entangling any degree of freedom of two uncorrelated identical particles from independent sources by a combination of two-particle interferometry and which-way detection. We show that this entanglement generation procedure works for completely random initial states of the variable to be entangled. We also demonstrate a curious complementarity exhibited by our scheme and its applications in estimating the generated entanglement as a function of wave packet overlap at the beamsplitter.
Multipartite entanglement in neutrino oscillations
Energy Technology Data Exchange (ETDEWEB)
Blasone, Massimo; Dell' Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio, E-mail: blasone@sa.infn.i [Dipartimento di Matematica e Informatica, Universita degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy)
2009-06-01
Particle mixing is related to multi-mode entanglement of single-particle states The occupation number of both flavor eigenstates and mass eigenstates can be used to define a multiqubit space. In such a framework, flavor neutrino states can be interpreted as multipartite mode-entangled states. By using two different entanglement measures, we analyze the behavior of multipartite entanglement in the phenomenon of neutrino oscillations.
Simulating Entangling Unitary Operator Using Non-maximally Entangled States
Institute of Scientific and Technical Information of China (English)
LI Chun-Xian; WANG Cheng-Zhi; NIE Liu-Ying; LI Jiang-Fan
2009-01-01
We use non-maximally entangled states (NMESs) to simulate an entangling unitary operator (EUO) w/th a certain probability. Given entanglement resources, the probability of the success we achieve is a decreasing function of the parameters of the EUO. Given an EUO, for certain entanglement resources the result is optimal, i.e., the probability obtains a maximal value, and for optimal result higher parameters of the EUO match more amount of entanglement resources. The probability of the success we achieve is higher than the known results under some condition.
Temperature from quantum entanglement
Kumar, S Santhosh
2015-01-01
It is still unclear how thermal states dynamically emerge from a microscopic quantum description. A complete understanding of the long time evolution of closed quantum systems may resolve the tension between a microscopic description and the one offered by equilibrium statistical mechanics. In an attempt in this direction, we consider a simple bipartite system (a quantum scalar field propagating in black-hole background) and study the evolution of the entanglement entropy --- by tracing over the degrees of freedom inside the event-horizon --- at different times. We define entanglement temperature which is similar to the one used in the microcanonical ensemble picture in statistical mechanics and show that (i) this temperature is a finite quantity while the entanglement entropy diverges and (ii) matches with the Hawking temperature for all several black-hole space-times. We also discuss the implications of our result for the laws of black-hole mechanics and eigen-state thermalization.
Entanglement in Classical Optics
Ghose, Partha
2013-01-01
The emerging field of entanglement or nonseparability in classical optics is reviewed, and its similarities with and differences from quantum entanglement clearly pointed out through a recapitulation of Hilbert spaces in general, the special restrictions on Hilbert spaces imposed in quantum mechanics and the role of Hilbert spaces in classical polarization optics. The production of Bell-like states in classical polarization optics is discussed, and new theorems are proved to discriminate between separable and nonseparable states in classical wave optics where no discreteness is involved. The influence of the Pancharatnam phase on a classical Bell-like state is deived. Finally, to what extent classical polarization optics can be used to simulate quantum information processing tasks is also discussed. This should be of great practical importance because coherence and entanglement are robust in classical optics but not in quantum systems.
Deriving covariant holographic entanglement
Dong, Xi; Lewkowycz, Aitor; Rangamani, Mukund
2016-11-01
We provide a gravitational argument in favour of the covariant holographic entanglement entropy proposal. In general time-dependent states, the proposal asserts that the entanglement entropy of a region in the boundary field theory is given by a quarter of the area of a bulk extremal surface in Planck units. The main element of our discussion is an implementation of an appropriate Schwinger-Keldysh contour to obtain the reduced density matrix (and its powers) of a given region, as is relevant for the replica construction. We map this contour into the bulk gravitational theory, and argue that the saddle point solutions of these replica geometries lead to a consistent prescription for computing the field theory Rényi entropies. In the limiting case where the replica index is taken to unity, a local analysis suffices to show that these saddles lead to the extremal surfaces of interest. We also comment on various properties of holographic entanglement that follow from this construction.
Deriving covariant holographic entanglement
Dong, Xi; Rangamani, Mukund
2016-01-01
We provide a gravitational argument in favour of the covariant holographic entanglement entropy proposal. In general time-dependent states, the proposal asserts that the entanglement entropy of a region in the boundary field theory is given by a quarter of the area of a bulk extremal surface in Planck units. The main element of our discussion is an implementation of an appropriate Schwinger-Keldysh contour to obtain the reduced density matrix (and its powers) of a given region, as is relevant for the replica construction. We map this contour into the bulk gravitational theory, and argue that the saddle point solutions of these replica geometries lead to a consistent prescription for computing the field theory Renyi entropies. In the limiting case where the replica index is taken to unity, a local analysis suffices to show that these saddles lead to the extremal surfaces of interest. We also comment on various properties of holographic entanglement that follow from this construction.
Entanglement without hidden nonlocality
Hirsch, Flavien; Túlio Quintino, Marco; Bowles, Joseph; Vértesi, Tamás; Brunner, Nicolas
2016-11-01
We consider Bell tests in which the distant observers can perform local filtering before testing a Bell inequality. Notably, in this setup, certain entangled states admitting a local hidden variable model in the standard Bell scenario can nevertheless violate a Bell inequality after filtering, displaying so-called hidden nonlocality. Here we ask whether all entangled states can violate a Bell inequality after well-chosen local filtering. We answer this question in the negative by showing that there exist entangled states without hidden nonlocality. Specifically, we prove that some two-qubit Werner states still admit a local hidden variable model after any possible local filtering on a single copy of the state.
Holographic entanglement chemistry
Caceres, Elena; Pedraza, Juan F
2016-01-01
We use the Iyer-Wald formalism to derive an extended first law of entanglement that includes variations in the cosmological constant, Newton's constant and --in the case of higher derivative theories-- all the additional couplings of the theory. In Einstein gravity, where the number of degrees of freedom $N^2$ of the dual field theory is a function of $\\Lambda$ and $G$, our approach allows us to vary $N$ keeping the field theory scale fixed or to vary the field theory scale keeping $N$ fixed. We also derive an extended first law of entanglement for Gauss-Bonnet and Lovelock gravity.
Yu, Ting
2009-01-01
A new development in the dynamical behavior of elementary quantum systems is the surprising discovery that correlation between two quantum units of information called qubits can be degraded by environmental noise in a way not seen previously in studies of dissipation. This new route for dissipation attacks quantum entanglement, the essential resource for quantum information as well as the central feature in the Einstein-Podolsky-Rosen so-called paradox and in discussions of the fate of Schr\\"{o}inger's cat. The effect has been labeled ESD, which stands for early-stage disentanglement or, more frequently, entanglement sudden death. We review recent progress in studies focused on this phenomenon.
Atomic entanglement and decoherence
Genes, Claudiu
The generation of entanglement in atomic systems plays a central topic in the fields of quantum information storage and processing. Moreover, a special category of entangled states of multi-atom ensembles, spin squeezed states, have been proven to lead to considerable improvement in the sensitivity of precision measurements compared to systems involving uncorrelated atoms. A treatment of entanglement in open systems is, however, incomplete without a precise description of the process of decoherence which necessarily accompanies it. The theory of entanglement and decoherence are the two main topics of this thesis. Methods are described for the generation of strong correlations in large atomic ensembles using either cavity quantum electrodynamics or measurement outcome conditioned quantum dynamics. Moreover, the description of loss of entanglement resulting from the coupling to a noise reservoir (electromagnetic vacuum) is explored. A spin squeezing parameter is used throughout this thesis as both a measure of entanglement strength and as an indication of the sensitivity improvement above the so-called standard quantum limit (sensitivity obtained with uncorrelated particles) in metrology. The first scheme considered consists of a single mode cavity field interacting with a collection of atoms for which spin squeezing is produced in both resonant and off-resonant regimes. In the resonant case, transfer of squeezing from a field state to the atoms is analyzed, while in the off-resonant regime squeezing is produced via an effective nonlinear interaction (one-axis twisting Hamiltonian). A second, more experimentally realistic case, is one involving the interaction of free space atoms with laser pulses; a projective measurement of a source field originating from atomic fluctuations provides a means of preparing atomic collective states such as spin squeezed and Schrodinger cat states. A new "unravelling" is proposed, that employs the detection of photon number in a single
Entanglement and topological interfaces
Brehm, Enrico M; Jaud, Daniel; Schmidt-Colinet, Cornelius
2015-01-01
In this paper we consider entanglement entropies in two-dimensional conformal field theories in the presence of topological interfaces. Tracing over one side of the interface, the leading term of the entropy remains unchanged. The interface however adds a subleading contribution, which can be interpreted as a relative (Kullback-Leibler) entropy with respect to the situation with no defect inserted. Reinterpreting boundaries as topological interfaces of a chiral half of the full theory, we rederive the left/right entanglement entropy in analogy with the interface case. We discuss WZW models and toroidal bosonic theories as examples.
Baez, John C.; Vicary, Jamie
2014-11-01
Maldacena and Susskind have proposed a correspondence between wormholes and entanglement, dubbed ER=EPR. We study this in the context of three-dimensional topological quantum field theory (TQFT), where we show that the formation of a wormhole is the same process as creating a particle-antiparticle pair. A key feature of the ER=EPR proposal is that certain apparently entangled degrees of freedom turn out to be the same. We name this phenomenon ‘fake entanglement’, and show how it arises in our TQFT model.
Cross-cultural examination of the tripartite model with children: data from the Barretstown studies.
Kiernan, G; Laurent, J; Joiner, T E; Catanzaro, S J; MacLachlan, M
2001-10-01
The Positive and Negative Affect Scale for Children (PANAS-C) and the Physiological Hyperarousal Scale for Children (PH-C) were administered to a group of 240 children from European countries to determine their utility in examining the tripartite model of anxiety and depression in a cross-cultural sample. Most of the children (n = 196) had been diagnosed with a medical illness; the remainder were siblings of these youngsters (n = 44). Only slight variations were noted in items between this sample and samples from the United States. Despite these minor differences, 3 distinct scales measuring the positive affect, negative affect, and physiological hyperarousal constructs of the tripartite model were identified. These findings illustrate that the PH-PANAS-C provides a useful measure of the tripartite model in a cross-cultural sample of youth. The findings also demonstrate that the tripartite model is generalizable to a cross-cultural milieu.
Recovering entanglement by local operations
Energy Technology Data Exchange (ETDEWEB)
D’Arrigo, A., E-mail: antonio.darrigo@dmfci.unict.it [CNR-IMM UOS Università (MATIS), Consiglio Nazionale delle Ricerche, Via Santa Sofia 64, 95123 Catania (Italy); Dipartimento di Fisica e Astronomia, Università degli Studi Catania, Via Santa Sofia 64, 95123 Catania (Italy); Centro Siciliano di Fisica Nucleare e Struttura della Materia (CSFNSM), Via Santa Sofia 64, 95123 Catania (Italy); Lo Franco, R. [Dipartimento di Fisica e Chimica, Università di Palermo, via Archirafi 36, 90123 Palermo (Italy); Centro Siciliano di Fisica Nucleare e Struttura della Materia (CSFNSM), Via Santa Sofia 64, 95123 Catania (Italy); Benenti, G. [CNISM and Center for Nonlinear and Complex Systems, Università degli Studi dell’Insubria, Via Valleggio 11, 22100 Como (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Milano, via Celoria 16, 20133 Milano (Italy); Paladino, E.; Falci, G. [Dipartimento di Fisica e Astronomia, Università degli Studi Catania, Via Santa Sofia 64, 95123 Catania (Italy); CNR-IMM UOS Università (MATIS), Consiglio Nazionale delle Ricerche, Via Santa Sofia 64, 95123 Catania (Italy); Centro Siciliano di Fisica Nucleare e Struttura della Materia (CSFNSM), Via Santa Sofia 64, 95123 Catania (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Viale S. Sofia 64, 95123 Catania (Italy)
2014-11-15
We investigate the phenomenon of bipartite entanglement revivals under purely local operations in systems subject to local and independent classical noise sources. We explain this apparent paradox in the physical ensemble description of the system state by introducing the concept of “hidden” entanglement, which indicates the amount of entanglement that cannot be exploited due to the lack of classical information on the system. For this reason this part of entanglement can be recovered without the action of non-local operations or back-transfer process. For two noninteracting qubits under a low-frequency stochastic noise, we show that entanglement can be recovered by local pulses only. We also discuss how hidden entanglement may provide new insights about entanglement revivals in non-Markovian dynamics.
Accessible quantification of multiparticle entanglement
Cianciaruso, Marco; Adesso, Gerardo
2015-01-01
Entanglement is a key ingredient for quantum technologies and a fundamental signature of quantumness in a broad range of phenomena encompassing many-body physics, thermodynamics, cosmology, and life sciences. For arbitrary multiparticle systems, the quantification of entanglement typically involves hard optimisation problems, and requires demanding tomographical techniques. In this paper we show that such difficulties can be overcome by developing an experimentally friendly method to evaluate measures of multiparticle entanglement via a geometric approach. The method provides exact analytical results for a relevant class of mixed states of $N$ qubits, and computable lower bounds to entanglement for any general state. For practical purposes, the entanglement determination requires local measurements in just three settings for any $N$. We demonstrate the power of our approach to quantify multiparticle entanglement in $N$-qubit bound entangled states and other states recently engineered in laboratory using quant...
Entangled black holes as ciphers of hidden information
Braunstein, Samuel L; Zyczkowski, Karol \\
2009-01-01
The black-hole information paradox has fueled a fascinating effort to reconcile the predictions of general relativity and those of quantum mechanics. Gravitational considerations teach us that black holes must trap everything that falls into them. Quantum mechanically the mass of a black hole leaks away as featureless (Hawking) radiation. However, if Hawking's analysis turned out to be accurate then the information would be irretrievably lost and a fundamental axiom of quantum mechanics, that of unitary evolution, would likewise fail. Here we show that the information about the matter that collapses to form a black hole becomes encoded into pure correlations within a tripartite quantum system, the quantum analog of a one-time pad until very late in the evaporation, provided we accept the view that the thermodynamic entropy of a black hole is due to entropy of entanglement. In this view the black hole entropy is primarily due to trans-event horizon entanglement between external modes neighboring the black hole...
Multimode entanglement and telecloning in a noisy environment
Ferraro, A
2005-01-01
We address generation, propagation and application of multipartite continuous variable entanglement in a noisy environment. In particular, we focus our attention on the multimode entangled states achievable by second order nonlinear crystals, {\\em i.e.} coherent states of ${\\rm SU}(m,1)$ group. The full inseparability in the ideal case is shown, whereas thresholds for separability are given for the tripartite case in the presence of noise. We then consider coherent states of ${\\rm SU}(m,1)$ as support for a telecloning protocol, providing the first example of a completely asymmetric $1 \\to m$ telecloning. We derive explicitly the optimal relation among the different fidelities of the clones. The effect of noise in the various stages of the protocol is taken into account, thus permitting its adaptive modifications to the noisy environment. In the optimized scheme the clones' fidelity remains maximal even in the presence of losses (in the absence of thermal noise), for propagation times that diverge as the numb...
Postcolonial Entanglements: Unruling Stories
Pacini-Ketchabaw, Veronica
2012-01-01
In this article, I use Donna Haraway's philosophy to think about postcolonial encounters between different species. I follow entangled stories of the deer/settler-child figure to trouble colonialisms and untangle the histories and trajectories that we inhabit with other species through colonial histories. I shy away from generalizations and…
Energy Technology Data Exchange (ETDEWEB)
Blasone, Massimo [Dipartimento di Fisica, Università degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy); INFN Sezione di Napoli, Gruppo collegato di Salerno (Italy); Dell' Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio [Dipartimento di Ingegneria Industriale, Università degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy)
2013-04-15
Neutrino oscillations can be equivalently described in terms of (dynamical) entanglement of neutrino flavor modes. We review previous results derived in the context of quantum mechanics and extend them to the quantum field theory framework, were a rich structure of quantum correlations appears.
Quantum entanglement and symmetry
Energy Technology Data Exchange (ETDEWEB)
Chruscinski, D; Kossakowski, A [Institute of Physics, Nicolaus Copernicus University, Grudziadzka 5/7, 87-100 Torun (Poland)
2007-11-15
One of the main problem in Quantum Information Theory is to test whether a given state of a composite quantum system is entangled or separable. It turns out that within a class of states invariant under the action of the symmetry group this problem considerably simplifies. We analyze multipartite invariant states and the corresponding symmetric quantum channels.
Quantum entanglement and symmetry
Chruściński, D.; Kossakowski, A.
2007-11-01
One of the main problem in Quantum Information Theory is to test whether a given state of a composite quantum system is entangled or separable. It turns out that within a class of states invariant under the action of the symmetry group this problem considerably simplifies. We analyze multipartite invariant states and the corresponding symmetric quantum channels.
Are all maximally entangled states pure?
Cavalcanti, D.; Brandão, F. G. S. L.; Terra Cunha, M. O.
2005-10-01
We study if all maximally entangled states are pure through several entanglement monotones. In the bipartite case, we find that the same conditions which lead to the uniqueness of the entropy of entanglement as a measure of entanglement exclude the existence of maximally mixed entangled states. In the multipartite scenario, our conclusions allow us to generalize the idea of the monogamy of entanglement: we establish the polygamy of entanglement, expressing that if a general state is maximally entangled with respect to some kind of multipartite entanglement, then it is necessarily factorized of any other system.
Tripartite Bell inequality, random matrices and trilinear forms
Pisier, Gilles
2012-01-01
In this seminar report, we present in detail the proof of a recent result due to J. Bri\\"et and T. Vidick, improving an estimate in a 2008 paper by D. P\\'erez-Garc\\'{\\i}a, M. Wolf, C. Palazuelos, I. Villanueva, and M. Junge, estimating the growth of the deviation in the tripartite Bell inequality. The proof requires a delicate estimate of the norms of certain trilinear (or $d$-linear) forms on Hilbert space with coefficients in the second Gaussian Wiener chaos. Let $E^n_{\\vee}$ (resp. $E^n_{\\min}$) denote $ \\ell_1^n \\otimes \\ell_1^n\\otimes \\ell_1^n$ equipped with the injective (resp. minimal) tensor norm. Here $ \\ell_1^n$ is equipped with its maximal operator space structure. The Bri\\"et-Vidick method yields that the identity map $I_n$ satisfies (for some $c>0$) $\\|I_n:\\ E^n_{\\vee}\\to E^n_{\\min}\\|\\ge c n^{1/4} (\\log n)^{-3/2}.$ Let $S^n_2$ denote the (Hilbert) space of $n\\times n$-matrices equipped with the Hilbert-Schmidt norm. While a lower bound closer to $n^{1/2} $ is still open, their method produces an ...
Creation of Entanglement with Nonlocal Operations
Institute of Scientific and Technical Information of China (English)
ZHANG Yong; CAO Wan-Cang; LONG Gui-Lu
2005-01-01
We discuss how to create more entanglement with nonlocal operations acting on two-particle states. For a given nonlocal operation, we find that some input states cannot produce entanglement and some produce the maximal entanglement, and find that any initial entangled states can produce more entanglement than initial product states.
Bound entangled states invariant under Ux
Institute of Scientific and Technical Information of China (English)
Wang Zhen; Wang Zhi-Xi
2008-01-01
This paper obtains an entangled condition for isotropic-like states by using an atomic map. It constructs a class of bound entangled states from the entangled condition and shows that the partial transposition of the state from the constructed bound entangled class is an edge bound entangled state by using range criterion.
Are all maximally entangled states pure?
Cavalcanti, D; Terra-Cunha, M O
2005-01-01
In this Letter we study if all maximally entangled states are pure through several entanglement monotones. Our conclusions allow us to generalize the idea of monogamy of entanglement. Then we propose a polygamy of entanglement, which express that if a general multipartite state is maximally entangled it is necessarily factorized by any other system.
General polygamy inequality of multiparty quantum entanglement
Kim, Jeong San
2012-06-01
Using entanglement of assistance, we establish a general polygamy inequality of multiparty entanglement in arbitrary-dimensional quantum systems. For multiparty closed quantum systems, we relate our result with the monogamy of entanglement, and clarify that the entropy of entanglement bounds both monogamy and polygamy of multiparty quantum entanglement.
Probabilistic Teleportation of the Three-Particle Entangled State viaEntanglement Swapping
Institute of Scientific and Technical Information of China (English)
路洪
2001-01-01
A scheme of teleportation of a three-particle entangled state via entanglement swapping is proposed. It is shown that if a two-particle entangled state and a three-particle entangled state (both are not maximum entangled states) are used as quantum channels, probabilistic teleportation of the three-particle entangled state can be realized.
Entanglement polytopes: multiparticle entanglement from single-particle information.
Walter, Michael; Doran, Brent; Gross, David; Christandl, Matthias
2013-06-01
Entangled many-body states are an essential resource for quantum computing and interferometry. Determining the type of entanglement present in a system usually requires access to an exponential number of parameters. We show that in the case of pure, multiparticle quantum states, features of the global entanglement can already be extracted from local information alone. This is achieved by associating any given class of entanglement with an entanglement polytope-a geometric object that characterizes the single-particle states compatible with that class. Our results, applicable to systems of arbitrary size and statistics, give rise to local witnesses for global pure-state entanglement and can be generalized to states affected by low levels of noise.
Entangled Fractional Fourier Transform for the Multipartite Entangled State Representation
Institute of Scientific and Technical Information of China (English)
QIAN Xiao-Qing; SONG Tong-Qiang
2006-01-01
We deduce entangled fractional Fourier transformation (EFFT) for the multipartite entangled state representation, which was newly constructed with two mutually conjugate n-mode entangled states of continuum variables in n-mode Fock space. We establish a formalism of EFFT for quantum mechanical wave functions, which provides us a convenient way to derive some wave functions. We find that the eigenmode of EFFT is different from the usual Hermite Polynomials. We also derive the EFFT of the n-mode squeezed state.
Degree of Entanglement for Some Bipartite Entangled Bosonic Systems
Institute of Scientific and Technical Information of China (English)
LIANG Xian-Ting
2004-01-01
We calculate the degree of entanglement for some bipartite entangled states of continuous variables.These states include common two-mode squeezed vacuum state, thermal vacuum state of a free single particle (where the fictitious tilde system is regarded as another particle), and the squeezed vacuum state of two coupling harmonic oscillators.The degree of entanglement for these quantum systems are shown clearly by using the technique of integration within an ordered product of operators.
Efficient entanglement purification for doubly entangled photon state
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
In this paper,we present an efficient purification scheme that improves the efficiency of entanglement purification of the recently proposed entanglement purification scheme for doubly entangled photon states (Phys.Rev.A,2008,77:042315).This modified scheme contains the bit-flip error correction where all the photon pairs can be kept while all the bit-flip errors are corrected and the entanglement purification of phase-flip errors where a wavelength conversion process is used.This scheme has the advantage of high efficiency and a much lower minimum fidelity of the original state.It works under existing technology.
Teleportation for an Ionic Entangled Internal State by Entanglement Swapping
Institute of Scientific and Technical Information of China (English)
ZHENG Xiao-Juan; FANG Mao-Fa; LIAO Xiang-Ping; CAI Jian-Wu
2006-01-01
@@ We present an effective scheme to teleport an unknown ionic entangled internal state via trapped ions without joint Bell-state measurement. In the constructed quantum channel process, we adopt entanglement swapping to avoid decrease of entanglement during the distribution of particles. Thus our scheme provides new prospects for quantum teleportation over longer distance. The distinct advantages of our scheme are that our scheme is insensitive to heating of vibrational mode and can be generalized to teleport an N-ion electronic entangled GHZ class state. Furthermore, in our scheme the success probability can reach 1.
Entanglement between Two Interacting CFTs and Generalized Holographic Entanglement Entropy
Mollabashi, Ali; Takayanagi, Tadashi
2014-01-01
In this paper we discuss behaviors of entanglement entropy between two interacting CFTs and its holographic interpretation using the AdS/CFT correspondence. We explicitly perform analytical calculations of entanglement entropy between two free scalar field theories which are interacting with each other in both static and time-dependent ways. We also conjecture a holographic calculation of entanglement entropy between two interacting $\\mathcal{N}=4$ super Yang-Mills theories by introducing a minimal surface in the S$^5$ direction, instead of the AdS$_5$ direction. This offers a possible generalization of holographic entanglement entropy.
Entanglement between two interacting CFTs and generalized holographic entanglement entropy
Mollabashi, Ali; Shiba, Noburo; Takayanagi, Tadashi
2014-04-01
In this paper we discuss behaviors of entanglement entropy between two interacting CFTs and its holographic interpretation using the AdS/CFT correspondence. We explicitly perform analytical calculations of entanglement entropy between two free scalar field theories which are interacting with each other in both static and time-dependent ways. We also conjecture a holographic calculation of entanglement entropy between two interacting = 4 super Yang-Mills theories by introducing a minimal surface in the S5 direction, instead of the AdS5 direction. This offers a possible generalization of holographic entanglement entropy.
Entanglement between two interacting CFTs and generalized holographic entanglement entropy
Energy Technology Data Exchange (ETDEWEB)
Mollabashi, Ali [School of physics, Institute for Research in Fundamental Sciences (IPM),Tehran (Iran, Islamic Republic of); Yukawa Institute for Theoretical Physics (YITP),Kyoto University, Kyoto 606-8502 (Japan); Shiba, Noburo [Yukawa Institute for Theoretical Physics (YITP),Kyoto University, Kyoto 606-8502 (Japan); Takayanagi, Tadashi [Yukawa Institute for Theoretical Physics (YITP),Kyoto University, Kyoto 606-8502 (Japan); Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU),University of Tokyo, Kashiwa, Chiba 277-8582 (Japan)
2014-04-30
In this paper we discuss behaviors of entanglement entropy between two interacting CFTs and its holographic interpretation using the AdS/CFT correspondence. We explicitly perform analytical calculations of entanglement entropy between two free scalar field theories which are interacting with each other in both static and time-dependent ways. We also conjecture a holographic calculation of entanglement entropy between two interacting N=4 super Yang-Mills theories by introducing a minimal surface in the S{sup 5} direction, instead of the AdS{sub 5} direction. This offers a possible generalization of holographic entanglement entropy.
Entanglement-assisted state discrimination and entanglement preservation
Güngör, Özenç; Turgut, Sadi
2016-09-01
In this paper, the following scenario is considered: there are two qubits possessed by two parties at different locations. Qubits have been prepared in one of a maximum of four, mutually-orthogonal, entangled states and the parties wish to distinguish between the states by using local operations and classical communication. Although in general it is not possible to distinguish between four arbitrary states, the parties can spend some preshared entanglement to achieve perfect discrimination between four qubit states and can also preserve the entanglement of the states after discrimination. This is shown by employing the theory of majorization and the connections between entanglement transformations and state discrimination protocols.
Efficient entanglement purification for doubly entangled photon state
Institute of Scientific and Technical Information of China (English)
WANG Chuan; SHENG YuBo; LI XiHan; DENG FuGuo; ZHANG Wei; LONG GuiLu
2009-01-01
In this paper,we present an efficient purification scheme that improves the efficiency of entanglement purification of the recently proposed entanglement purification scheme for doubly entangled photon states(Phys.Rev.A,2008,77:042315).This modified scheme contains the bit-flip error correction where all the photon pairs can be kept while all the bit-flip errors are corrected and the entanglement purification of phase-flip errors where a wavelength conversion process is used.This scheme has the advantage of high efficiency and a much lower minimum fidelity of the original state.It works under existing technology.
Entanglement structures in qubit systems
Rangamani, Mukund; Rota, Massimiliano
2015-09-01
Using measures of entanglement such as negativity and tangles we provide a detailed analysis of entanglement structures in pure states of non-interacting qubits. The motivation for this exercise primarily comes from holographic considerations, where entanglement is inextricably linked with the emergence of geometry. We use the qubit systems as toy models to probe the internal structure, and introduce some useful measures involving entanglement negativity to quantify general features of entanglement. In particular, our analysis focuses on various constraints on the pattern of entanglement which are known to be satisfied by holographic sates, such as the saturation of Araki-Lieb inequality (in certain circumstances), and the monogamy of mutual information. We argue that even systems as simple as few non-interacting qubits can be useful laboratories to explore how the emergence of the bulk geometry may be related to quantum information principles.
Entanglement structures in qubit systems
Rangamani, Mukund
2015-01-01
Using measures of entanglement such as negativity and tangles we provide a detailed analysis of entanglement structures in pure states of non-interacting qubits. The motivation for this exercise primarily comes from holographic considerations, where entanglement is inextricably linked with the emergence of geometry. We use the qubit systems as toy models to probe the internal structure, and introduce some useful measures involving entanglement negativity to quantify general features of entanglement. In particular, our analysis focuses on various constraints on the pattern of entanglement which are known to be satisfied by holographic sates, such as the saturation of Araki-Lieb inequality (in certain circumstances), and the monogamy of mutual information. We argue that even systems as simple as few non-interacting qubits can be useful laboratories to explore how the emergence of the bulk geometry may be related to quantum information principles.
High-dimensional entanglement certification.
