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Sample records for quantum information entropy

  1. Entropy Transfer of Quantum Gravity Information Processing

    NASA Astrophysics Data System (ADS)

    Gyongyosi, Laszlo; Imre, Sandor

    2015-05-01

    We introduce the term smooth entanglement entropy transfer, a phenomenon that is a consequence of the causality-cancellation property of the quantum gravity environment. The causality-cancellation of the quantum gravity space removes the causal dependencies of the local systems. We study the physical effects of the causality-cancellation and show that it stimulates entropy transfer between the quantum gravity environment and the independent local systems of the quantum gravity space. The entropy transfer reduces the entropies of the contributing local systems and increases the entropy of the quantum gravity environment. We discuss the space-time geometry structure of the quantum gravity environment and the local quantum systems. We propose the space-time geometry model of the smooth entropy transfer. We reveal on a smooth Cauchy slice that the space-time geometry of the quantum gravity environment dynamically adapts to the vanishing causality. We prove that the Cauchy area expansion, along with the dilation of the Rindler horizon area of the quantum gravity environment, is a corollary of the causality-cancellation of the quantum gravity environment. This work was partially supported by the GOP-1.1.1-11-2012-0092 (Secure quantum key distribution between two units on optical fiber network) project sponsored by the EU and European Structural Fund, and by the COST Action MP1006.

  2. Waveform information from quantum mechanical entropy

    NASA Astrophysics Data System (ADS)

    Funkhouser, Scott; Suski, William; Winn, Andrew

    2016-06-01

    Although the entropy of a given signal-type waveform is technically zero, it is nonetheless desirable to use entropic measures to quantify the associated information. Several such prescriptions have been advanced in the literature but none are generally successful. Here, we report that the Fourier-conjugated `total entropy' associated with quantum-mechanical probabilistic amplitude functions (PAFs) is a meaningful measure of information in non-probabilistic real waveforms, with either the waveform itself or its (normalized) analytic representation acting in the role of the PAF. Detailed numerical calculations are presented for both adaptations, showing the expected informatic behaviours in a variety of rudimentary scenarios. Particularly noteworthy are the sensitivity to the degree of randomness in a sequence of pulses and potential for detection of weak signals.

  3. Quantum information entropy for one-dimensional system undergoing quantum phase transition

    NASA Astrophysics Data System (ADS)

    Xu-Dong, Song; Shi-Hai, Dong; Yu, Zhang

    2016-05-01

    Calculations of the quantum information entropy have been extended to a non-analytically solvable situation. Specifically, we have investigated the information entropy for a one-dimensional system with a schematic “Landau” potential in a numerical way. Particularly, it is found that the phase transitional behavior of the system can be well expressed by the evolution of quantum information entropy. The calculated results also indicate that the position entropy Sx and the momentum entropy Sp at the critical point of phase transition may vary with the mass parameter M but their sum remains as a constant independent of M for a given excited state. In addition, the entropy uncertainty relation is proven to be robust during the whole process of the phase transition. Project supported by the National Natural Science Foundation of China (Grant No. 11375005) and partially by 20150964-SIP-IPN, Mexico.

  4. The information-theoretical entropy of some quantum oscillators

    SciTech Connect

    Popov, D. Pop, N.; Popov, M.

    2014-11-24

    The Wehrl entropy or the 'classical' entropy associated with a quantum system is the entropy of the probability distribution in phase space, corresponding to the Husimi Q-function in terms of coherent states. In the present paper, we shall focus our attention on the examination of the Wehrl entropy for both the pure and the mixed (thermal) states of the pseudoharmonic oscillator (PHO). The choice of the PHO is interesting because this oscillator is an intermediate between the ideal one-dimensional harmonic oscillator (HO-1D) and the more practical anharmonicone.

  5. Quantum games entropy

    NASA Astrophysics Data System (ADS)

    Guevara Hidalgo, Esteban

    2007-09-01

    We propose the study of quantum games from the point of view of quantum information theory and statistical mechanics. Every game can be described by a density operator, the von Neumann entropy and the quantum replicator dynamics. There exists a strong relationship between game theories, information theories and statistical physics. The density operator and entropy are the bonds between these theories. The analysis we propose is based on the properties of entropy, the amount of information that a player can obtain about his opponent and a maximum or minimum entropy criterion. The natural trend of a physical system is to its maximum entropy state. The minimum entropy state is a characteristic of a manipulated system, i.e., externally controlled or imposed. There exist tacit rules inside a system that do not need to be specified or clarified and search the system equilibrium based on the collective welfare principle. The other rules are imposed over the system when one or many of its members violate this principle and maximize its individual welfare at the expense of the group.

  6. State Ensembles and Quantum Entropy

    NASA Astrophysics Data System (ADS)

    Kak, Subhash

    2016-06-01

    This paper considers quantum communication involving an ensemble of states. Apart from the von Neumann entropy, it considers other measures one of which may be useful in obtaining information about an unknown pure state and another that may be useful in quantum games. It is shown that under certain conditions in a two-party quantum game, the receiver of the states can increase the entropy by adding another pure state.

  7. Entropic dynamics: From entropy and information geometry to Hamiltonians and quantum mechanics

    SciTech Connect

    Caticha, Ariel; Bartolomeo, Daniel; Reginatto, Marcel

    2015-01-13

    Entropic Dynamics is a framework in which quantum theory is derived as an application of entropic methods of inference. There is no underlying action principle. Instead, the dynamics is driven by entropy subject to the appropriate constraints. In this paper we show how a Hamiltonian dynamics arises as a type of non-dissipative entropic dynamics. We also show that the particular form of the 'quantum potential' that leads to the Schrödinger equation follows naturally from information geometry.

  8. Entropy: Order or Information

    ERIC Educational Resources Information Center

    Ben-Naim, Arieh

    2011-01-01

    Changes in entropy can "sometimes" be interpreted in terms of changes in disorder. On the other hand, changes in entropy can "always" be interpreted in terms of changes in Shannon's measure of information. Mixing and demixing processes are used to highlight the pitfalls in the association of entropy with disorder. (Contains 3 figures.)

  9. An upper bound on quantum entropy.

    SciTech Connect

    Zachos, C. K.; High Energy Physics

    2008-01-01

    Following ref [1], a classical upper bound for quantum entropy is identified and illustrated, 0 {le} S{sub q} {le} ln (e{sigma}{sup 2}/2{h_bar}), involving the variance {sigma}{sup 2} in phase space of the classical limit distribution of a given system. A fortiori, this further bounds the corresponding information-theoretical generalizations of the quantum entropy proposed by Renyi.

  10. On variational definition of quantum entropy

    SciTech Connect

    Belavkin, Roman V.

    2015-01-13

    Entropy of distribution P can be defined in at least three different ways: 1) as the expectation of the Kullback-Leibler (KL) divergence of P from elementary δ-measures (in this case, it is interpreted as expected surprise); 2) as a negative KL-divergence of some reference measure ν from the probability measure P; 3) as the supremum of Shannon’s mutual information taken over all channels such that P is the output probability, in which case it is dual of some transportation problem. In classical (i.e. commutative) probability, all three definitions lead to the same quantity, providing only different interpretations of entropy. In non-commutative (i.e. quantum) probability, however, these definitions are not equivalent. In particular, the third definition, where the supremum is taken over all entanglements of two quantum systems with P being the output state, leads to the quantity that can be twice the von Neumann entropy. It was proposed originally by V. Belavkin and Ohya [1] and called the proper quantum entropy, because it allows one to define quantum conditional entropy that is always non-negative. Here we extend these ideas to define also quantum counterpart of proper cross-entropy and cross-information. We also show inequality for the values of classical and quantum information.

  11. Entropies and correlations in classical and quantum systems

    NASA Astrophysics Data System (ADS)

    Man'ko, Margarita A.; Man'ko, Vladimir I.; Marmo, Giuseppe

    2016-09-01

    We present a review of entropy properties for classical and quantum systems including Shannon entropy, von Neumann entropy, Rényi entropy, and Tsallis entropy. We discuss known and new entropic and information inequalities for classical and quantum systems, both composite and noncomposite. We demonstrate matrix inequalities associated with the entropic subadditivity and strong subadditivity conditions and give a new inequality for matrix elements of unitary matrices.

  12. Quantum information entropies for position-dependent mass Schrödinger problem

    SciTech Connect

    Yañez-Navarro, G.; Sun, Guo-Hua; Dytrych, T.; Launey, K.D.; Dong, Shi-Hai; Draayer, J.P.

    2014-09-15

    The Shannon entropy for the position-dependent Schrödinger equation for a particle with a nonuniform solitonic mass density is evaluated in the case of a trivial null potential. The position S{sub x} and momentum S{sub p} information entropies for the three lowest-lying states are calculated. In particular, for these states, we are able to derive analytical solutions for the S{sub x} entropy as well as for the Fourier transformed wave functions, while the S{sub p} quantity is calculated numerically. We notice the behavior of the S{sub x} entropy, namely, it decreases as the mass barrier width narrows and becomes negative beyond a particular width. The negative Shannon entropy exists for the probability densities that are highly localized. The mass barrier determines the stability of the system. The dependence of S{sub p} on the width is contrary to the one for S{sub x}. Some interesting features of the information entropy densities ρ{sub s}(x) and ρ{sub s}(p) are demonstrated. In addition, the Bialynicki-Birula–Mycielski (BBM) inequality is tested for a number of states and found to hold for all the cases.

  13. A bound on the mutual information, and properties of entropy reduction, for quantum channels with inefficient measurements

    NASA Astrophysics Data System (ADS)

    Jacobs, Kurt

    2006-01-01

    The Holevo bound is a bound on the mutual information for a given quantum encoding. In 1996 Schumacher, Westmoreland, and Wootters [Phys. Rev. Lett. 76, 3452 (1996)] derived a bound that reduces to the Holevo bound for complete measurements, but that is tighter for incomplete measurements. The most general quantum operations may be both incomplete and inefficient. Here we show that the bound derived by SWW can be further extended to obtain one that is yet again tighter for inefficient measurements. This allows us, in addition, to obtain a generalization of a bound derived by Hall, and to show that the average reduction in the von Neumann entropy during a quantum operation is concave in the initial state, for all quantum operations. This is a quantum version of the concavity of the mutual information. We also show that both this average entropy reduction and the mutual information for pure state ensembles, are Schur concave for unitarily covariant measurements; that is, for these measurements, information gain increases with initial uncertainty.

  14. Applications of quantum entropy to statistics

    SciTech Connect

    Silver, R.N.; Martz, H.F.

    1994-07-01

    This paper develops two generalizations of the maximum entropy (ME) principle. First, Shannon classical entropy is replaced by von Neumann quantum entropy to yield a broader class of information divergences (or penalty functions) for statistics applications. Negative relative quantum entropy enforces convexity, positivity, non-local extensivity and prior correlations such as smoothness. This enables the extension of ME methods from their traditional domain of ill-posed in-verse problems to new applications such as non-parametric density estimation. Second, given a choice of information divergence, a combination of ME and Bayes rule is used to assign both prior and posterior probabilities. Hyperparameters are interpreted as Lagrange multipliers enforcing constraints. Conservation principles are proposed to act statistical regularization and other hyperparameters, such as conservation of information and smoothness. ME provides an alternative to heirarchical Bayes methods.

  15. Information Entropy of Fullerenes.

    PubMed

    Sabirov, Denis Sh; Ōsawa, Eiji

    2015-08-24

    The reasons for the formation of the highly symmetric C60 molecule under nonequilibrium conditions are widely discussed as it dominates over numerous similar fullerene structures. In such conditions, evolution of structure rather than energy defines the processes. We have first studied the diversity of fullerenes in terms of information entropy. Sorting 2079 structures from An Atlas of Fullerenes [ Fowler , P. W. ; Manolopoulos , D. E. An Atlas of Fullerenes ; Oxford : Clarendon , 1995 . ], we have found that the information entropies of only 14 fullerenes (<1% of the studied structures) lie between the values of C60 and C70, the two most abundant fullerenes. Interestingly, buckminsterfullerene is the only fullerene with zero information entropy, i.e., an exclusive compound among the other members of the fullerene family. Such an efficient sorting demonstrates possible relevance of information entropy to chemical processes. For this reason, we have introduced an algorithm for calculating changes in information entropy at chemical transformations. The preliminary calculations of changes in information entropy at the selected fullerene reactions show good agreement with thermochemical data.

  16. On quantum Rényi entropies: A new generalization and some properties

    SciTech Connect

    Müller-Lennert, Martin; Dupuis, Frédéric; Szehr, Oleg; Fehr, Serge; Tomamichel, Marco

    2013-12-15

    The Rényi entropies constitute a family of information measures that generalizes the well-known Shannon entropy, inheriting many of its properties. They appear in the form of unconditional and conditional entropies, relative entropies, or mutual information, and have found many applications in information theory and beyond. Various generalizations of Rényi entropies to the quantum setting have been proposed, most prominently Petz's quasi-entropies and Renner's conditional min-, max-, and collision entropy. However, these quantum extensions are incompatible and thus unsatisfactory. We propose a new quantum generalization of the family of Rényi entropies that contains the von Neumann entropy, min-entropy, collision entropy, and the max-entropy as special cases, thus encompassing most quantum entropies in use today. We show several natural properties for this definition, including data-processing inequalities, a duality relation, and an entropic uncertainty relation.

  17. On quantum Rényi entropies: A new generalization and some properties

    NASA Astrophysics Data System (ADS)

    Müller-Lennert, Martin; Dupuis, Frédéric; Szehr, Oleg; Fehr, Serge; Tomamichel, Marco

    2013-12-01

    The Rényi entropies constitute a family of information measures that generalizes the well-known Shannon entropy, inheriting many of its properties. They appear in the form of unconditional and conditional entropies, relative entropies, or mutual information, and have found many applications in information theory and beyond. Various generalizations of Rényi entropies to the quantum setting have been proposed, most prominently Petz's quasi-entropies and Renner's conditional min-, max-, and collision entropy. However, these quantum extensions are incompatible and thus unsatisfactory. We propose a new quantum generalization of the family of Rényi entropies that contains the von Neumann entropy, min-entropy, collision entropy, and the max-entropy as special cases, thus encompassing most quantum entropies in use today. We show several natural properties for this definition, including data-processing inequalities, a duality relation, and an entropic uncertainty relation.

  18. Entropy distance: New quantum phenomena

    SciTech Connect

    Weis, Stephan; Knauf, Andreas

    2012-10-15

    We study a curve of Gibbsian families of complex 3 Multiplication-Sign 3-matrices and point out new features, absent in commutative finite-dimensional algebras: a discontinuous maximum-entropy inference, a discontinuous entropy distance, and non-exposed faces of the mean value set. We analyze these problems from various aspects including convex geometry, topology, and information geometry. This research is motivated by a theory of infomax principles, where we contribute by computing first order optimality conditions of the entropy distance.

  19. Quantum geometry and gravitational entropy

    SciTech Connect

    Simon, Joan; Balasubramanian, Vijay; Czech, Bart Iomiej; Larjo, Klaus; Marolf, Donald; Simon, Joan

    2007-05-29

    Most quantum states have wavefunctions that are widely spread over the accessible Hilbert space and hence do not have a good description in terms of a single classical geometry. In order to understand when geometric descriptions are possible, we exploit the AdS/CFT correspondence in the half-BPS sector of asymptotically AdS_5 x S5 universes. In this sector we devise a"coarse-grained metric operator" whose eigenstates are well described by a single spacetime topology and geometry. We show that such half-BPS universes have a non-vanishing entropy if and only if the metric is singular, and that the entropy arises from coarse-graining the geometry. Finally, we use our entropy formula to find the most entropic spacetimes with fixed asymptotic moments beyond the global charges.

  20. Quantum algorithm for SAT problem andquantum mutual entropy

    NASA Astrophysics Data System (ADS)

    Ohya, Masanori

    2005-02-01

    It is von Neumann who opened the window for today's information epoch. He definedquantum entropy including Shannon's information more than 20 years ahead of Shannon, and he explained what computation means mathematically. In this paper I discuss two problems studied recently by me and my coworkers. One of them concerns a quantum algorithm in a generalized sense solving the SAT problem (one of NP complete problems) and another concerns quantum mutual entropy properly describing quantum communication processes.

  1. Entanglement Entropy and Mutual Information of Circular Entangling Surfaces in 2+1d Quantum Lifshitz Model

    NASA Astrophysics Data System (ADS)

    Zhou, Tianci; Chen, Xiao; Fradkin, Eduardo

    We investigate the entanglement entropy(EE) of circular entangling surfaces in the 2+1d quantum Lifshitz model, where the spatially conformal invariant ground state is a Rokhsar-Kivelson state with Gibbs weight of 2d free Boson. We use cut-off independent mutual information regulator to define and calculate the subleading correction in the EE. The subtlety due to the Boson compactification in the replica trick is carefully taken care of. Our results show that for circular entangling surface, the subleading term is a constant on both the sphere of arbitrary radius and infinite plane. For the latter case, it parallels the constancy of disk EE in 2+1d conformal field theory, despite the lack of full space time conformal invariance. In the end, we present the mutual information of two disjoint disks and compare its scaling function in the small parameter regime (radii much smaller than their separation) with Cardy's general CFT results. This work was supported in part by the National Science Foundation Grants NSF-DMR-13-06011(TZ) and DMR-1408713 (XC, EF).

  2. Measuring entanglement entropy in a quantum many-body system

    NASA Astrophysics Data System (ADS)

    Rispoli, Matthew; Preiss, Philipp; Tai, Eric; Lukin, Alex; Schittko, Robert; Kaufman, Adam; Ma, Ruichao; Islam, Rajibul; Greiner, Markus

    2016-05-01

    The presence of large-scale entanglement is a defining characteristic of exotic quantum phases of matter. It describes non-local correlations between quantum objects, and is at the heart of quantum information sciences. However, measuring entanglement remains a challenge. This is especially true in systems of interacting delocalized particles, for which a direct experimental measurement of spatial entanglement has been elusive. Here we measure entanglement in such a system of itinerant particles using quantum interference of many-body twins. We demonstrate a novel approach to the measurement of entanglement entropy of any bosonic system, using a quantum gas microscope with tailored potential landscapes. This protocol enables us to directly measure quantum purity, Rényi entanglement entropy, and mutual information. In general, these experiments exemplify a method enabling the measurement and characterization of quantum phase transitions and in particular would be apt for studying systems such as magnetic ordering within the quantum Ising model.