Huang, Zixin; Maccone, Lorenzo; Karim, Akib; Macchiavello, Chiara; Chapman, Robert J; Peruzzo, Alberto
2016-06-17
Quantum entanglement is the ability of joint quantum systems to possess global properties (correlation among systems) even when subsystems have no definite individual property. Whilst the 2-dimensional (qubit) case is well-understood, currently, tools to characterise entanglement in high dimensions are limited. We experimentally demonstrate a new procedure for entanglement certification that is suitable for large systems, based entirely on information-theoretics. It scales more efficiently than Bell's inequality and entanglement witness. The method we developed works for arbitrarily large system dimension d and employs only two local measurements of complementary properties. This procedure can also certify whether the system is maximally entangled. We illustrate the protocol for families of bipartite states of qudits with dimension up to 32 composed of polarisation-entangled photon pairs.
Entanglement quantification by local unitaries
Monras, A; Giampaolo, S M; Gualdi, G; Davies, G B; Illuminati, F
2011-01-01
Invariance under local unitary operations is a fundamental property that must be obeyed by every proper measure of quantum entanglement. However, this is not the only aspect of entanglement theory where local unitaries play a relevant role. In the present work we show that the application of suitable local unitary operations defines a family of bipartite entanglement monotones, collectively referred to as "shield entanglement". They are constructed by first considering the (squared) Hilbert- Schmidt distance of the state from the set of states obtained by applying to it a given local unitary. To the action of each different local unitary there corresponds a different distance. We then minimize these distances over the sets of local unitaries with different spectra, obtaining an entire family of different entanglement monotones. We show that these shield entanglement monotones are organized in a hierarchical structure, and we establish the conditions that need to be imposed on the spectrum of a local unitary f...
Quantum entanglement from random measurements
Tran, Minh Cong; Dakić, Borivoje; Arnault, François; Laskowski, Wiesław; Paterek, Tomasz
2015-11-01
We show that the expectation value of squared correlations measured along random local directions is an identifier of quantum entanglement in pure states, which can be directly experimentally assessed if two copies of the state are available. Entanglement can therefore be detected by parties who do not share a common reference frame and whose local reference frames, such as polarizers or Stern-Gerlach magnets, remain unknown. Furthermore, we also show that in every experimental run, access to only one qubit from the macroscopic reference is sufficient to identify entanglement, violate a Bell inequality, and, in fact, observe all phenomena observable with macroscopic references. Finally, we provide a state-independent entanglement witness solely in terms of random correlations and emphasize how data gathered for a single random measurement setting per party reliably detects entanglement. This is only possible due to utilized randomness and should find practical applications in experimental confirmation of multiphoton entanglement or space experiments.
Boundary effects in entanglement entropy
Berthiere, Clement
2016-01-01
We present a number of explicit calculations of Renyi and entanglement entropies in situations where the entangling surface intersects the boundary in $d$-dimensional Minkowski spacetime. When the boundary is a single plane we compute the contribution to the entropy due to this intersection, first in the case of the Neumann and Dirichlet boundary conditions, and then in the case of a generic Robin type boundary condition. The flow in the boundary coupling between the Neumann and Dirichlet phases is analyzed in arbitrary dimension $d$ and is shown to be monotonic, the peculiarity of $d=3$ case is noted. We argue that the translational symmetry along the entangling surface is broken due the presence of the boundary which reveals that the entanglement is not homogeneous. In order to characterize this quantitatively, we introduce a density of entanglement entropy and compute it explicitly. This quantity clearly indicates that the entanglement is maximal near the boundary. We then consider the situation where the ...
Entangled network and quantum communication
Energy Technology Data Exchange (ETDEWEB)
Metwally, Nasser, E-mail: Nmetwally@gmail.com [Math. Dept., Faculty of Science, South Valley University, Aswan (Egypt); Math. Dept., College of Science, University of Bahrain, P.O. Box 32038 (Bahrain)
2011-11-21
A theoretical scheme is introduced to generate entangled network via Dzyaloshinskii–Moriya (DM) interaction. The dynamics of entanglement between different nodes, which is generated by direct or indirect interaction, is investigated. It is shown that, the direction of (DM) interaction and the locations of the nodes have a sensational effect on the degree of entanglement. The minimum entanglement generated between all the nodes is quantified. The upper and lower bounds of the entanglement depend on the direction of DM interaction, and the repetition of the behavior depends on the strength of DM. The generated entangled nodes are used as quantum channel to perform quantum teleportation, where it is shown that the fidelity of teleporting unknown information between the network members depends on the locations of the members.
Entanglement and topological interfaces
Energy Technology Data Exchange (ETDEWEB)
Brehm, E.; Brunner, I.; Jaud, D.; Schmidt-Colinet, C. [Arnold Sommerfeld Center, Ludwig-Maximilians-Universitaet, Theresienstrasse 37, 80333, Muenchen (Germany)
2016-06-15
In this paper we consider entanglement entropies in two-dimensional conformal field theories in the presence of topological interfaces. Tracing over one side of the interface, the leading term of the entropy remains unchanged. The interface however adds a subleading contribution, which can be interpreted as a relative (Kullback-Leibler) entropy with respect to the situation with no defect inserted. Reinterpreting boundaries as topological interfaces of a chiral half of the full theory, we rederive the left/right entanglement entropy in analogy with the interface case. We discuss WZW models and toroidal bosonic theories as examples. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Review of Entangled Coherent States
Sanders, Barry C
2011-01-01
We review entangled coherent state research since its first implicit use in 1967 to the present. Entangled coherent states are important to quantum superselection principles, quantum information processing, quantum optics, and mathematical physics. Despite their inherent fragility they have produced in a conditional propagating-wave quantum optics realization. Fundamentally the states are intriguing because they are entanglements of the coherent states, which are in a sense the most classical of all states of a dynamical system.
Inter-Universal Quantum Entanglement
Robles-Pérez, S. J.; González-Díaz, P. F.
2015-01-01
The boundary conditions to be imposed on the quantum state of the whole multiverse could be such that the universes would be created in entangled pairs. Then, interuniversal entanglement would provide us with a vacuum energy for each single universe that might be fitted with observational data, making testable not only the multiverse proposal but also the boundary conditions of the multiverse. Furthermore, the second law of the entanglement thermodynamics would enhance the expansion of the single universes.
Gaussian maximally multipartite entangled states
Facchi, Paolo; Lupo, Cosmo; Mancini, Stefano; Pascazio, Saverio
2009-01-01
We introduce the notion of maximally multipartite entangled states (MMES) in the context of Gaussian continuous variable quantum systems. These are bosonic multipartite states that are maximally entangled over all possible bipartitions of the system. By considering multimode Gaussian states with constrained energy, we show that perfect MMESs, which exhibit the maximum amount of bipartite entanglement for all bipartitions, only exist for systems containing n=2 or 3 modes. We further numerically investigate the structure of MMESs and their frustration for n <= 7.
All maximally entangling unitary operators
Energy Technology Data Exchange (ETDEWEB)
Cohen, Scott M. [Department of Physics, Duquesne University, Pittsburgh, Pennsylvania 15282 (United States); Department of Physics, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213 (United States)
2011-11-15
We characterize all maximally entangling bipartite unitary operators, acting on systems A and B of arbitrary finite dimensions d{sub A}{<=}d{sub B}, when ancillary systems are available to both parties. Several useful and interesting consequences of this characterization are discussed, including an understanding of why the entangling and disentangling capacities of a given (maximally entangling) unitary can differ and a proof that these capacities must be equal when d{sub A}=d{sub B}.
Entanglement Continuous Unitary Transformations
Sahin, S; Orus, R
2016-01-01
Continuous unitary transformations are a powerful tool to extract valuable information out of quantum many-body Hamiltonians, in which the so-called flow equation transforms the Hamiltonian to a diagonal or block-diagonal form in second quantization. Yet, one of their main challenges is how to approximate the infinitely-many coupled differential equations that are produced throughout this flow. Here we show that tensor networks offer a natural and non-perturbative truncation scheme in terms of entanglement. The corresponding scheme is called "entanglement-CUT" or eCUT. It can be used to extract the low-energy physics of quantum many-body Hamiltonians, including quasiparticle energy gaps. We provide the general idea behind eCUT and explain its implementation for finite 1d systems using the formalism of matrix product operators, and we present proof-of-principle results for the spin-1/2 1d quantum Ising model in a transverse field. Entanglement-CUTs can also be generalized to higher dimensions and to the thermo...
Entanglement continuous unitary transformations
Sahin, Serkan; Schmidt, Kai Phillip; Orús, Román
2017-01-01
Continuous unitary transformations are a powerful tool to extract valuable information out of quantum many-body Hamiltonians, in which the so-called flow equation transforms the Hamiltonian to a diagonal or block-diagonal form in second quantization. Yet, one of their main challenges is how to approximate the infinitely-many coupled differential equations that are produced throughout this flow. Here we show that tensor networks offer a natural and non-perturbative truncation scheme in terms of entanglement. The corresponding scheme is called “entanglement-CUT” or eCUT. It can be used to extract the low-energy physics of quantum many-body Hamiltonians, including quasiparticle energy gaps. We provide the general idea behind eCUT and explain its implementation for finite 1d systems using the formalism of matrix product operators. We also present proof-of-principle results for the spin-(1/2) 1d quantum Ising model and the 3-state quantum Potts model in a transverse field. Entanglement-CUTs can also be generalized to higher dimensions and to the thermodynamic limit.
A Logical Approach to Entanglement
Das, Abhishek
2016-10-01
In this paper we innovate a logical approach to develop an intuition regarding the phenomenon of quantum entanglement. In the vein of the logic introduced we substantiate that particles that were entangled in the past will be entangled in perpetuity and thereby abide a rule that restricts them to act otherwise. We also introduce a game and by virtue of the concept of Nash equilibrium we have been able to show that entangled particles will mutually correspond to an experiment that is performed on any one of the particle.
Multipartite Entanglement in Heisenberg Model
Institute of Scientific and Technical Information of China (English)
WU Hao; REN Jie; FAN Hong-Yi; ZHU Shi-Qun
2008-01-01
The effects of anisotropy and magnetic field on multipaxtite entanglement of ground state in Heisenberg XY model axe investigated. The multipaxtite entanglement increases as a function of the inverse strength of the external field when the degree of anisotropy is finite. There axe two peaks when the degree of anisotropy is γ =± 1. When the degree of anisotropy increases further, the multipartite entanglement will decrease and tend to a constant. The threshold of the inverse strength of the external field for generating multipaxtite entanglement generally decreases with the increasing of qubits.
Extracting entanglement from identical particles.
Killoran, N; Cramer, M; Plenio, M B
2014-04-18
Identical particles and entanglement are both fundamental components of quantum mechanics. However, when identical particles are condensed in a single spatial mode, the standard notions of entanglement, based on clearly identifiable subsystems, break down. This has led many to conclude that such systems have limited value for quantum information tasks, compared to distinguishable particle systems. To the contrary, we show that any entanglement formally appearing amongst the identical particles, including entanglement due purely to symmetrization, can be extracted into an entangled state of independent modes, which can then be applied to any task. In fact, the entanglement of the mode system is in one-to-one correspondence with the entanglement between the inaccessible identical particles. This settles the long-standing debate about the resource capabilities of such states, in particular spin-squeezed states of Bose-Einstein condensates, while also revealing a new perspective on how and when entanglement is generated in passive optical networks. Our results thus reveal new fundamental connections between entanglement, squeezing, and indistinguishability.
Stabilizing entanglement against local dissipation
Energy Technology Data Exchange (ETDEWEB)
Sauer, Simeon; Gneiting, Clemens; Buchleitner, Andreas [Albert-Ludwigs-Universitaet, Freiburg (Germany)
2013-07-01
Natural dissipative processes in multipartite quantum systems are mostly of local nature and therefore affect entanglement adversely. In their presence, initially highly entangled states generically evolve into at most weakly entangled states. We investigate by what means this detrimental process can be counteracted. It is shown that a suitable, dissipator-adapted static system Hamiltonian can preserve entanglement in the stationary state to a significant but limited extend. We then extend our analysis to the general class of periodically driven Hamiltonians and show that they are subject to similar limitations. Finally, we develop incoherent but local control strategies which overcome these limits.
Institute of Scientific and Technical Information of China (English)
PANG Qian-Jun
2005-01-01
We study the eigenstate problem of a kind of three coupled oscillators in a new quantum mechanical representation composed by the spontaneous eigenvectors 〈p, q2, q3| for three operators (p1 +p2 +p3), (x3 - x2), and (x3 - x1). The eigenvalues and eigenvectors of the Hamiltonian are obtained. With the same method, the eigenstate problem of a generalized three-coupled oscillator Hamiltonian is studied, which has never been studied before.
Irreversibility for all bound entangled states
Yang, D; Horodecki, R; Synak-Radtke, B; Yang, Dong; Horodecki, Michal; Horodecki, Ryszard; Synak-Radtke, Barbara
2005-01-01
We derive a new inequality for entanglement for a mixed four-partite state. Employing this inequality, we present a one-shot lower bound for entanglement cost and prove that entanglement cost is strictly larger than zero for any entangled state. We demonstrate that irreversibility occurs in the process of formation for all non-distillable entangled states. In this way we solve a long standing problem, of how "real" is entanglement of bound entangled states. Using the new inequality we also prove impossibility of local-cloning and local-deleting of a known entangled state.
Marshall, Grant N; Sherbourne, Cathy D; Meredith, Lisa S; Camp, Patti; Hays, Ron D
2003-04-01
The structure of self-reported symptoms representative of the tripartite model was examined using data drawn from the Medical Outcomes Study (Tarlov et al., 1989). Participants were persons who had been diagnosed 48 months previously as suffering from either depression (N = 315) or hypertension (N = 403). Results of confirmatory factor analyses were broadly consistent with the tripartite model (L. A. Clark & Watson, 1991). Factors emerged corresponding to each of the 3 posited first-order dimensions of negative affect, positive affect, and physiologic arousal. Nonetheless, some discrepancies were found between the observed data and the hypothesized tripartite model. First, the obtained physiologic arousal factor was best viewed as reflecting nonspecific somatic distress rather than physiologic arousal. Finally, although differentiable in the strictest statistical sense, all three domains were significantly correlated (.36 to.86, absolute value). In particular, contrary to the tripartite model, positive and negative affect covaried markedly (-.81 to -.86). Findings raise issues concerning the utility of the tripartite model as a heuristic framework for enhancing understanding of individual differences in normal mood as well as mood disorders.
Universal corner contributions to entanglement negativity
Kim, Keun-Young; Pang, Da-Wei
2016-01-01
It has been realised that corners in entangling surfaces can induce new universal contributions to the entanglement entropy and R\\'enyi entropy. In this paper we study universal corner contributions to entanglement negativity in three- and four-dimensional CFTs using both field theory and holographic techniques. We focus on the quantity $\\chi$ defined by the ratio of the universal part of the entanglement negativity over that of the entanglement entropy, which may characterise the amount of distillable entanglement. We find that for most of the examples $\\chi$ takes bigger values for singular entangling regions, which may suggest increase in distillable entanglement. However, there also exist counterexamples where distillable entanglement decreases for singular surfaces. We also explore the behaviour of $\\chi$ as the coupling varies and observe that for singular entangling surfaces, the amount of distillable entanglement is mostly largest for free theories, while counterexample exists for free Dirac fermion i...
Energy Technology Data Exchange (ETDEWEB)
Banerjee, Subhashish; Alok, Ashutosh Kumar [Indian Institute of Technology Jodhpur, Jodhpur (India); Srikanth, R. [Poornaprajna Institute of Scientific Research, Banglore (India); Hiesmayr, Beatrix C. [University of Vienna, Vienna (Austria)
2015-10-15
Correlations exhibited by neutrino oscillations are studied via quantum-information theoretic quantities. We show that the strongest type of entanglement, genuine multipartite entanglement, is persistent in the flavor changing states. We prove the existence of Bell-type nonlocal features, in both its absolute and genuine avatars. Finally, we show that a measure of nonclassicality, dissension, which is a generalization of quantum discord to the tripartite case, is nonzero for almost the entire range of time in the evolution of an initial electron-neutrino. Via these quantum-information theoretic quantities, capturing different aspects of quantum correlations, we elucidate the differences between the flavor types, shedding light on the quantum-information theoretic aspects of the weak force. (orig.)
Banerjee, Subhashish; Alok, Ashutosh Kumar; Srikanth, R.; Hiesmayr, Beatrix C.
2015-10-01
Correlations exhibited by neutrino oscillations are studied via quantum-information theoretic quantities. We show that the strongest type of entanglement, genuine multipartite entanglement, is persistent in the flavor changing states. We prove the existence of Bell-type nonlocal features, in both its absolute and genuine avatars. Finally, we show that a measure of nonclassicality, dissension, which is a generalization of quantum discord to the tripartite case, is nonzero for almost the entire range of time in the evolution of an initial electron-neutrino. Via these quantum-information theoretic quantities, capturing different aspects of quantum correlations, we elucidate the differences between the flavor types, shedding light on the quantum-information theoretic aspects of the weak force.
The tripartite associations between bacteriophage, Wolbachia, and arthropods.
Directory of Open Access Journals (Sweden)
2006-05-01
Wolbachia densities and therefore reproductive parasitism. We conclude that phage, Wolbachia, and arthropods form a tripartite symbiotic association in which all three are integral to understanding the biology of this widespread endosymbiosis. Clarifying the roles of lytic and lysogenic phage development in Wolbachia biology will effectively structure inquiries into this research topic.
DEFF Research Database (Denmark)
Flindt, Christian; Sørensen, A. S.; Lukin, M. D.;
2007-01-01
We propose a semiconductor device that can electrically generate entangled electron spin-photon states, providing a building block for entanglement of distant spins. The device consists of a p-i-n diode structure that incorporates a coupled double quantum dot. We show that electronic control of t...
Entanglement for All Quantum States
de la Torre, A. C.; Goyeneche, D.; Leitao, L.
2010-01-01
It is shown that a state that is factorizable in the Hilbert space corresponding to some choice of degrees of freedom becomes entangled for a different choice of degrees of freedom. Therefore, entanglement is not a special case but is ubiquitous in quantum systems. Simple examples are calculated and a general proof is provided. The physical…
Entanglement Entropy of Black Holes
Solodukhin, Sergey N.
2011-12-01
The entanglement entropy is a fundamental quantity, which characterizes the correlations between sub-systems in a larger quantum-mechanical system. For two sub-systems separated by a surface the entanglement entropy is proportional to the area of the surface and depends on the UV cutoff, which regulates the short-distance correlations. The geometrical nature of entanglement-entropy calculation is particularly intriguing when applied to black holes when the entangling surface is the black-hole horizon. I review a variety of aspects of this calculation: the useful mathematical tools such as the geometry of spaces with conical singularities and the heat kernel method, the UV divergences in the entropy and their renormalization, the logarithmic terms in the entanglement entropy in four and six dimensions and their relation to the conformal anomalies. The focus in the review is on the systematic use of the conical singularity method. The relations to other known approaches such as ’t Hooft’s brick-wall model and the Euclidean path integral in the optical metric are discussed in detail. The puzzling behavior of the entanglement entropy due to fields, which non-minimally couple to gravity, is emphasized. The holographic description of the entanglement entropy of the blackhole horizon is illustrated on the two- and four-dimensional examples. Finally, I examine the possibility to interpret the Bekenstein-Hawking entropy entirely as the entanglement entropy.
Quantum entanglement purification in cavities
Romero, J L; Saavedra, C; Retamal, J C
2002-01-01
A physical implementation of an entanglement purification protocol is studied using a cavity quantum electrodynamic based proposal, where, the quantum information is stored in quantum field sates inside cavities. Also a procedure is given for quantifying the degree of entanglement between quantum fields. (Author)
Constructing optimal entanglement witnesses. II
Chruscinski, Dariusz
2010-01-01
We provide a class of optimal nondecomposable entanglement witnesses for 4N x 4N composite quantum systems or, equivalently, a new construction of nondecomposable positive maps in the algebra of 4N x 4N complex matrices. This construction provides natural generalization of the Robertson map. It is shown that their structural physical approximations give rise to entanglement breaking channels.
Entanglement Entropy of Black Holes
Directory of Open Access Journals (Sweden)
Sergey N. Solodukhin
2011-10-01
Full Text Available The entanglement entropy is a fundamental quantity, which characterizes the correlations between sub-systems in a larger quantum-mechanical system. For two sub-systems separated by a surface the entanglement entropy is proportional to the area of the surface and depends on the UV cutoff, which regulates the short-distance correlations. The geometrical nature of entanglement-entropy calculation is particularly intriguing when applied to black holes when the entangling surface is the black-hole horizon. I review a variety of aspects of this calculation: the useful mathematical tools such as the geometry of spaces with conical singularities and the heat kernel method, the UV divergences in the entropy and their renormalization, the logarithmic terms in the entanglement entropy in four and six dimensions and their relation to the conformal anomalies. The focus in the review is on the systematic use of the conical singularity method. The relations to other known approaches such as ’t Hooft’s brick-wall model and the Euclidean path integral in the optical metric are discussed in detail. The puzzling behavior of the entanglement entropy due to fields, which non-minimally couple to gravity, is emphasized. The holographic description of the entanglement entropy of the black-hole horizon is illustrated on the two- and four-dimensional examples. Finally, I examine the possibility to interpret the Bekenstein-Hawking entropy entirely as the entanglement entropy.
On partially entanglement breaking channels
Chruscinski, D; Chruscinski, Dariusz; Kossakowski, Andrzej
2005-01-01
Using well known duality between quantum maps and states of composite systems we introduce the notion of Schmidt number of a quantum channel. It enables one to define classes of quantum channels which partially break quantum entanglement. These classes generalize the well known class of entanglement breaking channels.
Spread of entanglement and causality
Casini, Horacio; Liu, Hong; Mezei, Márk
2016-07-01
We investigate causality constraints on the time evolution of entanglement entropy after a global quench in relativistic theories. We first provide a general proof that the so-called tsunami velocity is bounded by the speed of light. We then generalize the free particle streaming model of [1] to general dimensions and to an arbitrary entanglement pattern of the initial state. In more than two spacetime dimensions the spread of entanglement in these models is highly sensitive to the initial entanglement pattern, but we are able to prove an upper bound on the normalized rate of growth of entanglement entropy, and hence the tsunami velocity. The bound is smaller than what one gets for quenches in holographic theories, which highlights the importance of interactions in the spread of entanglement in many-body systems. We propose an interacting model which we believe provides an upper bound on the spread of entanglement for interacting relativistic theories. In two spacetime dimensions with multiple intervals, this model and its variations are able to reproduce intricate results exhibited by holographic theories for a significant part of the parameter space. For higher dimensions, the model bounds the tsunami velocity at the speed of light. Finally, we construct a geometric model for entanglement propagation based on a tensor network construction for global quenches.
Emergence of Symmetries from Entanglement
CERN. Geneva
2016-01-01
Maximal Entanglement appears to be a key ingredient for the emergence of symmetries. We first illustrate this phenomenon using two examples: the emergence of conformal symmetry in condensed matter systems and the relation of tensor networks to holography. We further present a Principle of Maximal Entanglement that seems to dictate to a large extend the structure of gauge symmetry.
Einstein-Podolsky-Rosen Entanglement in a Vacuum-Class Two-Mode Squeezed State
Eberle, Tobias; Duhme, Jörg; Franz, Torsten; Werner, Reinhard F; Schnabel, Roman
2011-01-01
Einstein-Podolsky-Rosen (EPR) entanglement is a criterion that is more demanding than just certifying entanglement. We theoretically and experimentally analyze the low resource generation of bi-partite continuous variable entanglement, as realized by mixing a squeezed mode with a vacuum mode at a balanced beam splitter, i.e. the generation of so-called vacuum-class entanglement. We find that in order to observe EPR entanglement the total optical loss must be smaller than 33.3 %. However, arbitrary strong EPR entanglement is generally possible with this scheme. We realize continuous wave squeezed light at 1550 nm with up to 9.9 dB of non-classical noise reduction, which is the highest value at a telecom wavelength so far. Using two phase controlled balanced homodyne detectors we observe an EPR co-variance product of 0.502 \\pm 0.006 < 1, where 1 is the critical value. We discuss the feasibility of strong Gaussian entanglement and its application for quantum key distribution in a short-distance fiber network.
Evaluating convex roof entanglement measures.
Tóth, Géza; Moroder, Tobias; Gühne, Otfried
2015-04-24
We show a powerful method to compute entanglement measures based on convex roof constructions. In particular, our method is applicable to measures that, for pure states, can be written as low order polynomials of operator expectation values. We show how to compute the linear entropy of entanglement, the linear entanglement of assistance, and a bound on the dimension of the entanglement for bipartite systems. We discuss how to obtain the convex roof of the three-tangle for three-qubit states. We also show how to calculate the linear entropy of entanglement and the quantum Fisher information based on partial information or device independent information. We demonstrate the usefulness of our method by concrete examples.
Efficient Generation of Generic Entanglement
Oliveira, R; Plenio, M B
2006-01-01
We find that generic entanglement is physical, in the sense that it can be generated in polynomial time from two-qubit gates picked at random. We prove as the main result that such a process generates the average entanglement of the uniform (Haar) measure in at most $O(N^3)$ steps for $N$ qubits. This is despite an exponentially growing number of such gates being necessary for generating that measure fully on the state space. Numerics furthermore show a variation cut-off allowing one to associate a specific time with the achievement of the uniform measure entanglement distribution. Various extensions of this work are discussed. The results are relevant to entanglement theory and to protocols that assume generic entanglement can be achieved efficiently.
Universal quantum computation with little entanglement.
Van den Nest, Maarten
2013-02-01
We show that universal quantum computation can be achieved in the standard pure-state circuit model while the entanglement entropy of every bipartition is small in each step of the computation. The entanglement entropy required for large-scale quantum computation even tends to zero. Moreover we show that the same conclusion applies to many entanglement measures commonly used in the literature. This includes e.g., the geometric measure, localizable entanglement, multipartite concurrence, squashed entanglement, witness-based measures, and more generally any entanglement measure which is continuous in a certain natural sense. These results demonstrate that many entanglement measures are unsuitable tools to assess the power of quantum computers.
The entangled accelerating universe
Energy Technology Data Exchange (ETDEWEB)
Gonzalez-Diaz, Pedro F. [Colina de los Chopos, Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain); Estacion Ecologica de Biocosmologia, Pedro de Alvarado, 14, 06411-Medellin (Spain)], E-mail: p.gonzalezdiaz@imaff.cfmac.csic.es; Robles-Perez, Salvador [Colina de los Chopos, Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain); Estacion Ecologica de Biocosmologia, Pedro de Alvarado, 14, 06411-Medellin (Spain)
2009-08-31
Using the known result that the nucleation of baby universes in correlated pairs is equivalent to spacetime squeezing, we show in this Letter that there exists a T-duality symmetry between two-dimensional warp drives, which are physically expressible as localized de Sitter little universes, and two-dimensional Tolman-Hawking and Gidding-Strominger baby universes respectively correlated in pairs, so that the creation of warp drives is also equivalent to spacetime squeezing. Perhaps more importantly, it has been also seen that the nucleation of warp drives entails a violation of the Bell's inequalities, and hence the phenomena of quantum entanglement, complementarity and wave function collapse. These results are generalized to the case of any dynamically accelerating universe filled with dark or phantom energy whose creation is also physically equivalent to spacetime squeezing and to the violation of the Bell's inequalities, so that the universe we are living in should be governed by essential sharp quantum theory laws and must be a quantum entangled system.
Spread of entanglement and causality
Casini, Horacio; Mezei, Márk
2015-01-01
We investigate causality constraints on the time evolution of entanglement entropy after a global quench in relativistic theories. We first provide a general proof that the so-called tsunami velocity is bounded by the speed of light. We then generalize the free particle streaming model of arXiv:cond-mat/0503393 to general dimensions and to an arbitrary entanglement pattern of the initial state. In more than two spacetime dimensions the spread of entanglement in these models is highly sensitive to the initial entanglement pattern, but we are able to prove an upper bound on the normalized rate of growth of entanglement entropy, and hence the tsunami velocity. The bound is smaller than what one gets for quenches in holographic theories, which highlights the importance of interactions in the spread of entanglement in many-body systems. We propose an interacting model which we believe provides an upper bound on the spread of entanglement for interacting relativistic theories. In two spacetime dimensions with multi...
Lethal entanglement in baleen whales.
Cassoff, Rachel M; Moore, Kathleen M; McLellan, William A; Barco, Susan G; Rotsteins, David S; Moore, Michael J
2011-10-06
Understanding the scenarios whereby fishing gear entanglement of large whales induces mortality is important for the development of mitigation strategies. Here we present a series of 21 cases involving 4 species of baleen whales in the NW Atlantic, describing the available sighting history, necropsy observations, and subsequent data analyses that enabled the compilation of the manners in which entanglement can be lethal. The single acute cause of entanglement mortality identified was drowning from entanglement involving multiple body parts, with the animal's inability to surface. More protracted causes of death included impaired foraging during entanglement, resulting in starvation after many months; systemic infection arising from open, unresolved entanglement wounds; and hemorrhage or debilitation due to severe gear-related damage to tissues. Serious gear-induced injury can include laceration of large vessels, occlusion of the nares, embedding of line in growing bone, and massive periosteal proliferation of new bone in an attempt to wall off constricting, encircling lines. These data show that baleen whale entanglement is not only a major issue for the conservation of some baleen whale populations, but is also a major concern for the welfare of each affected individual.
Quantum Entanglement on a Hypersphere
Peters, James F.; Tozzi, Arturo
2016-08-01
A quantum entanglement's composite system does not display separable states and a single constituent cannot be fully described without considering the other states. We introduce quantum entanglement on a hypersphere - which is a 4D space undetectable by observers living in a 3D world -, derived from signals originating on the surface of an ordinary 3D sphere. From the far-flung branch of algebraic topology, the Borsuk-Ulam theorem states that, when a pair of opposite (antipodal) points on a hypersphere are projected onto the surface of 3D sphere, the projections have matching description. In touch with this theorem, we show that a separable state can be achieved for each of the entangled particles, just by embedding them in a higher dimensional space. We view quantum entanglement as the simultaneous activation of signals in a 3D space mapped into a hypersphere. By showing that the particles are entangled at the 3D level and un-entangled at the 4D hypersphere level, we achieved a composite system in which each local constituent is equipped with a pure state. We anticipate this new view of quantum entanglement leading to what are known as qubit information systems.
Local approach to quantum entanglement
Ho-Chih, Lin
Quantum entanglement is the key property that makes quantum information theory different from its classical counterpart and is also a valuable physical resource with massive potential for technological applications. However, our understanding of entanglement is still far from com plete despite intense research activities. Like other physical resources, the first step towards exploiting them fully is to know how to quantify. There are many reasons to focus on the en tanglement of continuous-variable states since the underlying degrees of freedom of physical systems carrying quantum information are frequently continuous, rather than discrete. Much of the effort has been concentrated on Gaussian states, because these are common as the ground or thermal states of optical modes. Within this framework, many interesting topics have been stud ied and some significant progress made. Nevertheless, non-Gaussian states are also extremely important this is especially so in condensed-phase systems, where harmonic behaviour in any degree of freedom is likely to be only an approximation. So far, there is little knowledge about the quantification of entanglement in non-Gaussian states. This thesis aims to contribute to the active field of research in quantum entanglement by introducing a new approach to the analysis of entanglement, especially in continuous-variable states, and shows that it leads to the first systematic quantification of the (local) entanglement in arbitrary bipartite non-Gaussian states. By applying this local approach, many new insights can be gained. Notably, local entanglements of systems with smooth wavefunctions are fully characterised by the derived simple expressions, provided the wavefunction is known. The local (logarithmic) negativity of any two-mode mixed states can be directly computed from the closed-form formulae given. For multi-mode mixed states, this approach provides a scheme that permits much simpler numerical computation for quantifying
Boundary effects in entanglement entropy
Berthiere, Clément; Solodukhin, Sergey N.
2016-09-01
We present a number of explicit calculations of Renyi and entanglement entropies in situations where the entangling surface intersects the boundary of d-dimensional Minkowski spacetime. When the boundary is a single plane we compute the contribution to the entropy due to this intersection, first in the case of the Neumann and Dirichlet boundary conditions, and then in the case of a generic Robin type boundary condition. The flow in the boundary coupling between the Neumann and Dirichlet phases is analyzed in arbitrary dimension d and is shown to be monotonic, the peculiarity of d = 3 case is noted. We argue that the translational symmetry along the entangling surface is broken due the presence of the boundary which reveals that the entanglement is not homogeneous. In order to characterize this quantitatively, we introduce a density of entanglement entropy and compute it explicitly. This quantity clearly indicates that the entanglement is maximal near the boundary. We then consider the situation where the boundary is composed of two parallel planes at a finite separation and compute the entanglement entropy as well as its density in this case. The complete contribution to entanglement entropy due to the boundaries is shown not to depend on the distance between the planes and is simply twice the entropy in the case of single plane boundary. Additionally, we find how the area law, the part in the entropy proportional to the area of entire entangling surface, depends on the size of the separation between the two boundaries. The latter is shown to appear in the UV finite part of the entropy.
Abrams, Katie; Meyers, Courtney; Irani, Tracy; Baker, Lauri
2010-01-01
Several land-grant institutions have adopted a name to encompass the teaching, research, and Extension components of the university, creating a brand identity for those public services. But, in the mind of stakeholders, has the connection between the tripartite mission and the brand name been made? The study reported here sought to determine…
Structure of Anxiety and Depression in Urban Youth: An Examination of the Tripartite Model
Lambert, Sharon F.; McCreary, Beth T.; Joiner, Thomas E.; Schmidt, Norman B.; Ialongo, Nicolas S.
2004-01-01
In this study, the authors examined the validity of the tripartite model of anxiety and depression (L. A. Clark & D. Watson, 1991) in a community epidemiological sample of 467 urban African American youth. Participants completed the Baltimore How I Feel (N. S. Ialongo, S. G. Kellam, & J. Poduska, 1999), a measure of anxiety and depressive…
Entanglement routers using macroscopic singlets.
Bayat, Abolfazl; Bose, Sougato; Sodano, Pasquale
2010-10-29
We propose a mechanism where high entanglement between very distant boundary spins is generated by suddenly connecting two long Kondo spin chains. We show that this procedure provides an efficient way to route entanglement between multiple distant sites. We observe that the key features of the entanglement dynamics of the composite spin chain are well described by a simple model of two singlets, each formed by two spins. The proposed routing mechanism is a footprint of the emergence of a Kondo cloud in a Kondo system and can be engineered and observed in varied physical settings.
Constructing new optimal entanglement witnesses
Chruscinski, Dariusz; Sarbicki, Gniewomir
2009-01-01
We provide a new class of indecomposable entanglement witnesses. In 4 x 4 case it reproduces the well know Breuer-Hall witness. We prove that these new witnesses are optimal and atomic, i.e. they are able to detect the "weakest" quantum entanglement encoded into states with positive partial transposition (PPT). Equivalently, we provide a new construction of indecomposable atomic maps in the algebra of 2k x 2k complex matrices. It is shown that their structural physical approximations give rise to entanglement breaking channels. This result supports recent conjecture by Korbicz et. al.
Zero Modes and Entanglement Entropy
Yazdi, Yasaman K
2016-01-01
Ultraviolet divergences are widely discussed in studies of entanglement entropy. Also present, but much less understood, are infrared divergences due to zero modes in the field theory. In this note, we discuss the importance of carefully handling zero modes in entanglement entropy. We give an explicit example for a chain of harmonic oscillators in 1D, where a mass regulator is necessary to avoid an infrared divergence due to a zero mode. We also comment on a surprising contribution of the zero mode to the UV-scaling of the entanglement entropy.
Quantitative two-qutrit entanglement
Energy Technology Data Exchange (ETDEWEB)
Eltschka, Christopher [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany); Siewert, Jens [Departamento de Quimica Fisica, Universidad del Pais Vasco UPV/EHU, 48080 Bilbao (Spain); IKERBASQUE, Basque Foundation for Science, 48011 Bilbao (Spain)
2013-07-01
We introduce the new concept of axisymmetric bipartite states. For d x d-dimensional systems these states form a two-parameter family of nontrivial mixed states that include the isotropic states. We present exact quantitative results for class-specific entanglement as well as for the negativity and I-concurrence of two-qutrit axisymmetric states. These results have interesting applications such as for quantitative witnesses of class-specific entanglement in arbitrary two-qutrit states and as device-independent witness for the number of entangled dimensions.
Entangled light from white noise
Plenio, M B
2002-01-01
An atom that couples to two distinct leaky optical cavities is driven by an external optical white noise field. We describe how entanglement between the light fields sustained by two optical cavities arises in such a situation. The entanglement is maximized for intermediate values of the cavity damping rates and the intensity of the white noise field, vanishing both for small and for large values of these parameters and thus exhibiting a stochastic-resonance-like behaviour. This example illustrates the possibility of generating entanglement by exclusively incoherent means and sheds new light on the constructive role noise may play in certain tasks of interest for quantum information processing.
Entangled light from white noise.
Plenio, M B; Huelga, S F
2002-05-13
An atom that couples to two distinct leaky optical cavities is driven by an external optical white noise field. We describe how entanglement between the light fields sustained by two optical cavities arises in such a situation. The entanglement is maximized for intermediate values of the cavity damping rates and the intensity of the white noise field, vanishing both for small and for large values of these parameters and thus exhibiting a stochastic-resonancelike behavior. This example illustrates the possibility of generating entanglement by exclusively incoherent means and sheds new light on the constructive role noise may play in certain tasks of interest for quantum information processing.
Complementary sequential measurements generate entanglement
Coles, Patrick J.; Piani, Marco
2014-01-01
We present a paradigm for capturing the complementarity of two observables. It is based on the entanglement created by the interaction between the system observed and the two measurement devices used to measure the observables sequentially. Our main result is a lower bound on this entanglement and resembles well-known entropic uncertainty relations. Besides its fundamental interest, this result directly bounds the effectiveness of sequential bipartite operations—corresponding to the measurement interactions—for entanglement generation. We further discuss the intimate connection of our result with two primitives of information processing, namely, decoupling and coherent teleportation.
Teleportation of Squeezed Entangled State
Institute of Scientific and Technical Information of China (English)
HU Li-Yun; ZHOU Nan-Run
2007-01-01
Based on the coherent entangled state |α, x＞ we introduce the squeezed entangled state (SES). Then we propose a teleportation protocol for the SES by using Einstein-Podolsky-Rosen entangled state |η＞as a quantum channel.The calculation is greatly simplified by virtue of the Schmidt decompositions of both |α, x＞and |η＞. Any bipartite states that can be expanded in terms of |α, x＞may be teleported in this way due to the completeness of |α, x＞.
Entanglement entropy and entanglement spectrum of triplet topological superconductors.
Oliveira, T P; Ribeiro, P; Sacramento, P D
2014-10-22
We analyze the entanglement entropy properties of a 2D p-wave superconductor with Rashba spin-orbit coupling, which displays a rich phase-space that supports non-trivial topological phases, as the chemical potential and the Zeeman term are varied. We show that the entanglement entropy and its derivatives clearly signal the topological transitions and we find numerical evidence that for this model the derivative with respect to the magnetization provides a sensible signature of each topological phase. Following the area law for the entanglement entropy, we systematically analyze the contributions that are proportional to or independent of the perimeter of the system, as a function of the Hamiltonian coupling constants and the geometry of the finite subsystem. For this model, we show that even though the topological entanglement entropy vanishes, it signals the topological phase transitions in a finite system. We also observe a relationship between a topological contribution to the entanglement entropy in a half-cylinder geometry and the number of edge states, and that the entanglement spectrum has robust modes associated with each edge state, as in other topological systems.
Experimental higher dimensional entanglement
Energy Technology Data Exchange (ETDEWEB)
Richart, Daniel L.; Wieczorek, Witlef; Weinfurter, Harald [MPI fuer Quantenoptik, Hans Kopfermannstr. 1, 85748 Garching (Germany); Ludwig-Maximilians-Universitaet, Schellingstr. 4, D-80797 Muenchen (Germany)
2009-07-01
Higher dimensional states (qudits) allow to implement quantum communication schemes of increasing complexity, as e.g. superdense coding. Similarly, qudits allow further research into the fundaments of quantum theory. Here we report on first steps towards the implementation of states with correlated photon pairs in a 2 x 8 dimensional Hilbert space. To this end the photon pairs are prepared in the energy-time basis, as initially proposed in: Using unbalanced interferometers, information can be encoded in the different arrival times of the photon pairs, early and late, as was experimentally realized in. Here, we extend this scheme by proposing and characterizing a scalable multiple time delay interferometer. This interferometer system allows an exponential increase in the dimensionality of the entangled state with only a linear increase in the optical components used. Using the proposed interferometer system, first experimental tests on a two-dimensional state yielded a violation of a Bell inequality by four standard deviations.
Philosophical lessons of entanglement
Sudbery, Anthony
2011-01-01
The quantum-mechanical description of the world, including human observers, makes substantial use of entanglement. In order to understand this, we need to adopt concepts of truth, probability and time which are unfamiliar in modern scientific thought. There are two kinds of statements about the world: those made from inside the world, and those from outside. The conflict between contradictory statements which both appear to be true can be resolved by recognising that they are made in different perspectives. Probability, in an objective sense, belongs in the internal perspective, and to statements in the future tense. Such statements obey a many-valued logic, in which the truth values are identified as probabilities.
Generating entangled superqubit states
Borsten, L; Duff, M J
2014-01-01
We introduce the global unitary supergroup $\\text{UOSp}((3^n+1)/2 | (3^n-1)/2)$ for an $n$-superqubit system, which contains as a subgroup the local unitary supergroup $[\\text{UOSp}(2|1)]^n$. While for $4>n>1$ the bosonic subgroup in $\\text{UOSp}((3^n+1)/2 | (3^n-1)/2)$ does not contain the standard global unitary group $\\text{SU}(2^n)$, it does have an $\\text{USp}(2^n)\\subset\\text{SU}(2^n)$ subgroup which acts transitively on the $n$-qubit subspace, as required for consistency with the conventional multi-qubit framework. For two superqubits the $\\text{UOSp}(5|4)$ action is used to generate entangled states from the "bosonic" separable state $|00>$.
Entanglement Distribution in Optical Networks
Ciurana, Alex; Martinez-Mateo, Jesus; Schrenk, Bernhard; Peev, Momtchil; Poppe, Andreas
2014-01-01
The ability to generate entangled photon-pairs over a broad wavelength range opens the door to the simultaneous distribution of entanglement to multiple users in a network by using centralized sources and flexible wavelength-division multiplexing schemes. Here we show the design of a metropolitan optical network consisting of tree-type access networks whereby entangled photon-pairs are distributed to any pair of users, independent of their location. The network is constructed employing commercial off-the-shelf components and uses the existing infrastructure, which allows for moderate deployment costs. We further develop a channel plan and a network-architecture design to provide a direct optical path between any pair of users, thus allowing classical and one-way quantum communication as well as entanglement distribution. This allows the simultaneous operation of multiple quantum information technologies. Finally, we present a more flexible backbone architecture that pushes away the load limitations of the ori...
Entanglement properties of quantum polaritons
Suárez-Forero, D. G.; Cipagauta, G.; Vinck-Posada, H.; Fonseca Romero, K. M.; Rodríguez, B. A.; Ballarini, D.
2016-05-01
Exciton polaritons are coupled states of matter and light, originated by the strong interaction between an optical mode and semiconductor excitons. This interaction can be obtained also at a single-particle level, in which case it has been shown that a quantum treatment is mandatory. In this work we study the light-matter entanglement of polaritons from a fully quantum formalism including pumping and dissipation. We find that the entanglement is completely destroyed if the exciton and photon are tuned at the resonance condition, even under very low pumping rates. Instead, the best condition for maximizing entanglement and purity of the steady state is when the exciton and photon are out of resonance and when incoherent pumping exactly compensates the dissipation rate. In the presence of multiple quantum dots coupled to the light mode, matter-light entanglement survives only at larger detuning for a higher number of quantum dots considered.
Entanglement swapping without joint Measurement
Yang, M; Cao, Z L; Yang, Ming; Song, Wei; Cao, Zhuo-Liang
2004-01-01
We propose an entanglement swapping scheme in cavity QED. In the scheme, the previously used joint measurement is not needed. Only single measurement on cavity can realize the swapping process, which avoids the difficulty of measurement on atomic state.
DNA Replication via Entanglement Swapping
Pusuluk, Onur
2010-01-01
Quantum effects are mainly used for the determination of molecular shapes in molecular biology, but quantum information theory may be a more useful tool to understand the physics of life. Molecular biology assumes that function is explained by structure, the complementary geometries of molecules and weak intermolecular hydrogen bonds. However, both this assumption and its converse are possible if organic molecules and quantum circuits/protocols are considered as hardware and software of living systems that are co-optimized during evolution. In this paper, we try to model DNA replication as a multiparticle entanglement swapping with a reliable qubit representation of nucleotides. In the model, molecular recognition of a nucleotide triggers an intrabase entanglement corresponding to a superposition state of different tautomer forms. Then, base pairing occurs by swapping intrabase entanglements with interbase entanglements.
Entanglement scaling in lattice systems
Energy Technology Data Exchange (ETDEWEB)
Audenaert, K M R [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, Exhibition Road, London SW7 2PG (United Kingdom); Cramer, M [QOLS, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom); Eisert, J [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, Exhibition Road, London SW7 2PG (United Kingdom); Plenio, M B [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, Exhibition Road, London SW7 2PG (United Kingdom)
2007-05-15
We review some recent rigorous results on scaling laws of entanglement properties in quantum many body systems. More specifically, we study the entanglement of a region with its surrounding and determine its scaling behaviour with its size for systems in the ground and thermal states of bosonic and fermionic lattice systems. A theorem connecting entanglement between a region and the rest of the lattice with the surface area of the boundary between the two regions is presented for non-critical systems in arbitrary spatial dimensions. The entanglement scaling in the field limit exhibits a peculiar difference between fermionic and bosonic systems. In one-spatial dimension a logarithmic divergence is recovered for both bosonic and fermionic systems. In two spatial dimensions in the setting of half-spaces however we observe strict area scaling for bosonic systems and a multiplicative logarithmic correction to such an area scaling in fermionic systems. Similar questions may be posed and answered in classical systems.
Quantum entanglement distillation with metamaterials.
al Farooqui, Md Abdullah; Breeland, Justin; Aslam, Muhammad I; Sadatgol, Mehdi; Özdemir, Şahin K; Tame, Mark; Yang, Lan; Güney, Durdu Ö
2015-07-13
We propose a scheme for the distillation of partially entangled two-photon Bell and three-photon W states using metamaterials. The distillation of partially entangled Bell states is achieved by using two metamaterials with polarization dependence, one of which is rotated by π/2 around the direction of propagation of the photons. On the other hand, the distillation of three-photon W states is achieved by using one polarization dependent metamaterial and two polarization independent metamaterials. Upon transmission of the photons of the partially entangled states through the metamaterials the entanglement of the states increases and they become distilled. This work opens up new directions in quantum optical state engineering by showing how metamaterials can be used to carry out a quantum information processing task.
Quality of Spatial Entanglement Propagation
Reichert, Matthew; Fleischer, Jason W
2016-01-01
We explore, both experimentally and theoretically, the propagation dynamics of spatially entangled photon pairs (biphotons). Characterization of entanglement is done via the Schmidt number, which is a universal measurement of the degree of entanglement directly related to the non-separability of the state into its subsystems. We develop expressions for the terms of the Schmidt number that depend on the amplitude and phase of the commonly used double-Gaussian approximation for the biphoton wave function, and demonstrate migration of entanglement between amplitude and phase upon propagation. We then extend this analysis to incorporate both phase curvature in the pump beam and higher spatial frequency content of more realistic non-Gaussian wave functions. Specifically, we generalize the classical beam quality parameter $M^2$ to the biphotons, allowing the description of more information-rich beams and more complex dynamics. Agreement is found with experimental measurements using direct imaging and Fourier optics...
Gaussian Entanglement Distribution via Satellite
Hosseinidehaj, Nedasadat
2014-01-01
In this work we analyse three quantum communication schemes for the generation of Gaussian entanglement between two ground stations. Communication occurs via a satellite over two independent atmospheric fading channels dominated by turbulence-induced beam wander. In our first scheme the engineering complexity remains largely on the ground transceivers, with the satellite acting simply as a reflector. Although the channel state information of the two atmospheric channels remains unknown in this scheme, the Gaussian entanglement generation between the ground stations can still be determined. On the ground, distillation and Gaussification procedures can be applied, leading to a refined Gaussian entanglement generation rate between the ground stations. We compare the rates produced by this first scheme with two competing schemes in which quantum complexity is added to the satellite, thereby illustrating the trade-off between space-based engineering complexity and the rate of ground-station entanglement generation...
Orbital entanglement in quantum chemistry
Boguslawski, Katharina
2014-01-01
The basic concepts of orbital entanglement and its application to chemistry are briefly reviewed. The calculation of orbital entanglement measures from correlated wavefunctions is discussed in terms of reduced $n$-particle density matrices. Possible simplifications in their evaluation are highlighted in case of seniority-zero wavefunctions. Specifically, orbital entanglement allows us to dissect electron correlation effects in its strong and weak contributions, to determine bond orders, to assess the quality and stability of active space calculations, to monitor chemical reactions, and to identify points along the reaction coordinate where electronic wavefunctions change drastically. Thus, orbital entanglement represents a useful and intuitive tool to interpret complex electronic wavefunctions and to facilitate a qualitative understanding of electronic structure and how it changes in chemical processes.
Wavelength-multiplexed entanglement distribution
Lim, Han Chuen; Yoshizawa, Akio; Tsuchida, Hidemi; Kikuchi, Kazuro
2010-08-01
The realization of an entanglement distribution optical fiber network connecting multiple parties would permit implementation of many information security applications such as entanglement-based quantum key distribution and quantum secret sharing. However, due to material absorption and scattering in optical fiber, photons that are the carriers of quantum entanglement experience loss during propagation and the overall photon arrival rate can be very low in such a network. One way to increase photon arrival rate is to make full use of the available transmission bandwidth of optical fiber and this is achievable via wavelength-multiplexing. We review our recent work on wavelength-multiplexed entanglement distribution and discuss system design considerations from a telecommunication engineering perspective.
Genetic algorithm optimization of entanglement
Navarro-Munoz, J C; Rosu, H C; Navarro-Munoz, Jorge C.
2006-01-01
We present an application of a genetic algorithmic computational method to the optimization of the concurrence measure of entanglement for the cases of one dimensional chains, as well as square and triangular lattices in a simple tight-binding approach
Continuous-Variable Entanglement Swapping
Directory of Open Access Journals (Sweden)
Kevin Marshall
2015-05-01
Full Text Available We present a very brief overview of entanglement swapping as it relates to continuous-variable quantum information. The technical background required is discussed and the natural link to quantum teleportation is established before discussing the nature of Gaussian entanglement swapping. The limitations of Gaussian swapping are introduced, along with the general applications of swapping in the context of to quantum communication and entanglement distribution. In light of this, we briefly summarize a collection of entanglement swapping schemes which incorporate a non-Gaussian ingredient and the benefits of such schemes are noted. Finally, we motivate the need to further study and develop such schemes by highlighting requirements of a continuous-variable repeater.
Entanglement distribution in quantum networks
Energy Technology Data Exchange (ETDEWEB)
Perseguers, Sebastien
2010-04-15
This Thesis contributes to the theory of entanglement distribution in quantum networks, analyzing the generation of long-distance entanglement in particular. We consider that neighboring stations share one partially entangled pair of qubits, which emphasizes the difficulty of creating remote entanglement in realistic settings. The task is then to design local quantum operations at the stations, such that the entanglement present in the links of the whole network gets concentrated between few parties only, regardless of their spatial arrangement. First, we study quantum networks with a two-dimensional lattice structure, where quantum connections between the stations (nodes) are described by non-maximally entangled pure states (links). We show that the generation of a perfectly entangled pair of qubits over an arbitrarily long distance is possible if the initial entanglement of the links is larger than a threshold. This critical value highly depends on the geometry of the lattice, in particular on the connectivity of the nodes, and is related to a classical percolation problem. We then develop a genuine quantum strategy based on multipartite entanglement, improving both the threshold and the success probability of the generation of long-distance entanglement. Second, we consider a mixed-state definition of the connections of the quantum networks. This formalism is well-adapted for a more realistic description of systems in which noise (random errors) inevitably occurs. New techniques are required to create remote entanglement in this setting, and we show how to locally extract and globally process some error syndromes in order to create useful long-distance quantum correlations. Finally, we turn to networks that have a complex topology, which is the case for most real-world communication networks such as the Internet for instance. Besides many other characteristics, these systems have in common the small-world feature, stating that any two nodes are separated by a
Stability of Pairwise Entanglement in Decoherence Environment
Institute of Scientific and Technical Information of China (English)
蔡建明
2004-01-01
@@ Consider the dynamics of a bipartite entangled system in the decoherence environment, we investigate the stability of pairwise entanglement under decoherence.We find that with the same initial entanglement, the lifetime of entanglement in pure states and some mixed states is the longest.We call these special entangled states as Decoherence Path States (DPS).Besides, we present simple analytic evolution equations of the entanglement in these states.The lifetimes can also be obtained easily.Furthermore, we also study the stability of the nearest neighbor entanglement in the ground state of an antiferromagnetic spin-1/2 ring.Coincidentally, the conclusion is that it is as stable as Decoherence Path States.Thus the nearest neighbor entanglement in the ground state is not maximized but it is the most stable.This interesting result links the energy and entanglement in a spin system from a new point of view.
Purification of Logic-Qubit Entanglement.
Zhou, Lan; Sheng, Yu-Bo
2016-07-05
Recently, the logic-qubit entanglement shows its potential application in future quantum communication and quantum network. However, the entanglement will suffer from the noise and decoherence. In this paper, we will investigate the first entanglement purification protocol for logic-qubit entanglement. We show that both the bit-flip error and phase-flip error in logic-qubit entanglement can be well purified. Moreover, the bit-flip error in physical-qubit entanglement can be completely corrected. The phase-flip in physical-qubit entanglement error equals to the bit-flip error in logic-qubit entanglement, which can also be purified. This entanglement purification protocol may provide some potential applications in future quantum communication and quantum network.
Thermodynamic law from the entanglement entropy bound
Park, Chanyong
2016-04-01
From black hole thermodynamics, the Bekenstein bound has been proposed as a universal thermal entropy bound. It has been further generalized to an entanglement entropy bound which is valid even in a quantum system. In a quantumly entangled system, the non-negativity of the relative entropy leads to the entanglement entropy bound. When the entanglement entropy bound is saturated, a quantum system satisfies the thermodynamicslike law with an appropriately defined entanglement temperature. We show that the saturation of the entanglement entropy bound accounts for a universal feature of the entanglement temperature proportional to the inverse of the system size. In addition, we show that the deformed modular Hamiltonian under a global quench also satisfies the generalized entanglement entropy boundary after introducing a new quantity called the entanglement chemical potential.
Experimental implementation of a NMR entanglement witness
Filgueiras, J G; Auccaise, R E; Vianna, R O; Sarthour, R S; Oliveira, I S
2012-01-01
Entanglement witnesses (EW) allow the detection of entanglement in a quantum system, from the measurement of some few observables. They do not require the complete determination of the quantum state, which is regarded as a main advantage. On this paper it is experimentally analyzed an entanglement witness recently proposed in the context of Nuclear Magnetic Resonance (NMR) experiments to test it in some Bell-diagonal states. We also propose some optimal entanglement witness for Bell-diagonal states. The efficiency of the two types of EW's are compared to a measure of entanglement with tomographic cost, the generalized robustness of entanglement. It is used a GRAPE algorithm to produce an entangled state which is out of the detection region of the EW for Bell-diagonal states. Upon relaxation, the results show that there is a region in which both EW fails, whereas the generalized robustness still shows entanglement, but with the entanglement witness proposed here with a better performance.
Multi pulse control of entanglement
Uchiyama, C; Uchiyama, Chikako; Aihara, Masaki
2004-01-01
We study the effectiveness of multi pulse control to suppress the degradation of entanglement. Based on a linearly interacting spin-boson model, we show that the multi pulse application recovers the decay of concurrence when an entangled pair of spins interacts with a reservoir that has the non-Markovian nature. We present the effectiveness of multi pulse control for both the common bath case and the individual bath case.
Entanglement witnessing in superconducting beamsplitters
Soller, H.; Hofstetter, L.; Reeb, D.
2013-06-01
We analyse a large class of superconducting beamsplitters for which the Bell parameter (CHSH violation) is a simple function of the spin detector efficiency. For these superconducting beamsplitters all necessary information to compute the Bell parameter can be obtained in Y-junction setups for the beamsplitter. Using the Bell parameter as an entanglement witness, we propose an experiment which allows to verify the presence of entanglement in Cooper pair splitters.
Entanglement for all quantum states
Energy Technology Data Exchange (ETDEWEB)
De la Torre, A C; Goyeneche, D; Leitao, L [IFIMAR, (CONICET-UNMDP) Departamento de Fisica, Universidad Nacional de Mar del Plata, Funes 3350, 7600 Mar del Plata (Argentina)], E-mail: delatorre@mdp.edu.ar, E-mail: dgoyene@mdp.edu.ar, E-mail: lleitao@mdp.edu.ar
2010-03-15
It is shown that a state that is factorizable in the Hilbert space corresponding to some choice of degrees of freedom becomes entangled for a different choice of degrees of freedom. Therefore, entanglement is not a special case but is ubiquitous in quantum systems. Simple examples are calculated and a general proof is provided. The physical relevance of the change of tensor product structure is mentioned.
Entanglement for all quantum states
de la Torre, A C; Leitao, L; 10.1088/0143-0807/31/2/010
2010-01-01
It is shown that a state that is factorizable in the Hilbert space corresponding to some choice of degrees of freedom, becomes entangled for a different choice of degrees of freedom. Therefore, entanglement is not a special case but is ubiquitous in quantum systems. Simple examples are calculated and a general proof is provided. The physical relevance of the change of tensor product structure is mentioned.
Complementary sequential measurements generate entanglement
Coles, Patrick J.; Piani, Marco
2013-01-01
We present a new paradigm for capturing the complementarity of two observables. It is based on the entanglement created by the interaction between the system observed and the two measurement devices used to measure the observables sequentially. Our main result is a lower bound on this entanglement and resembles well-known entropic uncertainty relations. Besides its fundamental interest, this result directly bounds the effectiveness of sequential bipartite operations---corresponding to the mea...
Multipartite geometric entanglement in finite size XY model
Energy Technology Data Exchange (ETDEWEB)
Blasone, Massimo; Dell' Anno, Fabio; De Siena, Silvio; Giampaolo, Salvatore Marco; Illuminati, Fabrizio, E-mail: blasone@sa.infn.i [Dipartimento di Matematica e Informatica, Universita degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy)
2009-06-01
We investigate the behavior of the multipartite entanglement in the finite size XY model by means of the hierarchical geometric measure of entanglement. By selecting specific components of the hierarchy, we study both global entanglement and genuinely multipartite entanglement.