  3. The relations among Shannon information entropy, quantum discord, concurrence and localization properties of one-dimensional single-electron wave functions

    NASA Astrophysics Data System (ADS)

    Gong, Longyan; Zheng, Yongcui; Wang, Haihong; Cheng, Weiwen; Zhao, Shengmei

    2014-09-01

    Shannon information entropy (SE), concurrence (CC), quantum discord (QD) and localization properties for various one-dimensional one-electron wave functions are intensively studied, respectively. They include Gaussian functions, power-law functions, and functions in the Anderson model and the Harper ones. For all these wave functions, we find that SE, CC and QD increase as the localization length of a wave function increases, respectively. There are linear or quadratic relationships between two of them. Therefore, we can confirm for the analyzed models that SE, CC and QD are statistically equivalent quantities to reflect the localization properties of wave functions though they are different measures of quantum information.

  4. Black hole entropy in loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Agulló, Iván; Barbero G, J. Fernando; Borja, E. F.; Díaz-Polo, Jacobo; Villaseñor, Eduardo J. S.

    2012-05-01

    We discuss the recent progress on black hole entropy in loop quantum gravity, focusing in particular on the recently discovered discretization effect for microscopic black holes. Powerful analytical techniques have been developed to perform the exact computation of entropy. A statistical analysis of the structures responsible for this effect shows its progressive damping and eventual disappearance as one increases the considered horizon area.

  5. Gacs quantum algorithmic entropy in infinite dimensional Hilbert spaces

    SciTech Connect

    Benatti, Fabio; Oskouei, Samad Khabbazi Deh Abad, Ahmad Shafiei

    2014-08-15

    We extend the notion of Gacs quantum algorithmic entropy, originally formulated for finitely many qubits, to infinite dimensional quantum spin chains and investigate the relation of this extension with two quantum dynamical entropies that have been proposed in recent years.

  6. Quantum statistical entropy of Schwarzchild-de Sitter spacetime

    NASA Astrophysics Data System (ADS)

    Zhao, Ren; Zhang, Li-Chun; Zhao, Hui-Hua

    2012-10-01

    Using the quantum statistical method, we calculate quantum statistical entropy between the black hole horizon and the cosmological horizon in Schwarzchild spacetime and derive the expression of quantum statistical entropy in de Sitter spacetime. Under the Unruh-Verlinde temperature of Schwarzchild-de Sitter spacetime in the entropic force views, we obtain the expression of quantum statistical entropy in de Sitter spacetime. It is shown that in de Sitter spacetime quantum statistical entropy is the sum of thermodynamic entropy corresponding black hole horizon and the one corresponding cosmological horizon. And the correction term of de Sitter spacetime entropy is obtained. Therefore, it is confirmed that the black hole entropy is the entropy of quantum field outside the black hole horizon. The entropy of de Sitter spacetime is the entropy of quantum field between the black hole horizon and the cosmological horizon.

  7. Entropy, Fisher Information and Variance with Frost-Musulin Potenial

    NASA Astrophysics Data System (ADS)

    Idiodi, J. O. A.; Onate, C. A.

    2016-09-01

    This study presents the Shannon and Renyi information entropy for both position and momentum space and the Fisher information for the position-dependent mass Schrödinger equation with the Frost-Musulin potential. The analysis of the quantum mechanical probability has been obtained via the Fisher information. The variance information of this potential is equally computed. This controls both the chemical properties and physical properties of some of the molecular systems. We have observed the behaviour of the Shannon entropy. Renyi entropy, Fisher information and variance with the quantum number n respectively.

  8. Quantum Rényi relative entropies affirm universality of thermodynamics.

    PubMed

    Misra, Avijit; Singh, Uttam; Bera, Manabendra Nath; Rajagopal, A K

    2015-10-01

    We formulate a complete theory of quantum thermodynamics in the Rényi entropic formalism exploiting the Rényi relative entropies, starting from the maximum entropy principle. In establishing the first and second laws of quantum thermodynamics, we have correctly identified accessible work and heat exchange in both equilibrium and nonequilibrium cases. The free energy (internal energy minus temperature times entropy) remains unaltered, when all the entities entering this relation are suitably defined. Exploiting Rényi relative entropies we have shown that this "form invariance" holds even beyond equilibrium and has profound operational significance in isothermal process. These results reduce to the Gibbs-von Neumann results when the Rényi entropic parameter α approaches 1. Moreover, it is shown that the universality of the Carnot statement of the second law is the consequence of the form invariance of the free energy, which is in turn the consequence of maximum entropy principle. Further, the Clausius inequality, which is the precursor to the Carnot statement, is also shown to hold based on the data processing inequalities for the traditional and sandwiched Rényi relative entropies. Thus, we find that the thermodynamics of nonequilibrium state and its deviation from equilibrium together determine the thermodynamic laws. This is another important manifestation of the concepts of information theory in thermodynamics when they are extended to the quantum realm. Our work is a substantial step towards formulating a complete theory of quantum thermodynamics and corresponding resource theory. PMID:26565222

  9. Quantum Rényi relative entropies affirm universality of thermodynamics

    NASA Astrophysics Data System (ADS)

    Misra, Avijit; Singh, Uttam; Bera, Manabendra Nath; Rajagopal, A. K.

    2015-10-01

    We formulate a complete theory of quantum thermodynamics in the Rényi entropic formalism exploiting the Rényi relative entropies, starting from the maximum entropy principle. In establishing the first and second laws of quantum thermodynamics, we have correctly identified accessible work and heat exchange in both equilibrium and nonequilibrium cases. The free energy (internal energy minus temperature times entropy) remains unaltered, when all the entities entering this relation are suitably defined. Exploiting Rényi relative entropies we have shown that this "form invariance" holds even beyond equilibrium and has profound operational significance in isothermal process. These results reduce to the Gibbs-von Neumann results when the Rényi entropic parameter α approaches 1. Moreover, it is shown that the universality of the Carnot statement of the second law is the consequence of the form invariance of the free energy, which is in turn the consequence of maximum entropy principle. Further, the Clausius inequality, which is the precursor to the Carnot statement, is also shown to hold based on the data processing inequalities for the traditional and sandwiched Rényi relative entropies. Thus, we find that the thermodynamics of nonequilibrium state and its deviation from equilibrium together determine the thermodynamic laws. This is another important manifestation of the concepts of information theory in thermodynamics when they are extended to the quantum realm. Our work is a substantial step towards formulating a complete theory of quantum thermodynamics and corresponding resource theory.

  10. Tight Uniform Continuity Bounds for Quantum Entropies: Conditional Entropy, Relative Entropy Distance and Energy Constraints

    NASA Astrophysics Data System (ADS)

    Winter, Andreas

    2016-10-01

    We present a bouquet of continuity bounds for quantum entropies, falling broadly into two classes: first, a tight analysis of the Alicki-Fannes continuity bounds for the conditional von Neumann entropy, reaching almost the best possible form that depends only on the system dimension and the trace distance of the states. Almost the same proof can be used to derive similar continuity bounds for the relative entropy distance from a convex set of states or positive operators. As applications, we give new proofs, with tighter bounds, of the asymptotic continuity of the relative entropy of entanglement, E R , and its regularization {E_R^{∞}}, as well as of the entanglement of formation, E F . Using a novel "quantum coupling" of density operators, which may be of independent interest, we extend the latter to an asymptotic continuity bound for the regularized entanglement of formation, aka entanglement cost, {E_C=E_F^{∞}}. Second, we derive analogous continuity bounds for the von Neumann entropy and conditional entropy in infinite dimensional systems under an energy constraint, most importantly systems of multiple quantum harmonic oscillators. While without an energy bound the entropy is discontinuous, it is well-known to be continuous on states of bounded energy. However, a quantitative statement to that effect seems not to have been known. Here, under some regularity assumptions on the Hamiltonian, we find that, quite intuitively, the Gibbs entropy at the given energy roughly takes the role of the Hilbert space dimension in the finite-dimensional Fannes inequality.

  11. Entropy for quantum pure states and quantum H theorem

    NASA Astrophysics Data System (ADS)

    Han, Xizhi; Wu, Biao

    2015-06-01

    We construct a complete set of Wannier functions that are localized at both given positions and momenta. This allows us to introduce the quantum phase space, onto which a quantum pure state can be mapped unitarily. Using its probability distribution in quantum phase space, we define an entropy for a quantum pure state. We prove an inequality regarding the long-time behavior of our entropy's fluctuation. For a typical initial state, this inequality indicates that our entropy can relax dynamically to a maximized value and stay there most of time with small fluctuations. This result echoes the quantum H theorem proved by von Neumann [Zeitschrift für Physik 57, 30 (1929), 10.1007/BF01339852]. Our entropy is different from the standard von Neumann entropy, which is always zero for quantum pure states. According to our definition, a system always has bigger entropy than its subsystem even when the system is described by a pure state. As the construction of the Wannier basis can be implemented numerically, the dynamical evolution of our entropy is illustrated with an example.

  12. Steganography on quantum pixel images using Shannon entropy

    NASA Astrophysics Data System (ADS)

    Laurel, Carlos Ortega; Dong, Shi-Hai; Cruz-Irisson, M.

    2016-07-01

    This paper presents a steganographical algorithm based on least significant bit (LSB) from the most significant bit information (MSBI) and the equivalence of a bit pixel image to a quantum pixel image, which permits to make the information communicate secretly onto quantum pixel images for its secure transmission through insecure channels. This algorithm offers higher security since it exploits the Shannon entropy for an image.

  13. Quantum entropy and special relativity.

    PubMed

    Peres, Asher; Scudo, Petra F; Terno, Daniel R

    2002-06-10

    We consider a single free spin- 1 / 2 particle. The reduced density matrix for its spin is not covariant under Lorentz transformations. The spin entropy is not a relativistic scalar and has no invariant meaning.

  14. Wald entropy formula and loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Bodendorfer, N.; Neiman, Y.

    2014-10-01

    We outline how the Wald entropy formula naturally arises in loop quantum gravity based on recently introduced dimension-independent connection variables. The key observation is that in a loop quantization of a generalized gravity theory, the analog of the area operator turns out to measure, morally speaking, the Wald entropy rather than the area. We discuss the explicit example of (higher-dimensional) Lanczos-Lovelock gravity and comment on recent work on finding the correct numerical prefactor of the entropy by comparing it to a semiclassical effective action.

  15. Reexamination of quantum data compression and relative entropy

    NASA Astrophysics Data System (ADS)

    Kaltchenko, Alexei

    2008-08-01

    Schumacher and Westmoreland [Phys. Rev. A 64, 42304 (2001)] have established a quantum analog of a well-known classical information theory result on a role of relative entropy as a measure of nonoptimality in (classical) data compression. In this paper, we provide an alternative simple and constructive proof of this result by constructing quantum compression codes (schemes) from classical data compression codes. Moreover, as the quantum data compression or coding task can be effectively reduced to a (quasi)classical one, we show that relevant results from classical information theory and data compression become applicable and therefore can be extended to the quantum domain.

  16. Coherent Informational Energy and Entropy.

    ERIC Educational Resources Information Center

    Avramescu, Aurel

    1980-01-01

    Seeks to provide a common theoretical foundation for all known bibliometric laws by assimilating a systemic view of the information transfer process with a thermodynamic process, i.e., the conduction of heat in solids. The resulting diffusion model establishes new definitions for informational energy and entropy consistent with corresponding…

  17. Bayesian methods, maximum entropy, and quantum Monte Carlo

    SciTech Connect

    Gubernatis, J.E.; Silver, R.N. ); Jarrell, M. )

    1991-01-01

    We heuristically discuss the application of the method of maximum entropy to the extraction of dynamical information from imaginary-time, quantum Monte Carlo data. The discussion emphasizes the utility of a Bayesian approach to statistical inference and the importance of statistically well-characterized data. 14 refs.

  18. Dissipation and entropy production in open quantum systems

    NASA Astrophysics Data System (ADS)

    Majima, H.; Suzuki, A.

    2010-11-01

    A microscopic description of an open system is generally expressed by the Hamiltonian of the form: Htot = Hsys + Henviron + Hsys-environ. We developed a microscopic theory of entropy and derived a general formula, so-called "entropy-Hamiltonian relation" (EHR), that connects the entropy of the system to the interaction Hamiltonian represented by Hsys-environ for a nonequilibrium open quantum system. To derive the EHR formula, we mapped the open quantum system to the representation space of the Liouville-space formulation or thermo field dynamics (TFD), and thus worked on the representation space Script L := Script H otimes , where Script H denotes the ordinary Hilbert space while the tilde Hilbert space conjugates to Script H. We show that the natural transformation (mapping) of nonequilibrium open quantum systems is accomplished within the theoretical structure of TFD. By using the obtained EHR formula, we also derived the equation of motion for the distribution function of the system. We demonstrated that by knowing the microscopic description of the interaction, namely, the specific form of Hsys-environ on the representation space Script L, the EHR formulas enable us to evaluate the entropy of the system and to gain some information about entropy for nonequilibrium open quantum systems.

  19. Measuring entanglement entropy in a quantum many-body system

    NASA Astrophysics Data System (ADS)

    Islam, Rajibul; Ma, Ruichao; Preiss, Philipp M.; Eric Tai, M.; Lukin, Alexander; Rispoli, Matthew; Greiner, Markus

    2015-12-01

    Entanglement is one of the most intriguing features of quantum mechanics. It describes non-local correlations between quantum objects, and is at the heart of quantum information sciences. Entanglement is now being studied in diverse fields ranging from condensed matter to quantum gravity. However, measuring entanglement remains a challenge. This is especially so in systems of interacting delocalized particles, for which a direct experimental measurement of spatial entanglement has been elusive. Here, we measure entanglement in such a system of itinerant particles using quantum interference of many-body twins. Making use of our single-site-resolved control of ultracold bosonic atoms in optical lattices, we prepare two identical copies of a many-body state and interfere them. This enables us to directly measure quantum purity, Rényi entanglement entropy, and mutual information. These experiments pave the way for using entanglement to characterize quantum phases and dynamics of strongly correlated many-body systems.

  20. Measuring entanglement entropy in a quantum many-body system.

    PubMed

    Islam, Rajibul; Ma, Ruichao; Preiss, Philipp M; Tai, M Eric; Lukin, Alexander; Rispoli, Matthew; Greiner, Markus

    2015-12-01

    Entanglement is one of the most intriguing features of quantum mechanics. It describes non-local correlations between quantum objects, and is at the heart of quantum information sciences. Entanglement is now being studied in diverse fields ranging from condensed matter to quantum gravity. However, measuring entanglement remains a challenge. This is especially so in systems of interacting delocalized particles, for which a direct experimental measurement of spatial entanglement has been elusive. Here, we measure entanglement in such a system of itinerant particles using quantum interference of many-body twins. Making use of our single-site-resolved control of ultracold bosonic atoms in optical lattices, we prepare two identical copies of a many-body state and interfere them. This enables us to directly measure quantum purity, Rényi entanglement entropy, and mutual information. These experiments pave the way for using entanglement to characterize quantum phases and dynamics of strongly correlated many-body systems.

  1. Horizon Entropy from Quantum Gravity Condensates.

    PubMed

    Oriti, Daniele; Pranzetti, Daniele; Sindoni, Lorenzo

    2016-05-27

    We construct condensate states encoding the continuum spherically symmetric quantum geometry of a horizon in full quantum gravity, i.e., without any classical symmetry reduction, in the group field theory formalism. Tracing over the bulk degrees of freedom, we show how the resulting reduced density matrix manifestly exhibits a holographic behavior. We derive a complete orthonormal basis of eigenstates for the reduced density matrix of the horizon and use it to compute the horizon entanglement entropy. By imposing consistency with the horizon boundary conditions and semiclassical thermodynamical properties, we recover the Bekenstein-Hawking entropy formula for any value of the Immirzi parameter. Our analysis supports the equivalence between the von Neumann (entanglement) entropy interpretation and the Boltzmann (statistical) one. PMID:27284642

  2. Horizon Entropy from Quantum Gravity Condensates.

    PubMed

    Oriti, Daniele; Pranzetti, Daniele; Sindoni, Lorenzo

    2016-05-27

    We construct condensate states encoding the continuum spherically symmetric quantum geometry of a horizon in full quantum gravity, i.e., without any classical symmetry reduction, in the group field theory formalism. Tracing over the bulk degrees of freedom, we show how the resulting reduced density matrix manifestly exhibits a holographic behavior. We derive a complete orthonormal basis of eigenstates for the reduced density matrix of the horizon and use it to compute the horizon entanglement entropy. By imposing consistency with the horizon boundary conditions and semiclassical thermodynamical properties, we recover the Bekenstein-Hawking entropy formula for any value of the Immirzi parameter. Our analysis supports the equivalence between the von Neumann (entanglement) entropy interpretation and the Boltzmann (statistical) one.

  3. Gravity from quantum information

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Weon; Kim, Hyeong-Chan; Lee, Jungjai

    2013-09-01

    We suggest that the Einstein equation can be derived from Landauer's principle applied to an information erasing process at a local Rindler horizon and Jacobson's idea linking the Einstein equation with thermodynamics. When matter crosses the horizon, information on the matter disappears, and the horizon entanglement entropy increases to compensate for the entropy reduction. The Einstein equation describes an information-energy relation during this process, which implies that entropic gravity is related to the quantum entanglement of the vacuum and has a quantuminformation theoretic origin.

  4. Black holes, entropies, and semiclassical spacetime in quantum gravity

    NASA Astrophysics Data System (ADS)

    Nomura, Yasunori; Weinberg, Sean J.

    2014-10-01

    We present a coherent picture of the quantum mechanics of black holes. The picture does not require the introduction of any drastically new physical effect beyond what is already known; it arises mostly from synthesizing and (re)interpreting existing results in appropriate manners. We identify the Bekenstein-Hawking entropy as the entropy associated with coarse-graining performed to obtain semiclassical field theory from a fundamental microscopic theory of quantum gravity. This clarifies the issues around the unitary evolution, the existence of the interior spacetime, and the thermodynamic nature in black hole physics — any result in semiclassical field theory is a statement about the maximally mixed ensemble of microscopic quantum states consistent with the specified background, within the precision allowed by quantum mechanics. We present a detailed analysis of information transfer in Hawking emission and black hole mining processes, clarifying what aspects of the underlying dynamics are (not) visible in semiclassical field theory. We also discuss relations between the black hole entropy and the entanglement entropy across the horizon. We then extend our discussions to more general contexts in quantum gravity. The subjects include extensions to de Sitter and Minkowski spaces and implications for complementarity and cosmology, especially the eternally inflating multiverse.

  5. Optimal quantum networks and one-shot entropies

    NASA Astrophysics Data System (ADS)

    Chiribella, Giulio; Ebler, Daniel

    2016-09-01

    We develop a semidefinite programming method for the optimization of quantum networks, including both causal networks and networks with indefinite causal structure. Our method applies to a broad class of performance measures, defined operationally in terms of interative tests set up by a verifier. We show that the optimal performance is equal to a max relative entropy, which quantifies the informativeness of the test. Building on this result, we extend the notion of conditional min-entropy from quantum states to quantum causal networks. The optimization method is illustrated in a number of applications, including the inversion, charge conjugation, and controlization of an unknown unitary dynamics. In the non-causal setting, we show a proof-of-principle application to the maximization of the winning probability in a non-causal quantum game.

  6. Covariant entropy bound and loop quantum cosmology

    SciTech Connect

    Ashtekar, Abhay; Wilson-Ewing, Edward

    2008-09-15

    We examine Bousso's covariant entropy bound conjecture in the context of radiation filled, spatially flat, Friedmann-Robertson-Walker models. The bound is violated near the big bang. However, the hope has been that quantum gravity effects would intervene and protect it. Loop quantum cosmology provides a near ideal setting for investigating this issue. For, on the one hand, quantum geometry effects resolve the singularity and, on the other hand, the wave function is sharply peaked at a quantum corrected but smooth geometry, which can supply the structure needed to test the bound. We find that the bound is respected. We suggest that the bound need not be an essential ingredient for a quantum gravity theory but may emerge from it under suitable circumstances.

  7. Entropy and information causality in general probabilistic theories

    NASA Astrophysics Data System (ADS)

    Barnum, Howard; Barrett, Jonathan; Orloff Clark, Lisa; Leifer, Matthew; Spekkens, Robert; Stepanik, Nicholas; Wilce, Alex; Wilke, Robin

    2010-03-01

    We investigate the concept of entropy in probabilistic theories more general than quantum mechanics, with particular reference to the notion of information causality (IC) recently proposed by Pawlowski et al (2009 arXiv:0905.2292). We consider two entropic quantities, which we term measurement and mixing entropy. In the context of classical and quantum theory, these coincide, being given by the Shannon and von Neumann entropies, respectively; in general, however, they are very different. In particular, while measurement entropy is easily seen to be concave, mixing entropy need not be. In fact, as we show, mixing entropy is not concave whenever the state space is a non-simplicial polytope. Thus, the condition that measurement and mixing entropies coincide is a strong constraint on possible theories. We call theories with this property monoentropic. Measurement entropy is subadditive, but not in general strongly subadditive. Equivalently, if we define the mutual information between two systems A and B by the usual formula I(A: B)=H(A)+H(B)-H(AB), where H denotes the measurement entropy and AB is a non-signaling composite of A and B, then it can happen that I(A:BC)entropy is strongly subadditive, and also satisfies a version of the Holevo bound, is informationally causal, and on the other hand we observe that Popescu-Rohrlich boxes, which violate IC, also violate strong subadditivity. We also explore the interplay between measurement and mixing entropy and various natural conditions on theories that arise in quantum axiomatics.

  8. Entropy of quantum-corrected black holes

    SciTech Connect

    Matyjasek, Jerzy

    2006-11-15

    The approximate renormalized one-loop effective action of the quantized massive scalar, spinor and vector field in a large mass limit, i.e., the lowest order of the DeWitt-Schwinger expansion involves the coincidence limit of the Hadamard-DeWitt coefficient a{sub 3}. Building on this and using Wald's approach we shall construct the general expression describing entropy of the spherically-symmetric static black hole being the solution of the semiclassical field equations. For the concrete case of the quantum-corrected Reissner-Nordstroem black hole this result coincides, as expected, with the entropy obtained by integration of the first law of black hole thermodynamics with a suitable choice of the integration constant. The case of the extremal quantum-corrected black hole is briefly considered.

  9. Recoverability in quantum information theory

    NASA Astrophysics Data System (ADS)

    Wilde, Mark

    The fact that the quantum relative entropy is non-increasing with respect to quantum physical evolutions lies at the core of many optimality theorems in quantum information theory and has applications in other areas of physics. In this work, we establish improvements of this entropy inequality in the form of physically meaningful remainder terms. One of the main results can be summarized informally as follows: if the decrease in quantum relative entropy between two quantum states after a quantum physical evolution is relatively small, then it is possible to perform a recovery operation, such that one can perfectly recover one state while approximately recovering the other. This can be interpreted as quantifying how well one can reverse a quantum physical evolution. Our proof method is elementary, relying on the method of complex interpolation, basic linear algebra, and the recently introduced Renyi generalization of a relative entropy difference. The theorem has a number of applications in quantum information theory, which have to do with providing physically meaningful improvements to many known entropy inequalities. This is based on arXiv:1505.04661, now accepted for publication in Proceedings of the Royal Society A. I acknowledge support from startup funds from the Department of Physics and Astronomy at LSU, the NSF under Award No. CCF-1350397, and the DARPA Quiness Program through US Army Research Office award W31P4Q-12-1-0019.

  10. Entanglement entropy, decoherence, and quantum phase transitions of a dissipative two-level system

    SciTech Connect

    Le Hur, K.

    2008-09-15

    The concept of entanglement entropy appears in multiple contexts, from black hole physics to quantum information theory, where it measures the entanglement of quantum states. We investigate the entanglement entropy in a simple model, the spin-boson model, which describes a qubit (two-level system) interacting with a collection of harmonic oscillators that models the environment responsible for decoherence and dissipation. The entanglement entropy allows to make a precise unification between entanglement of the spin with its environment, decoherence, and quantum phase transitions. We derive exact analytical results which are confirmed by Numerical Renormalization Group arguments both for an ohmic and a subohmic bosonic bath. The entanglement entropy obeys universal scalings. We make comparisons with entanglement properties in the quantum Ising model and in the Dicke model. We also emphasize the possibility of measuring this entropy using charge qubits subject to electromagnetic noise; such measurements would provide an empirical proof of the existence of entanglement entropy.

  11. A family of generalized quantum entropies: definition and properties

    NASA Astrophysics Data System (ADS)

    Bosyk, G. M.; Zozor, S.; Holik, F.; Portesi, M.; Lamberti, P. W.

    2016-08-01

    We present a quantum version of the generalized (h,φ )-entropies, introduced by Salicrú et al. for the study of classical probability distributions. We establish their basic properties and show that already known quantum entropies such as von Neumann, and quantum versions of Rényi, Tsallis, and unified entropies, constitute particular classes of the present general quantum Salicrú form. We exhibit that majorization plays a key role in explaining most of their common features. We give a characterization of the quantum (h,φ )-entropies under the action of quantum operations and study their properties for composite systems. We apply these generalized entropies to the problem of detection of quantum entanglement and introduce a discussion on possible generalized conditional entropies as well.

  12. Entanglement entropy and mutual information of circular entangling surfaces in the 2  +  1-dimensional quantum Lifshitz model

    NASA Astrophysics Data System (ADS)

    Zhou, Tianci; Chen, Xiao; Faulkner, Thomas; Fradkin, Eduardo

    2016-09-01

    We investigate the entanglement entropy (EE) of circular entangling cuts in the 2  +  1-dimensional quantum Lifshitz model. The ground state in this model is a spatially conformal invariant state of the Rokhsar–Kivelson type, whose amplitude is the Gibbs weight of 2D Euclidean free boson. We show that the finite subleading corrections of EE to the area-law term, as well as the mutual information, are conformal invariants and calculate them for cylinder, disk-like and spherical manifolds with various spatial cuts. The subtlety due to the boson compactification in the replica trick is carefully addressed. We find that in the geometry of a punctured plane with many small holes, the constant piece of EE is proportional to the number of holes, indicating the ability of entanglement to detect topological information of the configuration. Finally, we compare the mutual information of two small distant disks with Cardy’s relativistic CFT scaling proposal. We find that in the quantum Lifshitz model, the mutual information also scales at long distance with a power determined by the lowest scaling dimension local operator in the theory.

  13. Entanglement entropy and mutual information of circular entangling surfaces in the 2  +  1-dimensional quantum Lifshitz model

    NASA Astrophysics Data System (ADS)

    Zhou, Tianci; Chen, Xiao; Faulkner, Thomas; Fradkin, Eduardo

    2016-09-01

    We investigate the entanglement entropy (EE) of circular entangling cuts in the 2  +  1-dimensional quantum Lifshitz model. The ground state in this model is a spatially conformal invariant state of the Rokhsar-Kivelson type, whose amplitude is the Gibbs weight of 2D Euclidean free boson. We show that the finite subleading corrections of EE to the area-law term, as well as the mutual information, are conformal invariants and calculate them for cylinder, disk-like and spherical manifolds with various spatial cuts. The subtlety due to the boson compactification in the replica trick is carefully addressed. We find that in the geometry of a punctured plane with many small holes, the constant piece of EE is proportional to the number of holes, indicating the ability of entanglement to detect topological information of the configuration. Finally, we compare the mutual information of two small distant disks with Cardy’s relativistic CFT scaling proposal. We find that in the quantum Lifshitz model, the mutual information also scales at long distance with a power determined by the lowest scaling dimension local operator in the theory.

  14. Quantum Information and Computing

    NASA Astrophysics Data System (ADS)

    Accardi, L.; Ohya, Masanori; Watanabe, N.

    2006-03-01

    Preface -- Coherent quantum control of [symbol]-atoms through the stochastic limit / L. Accardi, S. V. Kozyrev and A. N. Pechen -- Recent advances in quantum white noise calculus / L. Accardi and A. Boukas -- Control of quantum states by decoherence / L. Accardi and K. Imafuku -- Logical operations realized on the Ising chain of N qubits / M. Asano, N. Tateda and C. Ishii -- Joint extension of states of fermion subsystems / H. Araki -- Quantum filtering and optimal feedback control of a Gaussian quantum free particle / S. C. Edwards and V. P. Belavkin -- On existence of quantum zeno dynamics / P. Exner and T. Ichinose -- Invariant subspaces and control of decoherence / P. Facchi, V. L. Lepore and S. Pascazio -- Clauser-Horner inequality for electron counting statistics in multiterminal mesoscopic conductors / L. Faoro, F. Taddei and R. Fazio -- Fidelity of quantum teleportation model using beam splittings / K.-H. Fichtner, T. Miyadera and M. Ohya -- Quantum logical gates realized by beam splittings / W. Freudenberg ... [et al.] -- Information divergence for quantum channels / S. J. Hammersley and V. P. Belavkin -- On the uniqueness theorem in quantum information geometry / H. Hasegawa -- Noncanonical representations of a multi-dimensional Brownian motion / Y. Hibino -- Some of future directions of white noise theory / T. Hida -- Information, innovation and elemental random field / T. Hida -- Generalized quantum turing machine and its application to the SAT chaos algorithm / S. Iriyama, M. Ohya and I. Volovich -- A Stroboscopic approach to quantum tomography / A. Jamiolkowski -- Positive maps and separable states in matrix algebras / A. Kossakowski -- Simulating open quantum systems with trapped ions / S. Maniscalco -- A purification scheme and entanglement distillations / H. Nakazato, M. Unoki and K. Yuasa -- Generalized sectors and adjunctions to control micro-macro transitions / I. Ojima -- Saturation of an entropy bound and quantum Markov states / D. Petz -- An

  15. Book Review: Maxwell's Demon 2: Entropy, classical and quantum information, computing. Harvey Leff and Andrew Rex (Eds.); Institute of Physics, Bristol, 2003, 500pp., US 55, ISBN 0750307595

    NASA Astrophysics Data System (ADS)

    Shenker, Orly R.

    2004-09-01

    In 1867, James Clerk Maxwell proposed a perpetuum mobile of the second kind, that is, a counter example for the Second Law of thermodynamics, which came to be known as "Maxwell's Demon." Unlike any other perpetual motion machine, this one escaped attempts by the best scientists and philosophers to show that the Second Law or its statistical mechanical counterparts are universal after all. "Maxwell's demon lives on. After more than 130 years of uncertain life and at least two pronouncements of death, this fanciful character seems more vibrant than ever." These words of Harvey Leff and Andrew Rex (1990), which open their introduction to Maxwell's Demon 2: Entropy, Classical and Quantum Information, Computing (hereafter MD2) are very true: the Demon is as challenging and as intriguing as ever, and forces us to think and rethink about the foundations of thermodynamics and of statistical mechanics.

  16. Thermalization of topological entropy after a quantum quench

    NASA Astrophysics Data System (ADS)

    Zeng, Yu; Hamma, Alioscia; Fan, Heng

    2016-09-01

    Topologically ordered quantum phases are robust in the sense that perturbations in the Hamiltonian of the system will not change the topological nature of the ground-state wave function. However, in order to exploit topological order for applications such as self-correcting quantum memories and information processing, these states need to be also robust both dynamically and at finite temperature in the presence of an environment. It is well known that systems like the toric code in two spatial dimensions are fragile in temperature. In this paper, we show a completely analytic treatment of the toric code away from equilibrium, after a quantum quench of the system Hamiltonian. We show that, despite being subject to unitary evolution (and at zero temperature), the long-time behavior of the topological entropy is thermal, therefore vanishing. If the quench preserves a local gauge structure, there is a residual long-lived topological entropy. This also is the thermal behavior in presence of such gauge constraints. The result is obtained by studying the time evolution of the topological 2-Rényi entropy in a fully analytical, exact way.

  17. Average diagonal entropy in nonequilibrium isolated quantum systems.

    PubMed

    Giraud, Olivier; García-Mata, Ignacio

    2016-07-01

    The diagonal entropy was introduced as a good entropy candidate especially for isolated quantum systems out of equilibrium. Here we present an analytical calculation of the average diagonal entropy for systems undergoing unitary evolution and an external perturbation in the form of a cyclic quench. We compare our analytical findings with numerical simulations of various quantum systems. Our calculations elucidate various heuristic relations proposed recently in the literature. PMID:27575092

  18. Average diagonal entropy in nonequilibrium isolated quantum systems

    NASA Astrophysics Data System (ADS)

    Giraud, Olivier; García-Mata, Ignacio

    2016-07-01

    The diagonal entropy was introduced as a good entropy candidate especially for isolated quantum systems out of equilibrium. Here we present an analytical calculation of the average diagonal entropy for systems undergoing unitary evolution and an external perturbation in the form of a cyclic quench. We compare our analytical findings with numerical simulations of various quantum systems. Our calculations elucidate various heuristic relations proposed recently in the literature.

  19. Entanglement entropy in dynamic quantum-coherent conductors

    NASA Astrophysics Data System (ADS)

    Thomas, Konrad H.; Flindt, Christian

    2015-03-01

    We investigate the entanglement and the Rényi entropies of two electronic leads connected by a quantum point contact. For noninteracting electrons, the entropies can be related to the cumulants of the full counting statistics of transferred charge which in principle are measurable. We consider the entanglement entropy generated by operating the quantum point contact as a quantum switch which is opened and closed in a periodic manner. Using a numerically exact approach we analyze the conditions under which a logarithmic growth of the entanglement entropy predicted by conformal field theory should be observable in an electronic conductor. In addition, we consider clean single-particle excitations on top of the Fermi sea (levitons) generated by applying designed pulses to the leads. We identify a Hong-Ou-Mandel-like suppression of the entanglement entropy by interfering two levitons on a quantum point contact tuned to half transmission.

  20. Continuity of the entropy of macroscopic quantum systems.

    PubMed

    Swendsen, Robert H

    2015-11-01

    The proper definition of entropy is fundamental to the relationship between statistical mechanics and thermodynamics. It also plays a major role in the recent debate about the validity of the concept of negative temperature. In this paper, I analyze and calculate the thermodynamic entropy for large but finite quantum mechanical systems. A special feature of this analysis is that the thermodynamic energy of a quantum system is shown to be a continuous variable, rather than being associated with discrete energy eigenvalues. Calculations of the entropy as a function of energy can be carried out with a Legendre transform of thermodynamic potentials obtained from a canonical ensemble. The resultant expressions for the entropy are able to describe equilibrium between quantum systems having incommensurate energy-level spacings. This definition of entropy preserves all required thermodynamic properties, including satisfaction of all postulates and laws of thermodynamics. It demonstrates the consistency of the concept of negative temperature with the principles of thermodynamics.

  1. Continuity of the entropy of macroscopic quantum systems.

    PubMed

    Swendsen, Robert H

    2015-11-01

    The proper definition of entropy is fundamental to the relationship between statistical mechanics and thermodynamics. It also plays a major role in the recent debate about the validity of the concept of negative temperature. In this paper, I analyze and calculate the thermodynamic entropy for large but finite quantum mechanical systems. A special feature of this analysis is that the thermodynamic energy of a quantum system is shown to be a continuous variable, rather than being associated with discrete energy eigenvalues. Calculations of the entropy as a function of energy can be carried out with a Legendre transform of thermodynamic potentials obtained from a canonical ensemble. The resultant expressions for the entropy are able to describe equilibrium between quantum systems having incommensurate energy-level spacings. This definition of entropy preserves all required thermodynamic properties, including satisfaction of all postulates and laws of thermodynamics. It demonstrates the consistency of the concept of negative temperature with the principles of thermodynamics. PMID:26651650

  2. Impact of Information Entropy on Teaching Effectiveness

    ERIC Educational Resources Information Center

    Wang, Zhi-guo

    2007-01-01

    Information entropy refers to the process in which information is sent out from the information source, transmitted through information channel and acquired by information sink, while the teaching process is the one of transmitting teaching information from teachers and teaching material to students. How to improve teaching effectiveness is…

  3. The conditional entropy power inequality for Gaussian quantum states

    SciTech Connect

    Koenig, Robert

    2015-02-15

    We propose a generalization of the quantum entropy power inequality involving conditional entropies. For the special case of Gaussian states, we give a proof based on perturbation theory for symplectic spectra. We discuss some implications for entanglement-assisted classical communication over additive bosonic noise channels.