Quantum Entanglement and Chemical Reactivity.
Molina-Espíritu, M; Esquivel, R O; López-Rosa, S; Dehesa, J S
2015-11-10
The water molecule and a hydrogenic abstraction reaction are used to explore in detail some quantum entanglement features of chemical interest. We illustrate that the energetic and quantum-information approaches are necessary for a full understanding of both the geometry of the quantum probability density of molecular systems and the evolution of a chemical reaction. The energy and entanglement hypersurfaces and contour maps of these two models show different phenomena. The energy ones reveal the well-known stable geometry of the models, whereas the entanglement ones grasp the chemical capability to transform from one state system to a new one. In the water molecule the chemical reactivity is witnessed through quantum entanglement as a local minimum indicating the bond cleavage in the dissociation process of the molecule. Finally, quantum entanglement is also useful as a chemical reactivity descriptor by detecting the transition state along the intrinsic reaction path in the hypersurface of the hydrogenic abstraction reaction corresponding to a maximally entangled state.
Entanglement transfer between bipartite systems
Bougouffa, Smail
2011-01-01
The problem of a controlled transfer of an entanglement initially encoded into two two-level atoms that are successively sent through two single-mode cavities is investigated. The atoms and the cavity modes form a four qubit system and we demonstrate under which conditions the initial entanglement encoded into the atoms can be completely transferred to other pairs of qubits. We find that in the case of a nonzero detuning between the atomic transition frequencies and the cavity mode frequencies, no complete transfer of the initial entanglement is possible to any of the other pairs of qubits. In the case of exact resonance and equal coupling strengths of the atoms to the cavity modes, an initial maximally entangled state of the atoms can be completely transferred to the cavity modes. The complete transfer of the entanglement is restricted to the cavity modes only with the transfer to the other pairs being limited to up to 50%. We have found that the complete transfer of an initial entanglement to other pairs of...
Constructing entanglement measures for fermions
Johansson, Markus; Raissi, Zahra
2016-10-01
In this paper we describe a method for finding polynomial invariants under stochastic local operations and classical communication (SLOCC) for a system of delocalized fermions shared between different parties, with global particle-number conservation as the only constraint. These invariants can be used to construct entanglement measures for different types of entanglement in such a system. It is shown that the invariants, and the measures constructed from them, take a nonzero value only if the state of the system allows for the observation of Bell-nonlocal correlations. Invariants of this kind are constructed for systems of two and three spin-1/2 fermions and examples of maximally entangled states are given that illustrate the different types of entanglement distinguished by the invariants. A general condition for the existence of SLOCC invariants and their associated measures is given as a relation between the number of fermions, their spin, and the number of spatial modes of the system. In addition, the effect of further constraints on the system, including the localization of a subset of the fermions, is discussed. Finally, a hybrid Ising-Hubbard Hamiltonian is constructed for which the ground state of a three-site chain exhibits a high degree of entanglement at the transition between a regime dominated by on-site interaction and a regime dominated by Ising interaction. This entanglement is well described by a measure constructed by the introduced method.
Multiboundary Wormholes and Holographic Entanglement
Balasubramanian, Vijay; Maloney, Alexander; Marolf, Donald; Ross, Simon F
2014-01-01
The AdS/CFT correspondence relates quantum entanglement between boundary Conformal Field Theories and geometric connections in the dual asymptotically Anti-de Sitter space-time. We consider entangled states in the n-fold tensor product of a 1+1 dimensional CFT Hilbert space defined by the Euclidean path integral over a Riemann surface with n holes. In one region of moduli space, the dual bulk state is a black hole with $n$ asymptotically AdS_3 regions connected by a common wormhole, while in other regions the bulk fragments into disconnected components. We study the entanglement structure and compute the wave function explicitly in the puncture limit of the Riemann surface in terms of CFT n-point functions. We also use AdS minimal surfaces to measure entanglement more generally. In some regions of the moduli space the entanglement is entirely multipartite, though not of the GHZ type. However, even when the bulk is completely connected, in some regions of the moduli space the entanglement is almost entirely bi...
On Relativistic Quantum Information Properties of Entangled Wave Vectors of Massive Fermions
Cafaro, C; Mancini, S
2011-01-01
We study special relativistic effects on the entanglement between either spins or momenta of composite quantum systems of two spin-1/2 massive particles, either indistinguishable or distinguishable, in inertial reference frames in relative motion. For the case of indistinguishable particles, we consider a balanced scenario where the momenta of the pair are well-defined but not maximally entangled in the rest frame while the spins of the pair are described by a one-parameter ($\\eta$) family of entangled bipartite states. For the case of distinguishable particles, we consider an unbalanced scenario where the momenta of the pair are well-defined and maximally entangled in the rest frame while the spins of the pair are described by a one-parameter ($\\xi$) family of non-maximally entangled bipartite states. In both cases, we show that neither the spin-spin ($ss$) nor the momentum-momentum ($mm$) entanglements quantified by means of Wootters' concurrence are Lorentz invariant quantities: the total amount of entangl...
Proposal for quantum entanglement of six photons
Institute of Scientific and Technical Information of China (English)
You Jun; Li Jia-Hua; Xie Xiao-Tao
2005-01-01
We propose a different scheme to achieve six-photon entangled states based entirely on the concept of quantum erasure. To begin with, a scheme for making use of a group of four entangled photons to generate six-photon entangled states is presented. Then, with the same technique, the preparation of the six-photon entanglement from five-particle entanglement which is then combined with Bell states is considered. Our experimental methods can be used for the investigations of measurement-based quantum computation and multi-party quantum communication. We find that the success probability is determined by the small coefficients of the entangled states.
Entanglement concentration for two-mode Gaussian states in non-inertial frames
Di Noia, Maurizio; Giraldi, Filippo; Petruccione, Francesco
2017-04-01
Entanglement creation and concentration by means of a beam splitter (BS) is analysed for a generic two-mode bipartite Gaussian state in a relativistic framework. The total correlations, the purity and the entanglement in terms of logarithmic negativity are analytically studied for observers in an inertial state and in a non-inertial state of uniform acceleration. The dependence of entanglement on the BS transmissivity due to the Unruh effect is analysed in the case when one or both observers undergo uniform acceleration. Due to the Unruh effect, depending on the initial Gaussian state parameters and observed accelerations, the best condition for entanglement generation limited to the two modes of the observers in their regions is not always a balanced beam splitter, as it is for the inertial case.
Entanglement Properties in Two-Component Bose-Einstein Condensate
Jiang, Di-You
2016-10-01
We investigate entanglement inseparability and bipartite entanglement of in two-component Bose-Einstein condensate in the presence of the nonlinear interatomic interaction, interspecies interaction. Entanglement inseparability and bipartite entanglement have the similar properties. More entanglement can be generated by adjusting the nonlinear interatomic interaction and control the time interval of the entanglement by adjusting interspecies interaction.
General polygamy inequality of multi-party quantum entanglement
Kim, Jeong San
2012-01-01
Using entanglement of assistance, we establish a general polygamy inequality of multi-party entanglement in arbitrary dimensional quantum systems. For multi-party closed quantum systems, we relate our result with the monogamy of entanglement to show that the entropy of entanglement is an universal entanglement measure that bounds both monogamy and polygamy of multi-party quantum entanglement.
Generation and Purification of Atomic Entangled States
Institute of Scientific and Technical Information of China (English)
YANG Ming; SONG Wei; LI Yingqun; SHI Shouhua; CAO Zhuoliang
2004-01-01
@@ Entangled state plays a more and more important role in quantum information, so the generation of entangled state is of scientific value and practical significance.Although the experimental realization of entangled pairs of atoms and polarized photons have been reported recently, the current preparation schemes cannot meet the need of the practical application of entangled state in Quantum Communication and Quantum Computation.At the same time, resulting from the coupling between the quantum systems and its environment, decoherence of the quantum systems is unavoidable, which sets a vital obstacle on the way of the application of entanglement.There exist some entanglement generation and purification schemes, but the range of its application is relative small.So we proposed a more efficient scheme for entanglement generation and purification.The scheme is mainly based on the combination of linear optics and Cavity QED technique.The entanglement generation scheme can entangle two atoms by using MZI plus an optical cavity.Pure maximally entangled atomic states can be generated from product states or mixed states.Using a MZI, we can extract not only two-atom near-maximally entangled states but also four-atom maximally entangled states from less entangled pure or mixed states.
Entangled Harmonic Oscillators and Space-time Entanglement
Baskal, Sibel; Noz, Marilyn E
2016-01-01
The mathematical basis for the Gaussian entanglement is discussed in detail, as well as its implications in the internal space-time structure of relativistic extended particles. It is shown that the Gaussian entanglement shares the same set of mathematical formulas with the harmonic oscillator in the Lorentz-covariant world. It is thus possible to transfer the concept of entanglement to the Lorentz-covariant picture of the bound state which requires both space and time separations between two constituent particles. These space and time variables become entangled as the bound state moves with a relativistic speed. It is shown also that our inability to measure the time-separation variable leads to an entanglement entropy together with a rise in the temperature of the bound state. As was noted by Paul A. M. Dirac in 1963, the system of two oscillators contains the symmetries of O(3,2) de Sitter group containing two O(3,1) Lorentz groups as its subgroups. Dirac noted also that the system contains the symmetry of...
Teleportation of N-particle entangled W state via entanglement swapping
Institute of Scientific and Technical Information of China (English)
Zhan You-Bang
2004-01-01
A scheme for teleporting an unknown N-particle entangled W state is proposed via entanglement swapping. In this scheme, N maximally entangled particle pairs are used as quantum channel. As a special case, the teleportation of an unknown four-particle entangled W state is studied.
Separability criteria for genuine multiparticle entanglement
Guehne, O.; Seevinck, M.P.
2010-01-01
We present a method to derive separability criteria for different classes of multiparticle entanglement, especially genuine multiparticle entanglement. The resulting criteria are necessary and sufficient for certain families of states. This, for example, completely solves the problem of classifying
Experimental distribution of entanglement with separable carriers.
Fedrizzi, A; Zuppardo, M; Gillett, G G; Broome, M A; Almeida, M P; Paternostro, M; White, A G; Paterek, T
2013-12-01
The key requirement for quantum networking is the distribution of entanglement between nodes. Surprisingly, entanglement can be generated across a network without direct transfer-or communication-of entanglement. In contrast to information gain, which cannot exceed the communicated information, the entanglement gain is bounded by the communicated quantum discord, a more general measure of quantum correlation that includes but is not limited to entanglement. Here, we experimentally entangle two communicating parties sharing three initially separable photonic qubits by exchange of a carrier photon that is unentangled with either party at all times. We show that distributing entanglement with separable carriers is resilient to noise and in some cases becomes the only way of distributing entanglement through noisy environments.
Entanglement tsunami: universal scaling in holographic thermalization.
Liu, Hong; Suh, S Josephine
2014-01-10
We consider the time evolution of entanglement entropy after a global quench in a strongly coupled holographic system, whose subsequent equilibration is described in the gravity dual by the gravitational collapse of a thin shell of matter resulting in a black hole. In the limit of large regions of entanglement, the evolution of entanglement entropy is controlled by the geometry around and inside the event horizon of the black hole, resulting in regimes of pre-local-equilibration quadratic growth (in time), post-local-equilibration linear growth, a late-time regime in which the evolution does not carry memory of the size and shape of the entangled region, and a saturation regime with critical behavior resembling those in continuous phase transitions. Collectively, these regimes suggest a picture of entanglement growth in which an "entanglement tsunami" carries entanglement inward from the boundary. We also make a conjecture on the maximal rate of entanglement growth in relativistic systems.
Family of nonlocal bound entangled states
Yu, Sixia; Oh, C. H.
2017-03-01
Bound entanglement, being entangled yet not distillable, is essential to our understanding of the relations between nonlocality and entanglement besides its applications in certain quantum information tasks. Recently, bound entangled states that violate a Bell inequality have been constructed for a two-qutrit system, disproving a conjecture by Peres that bound entanglement is local. Here we construct this kind of nonlocal bound entangled state for all finite dimensions larger than two, making possible their experimental demonstration in most general systems. We propose a Bell inequality, based on a Hardy-type argument for nonlocality, and a steering inequality to identify their nonlocality. We also provide a family of entanglement witnesses to detect their entanglement beyond the Bell inequality and the steering inequality.
Thermodynamic law from the entanglement entropy bound
Park, Chanyong
2015-01-01
From black hole thermodynamics, the Bekenstein bound has been proposed as a universal thermal entropy bound. It has been further generalized to an entanglement entropy bound which is valid even in a quantum system. In a quantumly entangled system, the non-negativity of the relative entropy leads to the entanglement entropy bound. When the entanglement entropy bound is saturated, a quantum system satisfies the thermodynamics-like law with an appropriately defined entanglement temperature. We show that the saturation of the entanglement entropy bound accounts for a universal feature of the entanglement temperature proportional to the inverse of the system size. In addition, we also find that a global quench unlike the excitation does not preserve the entanglement entropy bound.
Entanglement Tsunami: Universal Scaling in Holographic Thermalization
Liu, Hong
2013-01-01
We consider the time evolution of entanglement entropy after a global quench in a strongly coupled holographic system, whose subsequent equilibration is described in the gravity dual by the gravitational collapse of a thin shell of matter resulting in a black hole. In the limit of large regions of entanglement, the evolution of entanglement entropy is controlled by the geometry around and inside the event horizon of the black hole, allowing us to identify regimes of pre-local- equilibration quadratic growth (in time), post-local-equilibration linear growth, a late-time regime in which the evolution does not carry any memory of the size and shape of the entangled region, and a saturation regime with critical behavior resembling those in continuous phase transitions. Collectively, these regimes suggest a picture of entanglement growth in which an "entanglement tsunami" carries entanglement inward from the boundary. We also make a conjecture on the maximal rate of entanglement growth in relativistic systems.
Entanglement Dynamics of Electrons and Photons
Wu, Xiang-Yao; Liu, Xiao-Jing; Lu, Jing-Bin; Li, Tian-Shun; Zhang, Si-Qi; Liang, Yu; Ma, Ji; Li, Hong
2016-12-01
Entanglement is a fundamental feature of quantum theory as well as a key resource for quantum computing and quantum communication, but the entanglement mechanism has not been found at present. We think when the two subsystems exist interaction directly or indirectly, they can be in entanglement state. such as, in the Jaynes-Cummings model, the entanglement between the atom and the light field comes from their interaction. In this paper, we have studied the entanglement mechanism of electron-electron and photon-photon, which are from the spin-spin interaction. We found their total entanglement states are relevant both space state and spin state. When two electrons or two photons are far away, their entanglement states should be disappeared even if their spin state is entangled.
HMSRP Hawaiian Monk Seal Entanglement data
National Oceanic and Atmospheric Administration, Department of Commerce — The data set contains records of all entanglements of Hawaiian monk seals in marine debris. The data set comprises records of seals entangled by derelict fishing...
Entanglement, Tensor Networks and Black Hole Horizons
Molina-Vilaplana, Javier
2014-01-01
We elaborate on a previous proposal by Hartman and Maldacena on a tensor network which accounts for the scaling of the entanglement entropy in a system at a finite temperature. In this construction, the ordinary entanglement renormalization flow given by the class of tensor networks known as the Multi Scale Entanglement Renormalization Ansatz (MERA), is supplemented by an additional entanglement structure at the length scale fixed by the temperature. The network comprises two copies of a MERA circuit with a fixed number of layers and a pure matrix product state which joins both copies by entangling the infrared degrees of freedom of both MERA networks. The entanglement distribution within this bridge state defines reduced density operators on both sides which cause analogous effects to the presence of a black hole horizon when computing the entanglement entropy at finite temperature in the AdS/CFT correspondence. The entanglement and correlations during the thermalization process of a system after a quantum q...
Entanglement Dynamics of Electrons and Photons
Wu, Xiang-Yao; Liu, Xiao-Jing; Lu, Jing-Bin; Li, Tian-Shun; Zhang, Si-Qi; Liang, Yu; Ma, Ji; Li, Hong
2016-08-01
Entanglement is a fundamental feature of quantum theory as well as a key resource for quantum computing and quantum communication, but the entanglement mechanism has not been found at present. We think when the two subsystems exist interaction directly or indirectly, they can be in entanglement state. such as, in the Jaynes-Cummings model, the entanglement between the atom and the light field comes from their interaction. In this paper, we have studied the entanglement mechanism of electron-electron and photon-photon, which are from the spin-spin interaction. We found their total entanglement states are relevant both space state and spin state. When two electrons or two photons are far away, their entanglement states should be disappeared even if their spin state is entangled.
Institute of Scientific and Technical Information of China (English)
刘堂昆; 张康隆; 陶宇; 单传家; 刘继兵
2016-01-01
The temporal evolution of the degree of entanglement between two atoms in a system of the binomial optical field interacting with two arbitrary entangled atoms is investigated. The influence of the strength of the dipole–dipole interaction between two atoms, probabilities of the Bernoulli trial, and particle number of the binomial optical field on the temporal evolution of the atomic entanglement are discussed. The result shows that the two atoms are always in the entanglement state. Moreover, if and only if the two atoms are initially in the maximally entangled state, the entanglement evolution is not affected by the parameters, and the degree of entanglement is always kept as 1.
Cosgrave Elizabeth M; Cotton Sue M; Buckby Joe A; Killackey Eoin J; Yung Alison R
2008-01-01
Abstract Background The Mood and Anxiety Symptom Questionnaire (MASQ) was designed to specifically measure the Tripartite model of affect and is proposed to offer a delineation between the core components of anxiety and depression. Factor analytic data from adult clinical samples has shown mixed results; however no studies employing confirmatory factor analysis (CFA) have supported the predicted structure of distinct Depression, Anxiety and General Distress factors. The Tripartite model has n...
Yang, Jae-Won; Hong, Sungdo D.; Joung, Yoo Sook; Kim, Ji-Hae
2006-01-01
Although the currently available literature has provided some empirical support for a tripartite model of child and adolescent anxiety and depression, one of the limitations of these studies was that they have been conducted in America, primarily with Caucasians. In order to make this model more applicable to diverse ethnic and cultural groups, this study used a tripartite model for child and adolescent anxiety and depression in Korea, using confirmatory factor analysis with logically selecte...
Mold, Andrew; Mukwaya, Rodgers
2015-01-01
This study evaluates the economic impact of the proposed COMESA-SADC-EAC Tripartite Free Trade Area (TFTA) on 26 African countries. It uses the global trade analysis project (GTAP) computable general equilibrium (CGE) model and database to measure the static effects of the establishment of the TFTA on industrial production, trade flows and consumption in the tripartite region. The results indicate a significant increase in intra-regional exports as a result of tariff elimination, boosting int...
Entanglement entropy of electronic excitations.
Plasser, Felix
2016-05-21
A new perspective into correlation effects in electronically excited states is provided through quantum information theory. The entanglement between the electron and hole quasiparticles is examined, and it is shown that the related entanglement entropy can be computed from the eigenvalue spectrum of the well-known natural transition orbital (NTO) decomposition. Non-vanishing entanglement is obtained whenever more than one NTO pair is involved, i.e., in the case of a multiconfigurational or collective excitation. An important implication is that in the case of entanglement it is not possible to gain a complete description of the state character from the orbitals alone, but more specific analysis methods are required to decode the mutual information between the electron and hole. Moreover, the newly introduced number of entangled states is an important property by itself giving information about excitonic structure. The utility of the formalism is illustrated in the cases of the excited states of two interacting ethylene molecules, the conjugated polymer para-phenylene vinylene, and the naphthalene molecule.
Symmetry-protected topological entanglement
Marvian, Iman
2017-01-01
We propose an order parameter for the symmetry-protected topological (SPT) phases which are protected by Abelian on-site symmetries. This order parameter, called the SPT entanglement, is defined as the entanglement between A and B , two distant regions of the system, given that the total charge (associated with the symmetry) in a third region C is measured and known, where C is a connected region surrounded by A , B , and the boundaries of the system. In the case of one-dimensional systems we prove that in the limit where A and B are large and far from each other compared to the correlation length, the SPT entanglement remains constant throughout a SPT phase, and furthermore, it is zero for the trivial phase while it is nonzero for all the nontrivial phases. Moreover, we show that the SPT entanglement is invariant under the low-depth quantum circuits which respect the symmetry, and hence it remains constant throughout a SPT phase in the higher dimensions as well. Also, we show that there is an intriguing connection between SPT entanglement and the Fourier transform of the string order parameters, which are the traditional tool for detecting SPT phases. This leads to an algorithm for extracting the relevant information about the SPT phase of the system from the string order parameters. Finally, we discuss implications of our results in the context of measurement-based quantum computation.
Information, Relative Entropy of Entanglement and Irreversibility
Henderson, L
2000-01-01
Previously proposed measures of entanglement, such as entanglement of formation and assistance, are shown to be special cases of the relative entropy of entanglement. The difference between these measures for an ensemble of mixed states is shown to depend on the availability of classical information about particular members of the ensemble. Based on this, relations between relative entropy of entanglement and mutual information are derived.
Quantum entanglement and the Bell matrix
Lai, Anna Chiara; Pedicini, Marco; Rognone, Silvia
2016-07-01
We present a class of maximally entangled states generated by a high-dimensional generalisation of the cnot gate. The advantage of our constructive approach is the simple algebraic structure of both entangling operator and resulting entangled states. In order to show that the method can be applied to any dimension, we introduce new sufficient conditions for global and maximal entanglement with respect to Meyer and Wallach's measure.
How to construct indecomposable entanglement witnesses
Energy Technology Data Exchange (ETDEWEB)
Chruscinski, Dariusz; Kossakowski, Andrzej [Institute of Physics, Nicolaus Copernicus University, Grudziadzka 5/7, 87-100 Torun (Poland)
2008-04-11
We present a very simple method for constructing indecomposable entanglement witnesses out of a given pair-an entanglement witness W and the corresponding state detected by W. This method may be used to produce new classes of atomic witnesses which are able to detect the 'weakest' quantum entanglement. Actually, it works perfectly in the multipartite case, too. Moreover, this method provides a powerful tool for constructing new examples of bound entangled states.
How to construct indecomposable entanglement witnesses
Chruściński, Dariusz; Kossakowski, Andrzej
2008-04-01
We present a very simple method for constructing indecomposable entanglement witnesses out of a given pair—an entanglement witness W and the corresponding state detected by W. This method may be used to produce new classes of atomic witnesses which are able to detect the 'weakest' quantum entanglement. Actually, it works perfectly in the multipartite case, too. Moreover, this method provides a powerful tool for constructing new examples of bound entangled states.
Experimental Creation of Entanglement Using Separable States
Institute of Scientific and Technical Information of China (English)
YANG Xiao-Dong; WANG An-Min; MA Xiao-San; XU Feng; YOU Hao; NIU Wan-Qing
2005-01-01
@@ We experimentally demonstrate that the entanglement can be created on two distant particles using separable states. We show that two working particles can share some entanglement, while one ancilla particle always remains separable from the two working particles during the experimental evolution of the system. Our experiment can be viewed as a benchmark to illustrate the idea that no prior entanglement is necessary to create entanglement.
A characterization of optimal entanglement witnesses
Qi, Xiaofei
2011-01-01
In this paper, we present a characterization of optimal entanglement witnesses in terms of positive maps and then provide a general method of checking optimality of entanglement witnesses. Applying it, we obtain new indecomposable optimal witnesses which have no spanning property. These also provide new examples which support a recent conjecture saying that the so-called structural physical approximations to optimal positive maps (optimal entanglement witnesses) give entanglement breaking maps (separable states).
DEFF Research Database (Denmark)
Rehm, Matthias; Rodil, Kasper
2017-01-01
In this paper we investigate the notion of intangible cultural heritage as a driver for smart city learning applications. To this end, we shortly explore the notion of intangible heritage before presenting the tripartite digitization model that was originally developed for indigenous cultural...... heritage but can equally be applied to the smart city context. We then discuss parts of the model making use of a specific case study aiming at re-creating places in the city....
Tri-partite complex for axonal transport drug delivery achieves pharmacological effect
Directory of Open Access Journals (Sweden)
Frederickson Martyn
2010-01-01
Full Text Available Abstract Background Targeted delivery of pharmaceutical agents into selected populations of CNS (Central Nervous System neurons is an extremely compelling goal. Currently, systemic methods are generally used for delivery of pain medications, anti-virals for treatment of dermatomal infections, anti-spasmodics, and neuroprotectants. Systemic side effects or undesirable effects on parts of the CNS that are not involved in the pathology limit efficacy and limit clinical utility for many classes of pharmaceuticals. Axonal transport from the periphery offers a possible selective route, but there has been little progress towards design of agents that can accomplish targeted delivery via this intraneural route. To achieve this goal, we developed a tripartite molecular construction concept involving an axonal transport facilitator molecule, a polymer linker, and a large number of drug molecules conjugated to the linker, then sought to evaluate its neurobiology and pharmacological behavior. Results We developed chemical synthesis methodologies for assembling these tripartite complexes using a variety of axonal transport facilitators including nerve growth factor, wheat germ agglutinin, and synthetic facilitators derived from phage display work. Loading of up to 100 drug molecules per complex was achieved. Conjugation methods were used that allowed the drugs to be released in active form inside the cell body after transport. Intramuscular and intradermal injection proved effective for introducing pharmacologically effective doses into selected populations of CNS neurons. Pharmacological efficacy with gabapentin in a paw withdrawal latency model revealed a ten fold increase in half life and a 300 fold decrease in necessary dose relative to systemic administration for gabapentin when the drug was delivered by axonal transport using the tripartite vehicle. Conclusion Specific targeting of selected subpopulations of CNS neurons for drug delivery by axonal
Entanglement Fidelity as a Measure of Preservation of Entanglement in Local Noisy Process
Institute of Scientific and Technical Information of China (English)
XIANG Yang; XIONG Shi-Jie
2011-01-01
A new formula of entanglement fidelity has been introduced, which can serve as a measure of the preservation of entanglement between two initially entangled subsystems exposed to local noisy environments. For a simple model we derive analytic expressions of concurrence and entanglement fidelity and draw the relationship between them. We find that such entanglement fidelity exhibits the behavior similar to that of the concurrence in quantum evolutions.
Concentration of Unknown Atomic Entangled States via Entanglement Swapping through Raman Interaction
Institute of Scientific and Technical Information of China (English)
ZOU Jin-Hua; HU Xiang-Ming
2008-01-01
We show that entanglement concentration of unknown atomic entangled states is achieved via the implementation of entanglement swapping based on Raman interaction in cavity QED. A maximally entangled state is obtained from a pair of partially entangled states probabilistically. Due to Raman interaction of two atoms with a cavity mode and an external driving field, the influence of atomic spontaneous emission has been eliminated. Because of the virtual excitation of the cavity mode, the decoherence of cavity decay and thermal field is neglected.
Entanglement swapping between atom and cavity and generation of entangled state of cavity fields
Institute of Scientific and Technical Information of China (English)
Chen Ai-Xi; Deng Li
2007-01-01
This paper proposes a scheme where entanglement swapping between atom and cavity can be realized. A-type three-level atoms interacting resonantly with cavity field are considered. By detecting atom and cavity field, it realizes entanglement swapping between atom and cavity. It uses the technique of entanglement swapping to generate an entangled state of two cavity fields by measuring on atoms. It discusses the experimental feasibility of the proposed scheme and application of entangled state of cavity fields.
Thermalization of mutual and tripartite information in strongly coupled two dimensional CFTs
Balasubramanian, V; Copland, N; Craps, B; Galli, F
2011-01-01
The mutual and tripartite information between pairs and triples of disjoint regions in a quantum field theory are sensitive probes of the spread of correlations in an equilibrating system. We compute these quantities in strongly coupled 2d CFTs with a gravity dual following the homogenous deposition of energy. The injected energy is modeled in AdS space as an infalling shell, and the information shared by disjoint intervals is computed in terms of geodesic lengths in this background. For given widths and separation of the intervals, the mutual information typically starts at its vacuum value, then increases in time to reach a maximum, and then declines to the value at thermal equilibrium. A simple causality argument qualitatively explains this behavior. The tripartite information is generically non-zero and time-dependent throughout the process. This contrasts with (but does not contradict) the time-independent tripartite information one finds after a 2d quantum quench in the limit of large time and distance ...
Remarks on entanglement assisted classical capacity
Fan, Heng
2003-06-01
The property of the optimal signal ensembles of entanglement assisted channel capacity is studied. A relationship between entanglement assisted channel capacity and one-shot capacity of unassisted channel is obtained. The data processing inequalities, convexity and additivity of the entanglement assisted channel capacity are reformulated by simple methods.
Remarks on entanglement assisted classical capacity
Fan, Heng
2003-01-01
The property of the optimal signal ensembles of entanglement assisted channel capacity is studied. A relationship between entanglement assisted channel capacity and one-shot capacity of unassisted channel is obtained. The data processing inequalities, convexity and additivity of the entanglement assisted channel capacity are reformulated by simple methods.