  4. Remainder terms for some quantum entropy inequalities

    SciTech Connect

    Carlen, Eric A.; Lieb, Elliott H.

    2014-04-15

    We consider three von Neumann entropy inequalities: subadditivity; Pinsker's inequality for relative entropy; and the monotonicity of relative entropy. For these we state conditions for equality, and we prove some new error bounds away from equality, including an improved version of Pinsker's inequality.

  5. A note on quantum entropy inequalities and channel capacities

    NASA Astrophysics Data System (ADS)

    Fan, Heng

    2003-12-01

    Quantum entropy inequalities are studied. Some quantum entropy inequalities are obtained by several methods. For an entanglement breaking channel, we show that the entanglement-assisted classical capacity is upper bounded by log d. A relationship between entanglement-assisted and one-shot unassisted capacities is obtained. This relationship shows the entanglement-assisted channel capacity is upper bounded by the sum of log d and the one-shot unassisted classical capacity.

  6. Minimum output entropy of a non-Gaussian quantum channel

    NASA Astrophysics Data System (ADS)

    Memarzadeh, Laleh; Mancini, Stefano

    2016-08-01

    We introduce a model of a non-Gaussian quantum channel that stems from the composition of two physically relevant processes occurring in open quantum systems, namely, amplitude damping and dephasing. For it we find input states approaching zero output entropy while respecting the input energy constraint. These states fully exploit the infinite dimensionality of the Hilbert space. Upon truncation of the latter, the minimum output entropy remains finite, and optimal input states for such a case are conjectured thanks to numerical evidence.

  7. On determining absolute entropy without quantum theory or the third law of thermodynamics

    NASA Astrophysics Data System (ADS)

    Steane, Andrew M.

    2016-04-01

    We employ classical thermodynamics to gain information about absolute entropy, without recourse to statistical methods, quantum mechanics or the third law of thermodynamics. The Gibbs–Duhem equation yields various simple methods to determine the absolute entropy of a fluid. We also study the entropy of an ideal gas and the ionization of a plasma in thermal equilibrium. A single measurement of the degree of ionization can be used to determine an unknown constant in the entropy equation, and thus determine the absolute entropy of a gas. It follows from all these examples that the value of entropy at absolute zero temperature does not need to be assigned by postulate, but can be deduced empirically.

  8. Symmetric polynomials in information theory: Entropy and subentropy

    SciTech Connect

    Jozsa, Richard; Mitchison, Graeme

    2015-06-15

    Entropy and other fundamental quantities of information theory are customarily expressed and manipulated as functions of probabilities. Here we study the entropy H and subentropy Q as functions of the elementary symmetric polynomials in the probabilities and reveal a series of remarkable properties. Derivatives of all orders are shown to satisfy a complete monotonicity property. H and Q themselves become multivariate Bernstein functions and we derive the density functions of their Levy-Khintchine representations. We also show that H and Q are Pick functions in each symmetric polynomial variable separately. Furthermore, we see that H and the intrinsically quantum informational quantity Q become surprisingly closely related in functional form, suggesting a special significance for the symmetric polynomials in quantum information theory. Using the symmetric polynomials, we also derive a series of further properties of H and Q.

  9. The Shannon information entropy of protein sequences.

    PubMed Central

    Strait, B J; Dewey, T G

    1996-01-01

    A comprehensive data base is analyzed to determine the Shannon information content of a protein sequence. This information entropy is estimated by three methods: a k-tuplet analysis, a generalized Zipf analysis, and a "Chou-Fasman gambler." The k-tuplet analysis is a "letter" analysis, based on conditional sequence probabilities. The generalized Zipf analysis demonstrates the statistical linguistic qualities of protein sequences and uses the "word" frequency to determine the Shannon entropy. The Zipf analysis and k-tuplet analysis give Shannon entropies of approximately 2.5 bits/amino acid. This entropy is much smaller than the value of 4.18 bits/amino acid obtained from the nonuniform composition of amino acids in proteins. The "Chou-Fasman" gambler is an algorithm based on the Chou-Fasman rules for protein structure. It uses both sequence and secondary structure information to guess at the number of possible amino acids that could appropriately substitute into a sequence. As in the case for the English language, the gambler algorithm gives significantly lower entropies than the k-tuplet analysis. Using these entropies, the number of most probable protein sequences can be calculated. The number of most probable protein sequences is much less than the number of possible sequences but is still much larger than the number of sequences thought to have existed throughout evolution. Implications of these results for mutagenesis experiments are discussed. PMID:8804598

  10. Comparison of quantum discord and relative entropy in some bipartite quantum systems

    NASA Astrophysics Data System (ADS)

    Mahdian, M.; Arjmandi, M. B.

    2016-04-01

    The study of quantum correlations in high-dimensional bipartite systems is crucial for the development of quantum computing. We propose relative entropy as a distance measure of correlations may be measured by means of the distance from the quantum state to the closest classical-classical state. In particular, we establish relations between relative entropy and quantum discord quantifiers obtained by means of orthogonal projection measurements. We show that for symmetrical X-states density matrices the quantum discord is equal to relative entropy. At the end of paper, various examples of X-states such as two-qubit and qubit-qutrit have been demonstrated.

  11. Quantum Fokker-Planck-Kramers equation and entropy production.

    PubMed

    de Oliveira, Mário J

    2016-07-01

    We use a canonical quantization procedure to set up a quantum Fokker-Planck-Kramers equation that accounts for quantum dissipation in a thermal environment. The dissipation term is chosen to ensure that the thermodynamic equilibrium is described by the Gibbs state. An expression for the quantum entropy production that properly describes quantum systems in a nonequilibrium stationary state is also provided. The time-dependent solution is given for a quantum harmonic oscillator in contact with a heat bath. We also obtain the stationary solution for a system of two coupled harmonic oscillators in contact with reservoirs at distinct temperatures, from which we obtain the entropy production and the quantum thermal conductance. PMID:27575097

  12. Reply to "Comment on 'Quantum Kaniadakis entropy under projective measurement' ".

    PubMed

    Ourabah, Kamel; Tribeche, Mouloud

    2016-08-01

    We rely on our proof of the nondecreasing character of quantum Kaniadakis entropy under projective measurement [Phys. Rev. E 92, 032114 (2015)PLEEE81539-375510.1103/PhysRevE.92.032114], and we put it into perspective with the results of Bosyk et al. [Quantum Inf Process 15, 3393 (2016)10.1007/s11128-016-1329-5]. Our method, adopted for the proof that Kaniadakis entropy does not decrease under a projective measurement, is based on Jensen's inequalities, while the method proposed by the authors of the Comment represents another alternative and clearly correct method to prove the same thing. Furthermore, we clarify that our interest in Kaniadakis entropy is due to the fact that this entropy has a transparent physical significance, emerging within the special relativity. PMID:27627426

  13. Reply to "Comment on `Quantum Kaniadakis entropy under projective measurement' "

    NASA Astrophysics Data System (ADS)

    Ourabah, Kamel; Tribeche, Mouloud

    2016-08-01

    We rely on our proof of the nondecreasing character of quantum Kaniadakis entropy under projective measurement [Phys. Rev. E 92, 032114 (2015), 10.1103/PhysRevE.92.032114], and we put it into perspective with the results of Bosyk et al. [Quantum Inf Process 15, 3393 (2016), 10.1007/s11128-016-1329-5]. Our method, adopted for the proof that Kaniadakis entropy does not decrease under a projective measurement, is based on Jensen's inequalities, while the method proposed by the authors of the Comment represents another alternative and clearly correct method to prove the same thing. Furthermore, we clarify that our interest in Kaniadakis entropy is due to the fact that this entropy has a transparent physical significance, emerging within the special relativity.

  14. Reply to "Comment on 'Quantum Kaniadakis entropy under projective measurement' ".

    PubMed

    Ourabah, Kamel; Tribeche, Mouloud

    2016-08-01

    We rely on our proof of the nondecreasing character of quantum Kaniadakis entropy under projective measurement [Phys. Rev. E 92, 032114 (2015)PLEEE81539-375510.1103/PhysRevE.92.032114], and we put it into perspective with the results of Bosyk et al. [Quantum Inf Process 15, 3393 (2016)10.1007/s11128-016-1329-5]. Our method, adopted for the proof that Kaniadakis entropy does not decrease under a projective measurement, is based on Jensen's inequalities, while the method proposed by the authors of the Comment represents another alternative and clearly correct method to prove the same thing. Furthermore, we clarify that our interest in Kaniadakis entropy is due to the fact that this entropy has a transparent physical significance, emerging within the special relativity.

  15. Information Entropy Squeezing for a Atom in Mode-Mode Competition System

    NASA Astrophysics Data System (ADS)

    Wu, Qin; Fang, Mao-Fa; Li, Shao-Xin; Li, Ying; Hu, Yao-Hua

    2008-12-01

    The entropy squeezing properties for a two-level atom interacting with a two-mode field via two different competing transitions are investigated from a quantum information point of view. The influences of the initial state of the system and the relative coupling strength between the atom and the field on the atomic information entropy squeezing are discussed. Our results show that the squeezed direction and the frequency of the information entropy squeezing can be controlled by choosing the phase of the atom dipole and the relative competing strength of atom-field, respectively. We find that, under the same condition, no atomic variance squeezing is predicted from the HUR while optimal entropy squeezing is obtained from the EUR, so the quantum information entropy is a remarkable precision measure for the atomic squeezing in the considered system.

  16. Quantum information does exist

    NASA Astrophysics Data System (ADS)

    Duwell, Armond

    2008-01-01

    This paper advocates a concept of quantum information whose origins can be traced to Schumacher [1995. Quantum coding. Physical Review A 51, 2738-2747]. The concept of quantum information advocated is elaborated using an analogy to Shannon's theory provided by Schumacher coding. In particular, this paper extends Timpson's [2004. Quantum information theory and the foundations of quantum mechanics. Ph.D. dissertation, University of Oxford. Preprint, quant-ph/0412063] framework for interpreting Shannon information theory to the quantum context. Entanglement fidelity is advocated as the appropriate success criterion for the reproduction of quantum information. The relationship between the Shannon theory and quantum information theory is discussed.

  17. Information, entropy and fidelity in visual communication

    NASA Technical Reports Server (NTRS)

    Huck, Friedrich O.; Fales, Carl L.; Alter-Gartenberg, Rachel; Rahman, Zia-Ur

    1992-01-01

    This paper presents an assessment of visual communication that integrates the critical limiting factors of image gathering and display with the digital processing that is used to code and restore images. The approach focuses on two mathematical criteria, information and fidelity, and on their relationships to the entropy of the encoded data and to the visual quality of the restored image.

  18. Approximate reversibility in the context of entropy gain, information gain, and complete positivity

    NASA Astrophysics Data System (ADS)

    Buscemi, Francesco; Das, Siddhartha; Wilde, Mark M.

    2016-06-01

    There are several inequalities in physics which limit how well we can process physical systems to achieve some intended goal, including the second law of thermodynamics, entropy bounds in quantum information theory, and the uncertainty principle of quantum mechanics. Recent results provide physically meaningful enhancements of these limiting statements, determining how well one can attempt to reverse an irreversible process. In this paper, we apply and extend these results to give strong enhancements to several entropy inequalities, having to do with entropy gain, information gain, entropic disturbance, and complete positivity of open quantum systems dynamics. Our first result is a remainder term for the entropy gain of a quantum channel. This result implies that a small increase in entropy under the action of a subunital channel is a witness to the fact that the channel's adjoint can be used as a recovery map to undo the action of the original channel. We apply this result to pure-loss, quantum-limited amplifier, and phase-insensitive quantum Gaussian channels, showing how a quantum-limited amplifier can serve as a recovery from a pure-loss channel and vice versa. Our second result regards the information gain of a quantum measurement, both without and with quantum side information. We find here that a small information gain implies that it is possible to undo the action of the original measurement if it is efficient. The result also has operational ramifications for the information-theoretic tasks known as measurement compression without and with quantum side information. Our third result shows that the loss of Holevo information caused by the action of a noisy channel on an input ensemble of quantum states is small if and only if the noise can be approximately corrected on average. We finally establish that the reduced dynamics of a system-environment interaction are approximately completely positive and trace preserving if and only if the data processing

  19. Entanglement entropy for non-coplanar regions in quantum field theory

    NASA Astrophysics Data System (ADS)

    Blanco, David D.; Casini, Horacio

    2011-11-01

    We study the entanglement entropy in a relativistic quantum field theory for regions which are not included in a single spatial hyperplane. This geometric configuration cannot be treated with the Euclidean time method and the replica trick. Instead, we use a real time method to calculate the entropy for a massive free Dirac field in two dimensions in some approximations. We find some specifically relativistic features of the entropy. First, there is a large enhancement of entanglement due to boosts. As a result, the mutual information between relatively boosted regions does not vanish in the limit of zero volume and large relative boost. We also find extensivity of the information in a deeply Lorentzian regime with large violations of the triangle inequalities for the distances. This last effect is relevant to an interpretation of the amount of entropy enclosed in the Hawking radiation emitted by a black hole.

  20. Chain rules for quantum Rényi entropies

    SciTech Connect

    Dupuis, Frédéric

    2015-02-15

    We present chain rules for a new definition of the quantum Rényi conditional entropy sometimes called the “sandwiched” Rényi conditional entropy. More precisely, we prove analogues of the equation H(AB|C) = H(A|BC) + H(B|C), which holds as an identity for the von Neumann conditional entropy. In the case of the Rényi entropy, this relation no longer holds as an equality but survives as an inequality of the form H{sub α}(AB|C) ⩾ H{sub β}(A|BC) + H{sub γ}(B|C), where the parameters α, β, γ obey the relation (α)/(α−1) =(β)/(β−1) +(γ)/(γ−1) and (α − 1)(β − 1)(γ − 1) > 1; if (α − 1)(β − 1)(γ − 1) < 1, the direction of the inequality is reversed.

  1. Quantum maximum entropy principle for fractional exclusion statistics.

    PubMed

    Trovato, M; Reggiani, L

    2013-01-11

    Using the Wigner representation, compatibly with the uncertainty principle, we formulate a quantum maximum entropy principle for the fractional exclusion statistics. By considering anyonic systems satisfying fractional exclusion statistic, all the results available in the literature are generalized in terms of both the kind of statistics and a nonlocal description for excluson gases. Gradient quantum corrections are explicitly given at different levels of degeneracy and classical results are recovered when ℏ→0.

  2. The Tsallis entropy of natural information

    NASA Astrophysics Data System (ADS)

    Sneddon, Robert

    2007-12-01

    Estimating the information contained in natural data, such as electroencephalography data, is unusually difficult because the relationship between the physical data and the information that it encodes is unknown. This unknown relationship is often called the encoding problem. The present work provides a solution to this problem by deriving a method to estimate the Tsallis entropy in natural data. The method is based on two findings. The first finding is that the physical instantiation of any information event, that is, the physical occurrence of a symbol of information, must begin and end at a discontinuity or critical point (maximum, minimum, or saddle point) in the data. The second finding is that, in certain data types such as the encephalogram (EEG), the variance within of an EEG waveform event is directly proportional to its probability of occurrence. These two outcomes yield two results. The first is the easy binning of data into separate information events. The second is the ability to estimate probabilities in two ways: frequency counting and computing the variance within of an EEG waveform. These results are used to derive a linear estimator of the Tsallis entropy functional, allowing it to be estimated without deducing the encoding. This method for estimating the Tsallis entropy is first used to estimate the information in simple signals. The amount of information estimated is highly accurate. The method is then applied to two problems in electroencephalography. The first is distinguishing normal aging from very early Alzheimer's disease (mild cognitive impairment), and the second is medication monitoring of Alzheimer's disease treatment. The former is done with an accuracy of 92% and the latter with an accuracy of 91%. This detection accuracy is the highest published accuracy in the literature, which suggests that this method for Tsallis entropy estimation is both accurate and useful.

  3. Entropy, complexity, and spatial information

    NASA Astrophysics Data System (ADS)

    Batty, Michael; Morphet, Robin; Masucci, Paolo; Stanilov, Kiril

    2014-10-01

    We pose the central problem of defining a measure of complexity, specifically for spatial systems in general, city systems in particular. The measures we adopt are based on Shannon's (in Bell Syst Tech J 27:379-423, 623-656, 1948) definition of information. We introduce this measure and argue that increasing information is equivalent to increasing complexity, and we show that for spatial distributions, this involves a trade-off between the density of the distribution and the number of events that characterize it; as cities get bigger and are characterized by more events—more places or locations, information increases, all other things being equal. But sometimes the distribution changes at a faster rate than the number of events and thus information can decrease even if a city grows. We develop these ideas using various information measures. We first demonstrate their applicability to various distributions of population in London over the last 100 years, then to a wider region of London which is divided into bands of zones at increasing distances from the core, and finally to the evolution of the street system that characterizes the built-up area of London from 1786 to the present day. We conclude by arguing that we need to relate these measures to other measures of complexity, to choose a wider array of examples, and to extend the analysis to two-dimensional spatial systems.

  4. Entropy, complexity, and spatial information

    NASA Astrophysics Data System (ADS)

    Batty, Michael; Morphet, Robin; Masucci, Paolo; Stanilov, Kiril

    2014-09-01

    We pose the central problem of defining a measure of complexity, specifically for spatial systems in general, city systems in particular. The measures we adopt are based on Shannon's (in Bell Syst Tech J 27:379-423, 623-656, 1948) definition of information. We introduce this measure and argue that increasing information is equivalent to increasing complexity, and we show that for spatial distributions, this involves a trade-off between the density of the distribution and the number of events that characterize it; as cities get bigger and are characterized by more events—more places or locations, information increases, all other things being equal. But sometimes the distribution changes at a faster rate than the number of events and thus information can decrease even if a city grows. We develop these ideas using various information measures. We first demonstrate their applicability to various distributions of population in London over the last 100 years, then to a wider region of London which is divided into bands of zones at increasing distances from the core, and finally to the evolution of the street system that characterizes the built-up area of London from 1786 to the present day. We conclude by arguing that we need to relate these measures to other measures of complexity, to choose a wider array of examples, and to extend the analysis to two-dimensional spatial systems.

  5. Quantum entropy and uncertainty for two-mode squeezed, coherent and intelligent spin states

    NASA Technical Reports Server (NTRS)

    Aragone, C.; Mundarain, D.