Universal corner contributions to entanglement negativity
Kim, Keun-Young; Niu, Chao; Pang, Da-Wei
2016-09-01
It has been realised that corners in entangling surfaces can induce new universal contributions to the entanglement entropy and Rényi entropy. In this paper we study universal corner contributions to entanglement negativity in three- and four-dimensional CFTs using both field theory and holographic techniques. We focus on the quantity χ defined by the ratio of the universal part of the entanglement negativity over that of the entanglement entropy, which may characterise the amount of distillable entanglement. We find that for most of the examples χ takes bigger values for singular entangling regions, which may suggest increase in distillable entanglement. However, there also exist counterexamples where distillable entanglement decreases for singular surfaces. We also explore the behaviour of χ as the coupling varies and observe that for singular entangling surfaces, the amount of distillable entanglement is mostly largest for free theories, while counterexample exists for free Dirac fermion in three dimensions. For holographic CFTs described by higher derivative gravity, χ may increase or decrease, depending on the sign of the relevant parameters. Our results may reveal a more profound connection between geometry and distillable entanglement.
Polygamy of entanglement in multipartite quantum systems
Kim, Jeong San
2009-08-01
We show that bipartite entanglement distribution (or entanglement of assistance) in multipartite quantum systems is by nature polygamous. We first provide an analytical upper bound for the concurrence of assistance in bipartite quantum systems and derive a polygamy inequality of multipartite entanglement in arbitrary-dimensional quantum systems.
Remarks on entanglement assisted classical capacity
Fan, H
2003-01-01
The property of the optimal signal ensembles of entanglement assisted channel capacity is studied. A relationship between entanglement assisted channel capacity and capacities of unassisted and enviornment channels is obtained. The data processing inequalities, convexity and additivity of the entanglement assisted channel capacity are reformulated by simple methods.
Entanglement in fermionic Fock space
Sárosi, Gábor
2013-01-01
We propose a generalization of the usual SLOCC and LU classification of entangled pure state fermionic systems based on the Spin group. Our generalization uses the fact that there is a representation of this group acting on the fermionic Fock space which when restricted to fixed particle number subspaces recovers naturally the usual SLOCC transformations. The new ingredient is the occurrence of Bogoliubov transformations of the whole Fock space changing the particle number. The classification scheme built on the Spin group prohibits naturally entanglement between states containing even and odd number of fermions. In our scheme the problem of classification of entanglement types boils down to the classification of spinors where totally separable states are represented by so called pure spinors. We construct the basic invariants of the Spin group and show how some of the known SLOCC invariants are just their special cases. As an example we present the classification of fermionic systems with a Fock space based ...
Relativity of pure states entanglement
Zyczkowski, K; Zyczkowski, Karol; Bengtsson, Ingemar
2002-01-01
Entanglement of any pure state of an N times N bi-partite quantum system may be characterized by the vector of coefficients arising by its Schmidt decomposition. We analyze various measures of entanglement derived from the generalized entropies of the vector of Schmidt coefficients. For N >= 3 they generate different ordering in the set of pure states and for some states their ordering depends on the measure of entanglement used. This odd-looking property is acceptable, since these incomparable states cannot be transformed to each other with unit efficiency by any local operation. In analogy to special relativity the set of pure states equivalent under local unitaries has a causal structure so that at each point the set splits into three parts: the 'Future', the 'Past' and the set of noncomparable states.
Entanglement entropy in particle decay
Lello, Louis; Holman, Richard
2013-01-01
The decay of a parent particle into two or more daughter particles results in an entangled quantum state, as a consequence of conservation laws in the decay process. We use the Wigner-Weisskopf formalism to construct an approximation to this state that evolves in time in a {\\em manifestly unitary} way. We then construct the entanglement entropy for one of the daughter particles by use of the reduced density matrix obtained by tracing out the unobserved states and follow its time evolution. We find that it grows over a time scale determined by the lifetime of the parent particle to a maximum, which when the width of the parent particle is narrow, describes the phase space distribution of maximally entangled Bell-like states.
Non-Gaussian entanglement swapping
Dell'Anno, F; Nocerino, G; De Siena, S; Illuminati, F
2016-01-01
We investigate the continuous-variable entanglement swapping protocol in a non-Gaussian setting, with non- Gaussian states employed either as entangled inputs and/or as swapping resources. The quality of the swapping protocol is assessed in terms of the teleportation fidelity achievable when using the swapped states as shared entangled resources in a teleportation protocol. We thus introduce a two-step cascaded quantum communication scheme that includes a swapping protocol followed by a teleportation protocol. The swapping protocol is fed by a general class of tunable non-Gaussian states, the squeezed Bell states, which, by means of controllable free parameters, allows for a continuous morphing from Gaussian twin beams up to maximally non-Gaussian squeezed number states. In the realistic instance, taking into account the effects of losses and imperfections, we show that as the input two-mode squeezing increases, optimized non-Gaussian swapping resources allow for a monotonically increasing enhancement of the ...
Entanglement Entropy for Singular Surfaces
Myers, Robert C
2012-01-01
We study entanglement entropy for regions with a singular boundary in higher dimensions using the AdS/CFT correspondence and find that various singularities make new universal contributions. When the boundary CFT has an even spacetime dimension, we find that the entanglement entropy of a conical surface contains a term quadratic in the logarithm of the UV cut-off. In four dimensions, the coefficient of this contribution is proportional to the central charge 'c'. A conical singularity in an odd number of spacetime dimensions contributes a term proportional to the logarithm of the UV cut-off. We also study the entanglement entropy for various boundary surfaces with extended singularities. In these cases, similar universal terms may appear depending on the dimension and curvature of the singular locus.
Quantum entanglement: theory and applications
Energy Technology Data Exchange (ETDEWEB)
Schuch, N.
2007-10-10
This thesis deals with various questions concerning the quantification, the creation, and the application of quantum entanglement. Entanglement arises due to the restriction to local operations and classical communication. We investigate how the notion of entanglement changes if additional restrictions in form of a superselection rule are imposed and show that they give rise to a new resource. We characterize this resource and demonstrate that it can be used to overcome the restrictions, very much as entanglement can overcome the restriction to local operations by teleportation. We next turn towards the optimal generation of resources. We show how squeezing can be generated as efficiently as possible from noisy squeezing operations supplemented by noiseless passive operations, and discuss the implications of this result to the optimal generation of entanglement. The difficulty in describing the behaviour of correlated quantum many-body systems is ultimately due to the complicated entanglement structure of multipartite states. Using quantum information techniques, we investigate the ground state properties of lattices of harmonic oscillators. We derive an exponential decay of correlations for gapped systems, compute the dependence of correlation length and gap, and investigate the notion of criticality by relating a vanishing energy gap to an algebraic decay of correlations. Recently, ideas from entanglement theory have been applied to the description of many-body systems. Matrix Product States (MPS), which have a particularly simple interpretation from the point of quantum information, perform extremely well in approximating the ground states of local Hamiltonians. It is generally believed that this is due to the fact that both ground states and MPS obey an entropic area law. We clarify the relation between entropy scaling laws and approximability by MPS, and in particular find that an area law does not necessarily imply approximability. Using the quantum
Bosonic behavior of entangled fermions
DEFF Research Database (Denmark)
C. Tichy, Malte; Alexander Bouvrie, Peter; Mølmer, Klaus
2012-01-01
Two bound, entangled fermions form a composite boson, which can be treated as an elementary boson as long as the Pauli principle does not affect the behavior of many such composite bosons. The departure of ideal bosonic behavior is quantified by the normalization ratio of multi-composite-boson st......Two bound, entangled fermions form a composite boson, which can be treated as an elementary boson as long as the Pauli principle does not affect the behavior of many such composite bosons. The departure of ideal bosonic behavior is quantified by the normalization ratio of multi...
Entanglement entropy of round spheres
Energy Technology Data Exchange (ETDEWEB)
Solodukhin, Sergey N., E-mail: Sergey.Solodukhin@lmpt.univ-tours.f [Laboratoire de Mathematiques et Physique Theorique, Universite Francois-Rabelais Tours Federation Denis Poisson - CNRS, Parc de Grandmont, 37200 Tours (France)
2010-10-18
We propose that the logarithmic term in the entanglement entropy computed in a conformal field theory for a (d-2)-dimensional round sphere in Minkowski spacetime is identical to the logarithmic term in the entanglement entropy of extreme black hole. The near horizon geometry of the latter is H{sub 2}xS{sub d-2}. For a scalar field this proposal is checked by direct calculation. We comment on relation of this and earlier calculations to the 'brick wall' model of 't Hooft. The case of generic 4d conformal field theory is discussed.
Group theoretical approach to entanglement
Korbicz, J K
2006-01-01
We examine a potential relevance of methods of harmonic analysis for the study of quantum entanglement. By changing the mathematical object representing quantum states, we reformulate the separability problem in group-theoretical terms. We also translate the positivity of partial transpose (PPT) criterion and one of the necessary-and-sufficient criteria for pure states to the group-theoretical language. The formal relation of our formalism to local hidden variable models is briefly examined. We also remark on the connection between entanglement and some certain non-commutativity.
Benchmarks and statistics of entanglement dynamics
Energy Technology Data Exchange (ETDEWEB)
Tiersch, Markus
2009-09-04
In the present thesis we investigate how the quantum entanglement of multicomponent systems evolves under realistic conditions. More specifically, we focus on open quantum systems coupled to the (uncontrolled) degrees of freedom of an environment. We identify key quantities that describe the entanglement dynamics, and provide efficient tools for its calculation. For quantum systems of high dimension, entanglement dynamics can be characterized with high precision. In the first part of this work, we derive evolution equations for entanglement. These formulas determine the entanglement after a given time in terms of a product of two distinct quantities: the initial amount of entanglement and a factor that merely contains the parameters that characterize the dynamics. The latter is given by the entanglement evolution of an initially maximally entangled state. A maximally entangled state thus benchmarks the dynamics, and hence allows for the immediate calculation or - under more general conditions - estimation of the change in entanglement. Thereafter, a statistical analysis supports that the derived (in-)equalities describe the entanglement dynamics of the majority of weakly mixed and thus experimentally highly relevant states with high precision. The second part of this work approaches entanglement dynamics from a topological perspective. This allows for a quantitative description with a minimum amount of assumptions about Hilbert space (sub-)structure and environment coupling. In particular, we investigate the limit of increasing system size and density of states, i.e. the macroscopic limit. In this limit, a universal behaviour of entanglement emerges following a ''reference trajectory'', similar to the central role of the entanglement dynamics of a maximally entangled state found in the first part of the present work. (orig.)
Assadi, Leila; Jafarpour, Mojtaba
2016-07-01
We use concurrence to study bipartite entanglement, Meyer-Wallach measure and its generalizations to study multi-partite entanglement and MABK and SASA inequalities to study the non-local properties of the 4-qubit entangled graph states, quantitatively. Then, we present 3 classifications, each one in accordance with one of the aforementioned properties. We also observe that the classification according to multipartite entanglement does exactly coincide with that according to nonlocal properties, but does not match with that according to bipartite entanglement. This observation signifies the fact that non-locality and multipartite entanglement enjoy the same basic underlying principles, while bipartite entanglement may not reveal the non-locality issue in its entirety.
Partial recovery of lost entanglement in bipartite entanglement transformations
Bandyopadhyay, S; Vatan, F; Roychowdhury, Vwani; Vatan, Farrokh
2002-01-01
We show that partial recovery of the entanglement lost in a bipartite pure state entanglement transformations is almost always possible irrespective of the dimension. Let $\\ket{\\psi}$ and $\\ket{\\vph}$ be $n\\times n$ states and $\\ket{\\psi} \\longrightarrow \\ket{\\vph}$ under local operations. We ask whether there exists $k\\times k$ states, $\\ket{\\chi}$ and $\\ket{\\omega}$, $k E(\\ket{\\chi})$, $E$ being the entropy of entanglement such that $\\ket{\\psi}\\otimes\\ket{\\chi} \\longrightarrow \\ket{\\vph}\\otimes\\ket{\\omega}$ under LOCC. We show that for almost all pairs of comparable states recovery is achievable by $2\\times 2$ states, no matter how large the dimension of the parent states are. For other cases we show that the dimension of the auxiliary entangled state depends on the presence of equalities in the majorization relations of the parent states. We identify those states and show that recovery is still possible using states in $k\\times k$, $2
Separable states can be used to distribute entanglement
Cubitt, T S; Dür, W; Cirac, J I
2003-01-01
We show that no entanglement is necessary to distribute entanglement; that is, two distant particles can be entangled by sending a third particle that is never entangled with the other two. Similarly, two particles can become entangled by continuous interaction with a highly mixed mediating particle that never itself becomes entangled. We also consider analogous properties of completely positive maps, in which the composition of two separable maps can create entanglement.
Approaches to measuring entanglement in chemical magnetometers.
Tiersch, M; Guerreschi, G G; Clausen, J; Briegel, H J
2014-01-01
Chemical magnetometers are radical pair systems such as solutions of pyrene and N,N-dimethylaniline (Py-DMA) that show magnetic field effects in their spin dynamics and their fluorescence. We investigate the existence and decay of quantum entanglement in free geminate Py-DMA radical pairs and discuss how entanglement can be assessed in these systems. We provide an entanglement witness and propose possible observables for experimentally estimating entanglement in radical pair systems with isotropic hyperfine couplings. As an application, we analyze how the field dependence of the entanglement lifetime in Py-DMA could in principle be used for magnetometry and illustrate the propagation of measurement errors in this approach.
Entanglement enhances cooling in microscopic quantum refrigerators.
Brunner, Nicolas; Huber, Marcus; Linden, Noah; Popescu, Sandu; Silva, Ralph; Skrzypczyk, Paul
2014-03-01
Small self-contained quantum thermal machines function without external source of work or control but using only incoherent interactions with thermal baths. Here we investigate the role of entanglement in a small self-contained quantum refrigerator. We first show that entanglement is detrimental as far as efficiency is concerned-fridges operating at efficiencies close to the Carnot limit do not feature any entanglement. Moving away from the Carnot regime, we show that entanglement can enhance cooling and energy transport. Hence, a truly quantum refrigerator can outperform a classical one. Furthermore, the amount of entanglement alone quantifies the enhancement in cooling.
Decoherence in time evolution of bound entanglement
Sun, Z; Sun, C P; Wang, X; Sun, Zhe; Wang, Xiaoguang
2007-01-01
We study a dynamic process of disentanglement by considering the time evolution of bound entanglement for a quantum open system, two qutrits coupling to a common environment. Here, the initial quantum correlations of the two qutrits are characterized by the bound entanglement. In order to show the universality of the role of environment on bound entanglement, both bosonic and spin environments are considered. We found that the bound entanglement displays collapses and revivals, and it can be stable against small temperature and time change. The thermal fluctuation effects on bound entanglement are also considered.
Entanglement and nonclassicality: A mutual impression
Gholipour, H.; Shahandeh, F.
2016-06-01
We find a sufficient condition to imprint the single-mode bosonic phase-space nonclassicality onto a bipartite state as modal entanglement and vice versa using an arbitrary beam splitter. Surprisingly, the entanglement produced or detected in this way depends only on the nonclassicality of the marginal input or output states, regardless of their purity and separability. In this way, our result provides a sufficient condition for generating entangled states of arbitrary high temperature and arbitrary large number of particles. We also study the evolution of the entanglement within a lossy Mach-Zehnder interferometer and show that unless both modes are totally lost, the entanglement does not diminish.
Reservoir-engineered entanglement in optomechanical systems.
Wang, Ying-Dan; Clerk, Aashish A
2013-06-21
We show how strong steady-state entanglement can be achieved in a three-mode optomechanical system (or other parametrically coupled bosonic system) by effectively laser cooling a delocalized Bogoliubov mode. This approach allows one to surpass the bound on the maximum stationary intracavity entanglement possible with a coherent two-mode squeezing interaction. In particular, we find that optimizing the relative ratio of optomechanical couplings, rather than simply increasing their magnitudes, is essential for achieving strong entanglement. Unlike typical dissipative entanglement schemes, our results cannot be described by treating the effects of the entangling reservoir via a Linblad master equation.
Spatial Entanglement of a Free Bosonic Field
Heaney, L; Vedral, V; Anders, Janet; Heaney, Libby; Vedral, Vlatko
2006-01-01
We investigate entanglement between two spatial regions of a free bosonic gas using a separability criterion for continuous variable systems. We find entanglement between the regions only when we post-select certain momenta related to the size of the regions under investigation. We relate the presence of entanglement to the temperature of the system and providing we can probe increasingly smaller regions we argue that entanglement exists at arbitrarily high temperatures. Moreover, the entanglement we find is useful as it can be extracted to a pair of atoms.
Universal distortion-free entanglement concentration
Hayashi, M; Hayashi, Masahito; Matsumoto, Keiji
2002-01-01
Entanglement concentration from many copies of unknown pure states is discussed, and we propose the protocol which not only achieves entropy rate, but also produces the perfect maximally entangled state. Our protocol is induced naturally from symmetry of $n$-tensored pure state, and is optimal for all the protocols which concentrates entanglement from unknown pure states, in the sense of failure probability. In the proof of optimality, the statistical estimation theory plays a key role, for concentrated entanglement gives a natural estimate of the entropy of entanglement.
Quantum cobwebs: Universal entangling of quantum states
Indian Academy of Sciences (India)
Arun Kumar Pati
2002-08-01
Entangling an unknown qubit with one type of reference state is generally impossible. However, entangling an unknown qubit with two types of reference states is possible. To achieve this, we introduce a new class of states called zero sum amplitude (ZSA) multipartite, pure entangled states for qubits and study their salient features. Using shared-ZSA states, local operations and classical communication, we give a protocol for creating multipartite entangled states of an unknown quantum state with two types of reference states at remote places. This provides a way of encoding an unknown pure qubit state into a multiqubit entangled state.
Restoring broken entanglement by injecting separable correlations
Pirandola, Stefano
2012-01-01
The distribution of entanglement is central in many protocols of quantum information and computation. However it is also known to be a very fragile process when loss and noise come into play. The inevitable interaction of the quantum systems with the external environment induces effects of decoherence which may be so strong to destroy any input entanglement, a phenomenon known as "entanglement breaking". Here we study this catastrophic process in a correlated-noise environment showing how the presence of classical-type correlations can restore the distribution of entanglement. In particular, we consider a Gaussian environment whose thermal noise is strong enough to break the entanglement of two bosonic modes of the electromagnetic field. In this scenario, we show that the injection of separable correlations from the same environment is able to reactivate the broken entanglement. This paradoxical effect happens both in schemes of direct distribution, where a third party (Charlie) broadcasts entangled states to...
Multipartite quantum entanglement evolution in photosynthetic complexes.
Zhu, Jing; Kais, Sabre; Aspuru-Guzik, Alán; Rodriques, Sam; Brock, Ben; Love, Peter J
2012-08-21
We investigate the evolution of entanglement in the Fenna-Matthew-Olson (FMO) complex based on simulations using the scaled hierarchical equations of motion approach. We examine the role of entanglement in the FMO complex by direct computation of the convex roof. We use monogamy to give a lower bound for entanglement and obtain an upper bound from the evaluation of the convex roof. Examination of bipartite measures for all possible bipartitions provides a complete picture of the multipartite entanglement. Our results support the hypothesis that entanglement is maximum primary along the two distinct electronic energy transfer pathways. In addition, we note that the structure of multipartite entanglement is quite simple, suggesting that there are constraints on the mixed state entanglement beyond those due to monogamy.
Bounds on entanglement in qudit subsystems
Kendon, V M; Munro, W J; Kendon, Vivien M; Zyczkowski, Karol; Munro, William J
2002-01-01
The entanglement in a pure state of N qudits (d-dimensional distinguishable quantum particles) can be characterised by specifying how entangled its subsystems are. A generally mixed subsystem of m qudits is obtained by tracing over the other N-m qudits. We examine the entanglement in this mixed space of m qudits. We show that for a typical pure state of N qudits, its subsystems smaller than N/3 qudits will have a positive partial transpose and hence are separable or bound entangled. Additionally, our numerical results show that the probability of finding entangled subsystems smaller than N/3 falls exponentially in the dimension of the Hilbert space. The bulk of pure state Hilbert space thus consists of highly entangled states with multipartite entanglement encompassing at least a third of the qudits in the pure state.
Entanglement production in Quantized Chaotic Systems
Bandyopadhyay, J N; Bandyopadhyay, Jayendra N.; Lakshminarayan, Arul
2005-01-01
Quantum chaos is a subject whose major goal is to identify and to investigate different quantum signatures of classical chaos. Here we study entanglement production in coupled chaotic systems as a possible quantum indicator of classical chaos. We use coupled kicked tops as a model for our extensive numerical studies. We find that, in general, presence of chaos in the system produces more entanglement. However, coupling strength between two subsystems is also very important parameter for the entanglement production. Here we show how chaos can lead to large entanglement which is universal and describable by random matrix theory (RMT). We also explain entanglement production in coupled strongly chaotic systems by deriving a formula based on RMT. This formula is valid for arbitrary coupling strengths, as well as for sufficiently long time. Here we investigate also the effect of chaos on the entanglement production for the mixed initial state. We find that many properties of the mixed state entanglement production...
Squashed entanglement and approximate private states
Wilde, Mark M.
2016-09-01
The squashed entanglement is a fundamental entanglement measure in quantum information theory, finding application as an upper bound on the distillable secret key or distillable entanglement of a quantum state or a quantum channel. This paper simplifies proofs that the squashed entanglement is an upper bound on distillable key for finite-dimensional quantum systems and solidifies such proofs for infinite-dimensional quantum systems. More specifically, this paper establishes that the logarithm of the dimension of the key system (call it log 2K ) in an ɛ -approximate private state is bounded from above by the squashed entanglement of that state plus a term that depends only ɛ and log 2K . Importantly, the extra term does not depend on the dimension of the shield systems of the private state. The result holds for the bipartite squashed entanglement, and an extension of this result is established for two different flavors of the multipartite squashed entanglement.
Multi-photon entanglement in high dimensions
Malik, Mehul; Huber, Marcus; Krenn, Mario; Fickler, Robert; Zeilinger, Anton
2015-01-01
Entanglement lies at the heart of quantum mechanics $-$ as a fundamental tool for testing its deep rift with classical physics, while also providing a key resource for quantum technologies such as quantum computation and cryptography. In 1987 Greenberger, Horne, and Zeilinger realized that the entanglement of more than two particles implies a non-statistical conflict between local realism and quantum mechanics. The resulting predictions were experimentally confirmed by entangling three photons in their polarization. Experimental efforts since have singularly focused on increasing the number of particles entangled, while remaining in a two-dimensional space for each particle. Here we show the experimental generation of the first multi-photon entangled state where both $-$ the number of particles and the number of dimensions $-$ are greater than two. Interestingly, our state exhibits an asymmetric entanglement structure that is only possible when one considers multi-particle entangled states in high dimensions....
Teleportation of entanglement over 143 km
Herbst, Thomas; Fink, Matthias; Handsteiner, Johannes; Wittmann, Bernhard; Ursin, Rupert; Zeilinger, Anton
2014-01-01
As a direct consequence of the no-cloning theorem, the deterministic amplification as in classical communication is impossible for quantum states. This calls for more advanced techniques in a future global quantum network, e.g. for cloud quantum computing. A unique solution is the teleportation of an entangled state, i.e. entanglement swapping, representing the central resource to relay entanglement between distant nodes. Together with entanglement purification and a quantum memory it constitutes a so-called quantum repeater. Since the afore mentioned building blocks have been individually demonstrated in laboratory setups only, the applicability of the required technology in real-world scenarios remained to be proven. Here we present a free-space entanglement-swapping experiment between the Canary Islands of La Palma and Tenerife, verifying the presence of quantum entanglement between two previously independent photons separated by 143 km. We obtained an expectation value for the entanglement-witness operato...
Should Entanglement Measures be Monogamous or Faithful?
Lancien, Cécilia; Huber, Marcus; Piani, Marco; Adesso, Gerardo; Winter, Andreas
2016-01-01
"Is entanglement monogamous?" asks the title of a popular article [B. Terhal, IBM J. Res. Dev. 48, 71 (2004)], celebrating C. H. Bennett's legacy on quantum information theory. While the answer is certainly affirmative in the qualitative sense, the situation is far less clear if monogamy is intended as a quantitative limitation on the distribution of bipartite entanglement in a multipartite system, given some particular measure of entanglement. Here, we clarify the most general form of a universal quantitative monogamy relation for a bipartite measure of entanglement. We then go on to show that an important class of entanglement measures fail to be monogamous in this most general sense of the term, with monogamy violations becoming generic with increasing dimension. In particular, we show that entanglement measures cannot satisfy monogamy while at the same time faithfully capturing the entanglement of the fully antisymmetric state in arbitrary dimension. Nevertheless, monogamy can be recovered if one allows f...
Analysis of the Entanglement with Centers
Huang, Xing
2016-01-01
Entanglement in gauge theories is difficult to define because of the issue of a tensor product decomposition of a Hilbert space. We choose centers to define quantities that quantify the entanglement, and also use quantization algebras and constraints to analyze the existence of the ambiguities in a system of first-order formulation. In interacting theories, lattice simulations is required to obtain quantitative behaviors of entanglement. Thus, we propose a method to study entanglement with centers on finite spacing lattice without breaking gauge symmetry. We also understand the relation between the extended lattice model and boundary condition, and discuss magnetic choices in the extended lattice model. Then we compute the entanglement entropy in $p$-form free theory in $2p+2$ dimensional Euclidean flat background with a $S^{2p}$ entangling surface, our results support that the ambiguities in non-gauge theories only affect the regulator dependent terms. The universal terms of the entanglement entropy in $p$-f...
Heralded quantum entanglement between two crystals
Usmani, Imam; Bussieres, Felix; Sangouard, Nicolas; Afzelius, Mikael; Gisin, Nicolas
2011-01-01
Quantum networks require the crucial ability to entangle quantum nodes. A prominent example is the quantum repeater which allows overcoming the distance barrier of direct transmission of single photons, provided remote quantum memories can be entangled in a heralded fashion. Here we report the observation of heralded entanglement between two ensembles of rare-earth-ions doped into separate crystals. A heralded single photon is sent through a 50/50 beamsplitter, creating a single-photon entangled state delocalized between two spatial modes. The quantum state of each mode is subsequently mapped onto a crystal, leading to an entangled state consisting of a single collective excitation delocalized between two crystals. This entanglement is revealed by mapping it back to optical modes and by estimating the concurrence of the retrieved light state. Our results highlight the potential of rare-earth-ions doped crystals for entangled quantum nodes and bring quantum networks based on solid-state resources one step clos...
Holographic entanglement entropy in the nonconformal medium
Park, Chanyong
2015-01-01
We investigate holographically the entanglement entropy of a nonconformal medium whose dual geometry is described by an Einstein-Maxwell-dilaton theory. Due to an additional conserved charge corresponding to the number operator in the dual field theory, its thermodynamics is governed by either a grand canonical or canonical ensemble. We calculate thermodynamic quantities of them by using the holographic renormalization. In addition, we study the entanglement entropy of a nonconformal medium. After defining the entanglement chemical potential analogous to the entanglement temperature, we find that the entanglement entropy of a small subsystem satisfies the relation resembling the first law of thermodynamics for the canonical ensemble. We further show that the entanglement chemical potential, unlike the entanglement temperature, is not universal.
Investigating student understanding of quantum entanglement
Kohnle, Antje
2015-01-01
Quantum entanglement is a central concept of quantum theory for multiple particles. Entanglement played an important role in the development of the foundations of the theory and makes possible modern applications in quantum information technology. As part of the QuVis Quantum Mechanics Visualization Project, we developed an interactive simulation "Entanglement: The nature of quantum correlations" using two-particle entangled spin states. We investigated student understanding of entanglement at the introductory and advanced undergraduate levels by collecting student activity and post-test responses using two versions of the simulation and carrying out a small number of student interviews. Common incorrect ideas found include statements that all entangled states must be maximally entangled (i.e. show perfect correlations or anticorrelations along all common measurement axes), that the spins of particles in a product state must have definite values (cannot be in a superposition state with respect to spin) and di...
Entangling light in high dimensions
Pors, Jan Bardeus
2011-01-01
Quantum entanglement is a fundamental trait of quantum mechanics that causes the information about the properties of two (or more) objects to be inextricably linked. When a measurement on one of the objects is performed, the state of the other object is immediately altered, even when these objects a
Remote entanglement of transmon qubits
Hatridge, M.; Sliwa, K.; Narla, A.; Shankar, S.; Leghtas, Z.; Mirrahimi, M.; Girvin, S. M.; Schoelkopf, R. J.; Devoret, M. H.
2014-03-01
An open challenge in quantum information processing with superconducting circuits is to entangle distant (non-nearest neighbor) qubits. This can be accomplished by entangling the qubits with flying microwave oscillators (traveling pulses), and then performing joint operations on a pair of these oscillators. Remarkably, such a process is embedded in the act of phase-preserving amplification, which transforms two input modes (termed signal and idler) into a two-mode squeezed output state. For an ideal system, this process generates heralded, perfectly entangled states between remote qubits with a fifty percent success rate. For an imperfect system, the loss of information from the flying states degrades the purity of the entanglement. We show data on such a protocol involving two transmon qubits imbedded in superconducting cavities connected to the signal and idler inputs of a Josephson Parametric Converter (JPC) operated as a nearly-quantum limited phase-preserving amplifier. Strategies for optimizing performance will also be discussed. Work supported by: IARPA, ARO, and NSF.
Entanglement concentration and teleportation of multipartite entangled states in an ion trap
Institute of Scientific and Technical Information of China (English)
Pan Chang-Ning; Fang Mao-Fa
2007-01-01
We propose an effective scheme for the entanglement concentration of a four-particle state via entanglement swapping in an ion trap. Taking the maximally entangled state after concentration as a quantum channel, we can faithfully and determinatively teleport quantum entangled states from Alice to Bob without the joint Bell-state measurement. In the process of constructing the quantum channel, we adopt entanglement swapping to avoid the decrease of entanglement during the distribution of particles. Thus our scheme provides a new prospect for quantum teleportation over a longer distance. Furthermore, the success probability of our scheme is 1.0.