    1993-01-01

    We compute the quantum entropy for monomode and two-mode systems set in squeezed states. Thereafter, the quantum entropy is also calculated for angular momentum algebra when the system is either in a coherent or in an intelligent spin state. These values are compared with the corresponding values of the respective uncertainties. In general, quantum entropies and uncertainties have the same minimum and maximum points. However, for coherent and intelligent spin states, it is found that some minima for the quantum entropy turn out to be uncertainty maxima. We feel that the quantum entropy we use provides the right answer, since it is given in an essentially unique way.

  6. Entanglement Entropy of d-DIMENSIONAL Black Hole and Quantum Isolated Horizon

    NASA Astrophysics Data System (ADS)

    Zhao, Hui-Hua; Li, Guang-Liang; Zhao, Ren; Ma, Meng-Sen; Zhang, Li-Chun

    2013-09-01

    Based on the works of Ghosh et al. who view the black hole entropy as the logarithm of the number of quantum states on the Quantum Isolated Horizon (QIH), the entropy of d-dimensional black hole is studied. According to the Unruh-Verlinde temperature deduced from the concept of entropic force, the statistical entropy of quantum fields under the background of d-dimensional spacetime is calculated by means of quantum statistics. The results reveal the relation between the entanglement entropy of black hole and the logarithm of the number of quantum states and display the effects of dimensions on the correction terms of the entanglement entropy.

  7. Information Flows? A Critique of Transfer Entropies

    NASA Astrophysics Data System (ADS)

    James, Ryan G.; Barnett, Nix; Crutchfield, James P.

    2016-06-01

    A central task in analyzing complex dynamics is to determine the loci of information storage and the communication topology of information flows within a system. Over the last decade and a half, diagnostics for the latter have come to be dominated by the transfer entropy. Via straightforward examples, we show that it and a derivative quantity, the causation entropy, do not, in fact, quantify the flow of information. At one and the same time they can overestimate flow or underestimate influence. We isolate why this is the case and propose several avenues to alternate measures for information flow. We also address an auxiliary consequence: The proliferation of networks as a now-common theoretical model for large-scale systems, in concert with the use of transferlike entropies, has shoehorned dyadic relationships into our structural interpretation of the organization and behavior of complex systems. This interpretation thus fails to include the effects of polyadic dependencies. The net result is that much of the sophisticated organization of complex systems may go undetected.

  8. Entanglement entropy in a periodically driven quantum Ising ring

    NASA Astrophysics Data System (ADS)

    Apollaro, Tony J. G.; Palma, G. Massimo; Marino, Jamir

    2016-10-01

    We numerically study the dynamics of entanglement entropy, induced by an oscillating time periodic driving of the transverse field, h (t ) , of a one-dimensional quantum Ising ring. We consider several realizations of h (t ) , and we find a number of results in analogy with entanglement entropy dynamics induced by a sudden quantum quench. After a short-time relaxation, the dynamics of entanglement entropy synchronizes with h (t ) , displaying an oscillatory behavior at the frequency of the driving. Synchronization in the dynamics of entanglement entropy is spoiled by the appearance of quasirevivals which fade out in the thermodynamic limit, and which we interpret using a quasiparticle picture adapted to periodic drivings. We show that the time-averaged entanglement entropy in the synchronized regime obeys a volume law scaling with the subsystem's size. Such result is reminiscent of a thermal state or a generalized Gibbs ensemble, although the system does not heat up towards infinite temperature as a consequence of the integrability of the model.

  9. Life, Information, Entropy, and Time

    PubMed Central

    Crofts, Antony R.

    2008-01-01

    Attempts to understand how information content can be included in an accounting of the energy flux of the biosphere have led to the conclusion that, in information transmission, one component, the semantic content, or “the meaning of the message,” adds no thermodynamic burden over and above costs arising from coding, transmission and translation. In biology, semantic content has two major roles. For all life forms, the message of the genotype encoded in DNA specifies the phenotype, and hence the organism that is tested against the real world through the mechanisms of Darwinian evolution. For human beings, communication through language and similar abstractions provides an additional supra-phenotypic vehicle for semantic inheritance, which supports the cultural heritages around which civilizations revolve. The following three postulates provide the basis for discussion of a number of themes that demonstrate some important consequences. (i) Information transmission through either pathway has thermodynamic components associated with data storage and transmission. (ii) The semantic content adds no additional thermodynamic cost. (iii) For all semantic exchange, meaning is accessible only through translation and interpretation, and has a value only in context. (1) For both pathways of semantic inheritance, translational and copying machineries are imperfect. As a consequence both pathways are subject to mutation and to evolutionary pressure by selection. Recognition of semantic content as a common component allows an understanding of the relationship between genes and memes, and a reformulation of Universal Darwinism. (2) The emergent properties of life are dependent on a processing of semantic content. The translational steps allow amplification in complexity through combinatorial possibilities in space and time. Amplification depends on the increased potential for complexity opened by 3D interaction specificity of proteins, and on the selection of useful variants

  10. Life, Information, Entropy, and Time

    PubMed Central

    Crofts, Antony R.

    2008-01-01

    Attempts to understand how information content can be included in an accounting of the energy flux of the biosphere have led to the conclusion that, in information transmission, one component, the semantic content, or “the meaning of the message,” adds no thermodynamic burden over and above costs arising from coding, transmission and translation. In biology, semantic content has two major roles. For all life forms, the message of the genotype encoded in DNA specifies the phenotype, and hence the organism that is tested against the real world through the mechanisms of Darwinian evolution. For human beings, communication through language and similar abstractions provides an additional supra-phenotypic vehicle for semantic inheritance, which supports the cultural heritages around which civilizations revolve. The following three postulates provide the basis for discussion of a number of themes that demonstrate some important consequences. (i) Information transmission through either pathway has thermodynamic components associated with data storage and transmission. (ii) The semantic content adds no additional thermodynamic cost. (iii) For all semantic exchange, meaning is accessible only through translation and interpretation, and has a value only in context. (1) For both pathways of semantic inheritance, translational and copying machineries are imperfect. As a consequence both pathways are subject to mutation and to evolutionary pressure by selection. Recognition of semantic content as a common component allows an understanding of the relationship between genes and memes, and a reformulation of Universal Darwinism. (2) The emergent properties of life are dependent on a processing of semantic content. The translational steps allow amplification in complexity through combinatorial possibilities in space and time. Amplification depends on the increased potential for complexity opened by 3D interaction specificity of proteins, and on the selection of useful variants

  11. Philosophy of Quantum Information and Entanglement

    NASA Astrophysics Data System (ADS)

    Bokulich, Alisa; Jaeger, Gregg

    2010-06-01

    Preface; Introduction; Part I. Quantum Entanglement and Nonlocality: 1. Nonlocality beyond quantum mechanics Sandu Popescu; 2. Entanglement and subsystems, entanglement beyond subsystems, and all that Lorenza Viola and Howard Barnum; 3. Formalism locality in quantum theory and quantum gravity Lucien Hardy; Part II. Quantum Probability: 4. Bell's inequality from the contextual probabilistic viewpoint Andrei Khrennikov; 5. Probabilistic theories: what is special about quantum mechanics? Giacomo Mauro D'Ariano; 6. What probabilities tell about quantum systems, with application to entropy and entanglement John Myers and Hadi Madjid; 7. Bayesian updating and information gain in quantum measurements Leah Henderson; Part III. Quantum Information: 8. Schumacher information and the philosophy of physics Arnold Duwell; 9. From physics to information theory and back Wayne Myrvold; 10. Information, immaterialism, and instrumentalism: old and new in quantum information Chris Timpson; Part IV. Quantum Communication and Computing: 11. Quantum computation: where does the speed-up come from? Jeff Bub; 12. Quantum mechanics, quantum computing and quantum cryptography Tai Wu.

  12. Quantum-corrected finite entropy of noncommutative acoustic black holes

    NASA Astrophysics Data System (ADS)

    Anacleto, M. A.; Brito, F. A.; Luna, G. C.; Passos, E.; Spinelly, J.

    2015-11-01

    In this paper we consider the generalized uncertainty principle in the tunneling formalism via Hamilton-Jacobi method to determine the quantum-corrected Hawking temperature and entropy for 2 + 1-dimensional noncommutative acoustic black holes. In our results we obtain an area entropy, a correction logarithmic in leading order, a correction term in subleading order proportional to the radiation temperature associated with the noncommutative acoustic black holes and an extra term that depends on a conserved charge. Thus, as in the gravitational case, there is no need to introduce the ultraviolet cut-off and divergences are eliminated.

  13. Increase of quantum volume entropy in presence of degenerate eigenenergies

    NASA Astrophysics Data System (ADS)

    Campisi, Michele

    2016-10-01

    The entropy of a classical thermally isolated Hamiltonian system is given by the logarithm of the measure of phase space enclosed by the constant energy hyper-surface, also known as volume entropy. It has been shown that on average the latter cannot decrease if the initial state is sampled from a classical passive distribution. Quantum extension of this result has been shown, but only for systems with a non-degenerate energy spectrum. Here we further extend to the case of possible degeneracies.

  14. GENERAL: Mutual Information and Relative Entropy of Sequential Effect Algebras

    NASA Astrophysics Data System (ADS)

    Wang, Jia-Mei; Wu, Jun-De; Cho, Minhyung

    2010-08-01

    In this paper, we introduce and investigate the mutual information and relative entropy on the sequential effect algebra, we also give a comparison of these mutual information and relative entropy with the classical ones by the venn diagrams. Finally, a nice example shows that the entropies of sequential effect algebra depend extremely on the order of its sequential product.

  15. Fuzzy geometry, entropy, and image information

    NASA Technical Reports Server (NTRS)

    Pal, Sankar K.

    1991-01-01

    Presented here are various uncertainty measures arising from grayness ambiguity and spatial ambiguity in an image, and their possible applications as image information measures. Definitions are given of an image in the light of fuzzy set theory, and of information measures and tools relevant for processing/analysis e.g., fuzzy geometrical properties, correlation, bound functions and entropy measures. Also given is a formulation of algorithms along with management of uncertainties for segmentation and object extraction, and edge detection. The output obtained here is both fuzzy and nonfuzzy. Ambiguity in evaluation and assessment of membership function are also described.

  16. Entropy of the information retrieved from black holes

    NASA Astrophysics Data System (ADS)

    Mersini-Houghton, Laura

    2016-07-01

    The retrieval of black hole information was recently presented in two interesting proposals in the ‘Hawking Radiation’ conference: a revised version by Hooft of a proposal he initially suggested 20 years ago and, a new proposal by Hawking. Both proposals address the problem of black hole information loss at the classical level and derive an expression for the scattering matrix. The former uses gravitation back reaction of incoming particles that imprints its information on the outgoing modes. The latter uses supertranslation symmetry of horizons to relate a phase delay of the outgoing wave packet compared to their incoming wave partners. The difficulty in both proposals is that the entropy obtained from them appears to be infinite. By including quantum effects into the Hawking and Hooft’s proposals, I show that a subtlety arising from the inescapable measurement process, the quantum Zeno effect, not only tames divergences but it actually recovers the correct 1/4 of the area Bekenstein-Hawking entropy law of black holes.

  17. Quantum information causality.

    PubMed

    Pitalúa-García, Damián

    2013-05-24

    How much information can a transmitted physical system fundamentally communicate? We introduce the principle of quantum information causality, which states the maximum amount of quantum information that a quantum system can communicate as a function of its dimension, independently of any previously shared quantum physical resources. We present a new quantum information task, whose success probability is upper bounded by the new principle, and show that an optimal strategy to perform it combines the quantum teleportation and superdense coding protocols with a task that has classical inputs. PMID:23745844

  18. Entanglement entropy in quantum spin chains with broken reflection symmetry

    SciTech Connect

    Kadar, Zoltan; Zimboras, Zoltan

    2010-09-15

    We investigate the entanglement entropy of a block of L sites in quasifree translation-invariant spin chains concentrating on the effect of reflection-symmetry breaking. The Majorana two-point functions corresponding to the Jordan-Wigner transformed fermionic modes are determined in the most general case; from these, it follows that reflection symmetry in the ground state can only be broken if the model is quantum critical. The large L asymptotics of the entropy are calculated analytically for general gauge-invariant models, which have, until now, been done only for the reflection-symmetric sector. Analytical results are also derived for certain nongauge-invariant models (e.g., for the Ising model with Dzyaloshinskii-Moriya interaction). We also study numerically finite chains of length N with a nonreflection-symmetric Hamiltonian and report that the reflection symmetry of the entropy of the first L spins is violated but the reflection-symmetric Calabrese-Cardy formula is recovered asymptotically. Furthermore, for noncritical reflection-symmetry-breaking Hamiltonians, we find an anomaly in the behavior of the saturation entropy as we approach the critical line. The paper also provides a concise but extensive review of the block-entropy asymptotics in translation-invariant quasifree spin chains with an analysis of the nearest-neighbor case and the enumeration of the yet unsolved parts of the quasifree landscape.

  19. Characterization of quantum phase transition using holographic entanglement entropy

    NASA Astrophysics Data System (ADS)

    Ling, Yi; Liu, Peng; Wu, Jian-Pin

    2016-06-01

    The entanglement exhibits extremal or singular behavior near quantum critical points (QCPs) in many condensed matter models. These intriguing phenomena, however, still call for a widely accepted understanding. In this paper we study this issue in holographic framework. We investigate the connection between the holographic entanglement entropy (HEE) and the quantum phase transition (QPT) in a lattice-deformed Einstein-Maxwell-Dilaton theory. Novel backgrounds exhibiting metal-insulator transitions (MIT) have been constructed in which both metallic phase and insulating phase have vanishing entropy density in zero temperature limit. We find that the first order derivative of HEE with respect to lattice parameters exhibits extremal behavior near QCPs. We propose that it would be a universal feature that HEE or its derivatives with respect to system parameters can characterize QPT in a generic holographic system. Our work opens a window for understanding the relation between entanglement and the QPT from a holographic perspective.

  20. Horizon entropy with loop quantum gravity methods

    NASA Astrophysics Data System (ADS)

    Pranzetti, Daniele; Sahlmann, Hanno

    2015-06-01

    We show that the spherically symmetric isolated horizon can be described in terms of an SU (2) connection and an su (2)-valued one-form, obeying certain constraints. The horizon symplectic structure is precisely the one of 3d gravity in a first order formulation. We quantize the horizon degrees of freedom in the framework of loop quantum gravity, with methods recently developed for 3d gravity with non-vanishing cosmological constant. Bulk excitations ending on the horizon act very similarly to particles in 3d gravity. The Bekenstein-Hawking law is recovered in the limit of imaginary Barbero-Immirzi parameter. Alternative methods of quantization are also discussed.

  1. Quantum information and computation

    SciTech Connect

    Bennett, C.H.

    1995-10-01

    A new quantum theory of communication and computation is emerging, in which the stuff transmitted or processed is not classical information, but arbitrary superpositions of quantum states. {copyright} 1995 {ital American} {ital Institute} {ital of} {ital Physics}.

  2. Quantum maximum-entropy principle for closed quantum hydrodynamic transport within a Wigner function formalism

    SciTech Connect

    Trovato, M.; Reggiani, L.

    2011-12-15

    By introducing a quantum entropy functional of the reduced density matrix, the principle of quantum maximum entropy is asserted as fundamental principle of quantum statistical mechanics. Accordingly, we develop a comprehensive theoretical formalism to construct rigorously a closed quantum hydrodynamic transport within a Wigner function approach. The theoretical formalism is formulated in both thermodynamic equilibrium and nonequilibrium conditions, and the quantum contributions are obtained by only assuming that the Lagrange multipliers can be expanded in powers of ({h_bar}/2{pi}){sup 2}. In particular, by using an arbitrary number of moments, we prove that (1) on a macroscopic scale all nonlocal effects, compatible with the uncertainty principle, are imputable to high-order spatial derivatives, both of the numerical density n and of the effective temperature T; (2) the results available from the literature in the framework of both a quantum Boltzmann gas and a degenerate quantum Fermi gas are recovered as a particular case; (3) the statistics for the quantum Fermi and Bose gases at different levels of degeneracy are explicitly incorporated; (4) a set of relevant applications admitting exact analytical equations are explicitly given and discussed; (5) the quantum maximum entropy principle keeps full validity in the classical limit, when ({h_bar}/2{pi}){yields}0.

  3. Universal corrections to entanglement entropy of local quantum quenches

    NASA Astrophysics Data System (ADS)

    David, Justin R.; Khetrapal, Surbhi; Kumar, S. Prem

    2016-08-01

    We study the time evolution of single interval Rényi and entanglement entropies following local quantum quenches in two dimensional conformal field theories at finite temperature for which the locally excited states have a finite temporal width ɛ. We show that, for local quenches produced by the action of a conformal primary field, the time dependence of Rényi and entanglement entropies at order ɛ2 is universal. It is determined by the expectation value of the stress tensor in the replica geometry and proportional to the conformal dimension of the primary field generating the local excitation. We also show that in CFTs with a gravity dual, the ɛ2 correction to the holographic entanglement entropy following a local quench precisely agrees with the CFT prediction. We then consider CFTs admitting a higher spin symmetry and turn on a higher spin chemical potential μ. We calculate the time dependence of the order ɛ2 correction to the entanglement entropy for small μ, and show that the contribution at order μ 2 is universal. We verify our arguments against exact results for minimal models and the free fermion theory.

  4. Comment on "Quantum Kaniadakis entropy under projective measurement".

    PubMed

    Bosyk, G M; Zozor, S; Holik, F; Portesi, M; Lamberti, P W

    2016-08-01

    We comment on the main result given by Ourabah et al. [Phys. Rev. E 92, 032114 (2015)PLEEE81539-375510.1103/PhysRevE.92.032114], noting that it can be derived as a special case of the more general study that we have provided in [Quantum Inf Process 15, 3393 (2016)10.1007/s11128-016-1329-5]. Our proof of the nondecreasing character under projective measurements of so-called generalized (h,ϕ) entropies (that comprise the Kaniadakis family as a particular case) has been based on majorization and Schur-concavity arguments. As a consequence, we have obtained that this property is obviously satisfied by Kaniadakis entropy but at the same time is fulfilled by all entropies preserving majorization. In addition, we have seen that our result holds for any bistochastic map, being a projective measurement a particular case. We argue here that looking at these facts from the point of view given in [Quantum Inf Process 15, 3393 (2016)10.1007/s11128-016-1329-5] not only simplifies the demonstrations but allows for a deeper understanding of the entropic properties involved.