Displacement-enhanced entanglement distillation of single-mode-squeezed entangled states
DEFF Research Database (Denmark)
Tipsmark, Anders; Neergaard-Nielsen, Jonas Schou; Andersen, Ulrik Lund
2013-01-01
It has been shown that entanglement distillation of Gaussian entangled states by means of local photon subtraction can be improved by local Gaussian transformations. Here we show that a similar effect can be expected for the distillation of an asymmetric Gaussian entangled state that is produced...... by a single squeezed beam. We show that for low initial entanglement, our largely simplified protocol generates more entanglement than previous proposed protocols. Furthermore, we show that the distillation scheme also works efficiently on decohered entangled states as well as with a practical photon...
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Two-Mode Excited Entangled Coherent State: Nonclassicality and Entanglement
Zhang, Hao-Liang; Wu, Jia-Ni; Liu, Cun-Jin; Hu, Yin-Quan; Hu, Li-Yun
2017-03-01
Two-mode excited entangled coherent states (TME-ECSs) are introduced by operating repeatedly the photon-excited operator on the ECSs. It is shown that the normalization constant is related to the product of two Laguerre polynomials. The influence of the operation on nonclassical behaviour of the ECSs is investigated in terms of cross-correlation function, anti-bunching effect and the negativity of Wigner function, which show that nonclassical properties can be enhanced. In addition, inseparability properties of the TME-ECSs are discussed by using Bell inequality and concurrence. It is found that the degree of quantum entanglement of even ECSs increases with the increase of the total excited photon number, and the violation of Bell inequality can be present for both even and odd case only when the total excited photon numbers are even and odd, respectively.
Panov, A A
2013-01-01
Contrary to members of the suborder Polyphaga; ground beetles have been found to possess tripartite mushroom bodies, which are poorly developed in members of basal taxa and maximally elaborated in evolutionarily advanced groups. Nevertheless, they do not reach the developmental stage, which has been previously found in particular families of beetles. It has been pointed out that anew formation of the Kenyon cells occurs during at least the first months of adult life, and inactive neuroblasts are found even in one-year-old beetles. It has been suggested that there is a relation between the Kenyon cell number and development of the centers of Kenyon cell new-formation.
Waghela, Chetan
2015-01-01
Hamiltonian Mechanics works for conserved systems and Quantum Mechanics is given in Hamiltonian language. It is considered that complexifying the quantum Hamiltonian, a balanced loss and gain model can be created. The usual mathematics of density operator formalism and entanglement is extrapolated to such systems and the consequences are studied. Namely, a complete formalism using Density operators is created for real eigenvalue regime of these Non- Hermitian systems and correct forms of Von-Neumann and Entanglement Entropy are created. The consequences are studied in this regime and depicted w.r.t recent papers by [9, 20].
Entanglement Preserving in Quantum Copying of Three－Qubit Entangled State
Institute of Scientific and Technical Information of China (English)
TONGZhao－Yang; KUANGLe－Man
2002-01-01
We study the degree to which quantum entanglement survives when a three-qubit entangled state is copied by using local and non-local processes,respectively,and investigate iterating quantum copying for the three-qubit system.There may exist inter-three-qubit entanglement and inter-two-qubit entanglement for the three-qubit system.We show that both local and non-local copying processes degrade quantum entanglement in the three-particle system due to a residual correlation between the copied output and the copying machine.we also show that the inter-two-qubit entanglement is preserved better than the inter-three-qubit entanglement in the local cloning process.We find that non-local cloning is much more efficient than the local copying for broadcasting entanglement,and output state via non-local cloning exhiits the fidelity better than local cloning.
Entanglement Capabilities of Non-local Hamiltonians with Maximally Entangled Ancillary Particles
Institute of Scientific and Technical Information of China (English)
YE Peng; ZHENG Yizhuang
2004-01-01
@@ The entanglement capacity of non-local two-qubit Hamiltonians with maximally entangled ancillary particles are investigated.We gain a complete expression of entanglement capacity and show that the maximal entanglement capacity Γmax of a non-local Hamiltonian with ancillary particles will be never less than the maximal entanglement capacity Γ*max of the non-local Hamiltonian without ancillary particles.By defining relative entanglement rate η=Γmax /Γ*max (Γmax, Γ*max are maximal entanglement rate with and without ancillas respectively), we find the range of the values of relative entanglement rate is 1η1.3220.
Delayed birth of distillable entanglement in the evolution of bound entangled states
Derkacz, Łukasz
2010-01-01
The dynamical creation of entanglement between three-level atoms coupled to the common vacuum is investigated. For the class of bound entangled initial states we show that the dynamics of closely separated atoms generates stationary distillable entanglement of asymptotic states. We also find that the effect of delayed sudden birth of distillable entanglement occurs in the case of atoms separated by a distance comparable with the radiation wavelength.
Four-photon orbital angular momentum entanglement
Hiesmayr, B C; Löffler, W
2015-01-01
Quantum entanglement shared between more than two particles is essential to foundational questions in quantum mechanics, and upcoming quantum information technologies. So far, up to 14 two-dimensional qubits have been entangled, and an open question remains if one can also demonstrate entanglement of higher-dimensional discrete properties of more than two particles. A promising route is the use of the photon orbital angular momentum (OAM), which enables implementation of novel quantum information protocols, and the study of fundamentally new quantum states. To date, only two of such multidimensional particles have been entangled albeit with ever increasing dimensionality. Here we use pulsed spontaneous parametric downconversion (SPDC) to produce photon quadruplets that are entangled in their OAM, or transverse-mode degrees of freedom; and witness genuine multipartite Dicke-type entanglement. Apart from addressing foundational questions, this could find applications in quantum metrology, imaging, and secret sh...
Efficient entanglement distillation without quantum memory
Abdelkhalek, Daniela; Syllwasschy, Mareike; Cerf, Nicolas J.; Fiurášek, Jaromír; Schnabel, Roman
2016-05-01
Entanglement distribution between distant parties is an essential component to most quantum communication protocols. Unfortunately, decoherence effects such as phase noise in optical fibres are known to demolish entanglement. Iterative (multistep) entanglement distillation protocols have long been proposed to overcome decoherence, but their probabilistic nature makes them inefficient since the success probability decays exponentially with the number of steps. Quantum memories have been contemplated to make entanglement distillation practical, but suitable quantum memories are not realised to date. Here, we present the theory for an efficient iterative entanglement distillation protocol without quantum memories and provide a proof-of-principle experimental demonstration. The scheme is applied to phase-diffused two-mode-squeezed states and proven to distil entanglement for up to three iteration steps. The data are indistinguishable from those that an efficient scheme using quantum memories would produce. Since our protocol includes the final measurement it is particularly promising for enhancing continuous-variable quantum key distribution.
Electronic entanglement in late transition metal oxides.
Thunström, Patrik; Di Marco, Igor; Eriksson, Olle
2012-11-01
We present a study of the entanglement in the electronic structure of the late transition metal monoxides--MnO, FeO, CoO, and NiO--obtained by means of density-functional theory in the local density approximation combined with dynamical mean-field theory. The impurity problem is solved through exact diagonalization, which grants full access to the thermally mixed many-body ground state density operator. The quality of the electronic structure is affirmed through a direct comparison between the calculated electronic excitation spectrum and photoemission experiments. Our treatment allows for a quantitative investigation of the entanglement in the electronic structure. Two main sources of entanglement are explicitly resolved through the use of a fidelity based geometrical entanglement measure, and additional information is gained from a complementary entropic entanglement measure. We show that the interplay of crystal field effects and Coulomb interaction causes the entanglement in CoO to take a particularly intricate form.
Efficient entanglement distillation without quantum memory.
Abdelkhalek, Daniela; Syllwasschy, Mareike; Cerf, Nicolas J; Fiurášek, Jaromír; Schnabel, Roman
2016-05-31
Entanglement distribution between distant parties is an essential component to most quantum communication protocols. Unfortunately, decoherence effects such as phase noise in optical fibres are known to demolish entanglement. Iterative (multistep) entanglement distillation protocols have long been proposed to overcome decoherence, but their probabilistic nature makes them inefficient since the success probability decays exponentially with the number of steps. Quantum memories have been contemplated to make entanglement distillation practical, but suitable quantum memories are not realised to date. Here, we present the theory for an efficient iterative entanglement distillation protocol without quantum memories and provide a proof-of-principle experimental demonstration. The scheme is applied to phase-diffused two-mode-squeezed states and proven to distil entanglement for up to three iteration steps. The data are indistinguishable from those that an efficient scheme using quantum memories would produce. Since our protocol includes the final measurement it is particularly promising for enhancing continuous-variable quantum key distribution.
Spatial entanglement of bosons in optical lattices.
Cramer, M; Bernard, A; Fabbri, N; Fallani, L; Fort, C; Rosi, S; Caruso, F; Inguscio, M; Plenio, M B
2013-01-01
Entanglement is a fundamental resource for quantum information processing, occurring naturally in many-body systems at low temperatures. The presence of entanglement and, in particular, its scaling with the size of system partitions underlies the complexity of quantum many-body states. The quantitative estimation of entanglement in many-body systems represents a major challenge, as it requires either full-state tomography, scaling exponentially in the system size, or the assumption of unverified system characteristics such as its Hamiltonian or temperature. Here we adopt recently developed approaches for the determination of rigorous lower entanglement bounds from readily accessible measurements and apply them in an experiment of ultracold interacting bosons in optical lattices of ~10(5) sites. We then study the behaviour of spatial entanglement between the sites when crossing the superfluid-Mott insulator transition and when varying temperature. This constitutes the first rigorous experimental large-scale entanglement quantification in a scalable quantum simulator.
Squeezing and Entanglement in Continuous Variable Systems
Institute of Scientific and Technical Information of China (English)
XIA Yun-Jie; GUO Guang-Can
2004-01-01
Based on total variance of a pair of Einstein-Podolsky-Rosen (EPR) type operators, the generalized EPR entangled states in continuous variable systems are defined. We show that such entangled states must correspond to two-mode squeezing states whether these states are Gaussian or not and whether they are pure or not. With help of the relation between the total variance and the entanglement, the degree of such entanglement is also defined. Through analysing some specific cases, we see that this method is very convenient and easy in practical applications. In addition, an entangled state with no squeezing is studied, which reveals that there certainly exists something unknown about entanglement in continuous variable systems.
Multipartite Quantum Entanglement Evolution in Photosynthetic Complexes
Zhu, Jing; Aspuru-Guzik, Alán; Rodriques, Sam; Brock, Ben; Love, Peter J
2012-01-01
We investigate the evolution of entanglement in the Fenna-Matthew-Olson (FMO) complex based on simulations using the scaled hierarchy equation of motion (HEOM) approach. We examine the role of multipartite entanglement in the FMO complex by direct computation of the convex roof optimization for a number of measures, including some that have not been previously evaluated. We also consider the role of monogamy of entanglement in these simulations. We utilize the fact that the monogamy bounds are saturated in the single exciton subspace. This enables us to compute more measures of entanglement exactly and also to validate the evaluation of the convex roof. We then use direct computation of the convex roof to evaluate measures that are not determined by monogamy. This approach provides a more complete account of the entanglement in these systems than has been available to date. Our results support the hypothesis that multipartite entanglement is maximum primary along the two distinct electronic energy transfer pa...
Entanglement of Distillation for Lattice Gauge Theories
Van Acoleyen, Karel; Bultinck, Nick; Haegeman, Jutho; Marien, Michael; Scholz, Volkher B.; Verstraete, Frank
2016-09-01
We study the entanglement structure of lattice gauge theories from the local operational point of view, and, similar to Soni and Trivedi [J. High Energy Phys. 1 (2016) 1], we show that the usual entanglement entropy for a spatial bipartition can be written as the sum of an undistillable gauge part and of another part corresponding to the local operations and classical communication distillable entanglement, which is obtained by depolarizing the local superselection sectors. We demonstrate that the distillable entanglement is zero for pure Abelian gauge theories at zero gauge coupling, while it is in general nonzero for the non-Abelian case. We also consider gauge theories with matter, and show in a perturbative approach how area laws—including a topological correction—emerge for the distillable entanglement. Finally, we also discuss the entanglement entropy of gauge fixed states and show that it has no relation to the physical distillable entropy.
Entanglement rules for holographic Fermi surfaces
Roychowdhury, Dibakar
2016-08-01
In this paper, based on the notion of Gauge/Gravity duality, we explore the laws of entanglement thermodynamics for most generic classes of Quantum Field Theories with hyperscaling violation. In our analysis, we note that for Quantum Field Theories with compressible quark like excitation, the first law of entanglement thermodynamics gets modified due to the presence of an additional term that could be identified as the entanglement chemical potential associated with hidden Fermi surfaces of the boundary theory. Most notably, we find that the so called entanglement chemical potential does not depend on the size of the entangling region and is purely determined by the quark d.o.f. encoded within the entangling region.
Entanglement in non-Hermitian quantum theory
Indian Academy of Sciences (India)
Arun K Pati
2009-09-01
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 $\\mathcal{PT}$ -symmetric Hamiltonians. We will show that maximally entangled states in usual quantum theory behave like non-maximally entangled states in $\\mathcal{PT}$ -symmetric quantum theory. Furthermore, we will show how to create entanglement between two $\\mathcal{PT}$ qubits using non-Hermitian Hamiltonians and discuss the entangling capability of such interaction Hamiltonians that are non-Hermitian in nature.
Orbital angular momentum-entanglement frequency transducer
Zhou, Zhi-Yuan; Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Dong, Ming-Xin; Shi, Bao-Sen; Guo, Guang-Can
2016-01-01
Entanglement is a vital resource for realizing many tasks such as teleportation, secure key distribution, metrology and quantum computations. To effectively build entanglement between different quantum systems and share information between them, a frequency transducer to convert between quantum states of different wavelengths while retaining its quantum features is indispensable. Information encoded in the photons orbital angular momentum OAM degrees of freedom is preferred in harnessing the information carrying capacity of a single photon because of its unlimited dimensions. A quantum transducer, which operates at wavelengths from 1558.3 nm to 525 nm for OAM qubits, OAMpolarization hybrid entangled states, and OAM entangled states, is reported for the first time. Nonclassical properties and entanglements are demonstrated following the conversion process by performing quantum tomography, interference, and Bell inequality measurements. Our results demonstrate the capability to create an entanglement link betwe...
Entanglement Enhancement in an XY Spin Chain
Institute of Scientific and Technical Information of China (English)
SU Xiao-Qiang
2011-01-01
We study evolution of entanglement in an XY-type spin channel and find that the entanglement can be enhanced by the spin channel. The parameter regions of the initial states for different numbers of sites are obtained.Furthermore, we consider a common spin environment coupling to the spin chains and find that the entanglement enhancement can also be implemented only for the chains with the odd numbers of sites.%@@ We study evolution of entanglement in an XY-type spin channel and find that the entanglement can be enhanced by the spin channel.The parameter regions of the initial states for different numbers of sites are obtained.Furthermore,we consider a common spin environment coupling to the spin chains and find that the entanglement enhancement can also be implemented only for the chains with the odd numbers of sites.
Entanglement rules for holographic Fermi surfaces
Directory of Open Access Journals (Sweden)
Dibakar Roychowdhury
2016-08-01
Full Text Available In this paper, based on the notion of Gauge/Gravity duality, we explore the laws of entanglement thermodynamics for most generic classes of Quantum Field Theories with hyperscaling violation. In our analysis, we note that for Quantum Field Theories with compressible quark like excitation, the first law of entanglement thermodynamics gets modified due to the presence of an additional term that could be identified as the entanglement chemical potential associated with hidden Fermi surfaces of the boundary theory. Most notably, we find that the so called entanglement chemical potential does not depend on the size of the entangling region and is purely determined by the quark d.o.f. encoded within the entangling region.
Gaussian entanglement in the turbulent atmosphere
Bohmann, M.; Semenov, A. A.; Sperling, J.; Vogel, W.
2016-07-01
We provide a rigorous treatment of the entanglement properties of two-mode Gaussian states in atmospheric channels by deriving and analyzing the input-output relations for the corresponding entanglement test. A key feature of such turbulent channels is a nontrivial dependence of the transmitted continuous-variable entanglement on coherent displacements of the quantum state of the input field. Remarkably, this allows one to optimize the entanglement certification by modifying local coherent amplitudes using a finite, but optimal amount of squeezing. In addition, we propose a protocol which, in principle, renders it possible to transfer the Gaussian entanglement through any turbulent channel over arbitrary distances. Therefore, our approach provides the theoretical foundation for advanced applications of Gaussian entanglement in free-space quantum communication.
Asymmetric EPR entanglement in continuous variable systems
Wagner, Katherine; Armstrong, Seiji; Morizur, Jean-Francois; Lam, Ping Koy; Bachor, Hans-Albert
2012-01-01
Continuous variable entanglement can be produced in nonlinear systems or via interference of squeezed states. In many of optical systems, such as parametric down conversion or interference of optical squeezed states, production of two perfectly symmetric subsystems is usually used for demonstrating the existence of entanglement. This symmetry simplifies the description of the concept of entanglement. However, asymmetry in entanglement may arise naturally in a real experiment, or be intentionally introduced in a given quantum information protocol. These asymmetries can emerge from having the output beams experience different losses and environmental contamination, or from the availability of non-identical input quantum states in quantum communication protocols. In this paper, we present a visualisation of entanglement using quadrature amplitude plots of the twin beams. We quantitatively discuss the strength of asymmetric entanglement using EPR and inseparability criteria and theoretically show that the optimal...
Increasing Entanglement between Gaussian States by Coherent Photon Subtraction
DEFF Research Database (Denmark)
Ourjoumtsev, Alexei; Dantan, Aurelien Romain; Tualle Brouri, Rosa;
2007-01-01
We experimentally demonstrate that the entanglement between Gaussian entangled states can be increased by non-Gaussian operations. Coherent subtraction of single photons from Gaussian quadrature-entangled light pulses, created by a nondegenerate parametric amplifier, produces delocalized states...
Towards an Urbanism of Entanglement
DEFF Research Database (Denmark)
Tietjen, Anne
2009-01-01
than being an autonomous field of work urban design is a transdisciplinary field that connects multiple practice and knowledge forms. Finally, an urbanism of entanglement brings about design interventions which stress performativity and connectivity. An urbanism of entanglement proposes new......This PhD thesis examines the concept of the urban site in relation to polarised spatial development in Denmark. At the core of this research project is a design based investigation that tests site based approaches in two study areas in East and North Jutland. Together with - and directly related...... to the design study - an investigation of the theoretical and methodological foundations of contemporary urban design practice is undertaken. The phenomenon of polarisation is a pertinent starting point to identify challenges and potentials of contemporary urban design. Polarised spatial development reflects...
Entanglement Entropy in Jammed CFTs
Mefford, Eric
2016-01-01
We construct solutions to the Einstein equations for asymptotically locally Anti-de Sitter spacetimes with four, five, and six dimensional Reissner-Nordstr\\"om boundary metrics. These spacetimes are gravitational duals to "jammed" CFTs on those backgrounds at infinite N and strong coupling. For these spacetimes, we calculate the boundary stress tensor as well as compute entanglement entropies for ball shaped regions as functions of the boundary black hole temperature $T_{BH}$. From this, we see how the CFT prevents heat flow from the black hole to the vacuum at spatial infinity. We also compute entanglement entropies for a three dimensional boundary black hole using the AdS C-metric. We compare our results to previous work done in similar spacetimes.
Electromagnetic Duality and Entanglement Anomalies
Donnelly, William; Wall, Aron
2016-01-01
Duality is an indispensable tool for describing the strong-coupling dynamics of gauge theories. However, its actual realization is often quite subtle: quantities such as the partition function can transform covariantly, with degrees of freedom rearranged in a nonlocal fashion. We study this phenomenon in the context of the electromagnetic duality of abelian $p$-forms. A careful calculation of the duality anomaly on an arbitrary $D$-dimensional manifold shows that the effective actions agree exactly in odd $D$, while in even $D$ they differ by a term proportional to the Euler number. Despite this anomaly, the trace of the stress tensor agrees between the dual theories. We also compute the change in the vacuum entanglement entropy under duality, relating this entanglement anomaly to the duality of an "edge mode" theory in two fewer dimensions. Previous work on this subject has led to conflicting results; we explain and resolve these discrepancies.
Experimental quantum computing without entanglement.
Lanyon, B P; Barbieri, M; Almeida, M P; White, A G
2008-11-14
Deterministic quantum computation with one pure qubit (DQC1) is an efficient model of computation that uses highly mixed states. Unlike pure-state models, its power is not derived from the generation of a large amount of entanglement. Instead it has been proposed that other nonclassical correlations are responsible for the computational speedup, and that these can be captured by the quantum discord. In this Letter we implement DQC1 in an all-optical architecture, and experimentally observe the generated correlations. We find no entanglement, but large amounts of quantum discord-except in three cases where an efficient classical simulation is always possible. Our results show that even fully separable, highly mixed, states can contain intrinsically quantum mechanical correlations and that these could offer a valuable resource for quantum information technologies.
Quantum steganography using prior entanglement
Energy Technology Data Exchange (ETDEWEB)
Mihara, Takashi, E-mail: mihara@toyo.jp
2015-06-05
Steganography is the hiding of secret information within innocent-looking information (e.g., text, audio, image, video, etc.). A quantum version of steganography is a method based on quantum physics. In this paper, we propose quantum steganography by combining quantum error-correcting codes with prior entanglement. In many steganographic techniques, embedding secret messages in error-correcting codes may cause damage to them if the embedded part is corrupted. However, our proposed steganography can separately create secret messages and the content of cover messages. The intrinsic form of the cover message does not have to be modified for embedding secret messages. - Highlights: • Our steganography combines quantum error-correcting codes with prior entanglement. • Our steganography can separately create secret messages and the content of cover messages. • Errors in cover messages do not have affect the recovery of secret messages. • We embed a secret message in the Steane code as an example of our steganography.
Psychological games of entangled players
Zak, Michail
2012-01-01
The paper introduces a new approach to theory of differential games in which entangled players try to predict and influence actions of their adversaries. The entanglement is generated be a joint probability density known by the players. Incase of complex density, its imaginary part represents a measure of uncertainty of the density distribution. The novelty of the approach is in non-Newtonian mathematical formalism thatis based upon a behavioral model of Livings. The model is quantum-inspired: it represented by a modified Madelung equation which the quantum potential is replaced by different, specially chosen "computational" potential. It consists of motor dynamics simulating actual behavior of the object, and mental dynamics representing evolution of the corresponding knowledge-based and incorporating this knowledge in the for m of information flows into the motor dynamics. Due to feedback from mental dynamics, motor dynamics attains quantum-like properties: its trajectory splits into a family of different t...
Entanglement Entropy of Two Spheres
Shiba, Noburo
2012-01-01
We study the entanglement entropy S_{AB} of a massless free scalar field on two spheres A and B whose radii are R_1 and R_2, respectively, and the distance between them is r. The state of the massless free scalar field is the vacuum state. We obtain the result that the mutual information S_{A;B}:=S_A+S_B-S_{AB} is independent of the ultraviolet cutoff and proportional to the product of the areas of the two spheres when r>>R_1,R_2, where S_A and S_B are the entanglement entropy on the inside region of A and B, respectively. We discuss possible connections of this result with the physics of black holes.
Entangled-photon Fourier optics
Abouraddy, A F; Sergienko, A V; Teich, M C; Abouraddy, Ayman F.; Saleh, Bahaa E. A.; Sergienko, Alexander V.; Teich, Malvin C.
2002-01-01
Entangled photons, generated by spontaneous parametric down-conversion from a second-order nonlinear crystal, present a rich potential for imaging and image-processing applications. Since this source is an example of a three-wave mixing process, there is more flexibility in the choices of illumination and detection wavelengths and in the placement of object(s) to be imaged. Moreover, this source is entangled, a fact that allows for imaging configurations and capabilities that cannot be achieved using classical sources of light. In this paper we examine a number of imaging and image-processing configurations that can be realized using this source. The formalism that we utilize facilitates the determination of the dependence of imaging resolution on the physical parameters of the optical arrangement.
Entangled qutrits for quantum communication
Thew, R T; Zbinden, H; Gisin, Nicolas
2003-01-01
We introduce a new technique to experimentally generate, control and measure entangled qutrits, 3-dimensional quantum systems. This scheme uses spontaneous parametric down converted photons and unbalanced 3-arm fiber optic interferometers in a scheme analogous to the Franson interferometric arrangement for qubits. The results reveal a source capable of generating maximally entangled states with a net state fidelity, F = 0.985 $\\pm$ 0.018. Further the control over the system reveals a high, net, 2-photon interference fringe visibility, V = 0.919 $\\pm$ 0.026, when the two phases are varied. This has all been done at telecom wavelengths thus facilitating the advancement to long distance higher dimensional quantum communication.
Quantum entanglement in the multiverse
Robles-Pérez, S.; González-Díaz, P. F.
2014-01-01
We show that the quantum state of a multiverse made up of classically disconnected regions of the space-time, whose dynamical evolution is dominated by a homogeneous and isotropic fluid, is given by a squeezed state. These are typical quantum states that have no classical counterpart and therefore allow analyzing the violation of classical inequalities as well as the EPR argument in the context of the quantum multiverse. The thermodynamical properties of entanglement are calculated for a composite quantum state of two universes whose states are quantum-mechanically correlated. The energy of entanglement between the positive and negative modes of a scalar field, which correspond to the expanding and contracting branches of a phantom universe, are also computed.
Internal entanglement amplification by external interactions
2007-01-01
We propose a scheme to control the level of entanglement between two fixed spin-1/2 systems by interaction with a third particle. For specific designs, entanglement is shown to be "pumped" into the system from the surroundings even when the spin-spin interaction within the system is small or nonexistent. The effect of the external particle on the system is introduced by including a dynamic spinor in the Hamiltonian. Controlled amplification of the internal entanglement to its maximum value is...
The Geometry of Entanglement Sudden Death
Terra-Cunha, M O
2007-01-01
In open quantum systems, entanglement can vanish faster than coherence. This phenomenon is usually called sudden death of entanglement. In this paper sudden death of entanglement is discussed from a geometrical point of view, in the context of two qubits. A classification of possible scenarios is presented, with important known examples classified. Theoretical and experimental construction of other examples is suggested as well as large dimensional and multipartite versions of the effect.
Modulated Entanglement Evolution Via Correlated Noises
Corn, Brittany
2009-01-01
We study entanglement dynamics in the presence of correlated environmental noises. Specifically, we investigate the quantum entanglement dynamics of two spins in the presence of correlated classical white noises, deriving Markov master equation and obtaining explicit solutions for several interesting classes of initial states including Bell states and X form density matrices. We show how entanglement can be enhanced or reduced by the correlation between the two participating noises.
Quantifying entanglement of overlapping indistinguishable particles
Gittings, Joseph R.
This thesis develops the quantitative study of quantum entanglement in systems of identical particles. Understanding this topic is essential for the construction of quantum information processing devices involving identical particles. A brief overview of necessary concepts and methods, such as the density matrix, the entanglement in pure and mixed states of distinguishable particles, and some common applications of entanglement is given in the introduction. Some competing methods of calculating the entanglement in bipartite pure states of indistinguishable particles are examined. It is shown that only the 'site entropy' measure introduced by Zanardi satisfies all the criteria for a correct entanglement measure. A teleportation protocol which utilizes all the entanglement carried (in both the spin and space degrees of freedom) in a doubly- occupied molecular bonding orbital is presented. The output from an interferometer in a thought experiment described by Omar et al. is studied as an example to see whether entanglement can be separated into space-only, spin-only, and space-spin components. A similar exercise is performed for a doubly-occupied molecular bonding orbital. The relationship between these results and the application of superselection rules (SSRs) to the quantification of useful entanglement is discussed. A numerical method for estimating the entanglement of formation of a mixed state of arbitrary dimension by a conjugate gradient algorithm is described. The results of applying an implementation of the algorithm to both random and isotropic states of 2 qutrits (i.e. two three-dimensional systems) is described. Existing work on calculating entanglement between two sites in various spin systems is outlined. New methods for calculating the entanglement between two sites in various types of degenerate quantum gas - a Fermi gas, a Bose condensate, and a BCS superconductor - are described. The results of numerical studies of the entanglement in a normal metal
Controllable entanglement sudden birth of Heisenberg spins
Institute of Scientific and Technical Information of China (English)
ZHENG Qiang; ZHI Qi-Jun; ZHANG Xiao-ping; REN Zhong-Zhou
2011-01-01
We investigate the Entanglement Sudden Birth (ESB) of two Heisenberg spins A and B. The third controller, qutrit C is introduced, which only has the Dzyaloshinskii-Moriya (DM) spin-orbit interaction with qubit B. We find that the DM interaction is necessary to induce the Entanglement Sudden Birth of the system qubits A and B, and the initial states of the system qubits and the qurit C are also important to control its Entanglement Sudden Birth.
Entanglement oscillations in open Heisenberg chains
Wang, T; Wang, X; Sun, Zhe; Wang, Ting; Wang, Xiaoguang
2006-01-01
We study pairwise entanglements in spin-half and spin-one Heisenberg chains with an open boundary condition, respectively. We find out that the ground-state and the first-excited-state entanglements are equal for the three-site spin-one chain. When the number of sites L>3, the concurrences and negativities display oscillatory behaviors, and the oscillations of the ground-state and the first-excited-state entanglements are out of phase or in phase.