  5. Comment on "Quantum Kaniadakis entropy under projective measurement".

    PubMed

    Bosyk, G M; Zozor, S; Holik, F; Portesi, M; Lamberti, P W

    2016-08-01

    We comment on the main result given by Ourabah et al. [Phys. Rev. E 92, 032114 (2015)PLEEE81539-375510.1103/PhysRevE.92.032114], noting that it can be derived as a special case of the more general study that we have provided in [Quantum Inf Process 15, 3393 (2016)10.1007/s11128-016-1329-5]. Our proof of the nondecreasing character under projective measurements of so-called generalized (h,ϕ) entropies (that comprise the Kaniadakis family as a particular case) has been based on majorization and Schur-concavity arguments. As a consequence, we have obtained that this property is obviously satisfied by Kaniadakis entropy but at the same time is fulfilled by all entropies preserving majorization. In addition, we have seen that our result holds for any bistochastic map, being a projective measurement a particular case. We argue here that looking at these facts from the point of view given in [Quantum Inf Process 15, 3393 (2016)10.1007/s11128-016-1329-5] not only simplifies the demonstrations but allows for a deeper understanding of the entropic properties involved. PMID:27627425

  6. Comment on "Quantum Kaniadakis entropy under projective measurement"

    NASA Astrophysics Data System (ADS)

    Bosyk, G. M.; Zozor, S.; Holik, F.; Portesi, M.; Lamberti, P. W.

    2016-08-01

    We comment on the main result given by Ourabah et al. [Phys. Rev. E 92, 032114 (2015), 10.1103/PhysRevE.92.032114], noting that it can be derived as a special case of the more general study that we have provided in [Quantum Inf Process 15, 3393 (2016), 10.1007/s11128-016-1329-5]. Our proof of the nondecreasing character under projective measurements of so-called generalized (h ,ϕ ) entropies (that comprise the Kaniadakis family as a particular case) has been based on majorization and Schur-concavity arguments. As a consequence, we have obtained that this property is obviously satisfied by Kaniadakis entropy but at the same time is fulfilled by all entropies preserving majorization. In addition, we have seen that our result holds for any bistochastic map, being a projective measurement a particular case. We argue here that looking at these facts from the point of view given in [Quantum Inf Process 15, 3393 (2016), 10.1007/s11128-016-1329-5] not only simplifies the demonstrations but allows for a deeper understanding of the entropic properties involved.

  7. Classicality condition on a system observable in a quantum measurement and a relative-entropy conservation law

    NASA Astrophysics Data System (ADS)

    Kuramochi, Yui; Ueda, Masahito

    2015-03-01

    We consider the information flow on a system observable X corresponding to a positive-operator-valued measure under a quantum measurement process Y described by a completely positive instrument from the viewpoint of the relative entropy. We establish a sufficient condition for the relative-entropy conservation law which states that the average decrease in the relative entropy of the system observable X equals the relative entropy of the measurement outcome of Y , i.e., the information gain due to measurement. This sufficient condition is interpreted as an assumption of classicality in the sense that there exists a sufficient statistic in a joint successive measurement of Y followed by X such that the probability distribution of the statistic coincides with that of a single measurement of X for the premeasurement state. We show that in the case when X is a discrete projection-valued measure and Y is discrete, the classicality condition is equivalent to the relative-entropy conservation for arbitrary states. The general theory on the relative-entropy conservation is applied to typical quantum measurement models, namely, quantum nondemolition measurement, destructive sharp measurements on two-level systems, a photon counting, a quantum counting, homodyne and heterodyne measurements. These examples except for the nondemolition and photon-counting measurements do not satisfy the known Shannon-entropy conservation law proposed by Ban [M. Ban, J. Phys. A: Math. Gen. 32, 1643 (1999), 10.1088/0305-4470/32/9/012], implying that our approach based on the relative entropy is applicable to a wider class of quantum measurements.

  8. Single particle in quantum gravity and Braunstein-Ghosh-Severini entropy of a spin network

    SciTech Connect

    Rovelli, Carlo; Vidotto, Francesca

    2010-02-15

    Passerini and Severini have recently shown that the Braunstein-Ghosh-Severini (BGS) entropy S{sub {Gamma}}=-Tr[{rho}{sub {Gamma}}log{rho}{sub {Gamma}}] of a certain density matrix {rho}{sub {Gamma}} naturally associated to a graph {Gamma}, is maximized, among all graphs with a fixed number of links and nodes, by regular graphs. We ask if this result can play a role in quantum gravity, and be related to the apparent regularity of the physical geometry of space. We show that in loop quantum gravity the matrix {rho}{sub {Gamma}} is precisely the Hamiltonian operator (suitably normalized) of a nonrelativistic quantum particle interacting with the quantum gravitational field, if we restrict elementary area and volume eigenvalues to a fixed value. This operator provides a spectral characterization of the physical geometry, and can be interpreted as a state describing the spectral information about the geometry available when geometry is measured by its physical interaction with matter. It is then tempting to interpret its BGS entropy S{sub {Gamma}} as a genuine physical entropy: we discuss the appeal and the difficulties of this interpretation.

  9. Magnetic quantum phase transitions and entropy in Van Vleck magnet

    NASA Astrophysics Data System (ADS)

    Lavanov, G. Yu.; Kalita, V. M.; Ivanova, I. M.; Loktev, V. M.

    2016-10-01

    Field-induced magnetic quantum phase transitions in the Van Vleck paramagnet with easy-plane single-ion anisotropy and competing Ising exchange between ions with the spin S=1 have been studied theoretically. The description was made by minimizing the Lagrange function at zero temperature (T=0) and the free energy at T ≠ 0 . Stable and unstable solutions of equations corresponding to the case ψ0 = | 0 > asymptotically transform into those following from the Lagrange function at T=0. First-order phase transitions from the Van Vleck paramagnet state into the ferromagnet one were found to take place at a sufficiently high single-ion anisotropy. The entropy of such a magnet was shown to grow with its magnetization, as it occurs for antiferromagnets. At the point of quantum phase transition, the entropy has a jump, which magnitude depends on the ratio between the Ising exchange and anisotropy constants, as well as on the temperature. The described magnetic phase transition was supposed to be accompanied by the magnetocaloric effect. In the case when the Ising exchange dominates over the single-ion anisotropy, the magnetization reversal of ferromagnetic state by an external field was shown to be a phase transition of the first kind, which does not belong to orientational ones and which should be regarded as a quantum order-order phase transition.

  10. Heat engine driven by purely quantum information.

    PubMed

    Park, Jung Jun; Kim, Kang-Hwan; Sagawa, Takahiro; Kim, Sang Wook

    2013-12-01

    The key question of this Letter is whether work can be extracted from a heat engine by using purely quantum mechanical information. If the answer is yes, what is its mathematical formula? First, by using a bipartite memory we show that the work extractable from a heat engine is bounded not only by the free energy change and the sum of the entropy change of an individual memory but also by the change of quantum mutual information contained inside the memory. We then find that the engine can be driven by purely quantum information, expressed as the so-called quantum discord, forming a part of the quantum mutual information. To confirm it, as a physical example we present the Szilard engine containing a diatomic molecule with a semipermeable wall.

  11. Thermodynamic and Information Entropy in Electroconvection

    NASA Astrophysics Data System (ADS)

    Cressman, John; Daum, Marcus; Patrick, David; Cerbus, Rory; Goldburg, Walter

    Transitions in driven systems often produce wild fluctuations that can be both detrimental and beneficial. Our fundamental understanding of these transients is inadequate to permit optimal interactions with systems ranging from biology, to energy generation, to finance. Here we report on experiments performed in electroconvecting liquid crystals where we abruptly change the electrical forcing across the sample from a state below defect turbulence into a state of defect turbulence. We simultaneously measure the electrical power flow through the liquid crystal as well as image the structure in the sample. These measurements enable us to simultaneously track the evolution of the thermodynamic and information entropies. Our experiments demonstrate that there are strong correlations between the fluctuations in these two entropic measures however they are not exact. We will discuss these discrepancies as well as the relevance of large transient fluctuations in non-equilibrium transitions in general.

  12. Statistics, holography, and black hole entropy in loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Ghosh, Amit; Noui, Karim; Perez, Alejandro

    2014-04-01

    In loop quantum gravity the quantum states of a black hole horizon consist of pointlike discrete quantum geometry excitations (or punctures) labeled by spin j. The excitations possibly carry other internal degrees of freedom, and the associated quantum states are eigenstates of the area A operator. The appropriately scaled area operator A/(8πℓ) can also be interpreted as the physical Hamiltonian associated with the quasilocal stationary observers located at a small distance ℓ from the horizon. Thus, the local energy is entirely accounted for by the geometric operator A. Assuming that: Close to the horizon the quantum state has a regular energy momentum tensor and hence the local temperature measured by stationary observers is the Unruh temperature. Degeneracy of matter states is exponential with the area exp(λA/ℓp2), which is supported by the well-established results of QFT in curved spacetimes, which do not determine λ but assert an exponential behavior. The geometric excitations of the horizon (punctures) are indistinguishable. And finally that the semiclassical limit the area of the black hole horizon is large in Planck units. It follows that: Up to quantum corrections, matter degrees of freedom saturate the holographic bound, viz., λ must be equal to 1/4. Up to quantum corrections, the statistical black hole entropy coincides with Bekenstein-Hawking entropy S =A/(4ℓp2). The number of horizon punctures goes like N∝√A/ℓp2 ; i.e., the number of punctures N remains large in the semiclassical limit. Fluctuations of the horizon area are small ΔA/A ∝(ℓp2/A)1/4, while fluctuations of the area of an individual puncture are large (large spins dominate). A precise notion of local conformal invariance of the thermal state is recovered in the A→∞ limit where the near horizon geometry becomes Rindler. We also show how the present model (constructed from loop quantum gravity) provides a regularization of (and gives a concrete meaning to) the formal

  13. A note on black hole entropy in loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Carlip, S.

    2015-08-01

    Several recent results have hinted that black hole thermodynamics in loop quantum gravity simplifies if one chooses an imaginary Barbero-Immirzi parameter γ =i. This suggests a connection with {SL}(2,{{C}}) or {SL}(2,{{R}}) conformal field theories at the ‘boundaries’ formed by spin network edges intersecting the horizon. I present a bit of background regarding the relevant conformal field theories, along with some speculations about how they might be used to count black hole states. I show, in particular, that a set of unproven but plausible assumptions can lead to a boundary conformal field theory whose density of states matches the Bekenstein-Hawking entropy.

  14. Hybrid quantum information processing

    SciTech Connect

    Furusawa, Akira

    2014-12-04

    I will briefly explain the definition and advantage of hybrid quantum information processing, which is hybridization of qubit and continuous-variable technologies. The final goal would be realization of universal gate sets both for qubit and continuous-variable quantum information processing with the hybrid technologies. For that purpose, qubit teleportation with a continuousvariable teleporter is one of the most important ingredients.

  15. Hybrid quantum information processing

    NASA Astrophysics Data System (ADS)

    Furusawa, Akira

    2014-12-01

    I will briefly explain the definition and advantage of hybrid quantum information processing, which is hybridization of qubit and continuous-variable technologies. The final goal would be realization of universal gate sets both for qubit and continuous-variable quantum information processing with the hybrid technologies. For that purpose, qubit teleportation with a continuousvariable teleporter is one of the most important ingredients.

  16. Minimax Quantum Tomography: Estimators and Relative Entropy Bounds.

    PubMed

    Ferrie, Christopher; Blume-Kohout, Robin

    2016-03-01

    A minimax estimator has the minimum possible error ("risk") in the worst case. We construct the first minimax estimators for quantum state tomography with relative entropy risk. The minimax risk of nonadaptive tomography scales as O(1/sqrt[N])-in contrast to that of classical probability estimation, which is O(1/N)-where N is the number of copies of the quantum state used. We trace this deficiency to sampling mismatch: future observations that determine risk may come from a different sample space than the past data that determine the estimate. This makes minimax estimators very biased, and we propose a computationally tractable alternative with similar behavior in the worst case, but superior accuracy on most states. PMID:26991163

  17. Quantum Gravity corrections and entropy at the Planck time

    SciTech Connect

    Basilakos, Spyros; Vagenas, Elias C.; Das, Saurya E-mail: saurya.das@uleth.ca

    2010-09-01

    We investigate the effects of Quantum Gravity on the Planck era of the universe. In particular, using different versions of the Generalized Uncertainty Principle and under specific conditions we find that the main Planck quantities such as the Planck time, length, mass and energy become larger by a factor of order 10−10{sup 4} compared to those quantities which result from the Heisenberg Uncertainty Principle. However, we prove that the dimensionless entropy enclosed in the cosmological horizon at the Planck time remains unchanged. These results, though preliminary, indicate that we should anticipate modifications in the set-up of cosmology since changes in the Planck era will be inherited even to the late universe through the framework of Quantum Gravity (or Quantum Field Theory) which utilizes the Planck scale as a fundamental one. More importantly, these corrections will not affect the entropic content of the universe at the Planck time which is a crucial element for one of the basic principles of Quantum Gravity named Holographic Principle.

  18. Quantum Entanglement and Information

    NASA Astrophysics Data System (ADS)

    Zeilinger, Anton

    2002-04-01

    The development of quantum entanglement presents a very interesting and typical case how fundamental reasearch leads to new technologically interesting concepts. Initially it was introduced by Einstein and Schroedinger because of its philosophical interest. This, together with Bell's theorem, led to experiments beginning in the early 1970-s which also were only motivated by their importance for the foundations of physics. Most remarkably, in recent years people discovered that quantum entanglement can be useful in completely novel ways of transmitting and processing of information with no analog in classical physics. Here the most developed areas are quantum communication, quantum cryptography, quantum teleportation and quantum computation. In the talk I will present the basics of these applications of entanglement and I will discuss some existing experimental realisations. Finally I will argue that, while it is impossible to foresee where the present development will lead us, it is very likely that in the end a novel kind of information technology will emerge.

  19. Quantum Hypothesis Testing and the Operational Interpretation of the Quantum Rényi Relative Entropies

    NASA Astrophysics Data System (ADS)

    Mosonyi, Milán; Ogawa, Tomohiro

    2015-03-01

    We show that the new quantum extension of Rényi's α-relative entropies, introduced recently by Müller-Lennert et al. (J Math Phys 54:122203, 2013) and Wilde et al. (Commun Math Phys 331(2):593-622, 2014), have an operational interpretation in the strong converse problem of quantum hypothesis testing. Together with related results for the direct part of quantum hypothesis testing, known as the quantum Hoeffding bound, our result suggests that the operationally relevant definition of the quantum Rényi relative entropies depends on the parameter α: for α < 1, the right choice seems to be the traditional definition , whereas for α > 1 the right choice is the newly introduced version .On the way to proving our main result, we show that the new Rényi α-relative entropies are asymptotically attainable by measurements for α > 1. From this, we obtain a new simple proof for their monotonicity under completely positive trace-preserving maps.

  20. Entropy, chaos, and excited-state quantum phase transitions in the Dicke model.

    PubMed

    Lóbez, C M; Relaño, A

    2016-07-01

    We study nonequilibrium processes in an isolated quantum system-the Dicke model-focusing on the role played by the transition from integrability to chaos and the presence of excited-state quantum phase transitions. We show that both diagonal and entanglement entropies are abruptly increased by the onset of chaos. Also, this increase ends in both cases just after the system crosses the critical energy of the excited-state quantum phase transition. The link between entropy production, the development of chaos, and the excited-state quantum phase transition is more clear for the entanglement entropy. PMID:27575109

  1. Similarity between quantum mechanics and thermodynamics: entropy, temperature, and Carnot cycle.

    PubMed

    Abe, Sumiyoshi; Okuyama, Shinji

    2011-02-01

    The similarity between quantum mechanics and thermodynamics is discussed. It is found that if the Clausius equality is imposed on the Shannon entropy and the analog of the quantity of heat, then the value of the Shannon entropy comes to formally coincide with that of the von Neumann entropy of the canonical density matrix, and pure-state quantum mechanics apparently transmutes into quantum thermodynamics. The corresponding quantum Carnot cycle of a simple two-state model of a particle confined in a one-dimensional infinite potential well is studied, and its efficiency is shown to be identical to the classical one.

  2. Entropy, chaos, and excited-state quantum phase transitions in the Dicke model

    NASA Astrophysics Data System (ADS)

    Lóbez, C. M.; Relaño, A.

    2016-07-01

    We study nonequilibrium processes in an isolated quantum system—the Dicke model—focusing on the role played by the transition from integrability to chaos and the presence of excited-state quantum phase transitions. We show that both diagonal and entanglement entropies are abruptly increased by the onset of chaos. Also, this increase ends in both cases just after the system crosses the critical energy of the excited-state quantum phase transition. The link between entropy production, the development of chaos, and the excited-state quantum phase transition is more clear for the entanglement entropy.

  3. Relating different quantum generalizations of the conditional Rényi entropy

    SciTech Connect

    Tomamichel, Marco; Berta, Mario; Hayashi, Masahito

    2014-08-15

    Recently a new quantum generalization of the Rényi divergence and the corresponding conditional Rényi entropies was proposed. Here, we report on a surprising relation between conditional Rényi entropies based on this new generalization and conditional Rényi entropies based on the quantum relative Rényi entropy that was used in previous literature. Our result generalizes the well-known duality relation H(A|B) + H(A|C) = 0 of the conditional von Neumann entropy for tripartite pure states to Rényi entropies of two different kinds. As a direct application, we prove a collection of inequalities that relate different conditional Rényi entropies and derive a new entropic uncertainty relation.

  4. Types of quantum information

    SciTech Connect

    Griffiths, Robert B.

    2007-12-15

    Quantum, in contrast to classical, information theory, allows for different incompatible types (or species) of information which cannot be combined with each other. Distinguishing these incompatible types is useful in understanding the role of the two classical bits in teleportation (or one bit in one-bit teleportation), for discussing decoherence in information-theoretic terms, and for giving a proper definition, in quantum terms, of 'classical information.' Various examples (some updating earlier work) are given of theorems which relate different incompatible kinds of information, and thus have no counterparts in classical information theory.

  5. Relativistic quantum information

    NASA Astrophysics Data System (ADS)

    Mann, R. B.; Ralph, T. C.