Experimental generation of complex noisy photonic entanglement
Dobek, K; Demkowicz-Dobrzanski, R; Banaszek, K; Horodecki, P
2011-01-01
We describe an experimental setup based on spontaneous parametric down-conversion to produce multiple photon pairs in maximally entangled polarization states using an arrangement of two type-I nonlinear crystals. By introducing correlated polarization noise in the paths of the generated photons one can prepare mixed entangled states whose properties illustrate fundamental results obtained recently in quantum information theory, in particular those concerning bound entanglement and privacy.
Shifting entanglement from states to observables
Energy Technology Data Exchange (ETDEWEB)
Ranade, Kedar [Institut fuer Quantenphysik, Universitaet Ulm, 89069 Ulm (Germany); Harshman, Nathan [Department of Physics, American University, Washington DC (United States); Institut fuer Quantenphysik, Universitaet Ulm, 89069 Ulm (Germany)
2011-07-01
We illustrate that for any pure state on a finite-dimensional Hilbert space we can construct observables that induce a tensor product structure such that the amount of entanglement of the state may take arbitrary values. In particular, we provide an example of how to construct observables on a d-dimensional system such that an arbitrary known pure state can be treated as maximally entangled. In effect, we show how entanglement properties can be shifted from states to observables.
Entangling Atoms and Ions in Dissipative Environments
Beige, A; Braun, D; Huelga, S F; Knight, P L; Plenio, M B; Vedral, V
2000-01-01
Quantum information processing rests on our ability to manipulate quantum superpositions through coherent unitary transformations, and to establish entanglement between constituent quantum components of the processor. The quantum information processor (a linear ion trap, or a cavity confining the radiation field for example) exists in a dissipative environment. We discuss ways in which entanglement can be established within such dissipative environments. We can even make use of a strong interaction of the system with its environment to produce entanglement in a controlled way.
Entanglement Generation by Electric Field Background
Ebadi, Zahra; Mirza, Behrouz
2014-01-01
The quantum vacuum is unstable under the influence of an external electric field and decays into pairs of charged particles, a process which is known as the Schwinger pair production. We propose and demonstrate that this electric field can generate entanglement. Using the Schwinger pair production for constant and pulsed electric fields, we study entanglement for scalar particles with zero spins and Dirac fermions. One can observe the variation of the entanglement produced for bosonic and fer...
Entanglement Generation by Electric Field Background
Ebadi, Zahra
2014-01-01
The quantum vacuum is unstable under the influence of an external electric field and decays into pairs of charged particles, a process which is known as the Schwinger pair production. We propose and demonstrate that this electric field can generate entanglement. Using the Schwinger pair production for constant and pulsed electric fields, we study entanglement for scalar particles with zero spins and Dirac fermions. One can observe the variation of the entanglement produced for bosonic and fermionic modes with respect to different parameters.
Entanglement of Formation for Quantum States
Institute of Scientific and Technical Information of China (English)
ZHAO Hui; WANG Zhi-Xi
2007-01-01
We investigate the entanglement of formation for a class of high-dimensional quantum mixed states. We present a kind of generalized concurrence for a class of high-dimensional quantum pure states such that the entanglement of formation is a monotonically increasing convex function of the generalized concurrence. From the monotonicity and convexity the entanglement of formation for a class of high-dimensional mixed states has been calculated analytically.
Entangled States and the Gravitational Quantum Well
Alves, Rui; Bertolami, Orfeu
2016-01-01
We study the continuous variable entanglement of a system of two particles under the influence of Earth's gravitational field. We determine a phase-space description of this bipartite system by calculating its Wigner function and verify its entanglement by applying a generalization of the PPT criterion for non-Gaussian states. We also examine the influence of gravity on an idealized entanglement protocol to be shared between stations at different potentials based on the correlation of states of the gravitational quantum well.
Institute of Scientific and Technical Information of China (English)
姚春梅; 李敏; 叶柳; 郭光灿
2002-01-01
We discuss two different schemes for the probabilistic preparation of N-particle cat states using pure multiparticle entangled states via entanglement swapping and entanglement concentration. At the centre of distribution A,Alice performs all of the operations required to achieve our goal.
Tensor 2-sums and entanglement
Klavzar, Sandi
2009-01-01
To define a minimal mathematical framework for isolating some of the characteristic properties of quantum entanglement, we introduce a generalization of the tensor product of graphs. Inspired by the notion of a density matrix, the generalization is a simple one: every graph can be obtained by addiction modulo two, possibly with many summands, of tensor products of adjacency matrices. In this picture, we are still able to prove a combinatorial analogue of the Peres-Horodecki criterion for testing separability.
Entanglement Measure and Quantum Violation of Bell-Type Inequality
Ding, Dong; He, Ying-Qiu; Yan, Feng-Li; Gao, Ting
2016-10-01
By calculating entanglement measures and quantum violation of Bell-type inequality, we reveal the relationship between entanglement measure and the amount of quantum violation for a family of four-qubit entangled states. It has been demonstrated that the Bell-type inequality is completely violated by these four-qubit entangled states. The plot of entanglement measure as a function of the expectation value of Bell operator shows that entanglement measure first decreases and then increases smoothly with increasing quantum violation.
Hammond, Marie S.; Lockman, Jennifer D.; Boling, Timothy
2010-01-01
Brown and Krane have posited a tripartite model of career indecision, which includes three higher order factors: negative affect, poor vocational identity development, and lack of career information. The purpose of this study was to examine the adequacy of their tripartite model of career indecision for African American students, considering that…
Bit threads and holographic entanglement
Freedman, Michael
2016-01-01
The Ryu-Takayanagi (RT) formula relates the entanglement entropy of a region in a holographic theory to the area of a corresponding bulk minimal surface. Using the max flow-min cut principle, a theorem from network theory, we rewrite the RT formula in a way that does not make reference to the minimal surface. Instead, we invoke the notion of a "flow", defined as a divergenceless norm-bounded vector field, or equivalently a set of Planck-thickness "bit threads". The entanglement entropy of a boundary region is given by the maximum flux out of it of any flow, or equivalently the maximum number of bit threads that can emanate from it. The threads thus represent entanglement between points on the boundary, and naturally implement the holographic principle. As we explain, this new picture clarifies several conceptual puzzles surrounding the RT formula. We give flow-based proofs of strong subadditivity and related properties; unlike the ones based on minimal surfaces, these proofs correspond in a transparent manner...
On entanglement spreading from holography
Mezei, Márk
2016-01-01
A global quench is an interesting setting where we can study thermalization of subsystems in a pure state. We investigate entanglement entropy (EE) growth in global quenches in holographic field theories and relate some of its aspects to quantities characterizing chaos. More specifically we obtain four key results: 1. We prove holographic bounds on the entanglement velocity $v_E$ and the butterfly effect speed $v_B$ that arises in the study of chaos. 2. We obtain the EE as a function of time for large spherical entangling surfaces analytically. We show that the EE is insensitive to the details of the initial state or quench protocol. 3. In a thermofield double state we determine analytically the two-sided mutual information between two large concentric spheres separated in time. 4. We derive a bound on the rate of growth of EE for arbitrary shapes, and develop an expansion for EE at early times. In a companion paper with Douglas Stanford arXiv:1608.05101, we put these results in the broader context of EE grow...
Bit Threads and Holographic Entanglement
Freedman, Michael; Headrick, Matthew
2016-11-01
The Ryu-Takayanagi (RT) formula relates the entanglement entropy of a region in a holographic theory to the area of a corresponding bulk minimal surface. Using the max flow-min cut principle, a theorem from network theory, we rewrite the RT formula in a way that does not make reference to the minimal surface. Instead, we invoke the notion of a "flow", defined as a divergenceless norm-bounded vector field, or equivalently a set of Planck-thickness "bit threads". The entanglement entropy of a boundary region is given by the maximum flux out of it of any flow, or equivalently the maximum number of bit threads that can emanate from it. The threads thus represent entanglement between points on the boundary, and naturally implement the holographic principle. As we explain, this new picture clarifies several conceptual puzzles surrounding the RT formula. We give flow-based proofs of strong subadditivity and related properties; unlike the ones based on minimal surfaces, these proofs correspond in a transparent manner to the properties' information-theoretic meanings. We also briefly discuss certain technical advantages that the flows offer over minimal surfaces. In a mathematical appendix, we review the max flow-min cut theorem on networks and on Riemannian manifolds, and prove in the network case that the set of max flows varies Lipshitz continuously in the network parameters.
Entanglement, Holography and Causal Diamonds
de Boer, Jan; Heller, Michal P; Myers, Robert C
2016-01-01
We argue that the degrees of freedom in a d-dimensional CFT can be re-organized in an insightful way by studying observables on the moduli space of causal diamonds (or equivalently, the space of pairs of timelike separated points). This 2d-dimensional space naturally captures some of the fundamental nonlocality and causal structure inherent in the entanglement of CFT states. For any primary CFT operator, we construct an observable on this space, which is defined by smearing the associated one-point function over causal diamonds. Known examples of such quantities are the entanglement entropy of vacuum excitations and its higher spin generalizations. We show that in holographic CFTs, these observables are given by suitably defined integrals of dual bulk fields over the corresponding Ryu-Takayanagi minimal surfaces. Furthermore, we explain connections to the operator product expansion and the first law of entanglement entropy from this unifying point of view. We demonstrate that for small perturbations of the va...
Time-bin Entanglement from Quantum Dots
Weihs, Gregor; Predojević, Ana
2016-01-01
The desire to have a source of single entangled photon pairs can be satisfied using single quantum dots as emitters. However, we are not bound to pursue only polarization entanglement, but can also exploit other degrees of freedom. In this chapter we focus on the time degree of freedom, to achieve so-called time-bin entanglement. This requires that we prepare the quantum dot coherently into the biexciton state and also build special interferometers for analysis. Finally this technique can be extended to achieve time-bin and polarization hyper-entanglement from a suitable quantum dot.
Entanglement classification with matrix product states.
Sanz, M; Egusquiza, I L; Di Candia, R; Saberi, H; Lamata, L; Solano, E
2016-07-26
We propose an entanglement classification for symmetric quantum states based on their diagonal matrix-product-state (MPS) representation. The proposed classification, which preserves the stochastic local operation assisted with classical communication (SLOCC) criterion, relates entanglement families to the interaction length of Hamiltonians. In this manner, we establish a connection between entanglement classification and condensed matter models from a quantum information perspective. Moreover, we introduce a scalable nesting property for the proposed entanglement classification, in which the families for N parties carry over to the N + 1 case. Finally, using techniques from algebraic geometry, we prove that the minimal nontrivial interaction length n for any symmetric state is bounded by .
Experimental entanglement redistribution under decoherence channels.
Aguilar, G H; Valdés-Hernández, A; Davidovich, L; Walborn, S P; Souto Ribeiro, P H
2014-12-12
When an initially entangled pair of qubits undergoes local decoherence processes, there are a number of ways in which the original entanglement can spread throughout the multipartite system consisting of the two qubits and their environments. Here, we report theoretical and experimental results regarding the dynamics of the distribution of entanglement in this system. The experiment employs an all optical setup in which the qubits are encoded in the polarization degrees of freedom of two photons, and each local decoherence channel is implemented with an interferometer that couples the polarization to the path of each photon, which acts as an environment. We monitor the dynamics and distribution of entanglement and observe the transition from bipartite to multipartite entanglement and back, and show how these transitions are intimately related to the sudden death and sudden birth of entanglement. The multipartite entanglement is further analyzed in terms of three- and four-partite entanglement contributions, and genuine four-qubit entanglement is observed at some points of the evolution.
Radiative processes of uniformly accelerated entangled atoms
Menezes, G
2015-01-01
We study radiative processes of uniformly accelerated entangled atoms, interacting with an electromagnetic field prepared in the Minkowski vacuum state. We discuss the structure of the rate of variation of the atomic energy for two atoms travelling in different hyperbolic world lines. We identify the contributions of vacuum fluctuations and radiation reaction to the generation of entanglement as well as to the decay of entangled states. Our results resemble the situation in which two inertial atoms are coupled individually to two spatially separated cavities at different temperatures. In addition, for equal accelerations we obtain that the maximally entangled antisymmetric Bell state is a decoherence-free state.
Efficient entanglement purification in quantum repeaters
Institute of Scientific and Technical Information of China (English)
Sheng Yu-Bo; Zhou Lan; Cheng Wei-Wen; Gong Long-Yan; Zhao Sheng-Mei; Zheng Bao-Yu
2012-01-01
We present an efficient entanglement purification protocol (EPP) with controlled-not (CNOT) gates and linear optics.With the CNOT gates,our EPP can reach a higher fidelity than the conventional one.Moreover,it does not require the fidelity of the initial mixed state to satisfy · · 1· 2.If the initial state is not entangled,it still can be purified.With the linear optics,this protocol can get pure maximally entangled pairs with some probabilities.Meanwhile,it can be used to purify the entanglement between the atomic ensembles in distant locations.This protocol may be useful in long-distance quantum communication.
Bounds on entanglement in qudit subsystems
Kendon, Vivien M.; Zyczkowski, Karol; Munro, William J.
2002-01-01
The entanglement in a pure state of N qudits (d-dimensional distinguishable quantum particles) can be characterised by specifying how entangled its subsystems are. A generally mixed subsystem of m qudits is obtained by tracing over the other N-m qudits. We examine the entanglement in the space of mixed states of m qudits. We show that for a typical pure state of N qudits, its subsystems smaller than N/3 qudits will have a positive partial transpose and hence are separable or bound entangled. ...
Can Holographic Entanglement Entropy Distinguish Relaxation Timescales?
Rahimi, M; Lezgi, M
2016-01-01
We use gauge-gravity duality to compute entanglement entropy in a non-conformal background with an energy scale $\\Lambda$. At zero temperature, we observe that entanglement entropy decreases by raising $\\Lambda$. However, at finite temperature, we realize that both $\\frac{\\Lambda}{T}$ and entanglement entropy rise together. Comparing entanglement entropy of the non-conformal theory, $S_{A(N)}$, and of its conformal theory at the $UV$ limit, $ S_{A(C)}$, rereals that $S_{A(N)}$ can be larger or smaller than $S_{A(C)}$, depending on the value of $\\frac{\\Lambda}{T}$
Entanglement property in matrix product spin systems
Institute of Scientific and Technical Information of China (English)
ZHU Jing-Min
2012-01-01
We study the entanglement property in matrix product spin-ring systems systemically by von Neumann entropy.We find that:(i) the Hilbert space dimension of one spin determines the upper limit of the maximal value of the entanglement entropy of one spin,while for multiparticle entanglement entropy,the upper limit of the maximal value depends on the dimension of the representation matrices.Based on the theory,we can realize the maximum of the entanglement entropy of any spin block by choosing the appropriate control parameter values.(ii) When the entanglement entropy of one spin takes its maximal value,the entanglement entropy of an asymptotically large spin block,i.e. the renormalization group fixed point,is not likely to take its maximal value,and so only the entanglement entropy Sn of a spin block that varies with size n can fully characterize the spin-ring entanglement feature.Finally,we give the entanglement dynamics,i.e.the Hamiltonian of the matrix product system.
Nonlocality and entanglement as opposite properties
Vallone, G; Gómez, E S; Cañas, G; Larsson, J -A; Mataloni, P; Cabello, A
2011-01-01
We show that, for any chained Bell inequality with any number of settings, nonlocality and entanglement are not only essentially different properties but opposite ones. We first show that, in the absence of noise, the threshold detection efficiency for a loophole-free Bell test increases with the degree of entanglement, so that the closer the quantum states are to product states, the harder it is to reproduce the quantum predictions with local models. In the presence of white noise, we show that nonlocality and entanglement are simultaneously maximized only in the presence of extreme noise; in any other case, the lowest threshold detection efficiency is obtained by reducing the entanglement.
Entanglement Equilibrium and the Einstein Equation.
Jacobson, Ted
2016-05-20
A link between the semiclassical Einstein equation and a maximal vacuum entanglement hypothesis is established. The hypothesis asserts that entanglement entropy in small geodesic balls is maximized at fixed volume in a locally maximally symmetric vacuum state of geometry and quantum fields. A qualitative argument suggests that the Einstein equation implies the validity of the hypothesis. A more precise argument shows that, for first-order variations of the local vacuum state of conformal quantum fields, the vacuum entanglement is stationary if and only if the Einstein equation holds. For nonconformal fields, the same conclusion follows modulo a conjecture about the variation of entanglement entropy.
Quantum entanglement and quantum computational algorithms
Indian Academy of Sciences (India)
Arvind
2001-02-01
The existence of entangled quantum states gives extra power to quantum computers over their classical counterparts. Quantum entanglement shows up qualitatively at the level of two qubits. We demonstrate that the one- and the two-bit Deutsch-Jozsa algorithm does not require entanglement and can be mapped onto a classical optical scheme. It is only for three and more input bits that the DJ algorithm requires the implementation of entangling transformations and in these cases it is impossible to implement this algorithm classically
Geometry induced entanglement transitions in nanostructures
Coe, J P; D'Amico, I
2010-01-01
We model quantum dot nanostructures using a one-dimensional system of two interacting electrons. We show that strong and rapid variations may be induced in the spatial entanglement by varying the nanostructure geometry. We investigate the position-space information entropy as an indicator of the entanglement in this system. We also consider the expectation value of the Coulomb interaction and the ratio of this expectation to the expectation of the confining potential and their link to the entanglement. We look at the first derivative of the entanglement and the position-space information entropy to infer information about a possible quantum phase transition.
Non-Markovianity assisted Steady State Entanglement
Huelga, Susana F; Plenio, Martin B
2011-01-01
We analyze the dependence of steady state entanglement in a dimer system with a coherent exchange interaction and subject to local dephasing on the degree of Markovianity of the system-environment interaction. We demonstrate that non-Markovianity of the system-environment interaction is an essential resource that may support the formation of steady state entanglement whereas purely Markovian dynamics governed by Lindblad master equations results in separable steady states. This result illustrates possible mechanisms leading to long lived entanglement in purely decohering local environments. A feasible experimental demonstration of this non-Markovianity assisted steady state entanglement using a system of trapped ions is presented.
Cavity Loss Induced Generation of Entangled Atoms
Plenio, M B; Beige, A; Knight, P L
1999-01-01
We discuss the generation of entangled states of two two-level atoms inside an optical resonator. When the cavity decay is continuously monitored, the absence of photon-counts is associated with the presence of an atomic entangled state. In addition to being conceptually simple, this scheme could be demonstrated with presently available technology. We describe how such a state is generated through conditional dynamics, using quantum jump methods, including both cavity damping and spontaneous emission decay, and evaluate the fidelity and relative entropy of entanglement of the generated state compared with the target entangled state.
Entanglement production in quantized chaotic systems
Indian Academy of Sciences (India)
Jayendra N Bandyopadhyay; Arul Lakshminarayan
2005-04-01
Quantum chaos is a subject whose major goal is to identify and to investigate different quantum signatures of classical chaos. Here we study entanglement production in coupled chaotic systems as a possible quantum indicator of classical chaos. We use coupled kicked tops as a model for our extensive numerical studies. We find that, in general, chaos in the system produces more entanglement. However, coupling strength between two subsystems is also a very important parameter for entanglement production. Here we show how chaos can lead to large entanglement which is universal and describable by random matrix theory (RMT). We also explain entanglement production in coupled strongly chaotic systems by deriving a formula based on RMT. This formula is valid for arbitrary coupling strengths, as well as for sufficiently long time. Here we investigate also the effect of chaos on the entanglement production for the mixed initial state. We find that many properties of the mixed-state entanglement production are qualitatively similar to the pure state entanglement production. We however still lack an analytical understanding of the mixed-state entanglement production in chaotic systems.
Entanglement, tensor networks and black hole horizons
Molina-Vilaplana, J.; Prior, J.
2014-11-01
We elaborate on a previous proposal by Hartman and Maldacena on a tensor network which accounts for the scaling of the entanglement entropy in a system at a finite temperature. In this construction, the ordinary entanglement renormalization flow given by the class of tensor networks known as the Multi Scale Entanglement Renormalization Ansatz (MERA), is supplemented by an additional entanglement structure at the length scale fixed by the temperature. The network comprises two copies of a MERA circuit with a fixed number of layers and a pure matrix product state which joins both copies by entangling the infrared degrees of freedom of both MERA networks. The entanglement distribution within this bridge state defines reduced density operators on both sides which cause analogous effects to the presence of a black hole horizon when computing the entanglement entropy at finite temperature in the AdS/CFT correspondence. The entanglement and correlations during the thermalization process of a system after a quantum quench are also analyzed. To this end, a full tensor network representation of the action of local unitary operations on the bridge state is proposed. This amounts to a tensor network which grows in size by adding succesive layers of bridge states. Finally, we discuss on the holographic interpretation of the tensor network through a notion of distance within the network which emerges from its entanglement distribution.
Quantum communication using a multiqubit entangled channel
Energy Technology Data Exchange (ETDEWEB)
Ghose, Shohini, E-mail: sghose@wlu.ca [Department of Physics and Computer Science, Wilfrid Laurier University, Waterloo, Ontario (Canada); Institute for Quantum Computing, University of Waterloo, Ontario (Canada); Hamel, Angele [Department of Physics and Computer Science, Wilfrid Laurier University, Waterloo, Ontario (Canada)
2015-12-31
We describe a protocol in which two senders each teleport a qubit to a receiver using a multiqubit entangled state. The multiqubit channel used for teleportation is genuinely 4-qubit entangled and is not equivalent to a product of maximally entangled Bell pairs under local unitary operations. We discuss a scenario in which both senders must participate for the qubits to be successfully teleported. Such an all-or-nothing scheme cannot be implemented with standard two-qubit entangled Bell pairs and can be useful for different communication and computing tasks.
de Vega, Clara; Arista, Montserrat; Ortiz, Pedro L; Talavera, Salvador
2010-05-01
Mycorrhizae are widespread mutualistic symbioses crucial for the functioning of terrestrial ecosystems. Not all plants associate with mycorrhizae; most parasitic plants have been suggested to be nonmycorrhizal because they have developed alternative strategies to obtain nutrients. In endophytic parasitic plants, whose vegetative bodies grow completely inside their mycorrhizal host roots, the opportunity for establishing a tripartite association seems evident, but information on these systems is lacking. In studying natural associations among the endophytic holoparasite Cytinus hypocistis, their Cistaceae host species, and associated mycorrhizal fungi, we found that mycorrhizae were associated with the hosts and the parasites, reaching high frequencies of colonization. In parasitic and host root tissues, mycorrhizal fungi spread in the parenchymatic cells by intracellular growth and formed hyphal coils and vesicles, while the cambium and the vascular tissues were never colonized. This report is the first on a tripartite association of an endophytic parasitic plant, its host, and mycorrhizae in natural conditions, representing a novel trophic interaction not previously reported within the angiosperms. Additional studies on the interactions occurring among these three players are needed because they may be crucial to our understanding of how this mutualistic-antagonistic system is functioning and evolving.
Directory of Open Access Journals (Sweden)
Rouh-Mei Hu
Full Text Available BACKGROUND: Fusaric acid (5-butylpicolinic acid, a mycotoxin, is noxious to some microorganisms. Stenotrophomonas maltophilia displays an intrinsic resistance to fusaric acid. This study aims to elucidate the mechanism responsible for the intrinsic fusaric acid resistance in S. maltophilia. METHODOLOGY: A putative fusaric acid resistance-involved regulon fuaR-fuaABC was identified by the survey of the whole genome sequence of S. maltophilia K279a. The fuaABC operon was verified by reverse transcriptase-PCR. The contribution of the fuaABC operon to the antimicrobial resistance was evaluated by comparing the antimicrobials susceptibility between the wild-type strain and fuaABC knock-out mutant. The regulatory role of fuaR in the expression of the fuaABC operon was assessed by promoter transcription fusion assay. RESULTS: The fuaABC operon was inducibly expressed by fusaric acid and the inducibility was fuaR dependent. FuaR functioned as a repressor of the fuaABC operon in absence of a fusaric acid inducer and as an activator in its presence. Overexpression of the fuaABC operon contributed to the fusaric acid resistance. SIGNIFICANCE: A novel tripartite fusaric acid efflux pump, FuaABC, was identified in this study. Distinct from the formally classification, the FuaABC may constitute a new type of subfamily of the tripartite efflux pump.
Gaussification and entanglement distillation of continuous variable systems: a unifying picture
Energy Technology Data Exchange (ETDEWEB)
Campbell, Earl; Eisert, Jens [Dahlem Center for Complex Quantum Systems, Freie Universitaet Berlin, 14195 Berlin (Germany)
2012-07-01
Distillation of entanglement using only Gaussian operations is an important primitive in quantum communication, quantum repeater architectures, and distributed quantum computing. Existing distillation protocols for continuous degrees of freedom are only known to converge to a Gaussian state when measurements yield precisely the vacuum outcome. In sharp contrast, non-Gaussian states can be deterministically converted into Gaussian states while preserving their second moments, albeit by usually reducing their degree of entanglement. In this work - based on a novel instance of a non-commutative central limit theorem - we introduce a picture general enough to encompass the known protocols leading to Gaussian states, and also demonstrate convergence for a class of new protocols. This gives the experimental option of balancing the merits of success probability against entanglement produced. The generality of results also opens up entirely new territory, by providing means of multi-partite distillation and more efficient hybrid quantum repeater schemes.
Electronic Elections: A Balancing Act
Rezende, Pedro A. D.
This article aims to share some major lessons learned from the pioneering experience in Brazil with the world's first full national implementation of universal electronic voting. Differing notions of security, and their "collateral entanglements", appear to play a key role and are contrasted in Brazil's pioneering electronic voting saga. After an introduction, we puzzle through what election security may mean. We elaborate on how technological innovations may affect the underlying risks, their nature, corrections and balance. Then we describe some ways in which innovations have been deployed and validated, and how the results are being perceived, before some closing remarks.
Engineering of Multi-Dimensional Entangled States of Photon Pairs Using Hyper-Entanglement
Institute of Scientific and Technical Information of China (English)
REN Xi-Feng; GUO Guo-Ping; LI Jian; LI Chuan-Feng; GUO Guang-Can
2006-01-01
@@ Multi-dimensional entangled states have been proven to be more powerful in some quantum information processes.Down-converted photons from spontaneous parametric down-conversion are used to engineer multi-dimensional entangled states. A kind of multi-degree multi-dimensional Greenberger-Horne-Zeilinger states can also be generated. The hyper-entangled photons are entangled in energy-time, polarization and orbital angular momentum,which is proven to be useful to increase the dimension of systems and to investigate higher-dimensional entangled states.
Entanglement Preserving in Quantum Copying of Three-Qubit Entangled State
Institute of Scientific and Technical Information of China (English)
TONG Zhao-Yang; KUANG Le-Man
2002-01-01
We study the degree to which quantum entanglement survives when a three-qubit entangled state iscopied by using local and non-local processes, respectively, and investigate iterating quantum copyingfor the three-qubitsystem. There may exist inter-three-qubit entanglement and inter-two-qubit entanglement for the three-qubit system.We show that both local and non-local copying processes degrade quantum entanglement in the three-particle systemdue to a residual correlation between the copied output and the copying machine. We also show that the inter-two-qubitentanglement is preserved better than the inter-three-qubit entanglement in the local cloning process. We find thatnon-local cloning is much more efficient than the local copying for broadcasting entanglement, and output state vianon-local cloning exhibits the fidelity better than local cloning.
Two-mode excited entangled coherent states and their entanglement properties
Institute of Scientific and Technical Information of China (English)
Zhou Dong-Lin; Kuang Le-Man
2009-01-01
This paper introduces two types of two-mode excited entangled coherent states(TMEECSs)|Ψ±(α,m,n)>,studies their entanglement characteristics,and investigates the influence of photon excitations on quantum entanglement.It shows that for the state|Ψ+(α,m,m)>the two-mode photon excitations affect seriously entanglement character while the state |Ψ-(α,m,m)>is always a maximally entangled state,and shows how such states can be produced by using cavity quantum electrodynamics and quantum measurements.It finds that the entanglement amount of the TMEECSs is larger than that of the single-mode excited entangled coherent states with the same photon excitation number.
Entanglement and entangling power of the dynamics in light-harvesting complexes
Caruso, Filippo; Datta, Animesh; Huelga, Susana F; Plenio, Martin B
2009-01-01
We study the evolution of quantum entanglement during exciton energy transfer (EET) in a network model of the Fenna-Matthews-Olson (FMO) complex, a biological pigment-protein complex involved in the early steps of photosynthesis in sulphur bacteria. The influence of Markovian, as well as spatially and temporally correlated (non-Markovian) noise on the generation of entanglement across distinct chromophores (site entanglement) and different excitons (mode entanglement) is studied for different injection mechanisms, like thermal and coherent laser excitation. Additionally, we study the entangling power of the FMO complex under natural operating conditions. While quantum information processing tends to favor maximal entanglement, near unit EET is achieved when the initial part of the evolution displays intermediate values of both forms of entanglement which is the result of an intricate interplay between coherent and noisy processes in these complex systems.
Acceleration-assisted entanglement harvesting and rangefinding
Salton, Grant; Mann, Robert B.; Menicucci, Nicolas C.