    2012-11-01

    Over the past few years, a new field of high research intensity has emerged that blends together concepts from gravitational physics and quantum computing. Known as relativistic quantum information, or RQI, the field aims to understand the relationship between special and general relativity and quantum information. Since the original discoveries of Hawking radiation and the Unruh effect, it has been known that incorporating the concepts of quantum theory into relativistic settings can produce new and surprising effects. However it is only in recent years that it has become appreciated that the basic concepts involved in quantum information science undergo significant revision in relativistic settings, and that new phenomena arise when quantum entanglement is combined with relativity. A number of examples illustrate that point. Quantum teleportation fidelity is affected between observers in uniform relative acceleration. Entanglement is an observer-dependent property that is degraded from the perspective of accelerated observers moving in flat spacetime. Entanglement can also be extracted from the vacuum of relativistic quantum field theories, and used to distinguish peculiar motion from cosmological expansion. The new quantum information-theoretic framework of quantum channels in terms of completely positive maps and operator algebras now provides powerful tools for studying matters of causality and information flow in quantum field theory in curved spacetimes. This focus issue provides a sample of the state of the art in research in RQI. Some of the articles in this issue review the subject while others provide interesting new results that will stimulate further research. What makes the subject all the more exciting is that it is beginning to enter the stage at which actual experiments can be contemplated, and some of the articles appearing in this issue discuss some of these exciting new developments. The subject of RQI pulls together concepts and ideas from

  6. Analytic continuation of black hole entropy in Loop Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Jibril, Ben Achour; Mouchet, Amaury; Noui, Karim

    2015-06-01

    We define the analytic continuation of the number of black hole microstates in Loop Quantum Gravity to complex values of the Barbero-Immirzi parameter γ. This construction deeply relies on the link between black holes and Chern-Simons theory. Technically, the key point consists in writing the number of microstates as an integral in the complex plane of a holomorphic function, and to make use of complex analysis techniques to perform the analytic continuation. Then, we study the thermodynamical properties of the corresponding system (the black hole is viewed as a gas of indistinguishable punctures) in the framework of the grand canonical ensemble where the energy is defined à la Frodden-Gosh-Perez from the point of view of an observer located close to the horizon. The semi-classical limit occurs at the Unruh temperature T U associated to this local observer. When γ = ± i, the entropy reproduces at the semi-classical limit the area law with quantum corrections. Furthermore, the quantum corrections are logarithmic provided that the chemical potential is fixed to the simple value μ = 2 T U.

  7. Entanglement entropy of U (1) quantum spin liquids

    NASA Astrophysics Data System (ADS)

    Pretko, Michael; Senthil, T.

    2016-09-01

    We here investigate the entanglement structure of the ground state of a (3 +1 )-dimensional U (1 ) quantum spin liquid, which is described by the deconfined phase of a compact U (1 ) gauge theory. A gapless photon is the only low-energy excitation, with matter existing as deconfined but gapped excitations of the system. It is found that, for a given bipartition of the system, the elements of the entanglement spectrum can be grouped according to the electric flux between the two regions, leading to a useful interpretation of the entanglement spectrum in terms of electric charges living on the boundary. The entanglement spectrum is also given additional structure due to the presence of the gapless photon. Making use of the Bisognano-Wichmann theorem and a local thermal approximation, these two contributions to the entanglement (particle and photon) are recast in terms of boundary and bulk contributions, respectively. Both pieces of the entanglement structure give rise to universal subleading terms (relative to the area law) in the entanglement entropy, which are logarithmic in the system size (logL ), as opposed to the subleading constant term in gapped topologically ordered systems. The photon subleading logarithm arises from the low-energy conformal field theory and is essentially local in character. The particle subleading logarithm arises due to the constraint of closed electric loops in the wave function and is shown to be the natural generalization of topological entanglement entropy to the U (1 ) spin liquid. This contribution to the entanglement entropy can be isolated by means of the Grover-Turner-Vishwanath construction (which generalizes the Kitaev-Preskill scheme to three dimensions).

  8. Information entropy of conditionally exactly solvable potentials

    SciTech Connect

    Dutta, D.; Roy, P.

    2011-03-15

    We evaluate Shannon entropy for the position and momentum eigenstates of some conditionally exactly solvable potentials which are isospectral to harmonic oscillator and whose solutions are given in terms of exceptional orthogonal polynomials. The Bialynicki-Birula-Mycielski inequality has also been tested for a number of states.

  9. Entanglement entropy of charged dilaton-axion black hole and quantum isolated horizon

    NASA Astrophysics Data System (ADS)

    Yang, Ze-Min; Li, Xiu-Lan; Gao, Ying

    2016-09-01

    Based on the work of Ghosh and Perez, we calculate the statistical entropy of charged dilaton-axion black hole. In the calculations we take the integral from the position of QIH to infinity, so the obtained entropy is the entanglement entropy outside the QIH. It is shown that only if the position of QIH is properly chosen the leading term of logarithm of the number of quantum states on the QIH is equal to the leading term of the entanglement entropy outside the black hole horizon, and both are the Bekenstein-Hawking entropy. The results reveal the relation between the entanglement entropy of black hole and the logarithm of the number of quantum states.

  10. Quantum hairs’ and entropy of the quantum isolated horizon from Chern-Simons theory

    NASA Astrophysics Data System (ADS)

    Majhi, Abhishek; Majumdar, Parthasarathi

    2014-10-01

    We articulate the fact that the loop quantum gravity (LQG) description of the quantum macrostates of black hole horizons, modeled as quantum isolated horizons (QIHs), is completely characterized in terms of two independent integer-valued ‘quantum hairs’, viz, the coupling constant (k) of the quantum SU(2) Chern-Simons (CS) theory describing QIH dynamics, and the number of punctures (N) produced by the bulk spin network edges piercing the isolated horizon (which act as pointlike sources for the CS fields). We demonstrate that the microcanonical entropy of macroscopic (both parameters assuming very large values) QIHs can be obtained directly from the microstates of this CS theory using standard statistical mechanical methods, without having to additionally postulate the horizon as an ideal gas of punctures, or incorporate any additional classical or semiclassical input from general relativity vis-a-vis the functional dependence of the isolated horizon mass on its area, or indeed, without having to restrict to any special class of spins. Requiring the validity of the Bekenstein-Hawking area law relates these two parameters (as an equilibrium ‘equation of state’), and consequently allows the Barbero-Immirzi parameter to take any real and positive value depending on the value of k/N. The logarithmic correction to the area law obtained a decade ago by R Kaul and one of us (PM), ensues straightforwardly, with precisely the coefficient -3/2, making it a signature of the LQG approach to black hole entropy.

  11. PREFACE: Quantum information processing

    NASA Astrophysics Data System (ADS)

    Briggs, Andrew; Ferry, David; Stoneham, Marshall

    2006-05-01

    Microelectronics and the classical information technologies transformed the physics of semiconductors. Photonics has given optical materials a new direction. Quantum information technologies, we believe, will have immense impact on condensed matter physics. The novel systems of quantum information processing need to be designed and made. Their behaviours must be manipulated in ways that are intrinsically quantal and generally nanoscale. Both in this special issue and in previous issues (see e.g., Spiller T P and Munro W J 2006 J. Phys.: Condens. Matter 18 V1-10) we see the emergence of new ideas that link the fundamentals of science to the pragmatism of market-led industry. We hope these papers will be followed by many others on quantum information processing in the Journal of Physics: Condensed Matter.

  12. Role of information theoretic uncertainty relations in quantum theory

    SciTech Connect

    Jizba, Petr; Dunningham, Jacob A.; Joo, Jaewoo

    2015-04-15

    Uncertainty relations based on information theory for both discrete and continuous distribution functions are briefly reviewed. We extend these results to account for (differential) Rényi entropy and its related entropy power. This allows us to find a new class of information-theoretic uncertainty relations (ITURs). The potency of such uncertainty relations in quantum mechanics is illustrated with a simple two-energy-level model where they outperform both the usual Robertson–Schrödinger uncertainty relation and Shannon entropy based uncertainty relation. In the continuous case the ensuing entropy power uncertainty relations are discussed in the context of heavy tailed wave functions and Schrödinger cat states. Again, improvement over both the Robertson–Schrödinger uncertainty principle and Shannon ITUR is demonstrated in these cases. Further salient issues such as the proof of a generalized entropy power inequality and a geometric picture of information-theoretic uncertainty relations are also discussed.

  13. Role of information theoretic uncertainty relations in quantum theory

    NASA Astrophysics Data System (ADS)

    Jizba, Petr; Dunningham, Jacob A.; Joo, Jaewoo

    2015-04-01

    Uncertainty relations based on information theory for both discrete and continuous distribution functions are briefly reviewed. We extend these results to account for (differential) Rényi entropy and its related entropy power. This allows us to find a new class of information-theoretic uncertainty relations (ITURs). The potency of such uncertainty relations in quantum mechanics is illustrated with a simple two-energy-level model where they outperform both the usual Robertson-Schrödinger uncertainty relation and Shannon entropy based uncertainty relation. In the continuous case the ensuing entropy power uncertainty relations are discussed in the context of heavy tailed wave functions and Schrödinger cat states. Again, improvement over both the Robertson-Schrödinger uncertainty principle and Shannon ITUR is demonstrated in these cases. Further salient issues such as the proof of a generalized entropy power inequality and a geometric picture of information-theoretic uncertainty relations are also discussed.

  14. Black Hole Entropy with and without Log Correction in Loop Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Mitra, P.

    2014-06-01

    Earlier calculations of black hole entropy in loop quantum gravity have given a term proportional to the area with a correction involving the logarithm of the area when the area eigenvalue is close to the classical area. However the calculations yield an entropy proportional to the area eigenvalue with no such correction when the area eigenvalue is large compared to the classical area.

  15. Quantum-corrected self-dual black hole entropy in tunneling formalism with GUP

    NASA Astrophysics Data System (ADS)

    Anacleto, M. A.; Brito, F. A.; Passos, E.

    2015-10-01

    In this paper we focus on the Hamilton-Jacobi method to determine the entropy of a self-dual black hole by using linear and quadratic GUPs (generalized uncertainty principles). We have obtained the Bekenstein-Hawking entropy of self-dual black holes and its quantum corrections that are logarithm and also of several other types.

  16. Reasonable fermionic quantum information theories require relativity

    NASA Astrophysics Data System (ADS)

    Friis, Nicolai

    2016-03-01

    We show that any quantum information theory based on anticommuting operators must be supplemented by a superselection rule deeply rooted in relativity to establish a reasonable notion of entanglement. While quantum information may be encoded in the fermionic Fock space, the unrestricted theory has a peculiar feature: the marginals of bipartite pure states need not have identical entropies, which leads to an ambiguous definition of entanglement. We solve this problem, by proving that it is removed by relativity, i.e., by the parity superselection rule that arises from Lorentz invariance via the spin-statistics connection. Our results hence unveil a fundamental conceptual inseparability of quantum information and the causal structure of relativistic field theory.

  17. Entropy of orthogonal polynomials with Freud weights and information entropies of the harmonic oscillator potential

    NASA Astrophysics Data System (ADS)

    Van Assche, W.; Yáñez, R. J.; Dehesa, J. S.

    1995-08-01

    The information entropy of the harmonic oscillator potential V(x)=1/2λx2 in both position and momentum spaces can be expressed in terms of the so-called ``entropy of Hermite polynomials,'' i.e., the quantity Sn(H):= -∫-∞+∞H2n(x)log H2n(x) e-x2dx. These polynomials are instances of the polynomials orthogonal with respect to the Freud weights w(x)=exp(-||x||m), m≳0. Here, a very precise and general result of the entropy of Freud polynomials recently established by Aptekarev et al. [J. Math. Phys. 35, 4423-4428 (1994)], specialized to the Hermite kernel (case m=2), leads to an important refined asymptotic expression for the information entropies of very excited states (i.e., for large n) in both position and momentum spaces, to be denoted by Sρ and Sγ, respectively. Briefly, it is shown that, for large values of n, Sρ+1/2logλ≂log(π√2n/e)+o(1) and Sγ-1/2log λ≂log(π√2n/e)+o(1), so that Sρ+Sγ≂log(2π2n/e2)+o(1) in agreement with the generalized indetermination relation of Byalinicki-Birula and Mycielski [Commun. Math. Phys. 44, 129-132 (1975)]. Finally, the rate of convergence of these two information entropies is numerically analyzed. In addition, using a Rakhmanov result, we describe a totally new proof of the leading term of the entropy of Freud polynomials which, naturally, is just a weak version of the aforementioned general result.

  18. Dynamics of Entropy in Quantum-like Model of Decision Making

    NASA Astrophysics Data System (ADS)

    Basieva, Irina; Khrennikov, Andrei; Asano, Masanari; Ohya, Masanori; Tanaka, Yoshiharu

    2011-03-01

    We present a quantum-like model of decision making in games of the Prisoner's Dilemma type. By this model the brain processes information by using representation of mental states in complex Hilbert space. Driven by the master equation the mental state of a player, say Alice, approaches an equilibrium point in the space of density matrices. By using this equilibrium point Alice determines her mixed (i.e., probabilistic) strategy with respect to Bob. Thus our model is a model of thinking through decoherence of initially pure mental state. Decoherence is induced by interaction with memory and external environment. In this paper we study (numerically) dynamics of quantum entropy of Alice's state in the process of decision making. Our analysis demonstrates that this dynamics depends nontrivially on the initial state of Alice's mind on her own actions and her prediction state (for possible actions of Bob.)

  19. Two faces of entropy and information in biological systems.

    PubMed

    Mitrokhin, Yuriy

    2014-10-21

    The article attempts to overcome the well-known paradox of contradictions between the emerging biological organization and entropy production in biological systems. It is assumed that quality, speculative correlation between entropy and antientropy processes taking place both in the past and today in the metabolic and genetic cellular systems may be perfectly authorized for adequate description of the evolution of biological organization. So far as thermodynamic entropy itself cannot compensate for the high degree of organization which exists in the cell, we discuss the mode of conjunction of positive entropy events (mutations) in the genetic systems of the past generations and the formation of organized structures of current cells. We argue that only the information which is generated in the conditions of the information entropy production (mutations and other genome reorganization) in genetic systems of the past generations provides the physical conjunction of entropy and antientropy processes separated from each other in time generations. It is readily apparent from the requirements of the Second law of thermodynamics.

  20. Entanglement entropy of local operators in quantum Lifshitz theory

    NASA Astrophysics Data System (ADS)

    Zhou, Tianci

    2016-09-01

    We study the growth of entanglement entropy (EE) of local operator excitation in the quantum Lifshitz model with dynamic exponent z  =  2. Specifically, we apply a local vertex operator to the groundstate at a distance l to the entanglement cut and calculate the EE as a function of time for the state’s subsequent time evolution. We find that the excess EE compared with the groundstate is a monotonically increasing function which is vanishingly small before the onset at t∼ {{l}2} and eventually saturates at a constant value proportional to the scaling dimension of the vertex operator. The quasi-particle picture can interpret the final saturation as the exhaustion of the quasi-particle pairs, while the diffusive nature of the time scale t∼ {{l}2} replaces the common causality constraint in CFT calculations. To further understand this property, we compute the excess EE of a small disk probe far from the excitation point and find chromatography patterns in EE generated by quasi-particles of different propagation speeds.

  1. Optimization of Secondary Concentrators with the Continuous Information Entropy Strategy

    NASA Astrophysics Data System (ADS)

    Schmidt, Tobias Christian; Ries, Harald

    2010-10-01

    In this contribution, a method for global optimization of noisy functions, the Continuous Information Entropy Strategy (CIES), is explained and its applicability for the optimization of solar concentrators is shown. The CIES is efficient because all decisions made during optimizations are based on criteria that are derived from the concept of information entropy. Two secondary concentrators have been optimized with the CIES. The optimized secondary concentrators convert circular light distributions of round focal spots to square light distributions to match with the shape of square PV cells. The secondary concentrators are highly efficient and have geometrical concentration ratios of 2.25 and 8 respectively. Part of this material has been published in: T. C. Schmidt, "Information Entropy-Based Decision Making in Optimization", Ph.D. Thesis, Philipps University Marburg, 2010.

  2. Atomistic-level non-equilibrium model for chemically reactive systems based on steepest-entropy-ascent quantum thermodynamics

    NASA Astrophysics Data System (ADS)

    Li, Guanchen; Al-Abbasi, Omar; von Spakovsky, Michael R.

    2014-10-01

    This paper outlines an atomistic-level framework for modeling the non-equilibrium behavior of chemically reactive systems. The framework called steepest- entropy-ascent quantum thermodynamics (SEA-QT) is based on the paradigm of intrinsic quantum thermodynamic (IQT), which is a theory that unifies quantum mechanics and thermodynamics into a single discipline with wide applications to the study of non-equilibrium phenomena at the atomistic level. SEA-QT is a novel approach for describing the state of chemically reactive systems as well as the kinetic and dynamic features of the reaction process without any assumptions of near-equilibrium states or weak-interactions with a reservoir or bath. Entropy generation is the basis of the dissipation which takes place internal to the system and is, thus, the driving force of the chemical reaction(s). The SEA-QT non-equilibrium model is able to provide detailed information during the reaction process, providing a picture of the changes occurring in key thermodynamic properties (e.g., the instantaneous species concentrations, entropy and entropy generation, reaction coordinate, chemical affinities, reaction rate, etc). As an illustration, the SEA-QT framework is applied to an atomistic-level chemically reactive system governed by the reaction mechanism F + H2 leftrightarrow FH + H.

  3. Theory of entropy production in quantum many-body systems

    NASA Astrophysics Data System (ADS)

    Solano-Carrillo, E.; Millis, A. J.

    2016-06-01

    We define the entropy operator as the negative of the logarithm of the density matrix, give a prescription for extracting its thermodynamically measurable part, and discuss its dynamics. For an isolated system we derive the first, second, and third laws of thermodynamics. For weakly coupled subsystems of an isolated system, an expression for the long-time limit of the expectation value of the rate of change of the thermodynamically measurable part of the entropy operator is derived and interpreted in terms of entropy production and entropy transport terms. The interpretation is justified by comparison to the known expression for the entropy production in an aged classical Markovian system with Gaussian fluctuations and by a calculation of the current-induced entropy production in a conductor with electron-phonon scattering.