2015-03-01
We study entanglement harvested from a quantum field through local interaction with Unruh-DeWitt detectors undergoing linear acceleration. The interactions allow entanglement to be swapped locally from the field to the detectors. We find an enhancement in the entanglement harvesting by two detectors with anti-parallel acceleration over those with inertial motion. This enhancement is characterized by the presence of entanglement between two detectors that would otherwise maintain a separable state in the absence of relativistic motion (with the same distance of closest approach in both cases). We also find that entanglement harvesting is degraded for two detectors undergoing parallel acceleration in the same way as for two static, comoving detectors in a de Sitter universe. This degradation is known to be different from that of two inertial detectors in a thermal bath. We comment on the physical origin of the harvested entanglement and present three methods for determining distance between two detectors using properties of the harvested entanglement. Information about the separation is stored nonlocally in the joint state of the accelerated detectors after the interaction; a single detector alone contains none. We also find an example of entanglement sudden death exhibited in parameter space.
On-chip entangled photon source
Energy Technology Data Exchange (ETDEWEB)
Soh, Daniel B. S.; Bisson, Scott E.
2016-11-22
Various technologies pertaining to an on-chip entangled photon source are described herein. A light source is used to pump two resonator cavities that are resonant at two different respective wavelengths and two different respective polarizations. The resonator cavities are coupled to a four-wave mixing cavity that receives the light at the two wavelengths and outputs polarization-entangled photons.
On entanglement-assisted classical capacity
Holevo, A. S.
2002-09-01
We give a modified proof of the recent result of C. H. Bennett, P. W. Shor, J. A. Smolin, and A. V. Thapliyal concerning entanglement-assisted classical capacity of a quantum channel and discuss the relation between entanglement-assisted and unassisted classical capacities.
Black holes as parts of entangled systems
Basini, G.; Capozziello, S.; Longo, G.
A possible link between EPR-type quantum phenomena and astrophysical objects like black holes, under a new general definition of entanglement, is established. A new approach, involving backward time evolution and topology changes, is presented bringing to a definition of the system black hole-worm hole-white hole as an entangled system.
Multiparticle entanglement under the influence of decoherence
Gühne, O.; Bodoky, F.; Blaauboer, M.
2008-01-01
We present a method to determine the decay of multiparticle quantum correlations as quantified by the geometric measure of entanglement under the influence of decoherence. With this, we compare the robustness of entanglement in Greenberger-Horne-Zeilinger (GHZ), cluster, W, and Dicke states of four
Teleportation of entanglement over 143 km.
Herbst, Thomas; Scheidl, Thomas; Fink, Matthias; Handsteiner, Johannes; Wittmann, Bernhard; Ursin, Rupert; Zeilinger, Anton
2015-11-17
As a direct consequence of the no-cloning theorem, the deterministic amplification as in classical communication is impossible for unknown quantum states. This calls for more advanced techniques in a future global quantum network, e.g., for cloud quantum computing. A unique solution is the teleportation of an entangled state, i.e., entanglement swapping, representing the central resource to relay entanglement between distant nodes. Together with entanglement purification and a quantum memory it constitutes a so-called quantum repeater. Since the aforementioned building blocks have been individually demonstrated in laboratory setups only, the applicability of the required technology in real-world scenarios remained to be proven. Here we present a free-space entanglement-swapping experiment between the Canary Islands of La Palma and Tenerife, verifying the presence of quantum entanglement between two previously independent photons separated by 143 km. We obtained an expectation value for the entanglement-witness operator, more than 6 SDs beyond the classical limit. By consecutive generation of the two required photon pairs and space-like separation of the relevant measurement events, we also showed the feasibility of the swapping protocol in a long-distance scenario, where the independence of the nodes is highly demanded. Because our results already allow for efficient implementation of entanglement purification, we anticipate our research to lay the ground for a fully fledged quantum repeater over a realistic high-loss and even turbulent quantum channel.
Should Entanglement Measures be Monogamous or Faithful?
Lancien, Cécilia; Di Martino, Sara; Huber, Marcus; Piani, Marco; Adesso, Gerardo; Winter, Andreas
2016-08-01
"Is entanglement monogamous?" asks the title of a popular article [B. Terhal, IBM J. Res. Dev. 48, 71 (2004)], celebrating C. H. Bennett's legacy on quantum information theory. While the answer is affirmative in the qualitative sense, the situation is less clear if monogamy is intended as a quantitative limitation on the distribution of bipartite entanglement in a multipartite system, given some particular measure of entanglement. Here, we formalize what it takes for a bipartite measure of entanglement to obey a general quantitative monogamy relation on all quantum states. We then prove that an important class of entanglement measures fail to be monogamous in this general sense of the term, with monogamy violations becoming generic with increasing dimension. In particular, we show that every additive and suitably normalized entanglement measure cannot satisfy any nontrivial general monogamy relation while at the same time faithfully capturing the geometric entanglement structure of the fully antisymmetric state in arbitrary dimension. Nevertheless, monogamy of such entanglement measures can be recovered if one allows for dimension-dependent relations, as we show explicitly with relevant examples.
Rank-dependant factorization of entanglement evolution
Energy Technology Data Exchange (ETDEWEB)
Siomau, Michael, E-mail: siomau@nld.ds.mpg.de [Physics Department, Jazan University, P.O. Box 114, 45142 Jazan (Saudi Arabia); Network Dynamics, Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen (Germany)
2016-05-20
Highlights: • In some cases the complex entanglement evolution can be factorized on simple terms. • We suggest factorization equations for multiqubit entanglement evolution. • The factorization is solely defined by the rank of the final state density matrices. • The factorization is independent on the local noisy channels and initial pure states. - Abstract: The description of the entanglement evolution of a complex quantum system can be significantly simplified due to the symmetries of the initial state and the quantum channels, which simultaneously affect parts of the system. Using concurrence as the entanglement measure, we study the entanglement evolution of few qubit systems, when each of the qubits is affected by a local unital channel independently on the others. We found that for low-rank density matrices of the final quantum state, such complex entanglement dynamics can be completely described by a combination of independent factors representing the evolution of entanglement of the initial state, when just one of the qubits is affected by a local channel. We suggest necessary conditions for the rank of the density matrices to represent the entanglement evolution through the factors. Our finding is supported with analytical examples and numerical simulations.
On entanglement in neutrino mixing and oscillations
Energy Technology Data Exchange (ETDEWEB)
Blasone, Massimo; Dell' Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio, E-mail: blasone@sa.infn.i [Dipartimento di Matematica e Informatica, Universita degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy)
2010-06-01
We report on recent results about entanglement in the context of particle mixing and oscillations. We study in detail single-particle entanglement arising in two-flavor neutrino mixing. The analysis is performed first in the context of Quantum Mechanics, and then for the case of Quantum Field Theory.
On entanglement in neutrino mixing and oscillations
Blasone, M; De Siena, S; Illuminati, F
2010-01-01
We report on recent results about entanglement in the context of particle mixing and oscillations. We study in detail single-particle entanglement arising in two-flavor neutrino mixing. The analysis is performed first in the context of Quantum Mechanics, and then for the case of Quantum Field Theory.
Witnessing entanglement in an undergraduate laboratory
Beck, Marisol N.; Beck, M.
2016-02-01
An entangled state of a two-particle system is a quantum state that cannot be separated, meaning it cannot be written as the product of states of the individual particles. One way to tell if a system is entangled is to use it to violate a Bell inequality (such as the Clauser-Horne-Shimony-Holt, CHSH, inequality), because entanglement is necessary for such a violation. However, there are other, easier-to-perform measurements that determine whether or not a system is entangled. An operator that corresponds to such a measurement is referred to as an entanglement witness. Here, we present the theory of witness operators and an undergraduate experiment that measures entanglement witnesses for the joint polarization state of two photons. We are able to produce states for which the expectation value of a witness operator is entangled by more than 300 standard deviations. In order to further examine the performance of these witness operators, we present a simple way to generate states that closely approximate Werner states, which have a controllable degree of entanglement.
Holographic entanglement entropy in Lovelock gravities
de Boer, J.; Kulaxizi, M.; Parnachev, A.
2011-01-01
We study entanglement entropies of simply connected surfaces in field theories dual to Lovelock gravities. We consider Gauss-Bonnet and cubic Lovelock gravities in detail. In the conformal case the logarithmic terms in the entanglement entropy are governed by the conformal anomalies of the CFT; we v
Measuring the entanglement of bipartite pure states
Sancho, J M
2000-01-01
The problem of the experimental determination of the amount of entanglement of a bipartite pure state is addressed. We show that measuring a single observable does not suffice to determine the entanglement of a given unknown pure state of two particles. Possible minimal local measuring strategies are discussed and a comparison is made on the basis of their best achievable precision.
Entanglement as minimal discord over state extensions
Luo, Shunlong
2016-09-01
The characterization and quantification of quantum correlations, which play an instrumental role in exploring and exploiting the quantum world, have been extensively and intensively studied in the past few decades. Of special prominence and significance are the concepts of entanglement and discord, which are usually regarded as very distinctive quantum correlations, with the latter going beyond the former. In this work we establish a direct and natural link between entanglement and discord via state extensions and reveal that entanglement is actually the intrinsic discord, by which we mean that entanglement is the irreducible residue of discord viewed from ambient spaces. Our approach, taking into account the contextuality of a quantum state and being of a global nature, stands in sharp contrast to the local operations and classical communication paradigm of entanglement, which focuses on the state itself via a local approach. Furthermore, we introduce a figure of merit which, on the one hand, captures the essence of entanglement, i.e., nonlocality and quantumness of correlations, and, on the other hand, leads to a quantitative decomposition of total correlations into classical correlations, dissonance, and entanglement. This demystifies the meaning of entanglement from the perspective of quantum measurements and provides a unified framework for the interplay of various correlations in terms of quantum measurements and mutual information.
Fractional topological phase for entangled qudits
Oxman, L E
2010-01-01
We investigate the topological structure of entangled qudits under unitary local operations. Different sectors are identified in the evolution, and their geometrical and topological aspects are analyzed. The geometric phase is explicitly calculated in terms of the concurrence. As a main result, we predict a fractional topological phase for cyclic evolutions in the multiply connected space of maximally entangled states.
Detecting Multiparticle Entanglement of Dicke States
DEFF Research Database (Denmark)
Lücke, Bernd; Peise, Jan; Vitagliano, Giuseppe
2014-01-01
of entangled states, including Dicke states. Experimentally, we produce a Dicke-like state using spin dynamics in a Bose-Einstein condensate. Our criterion proves that it contains at least genuine 28-particle entanglement. We infer a generalized squeezing parameter of −11.4(5) dB....
Hybrid Long-Distance Entanglement Distribution Protocol
DEFF Research Database (Denmark)
Brask, J.B.; Rigas, I.; Polzik, E.S.;
2010-01-01
We propose a hybrid (continuous-discrete variable) quantum repeater protocol for long-distance entanglement distribution. Starting from states created by single-photon detection, we show how entangled coherent state superpositions can be generated by means of homodyne detection. We show that near...
van Veen, T.; Wardenaar, K. J.; Carlier, I. V. E.; Spinhoven, P.; Penninx, B. W. J. H.; Zitman, F. G.
2013-01-01
Background: Different types of adverse events may have general or specific effects on depression and anxiety symptomatology. We examined the effects of adversities on the dimensions of the tripartite model: general distress, anhedonic depression and anxious arousal. Methods: Data were from 2615 indi
Report of the Australian Tripartite Mission on the Training of Skilled Workers in Europe; 1968-69.
Australian Tripartite Mission.
This document is an English-language abstract (approximately 1,500 words) of an Australian Tripartite Mission appointed by the Minister of State for Labor and National Service to examine the methods of training skilled workers in a number of European nations from which Australia is obtaining migrant labor. The Mission summarized its findings of…
Wegener, Charlotte; Tanggaard, Lene
2013-01-01
This article investigates the innovation concept in two key welfare areas where the demands for innovation are substantial, namely vocational education and elder care. On the basis of ethnographic fieldwork and interviews on the collaboration between an educational institution and elder care services, the article develops a tripartite empirical…
Hughes, Alicia A; Heimberg, Richard G; Coles, Meredith E; Gibb, Brandon E; Liebowitz, Michael R; Schneier, Franklin R
2006-11-01
Our primary goal was to examine the relations of the specific components of the tripartite model of anxiety and depression [Clark, L. A., Watson, D. (1991). Tripartite model of anxiety and depression: Psychometric evidence and taxonomic implications. Journal of Abnormal Psychology, 100, 316-336] to two types of social anxiety (social interaction anxiety and performance anxiety) in 148 individuals with social phobia. In line with previous research, overall social anxiety was more closely related to the anhedonic depression (AD) or low positive affect factor of the tripartite model than to the physiological hyerarousal factor, controlling for general distress. However, as hypothesized, performance anxiety was more closely associated with the physiological hyerarousal factor, whereas social interaction anxiety was more closely associated with the AD or low positive affect factor. We also examined the convergent and discriminant validity of the Mood and Anxiety Symptom Questionnaire (MASQ; [Watson, D., Clark, L. A. (1991). The mood and anxiety symptom questionnaire. Unpublished manuscript, University of Iowa City]). Intercorrelations of the MASQ subscales were as expected, but correlations with measures of social anxiety, nonsocial anxiety, and depression provided only modest support for convergent and discriminant validity. Findings from this study provide a more detailed account of the specific components of the tripartite model that characterize the diversity of symptoms subsumed by social phobia.
Jacques, Heather A. K.; Mash, Eric J.
2004-01-01
The applicability of the tripartite model of emotion, which distinguishes the shared aspect of depression and anxiety, negative affect (NA), from their respective specific components of low positive affect (PA) and physiological hyperarousal (PH), was examined in 472 elementary and high school students. The relations among depression, anxiety, and…
Basit, Tehmina N.; Eardley, Alan; Borup, Rosemary; Shah, Hanifa; Slack, Kim; Hughes, Amanda
2015-01-01
Higher education institutions (HEIs) in the UK are increasingly engaging in work-based learning. The tripartite relationship between the HEI, the employer and the employee is viewed to be of great significance in work-based learning, not only in the initial stages of procurement of a contract, but also in designing and delivering the programme to…
Institute of Scientific and Technical Information of China (English)
ZHANG Yong; LONG Gui-Lu; WU Yu-Chun; GUO Guang-Can
2007-01-01
Natural thermal entanglement between two qubits with ⅩⅩⅩ Heisenberg interaction is studied. For the antiferromagnet, increasing coupling strength or decreasing temperature under critical point increases the entanglement.Based on the thermal entanglement as quantum channel, entanglement and information of an input entangled state are transferred via partial teleportation. We find that the entanglement transferred will be lost during the process, and for the entanglement fidelity the partial teleportation is superior to classical communication as concurrence of entangled channel beyond 1/4. We show that both correlation information in input entangled state and individual information of the teleported particle are linearly dissipated. With more entanglement in quantum channel, more entanglement and correlation information can be transferred.
Entanglement creation in low-energy scattering
Energy Technology Data Exchange (ETDEWEB)
Weder, Ricardo [Institut National de Recherche en Informatique et en Automatique Paris-Rocquencourt, Projet POEMS, Domaine de Voluceau-Rocquencourt, BP 105, F-78153, Le Chesnay Cedex (France)
2011-12-15
We study the entanglement creation in the low-energy scattering of two particles in three dimensions, for a general class of interaction potentials that are not required to be spherically symmetric. The incoming asymptotic state, before the collision, is a product of two normalized Gaussian states. After the scattering, the particles are entangled. We take as a measure of the entanglement the purity of one of them. We provide a rigorous explicit computation, with error bound, of the leading order of the purity at low energy. The entanglement depends strongly on the difference of the masses. It takes its minimum when the masses are equal, and it increases rapidly with the difference of the masses. It is quite remarkable that the anisotropy of the potential gives no contribution to the leading order of the purity, in spite of the fact that entanglement is a second-order effect.
Robust macroscopic entanglement without complex encodings
Chaves, Rafael; Acín, Antonio
2011-01-01
One of the main challenges for the experimental manipulation and storage of macroscopic entanglement is its fragility under noise. We present a simple recipe for the systematic enhancement of the resistance of multipartite entanglement against any local noise with a privileged direction in the Bloch sphere. For the case of exact local dephasing along any given basis, and for all noise strengths, our prescription grants full robustness: even states whose entanglement decays exponentially with the number of parts are mapped to states whose entanglement is constant. In contrast to previous techniques resorting to complex logical-qubit encodings, such enhancement is attained simply by performing local unitary rotations before the noise acts. The scheme is therefore highly experimentally-friendly, as it brings no overhead of extra physical qubits to encode logical ones. In addition, we show that, apart from entanglement, the resilience of the states as resources for useful practical tasks such as metrology and non...
Diagnosing Topological Edge States via Entanglement Monogamy.
Meichanetzidis, K; Eisert, J; Cirio, M; Lahtinen, V; Pachos, J K
2016-04-01
Topological phases of matter possess intricate correlation patterns typically probed by entanglement entropies or entanglement spectra. In this Letter, we propose an alternative approach to assessing topologically induced edge states in free and interacting fermionic systems. We do so by focussing on the fermionic covariance matrix. This matrix is often tractable either analytically or numerically, and it precisely captures the relevant correlations of the system. By invoking the concept of monogamy of entanglement, we show that highly entangled states supported across a system bipartition are largely disentangled from the rest of the system, thus, usually appearing as gapless edge states. We then define an entanglement qualifier that identifies the presence of topological edge states based purely on correlations present in the ground states. We demonstrate the versatility of this qualifier by applying it to various free and interacting fermionic topological systems.
Entanglement Between Qubits Interacting with Thermal Field
Directory of Open Access Journals (Sweden)
Bashkirovaa E.K.
2015-01-01
Full Text Available We have investigated the entanglement between two dipole coupled two-level artificial atoms (superconducting qubits, ion, spins etc.. The model, in which only one atom is trapped in an lossless cavity and interacts with single-mode thermal field, and the other one can be spatially moved freely outside the cavity has been carried out. We have considered the effect of the atomic coherence on the entanglement behavior. We have shown that a thermal field might cause high entanglement between the atoms both for coherent and incoherent initial atomic states only for small values of cavity mean photon number. We have also derived that the degree of entanglement is weakly dependent on the strength of dipole-dipole interaction for coherent initial states. In the considered model the atoms would get entangled even when both atoms are initially in the excited state.
Bipartite and Multipartite Entanglement of Gaussian States
Adesso, G; Adesso, Gerardo; Illuminati, Fabrizio
2005-01-01
In this chapter we review the characterization of entanglement in Gaussian states of continuous variable systems. For two-mode Gaussian states, we discuss how their bipartite entanglement can be accurately quantified in terms of the global and local amounts of mixedness, and efficiently estimated by direct measurements of the associated purities. For multimode Gaussian states endowed with local symmetry with respect to a given bipartition, we show how the multimode block entanglement can be completely and reversibly localized onto a single pair of modes by local, unitary operations. We then analyze the distribution of entanglement among multiple parties in multimode Gaussian states. We introduce the continuous-variable tangle to quantify entanglement sharing in Gaussian states and we prove that it satisfies the Coffman-Kundu-Wootters monogamy inequality. Nevertheless, we show that pure, symmetric three-mode Gaussian states, at variance with their discrete-variable counterparts, allow a promiscuous sharing of ...
Classification of Entanglement in Symmetric States
Aulbach, Martin
2011-01-01
Quantum states that are symmetric with respect to permutations of their subsystems appear in a wide range of physical settings, and they have a variety of promising applications in quantum information science. In this thesis the entanglement of symmetric multipartite states is categorised, with a particular focus on the pure multi-qubit case and the geometric measure of entanglement. An essential tool for this analysis is the Majorana representation, a generalisation of the single-qubit Bloch sphere representation, which allows for a unique representation of symmetric n qubit states by n points on the surface of a sphere. Here this representation is employed to search for the maximally entangled symmetric states of up to 12 qubits in terms of the geometric measure, and an intuitive visual understanding of the upper bound on the maximal symmetric entanglement is given. Furthermore, it will be seen that the Majorana representation facilitates the characterisation of entanglement equivalence classes such as Stoc...
Enhanced dynamical entanglement transfer with multiple qubits
Serafini, A; Kim, M S; Paternostro, M
2005-01-01
We present two strategies to enhance the dynamical entanglement transfer from continuous variable (CV) to finite dimensional systems by employing multiple qubits. First, we consider the entanglement transfer to a composite finite dimensional system of many qubits simultaneously interacting with a bipartite CV field. We show that, considering realistic conditions in the generation of CV entanglement, a small (``mesoscopic'') number of qubits resonantly coupled to the CV system is sufficient for an almost complete dynamical transfer of the entanglement. Our analysis also sheds further light on the transition between mesoscopic and macroscopic behaviours of composite finite dimensional systems coupled to bosonic fields (like atomic clouds interacting with light). Furthermore, we present a protocol based on sequential interactions of the CV system with some ancillary qubit systems and on subsequent measurements, allowing to probabilistically convert CV entanglement into `almost perfect' Bell pairs of two qubits. ...
Entanglement Temperature With Gauss-Bonnet Term
Pal, Shesansu Sekhar
2015-01-01
We compute the entanglement temperature using the first law-like of thermodynamics, $\\Delta E=T_{ent} \\Delta S_{EE}$, up to Gauss-Bonnet term in the Jacobson-Myers entropy functional in any arbitrary spacetime dimension. The computation is done when the entangling region is the geometry of a slab. We also show that such a Gauss-Bonnet term, which becomes a total derivative, when the co-dimension two hypersurface is four dimensional, does not contribute to the finite term in the entanglement entropy. We observe that the Weyl-squared term does not contribute to the entanglement entropy. It is important to note that the calculations are performed when the entangling region is very small and the energy is calculated using the normal Hamiltonian.
Quantum Entanglement of Very High Angular Momenta
Fickler, Robert; Plick, William N; Krenn, Mario; Schaeff, Christoph; Ramelow, Sven; Zeilinger, Anton
2012-01-01
Single photons with helical phase structure may carry a quantized amount of orbital angular momentum (OAM) and are of great interest in quantum information science and fundamental tests of quantum theory. Since there is no theoretical upper limit on how many quanta of OAM a single photon can carry, those systems offer the possibility to create superpositions for one particle and entanglement between two particles with an arbitrary high difference in the quantum number. By transferring polarization entanglement to the OAM degree-of-freedom with an interferometric scheme, we created and observed entanglement up to $600\\bar{h}$ difference in the orbital angular momentum. To our knowledge, we have thus demonstrated entanglement of the highest quantum number in any experiment so far. The only restrictive factor towards even higher numbers arises due to current technical limitations. Furthermore, we show experimentally that the entanglement of very high OAM can be used to improve applications, like the sensitivity ...
Assymptotic multipartite entanglement at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Sauer, Simeon; Mintert, Florian; Buchleitner, Andreas [Physikalisches Institut, Albert-Ludwigs-Universitaet Freiburg (Germany)
2010-07-01
When a many-body system is coupled to a noisy, thermal environment, it rapidly loses its coherences. Multipartite entanglement relies on such coherences, and therefore decays accordingly; and it does so, the faster, the larger the system and the hotter the environment is. However, external coherent driving is likely to slow down such decay, and it might even stabilize entanglement at a finite level. Here, we study the entanglement dynamics in a periodically driven many-body system, embedded in a thermal environment. With the help of the Floquet formalism, we identify steady states and characterize their entanglement properties. With this approach, we look for conditions (such as strength and frequency of the driving, and environmental temperature) that maintain a finite amount of multipartite entanglement for asymptotically large times.
Entanglement, Bell inequality and all that
Narnhofer, Heide; Thirring, Walter
2012-09-01
We start from the geometrical observation that a finite set of pure states correspond to some points on a sphere and their convex span cannot be the whole set of states. If we call the left over entangled we can pursue this picture from the simplest case of a two dimensional Hilbert space to the usual Alice-and-Bob game of entangled states and then move to bigger systems and finely to quantum field theory where almost everything is entangled. On the way we encounter more or less known old friends up from the shell structure of states to the monogamy of squashed entanglement. We study how entanglement can be concentrated on a small slice and how it depends on the particular factorization of the Hilbert space.
Entanglement entropy in top-down models
Jones, Peter A. R.; Taylor, Marika
2016-08-01
We explore holographic entanglement entropy in ten-dimensional supergravity solutions. It has been proposed that entanglement entropy can be computed in such top-down models using minimal surfaces which asymptotically wrap the compact part of the geometry. We show explicitly in a wide range of examples that the holographic entan-glement entropy thus computed agrees with the entanglement entropy computed using the Ryu-Takayanagi formula from the lower-dimensional Einstein metric obtained from reduc-tion over the compact space. Our examples include not only consistent truncations but also cases in which no consistent truncation exists and Kaluza-Klein holography is used to identify the lower-dimensional Einstein metric. We then give a general proof, based on the Lewkowycz-Maldacena approach, of the top-down entanglement entropy formula.
Entanglement entropy in top-down models
Jones, Peter A R
2016-01-01
We explore holographic entanglement entropy in ten-dimensional supergravity solutions. It has been proposed that entanglement entropy can be computed in such top-down models using minimal surfaces which asymptotically wrap the compact part of the geometry. We show explicitly in a wide range of examples that the holographic entanglement entropy thus computed agrees with the entanglement entropy computed using the Ryu-Takayanagi formula from the lower-dimensional Einstein metric obtained from reduction over the compact space. Our examples include not only consistent truncations but also cases in which no consistent truncation exists and Kaluza-Klein holography is used to identify the lower-dimensional Einstein metric. We then give a general proof, based on the Lewkowycz-Maldacena approach, of the top-down entanglement entropy formula.
Experimental delayed-choice entanglement swapping
Ma, Xiao-Song; Zotter, Stefan; Kofler, Johannes; Ursin, Rupert; Jennewein, Thomas; Brukner, Časlav; Zeilinger, Anton
2012-06-01
Motivated by the question of which kind of physical interactions and processes are needed for the production of quantum entanglement, Peres has put forward the radical idea of delayed-choice entanglement swapping. There, entanglement can be `produced a posteriori, after the entangled particles have been measured and may no longer exist'. Here, we report the realization of Peres's gedanken experiment. Using four photons, we can actively delay the choice of measurement--implemented through a high-speed tunable bipartite-state analyser and a quantum random-number generator--on two of the photons into the time-like future of the registration of the other two photons. This effectively projects the two already registered photons onto one of two mutually exclusive quantum states in which the photons are either entangled (quantum correlations) or separable (classical correlations). This can also be viewed as `quantum steering into the past'.
Experimental delayed-choice entanglement swapping
Ma, Xiao-song; Kofler, Johannes; Ursin, Rupert; Jennewein, Thomas; Brukner, Časlav; Zeilinger, Anton
2012-01-01
Motivated by the question, which kind of physical interactions and processes are needed for the production of quantum entanglement, Peres has put forward the radical idea of delayed-choice entanglement swapping. There, entanglement can be "produced a posteriori, after the entangled particles have been measured and may no longer exist". In this work we report the first realization of Peres' gedanken experiment. Using four photons, we can actively delay the choice of measurement-implemented via a high-speed tunable bipartite state analyzer and a quantum random number generator-on two of the photons into the time-like future of the registration of the other two photons. This effectively projects the two already registered photons onto one definite of two mutually exclusive quantum states in which either the photons are entangled (quantum correlations) or separable (classical correlations). This can also be viewed as "quantum steering into the past".
Optimized entanglement witnesses for Dicke states
Energy Technology Data Exchange (ETDEWEB)
Bergmann, Marcel; Guehne, Otfried [Naturwissenschaftlich-Technische Fakultaet, Universitaet Siegen, Department Physik, Walter-Flex-Strasse 3, D-57068 Siegen (Germany)
2013-07-01
Quantum entanglement is an important resource for applications in quantum information processing like quantum teleportation and cryptography. Moreover, the number of particles that can be entangled experimentally using polarized photons or ion traps has been significantly enlarged. Therefore, criteria to decide the question whether a given multi-particle state is entangled or not have to be improved. Our approach to this problem uses the notion of PPT mixtures which form an approximation to the set of bi-separable states. With this method, entanglement witnesses can be obtained in a natural manner via linear semi-definite programming. In our contribution, we will present analytical results for entanglement witnesses for Dicke states. This allows to overcome the limitations of convex optimization.
Entanglement, holography and causal diamonds
de Boer, Jan; Haehl, Felix M.; Heller, Michal P.; Myers, Robert C.
2016-08-01
We argue that the degrees of freedom in a d-dimensional CFT can be reorganized in an insightful way by studying observables on the moduli space of causal diamonds (or equivalently, the space of pairs of timelike separated points). This 2 d-dimensional space naturally captures some of the fundamental nonlocality and causal structure inherent in the entanglement of CFT states. For any primary CFT operator, we construct an observable on this space, which is defined by smearing the associated one-point function over causal diamonds. Known examples of such quantities are the entanglement entropy of vacuum excitations and its higher spin generalizations. We show that in holographic CFTs, these observables are given by suitably defined integrals of dual bulk fields over the corresponding Ryu-Takayanagi minimal surfaces. Furthermore, we explain connections to the operator product expansion and the first law of entanglemententropy from this unifying point of view. We demonstrate that for small perturbations of the vacuum, our observables obey linear two-derivative equations of motion on the space of causal diamonds. In two dimensions, the latter is given by a product of two copies of a two-dimensional de Sitter space. For a class of universal states, we show that the entanglement entropy and its spin-three generalization obey nonlinear equations of motion with local interactions on this moduli space, which can be identified with Liouville and Toda equations, respectively. This suggests the possibility of extending the definition of our new observables beyond the linear level more generally and in such a way that they give rise to new dynamically interacting theories on the moduli space of causal diamonds. Various challenges one has to face in order to implement this idea are discussed.