  4. Kinetics of the Dynamical Information Shannon Entropy for Complex Systems

    NASA Astrophysics Data System (ADS)

    Yulmetyev, R. M.; Yulmetyeva, D. G.

    1999-08-01

    Kinetic behaviour of dynamical information Shannon entropy is discussed for complex systems: physical systems with non-Markovian property and memory in correlation approximation, and biological and physiological systems with sequences of the Markovian and non-Markovian random noises. For the stochastic processes, a description of the information entropy in terms of normalized time correlation functions is given. The influence and important role of two mutually dependent channels of the entropy change, correlation (creation or generation of correlations) and anti-correlation (decay or annihilation of correlation) is discussed. The method developed here is also used in analysis of the density fluctuations in liquid cesium obtained from slow neutron scattering data, fractal kinetics of the long-range fluctuation in the short-time human memory and chaotic dynamics of R-R intervals of human ECG.

  5. Entropy and Information Transmission in Causation and Retrocausation

    NASA Astrophysics Data System (ADS)

    Moddel, Garret

    2006-10-01

    Although experimental evidence for retrocausation exists, there are clearly subtleties to the phenomenon. The bilking paradox, in which one intervenes to eliminate a subsequent cause after a preceding effect has occurred, appears on the surface to show that retrocausation is logically impossible. In a previous paper, the second law of thermodynamics was invoked to show that the entropy in each process of a psi interaction (presentience, telepathy, remote perception, and psychokinesis) cannot decrease, prohibiting psi processes in which signals condense from background fluctuations. Here it is shown, perhaps contrary to one's intuition, that reversible processes cannot be influenced through retrocausation, but irreversible processes can. The increase in thermodynamic entropy in irreversible processes — which are generally described by Newtonian mechanics but not Lagrangian dynamics and Hamilton's Principle — is required for causation. Thermodynamically reversible processes cannot be causal and hence also cannot be retrocausal. The role of entropy in psi interactions is extended by using the bilking paradox to consider information transmission in retroactive psychokinesis (PK). PK efficiency, ηPK, is defined. A prediction of the analysis is that ηPK ⩽ H/H0, where H is the information uncertainty or entropy in the retro-PK agent's knowledge of the event that is to be influenced retrocausally. The information entropy can provide the necessary ingredient for non-reversibility, and hence retrocausation. Noise and bandwidth limitations in the communication to the agent of the outcome of the event increase the maximum PK efficiency. Avoidance of the bilking paradox does not bar a subject from using the premonition of an event to prevent it from occurring. The necessity for large information entropy, which is the expected value of the surprisal, is likely to be essential for any successful PK process, not just retro-PK processes. Hence uncertainty in the

  6. Quantum entanglement and informational activities of biomolecules

    NASA Astrophysics Data System (ADS)

    Al-Shargi, Hanan; Berkovich, Simon

    2009-03-01

    Our model of holographic Universe [1] explains the surprising property of quantum entanglement and reveals its biological implications. The suggested holographic mechanism handles 2D slices of the physical world as a whole. Fitting this simple holistic process in the Procrustean bed of individual particles interactions leads to intricacies of quantum theory with an unintelligible protrusion of distant correlations. Holographic medium imposes dependence of quantum effects on absolute positioning. Testing this prediction for a non-exponential radioactive decay could resolutely point to outside ``memory.'' The essence of Life is in the sophistication of macromolecules. Distinctions in biological information processing of nucleotides in DNA and amino acids in proteins are related to entropies of their structures. Randomness of genetic configurations as exposed by their maximal entropy is characteristic of passive identification rather than active storage functionality. Structural redundancy of proteins shows their operability, of which different foldings of prions is most indicative. Folding of one prion can reshape another prion without a direct contact appearing like ``quantum entanglement,'' or ``teleportation.'' Testing the surmised influence of absolute orientation on the prion reshaping can uncover the latency effects in the ``mad cow'' disease. 1. Simon Berkovich, TR-GWU-CS-07-006, http://www.cs.gwu.edu/research/reports.php

  7. Informational power of quantum measurements

    SciTech Connect

    Dall'Arno, Michele; D'Ariano, Giacomo Mauro; Sacchi, Massimiliano F.

    2011-06-15

    We introduce the informational power of a quantum measurement as the maximum amount of classical information that the measurement can extract from any ensemble of quantum states. We prove the additivity by showing that the informational power corresponds to the classical capacity of a quantum-classical channel. We restate the problem of evaluating the informational power as the maximization of the accessible information of a suitable ensemble. We provide a numerical algorithm to find an optimal ensemble and quantify the informational power.

  8. {theta} parameter in loop quantum gravity: Effects on quantum geometry and black hole entropy

    SciTech Connect

    Rezende, Danilo Jimenez; Perez, Alejandro

    2008-10-15

    The precise analog of the {theta}-quantization ambiguity of Yang-Mills theory exists for the real SU(2) connection formulation of general relativity. As in the former case {theta} labels representations of large gauge transformations, which are superselection sectors in loop quantum gravity. We show that unless {theta}=0, the (kinematical) geometric operators such as area and volume are not well defined on spin network states. More precisely the intersection of their domain with the dense set Cyl in the kinematical Hilbert space H of loop quantum gravity is empty. The absence of a well-defined notion of area operator acting on spin network states seems at first in conflict with the expected finite black hole entropy. However, we show that the black hole (isolated) horizon area--which in contrast to kinematical area is a (Dirac) physical observable--is indeed well defined, and quantized so that the black hole entropy is proportional to the area. The effect of {theta} is negligible in the semiclassical limit where proportionality to area holds.

  9. Competition between Homophily and Information Entropy Maximization in Social Networks

    PubMed Central

    Zhao, Jichang; Liang, Xiao; Xu, Ke

    2015-01-01

    In social networks, it is conventionally thought that two individuals with more overlapped friends tend to establish a new friendship, which could be stated as homophily breeding new connections. While the recent hypothesis of maximum information entropy is presented as the possible origin of effective navigation in small-world networks. We find there exists a competition between information entropy maximization and homophily in local structure through both theoretical and experimental analysis. This competition suggests that a newly built relationship between two individuals with more common friends would lead to less information entropy gain for them. We demonstrate that in the evolution of the social network, both of the two assumptions coexist. The rule of maximum information entropy produces weak ties in the network, while the law of homophily makes the network highly clustered locally and the individuals would obtain strong and trust ties. A toy model is also presented to demonstrate the competition and evaluate the roles of different rules in the evolution of real networks. Our findings could shed light on the social network modeling from a new perspective. PMID:26334994

  10. Competition between Homophily and Information Entropy Maximization in Social Networks.

    PubMed

    Zhao, Jichang; Liang, Xiao; Xu, Ke

    2015-01-01

    In social networks, it is conventionally thought that two individuals with more overlapped friends tend to establish a new friendship, which could be stated as homophily breeding new connections. While the recent hypothesis of maximum information entropy is presented as the possible origin of effective navigation in small-world networks. We find there exists a competition between information entropy maximization and homophily in local structure through both theoretical and experimental analysis. This competition suggests that a newly built relationship between two individuals with more common friends would lead to less information entropy gain for them. We demonstrate that in the evolution of the social network, both of the two assumptions coexist. The rule of maximum information entropy produces weak ties in the network, while the law of homophily makes the network highly clustered locally and the individuals would obtain strong and trust ties. A toy model is also presented to demonstrate the competition and evaluate the roles of different rules in the evolution of real networks. Our findings could shed light on the social network modeling from a new perspective.

  11. Dynamics of the information entropy in random processes

    NASA Astrophysics Data System (ADS)

    Yulmetyev, R. M.; Gafarov, F. M.

    1999-12-01

    The problem of the description of temporal evolution of the random variables in terms of the information (Shannon) entropy of correlation processes has been considered. The influence and important role of the two mutually dependent channels of the entropy alternation: correlation (creation or the generation of correlations) and anti-correlation (decay or the annihilation of correlation) have been discussed. The method developed is used for the analysis of chaotic dynamics of the long-range fluctuation in the short-time human memory.

  12. Quantum Markov chains, sufficiency of quantum channels, and Rényi information measures

    NASA Astrophysics Data System (ADS)

    Datta, Nilanjana; Wilde, Mark M.

    2015-12-01

    A short quantum Markov chain is a tripartite state {ρ }{ABC} such that system A can be recovered perfectly by acting on system C of the reduced state {ρ }{BC}. Such states have conditional mutual information I(A;B| C) equal to zero and are the only states with this property. A quantum channel {N} is sufficient for two states ρ and σ if there exists a recovery channel using which one can perfectly recover ρ from {N}(ρ ) and σ from {N}(σ ). The relative entropy difference D(ρ \\parallel σ )-D({N}(ρ )\\parallel {N}(σ )) is equal to zero if and only if {N} is sufficient for ρ and σ. In this paper, we show that these properties extend to Rényi generalizations of these information measures which were proposed in (Berta et al 2015 J. Math. Phys. 56 022205; Seshadreesan et al 2015 J. Phys. A: Math. Theor. 48 395303), thus providing an alternate characterization of short quantum Markov chains and sufficient quantum channels. These results give further support to these quantities as being legitimate Rényi generalizations of the conditional mutual information and the relative entropy difference. Along the way, we solve some open questions of Ruskai and Zhang, regarding the trace of particular matrices that arise in the study of monotonicity of relative entropy under quantum operations and strong subadditivity of the von Neumann entropy.

  13. Relative entropies in conformal field theory.

    PubMed

    Lashkari, Nima

    2014-08-01

    Relative entropy is a measure of distinguishability for quantum states, and it plays a central role in quantum information theory. The family of Renyi entropies generalizes to Renyi relative entropies that include, as special cases, most entropy measures used in quantum information theory. We construct a Euclidean path-integral approach to Renyi relative entropies in conformal field theory, then compute the fidelity and the relative entropy of states in one spatial dimension at zero and finite temperature using a replica trick. In contrast to the entanglement entropy, the relative entropy is free of ultraviolet divergences, and is obtained as a limit of certain correlation functions. The relative entropy of two states provides an upper bound on their trace distance.

  14. Relative entropies in conformal field theory.

    PubMed

    Lashkari, Nima

    2014-08-01

    Relative entropy is a measure of distinguishability for quantum states, and it plays a central role in quantum information theory. The family of Renyi entropies generalizes to Renyi relative entropies that include, as special cases, most entropy measures used in quantum information theory. We construct a Euclidean path-integral approach to Renyi relative entropies in conformal field theory, then compute the fidelity and the relative entropy of states in one spatial dimension at zero and finite temperature using a replica trick. In contrast to the entanglement entropy, the relative entropy is free of ultraviolet divergences, and is obtained as a limit of certain correlation functions. The relative entropy of two states provides an upper bound on their trace distance. PMID:25126908

  15. Effects of Shannon entropy and electric field on polaron in RbCl triangular quantum dot

    NASA Astrophysics Data System (ADS)

    M, Tiotsop; A, J. Fotue; S, C. Kenfack; N, Issofa; H, Fotsin; L, C. Fai

    2016-04-01

    In this paper, the time evolution of the quantum mechanical state of a polaron is examined using the Pekar type variational method on the condition of the electric-LO-phonon strong-coupling and polar angle in RbCl triangular quantum dot. We obtain the eigenenergies, and the eigenfunctions of the ground state, and the first excited state respectively. This system in a quantum dot can be treated as a two-level quantum system qubit and the numerical calculations are performed. The effects of Shannon entropy and electric field on the polaron in the RbCl triangular quantum dot are also studied.

  16. Maximal entanglement versus entropy for mixed quantum states

    SciTech Connect

    Wei, T.-C.; Goldbart, Paul M.; Kwiat, Paul G.; Nemoto, Kae; Munro, William J.; Verstraete, Frank

    2003-02-01

    Maximally entangled mixed states are those states that, for a given mixedness, achieve the greatest possible entanglement. For two-qubit systems and for various combinations of entanglement and mixedness measures, the form of the corresponding maximally entangled mixed states is determined primarily analytically. As measures of entanglement, we consider entanglement of formation, relative entropy of entanglement, and negativity; as measures of mixedness, we consider linear and von Neumann entropies. We show that the forms of the maximally entangled mixed states can vary with the combination of (entanglement and mixedness) measures chosen. Moreover, for certain combinations, the forms of the maximally entangled mixed states can change discontinuously at a specific value of the entropy. Along the way, we determine the states that, for a given value of entropy, achieve maximal violation of Bell's inequality.

  17. Wang-Landau method for calculating Rényi entropies in finite-temperature quantum Monte Carlo simulations.

    PubMed

    Inglis, Stephen; Melko, Roger G

    2013-01-01

    We implement a Wang-Landau sampling technique in quantum Monte Carlo (QMC) simulations for the purpose of calculating the Rényi entanglement entropies and associated mutual information. The algorithm converges an estimate for an analog to the density of states for stochastic series expansion QMC, allowing a direct calculation of Rényi entropies without explicit thermodynamic integration. We benchmark results for the mutual information on two-dimensional (2D) isotropic and anisotropic Heisenberg models, a 2D transverse field Ising model, and a three-dimensional Heisenberg model, confirming a critical scaling of the mutual information in cases with a finite-temperature transition. We discuss the benefits and limitations of broad sampling techniques compared to standard importance sampling methods.

  18. Entropy of massive quantum fields in de Sitter space-time

    NASA Astrophysics Data System (ADS)

    Takook, M. V.

    2016-04-01

    Using the quantum states or Hilbert spaces for the quantum field theory in de Sitter ambient space formalism the entropy of the massive quantum field theory is calculated. In this formalism, the homogeneous spaces which are used for construction of the unitary irreducible representation of de Sitter group are compact. The unique feature of this homogeneous space is that by imposing certain physical conditions its total number of quantum one-particle states, N1-p, becomes finite although the Hilbert space has infinite dimensions. N1-p is de Sitter invariant and a continuous function of the Hubble constant H and the eigenvalue of the Casimir operators of de Sitter group. The entropy of the quantum fields is finite and invariant for all inertial observers on de Sitter hyperboloid.

  19. Renyi entanglement entropy of interacting fermions calculated using the continuous-time quantum Monte Carlo method.

    PubMed

    Wang, Lei; Troyer, Matthias

    2014-09-12

    We present a new algorithm for calculating the Renyi entanglement entropy of interacting fermions using the continuous-time quantum Monte Carlo method. The algorithm only samples the interaction correction of the entanglement entropy, which by design ensures the efficient calculation of weakly interacting systems. Combined with Monte Carlo reweighting, the algorithm also performs well for systems with strong interactions. We demonstrate the potential of this method by studying the quantum entanglement signatures of the charge-density-wave transition of interacting fermions on a square lattice.

  20. Characterizing the dynamical semigroups that do not decrease a quantum entropy

    NASA Astrophysics Data System (ADS)

    Aniello, Paolo; Chruściński, Dariusz

    2016-08-01

    In finite dimensions, we provide characterizations of the quantum dynamical semigroups that do not decrease the von Neumann, the Tsallis and the Rényi entropies, as well as a family of functions of density operators strictly related to the Schatten norms. A few remarkable consequences—in particular, a description of the associated infinitesimal generators—are derived, and some significant examples are discussed. Extensions of these results to semigroups of trace-preserving positive (i.e., not necessarily completely positive) maps and to a more general class of quantum entropies are also considered.

  1. Quantum information does not exist

    NASA Astrophysics Data System (ADS)

    Duwell, Armond

    Some physicists seem to believe that quantum information theory requires a new concept of information (Jozsa, 1998, Quantum information and its properties. In: Hoi-Kwong Lo, S. Popescu, T. Spiller (Eds.), Introduction to Quantum Computation and Information, World Scientific, Singapore, (pp. 49-75); Deutsch & Hayden, 1999, Information flow in entangled quantum subsystems, preprint quant-ph/9906007). I will argue that no new concept is necessary. Shannon's concept of information is sufficient for quantum information theory. Properties that are cited to contrast quantum information and classical information (i.e., Shannon information) actually point to differences in our ability to manipulate, access, and transfer information depending on whether quantum systems, opposed to classical systems, are used in a communication system. I also demonstrate that conceptually puzzling phenomena in quantum information theory, such as dense coding, teleportation, and Schumacher coding, all of which are cited as evidence that a new concept of information is required, do not have to be regarded as such.

  2. Measuring entanglement entropy of a generic many-body system with a quantum switch.

    PubMed

    Abanin, Dmitry A; Demler, Eugene

    2012-07-13

    Entanglement entropy has become an important theoretical concept in condensed matter physics because it provides a unique tool for characterizing quantum mechanical many-body phases and new kinds of quantum order. However, the experimental measurement of entanglement entropy in a many-body system is widely believed to be unfeasible, owing to the nonlocal character of this quantity. Here, we propose a general method to measure the entanglement entropy. The method is based on a quantum switch (a two-level system) coupled to a composite system consisting of several copies of the original many-body system. The state of the switch controls how different parts of the composite system connect to each other. We show that, by studying the dynamics of the quantum switch only, the Rényi entanglement entropy of the many-body system can be extracted. We propose a possible design of the quantum switch, which can be realized in cold atomic systems. Our work provides a route towards testing the scaling of entanglement in critical systems as well as a method for a direct experimental detection of topological order.

  3. The permutation entropy rate equals the metric entropy rate for ergodic information sources and ergodic dynamical systems

    NASA Astrophysics Data System (ADS)

    Amigó, José M.; Kennel, Matthew B.; Kocarev, Ljupco

    2005-10-01

    Permutation entropy quantifies the diversity of possible orderings of the values a random or deterministic system can take, as Shannon entropy quantifies the diversity of values. We show that the metric and permutation entropy rates-measures of new disorder per new observed value-are equal for ergodic finite-alphabet information sources (discrete-time stationary stochastic processes). With this result, we then prove that the same holds for deterministic dynamical systems defined by ergodic maps on n-dimensional intervals. This result generalizes a previous one for piecewise monotone interval maps on the real line [C. Bandt, G. Keller, B. Pompe, Entropy of interval maps via permutations, Nonlinearity 15 (2002) 1595-1602.] at the expense of requiring ergodicity and using a definition of permutation entropy rate differing modestly in the order of two limits. The case of non-ergodic finite-alphabet sources is also studied and an inequality developed. Finally, the equality of permutation and metric entropy rates is extended to ergodic non-discrete information sources when entropy is replaced by differential entropy in the usual way.

  4. Local Stereo Matching Based on Information Entropy of Image

    NASA Astrophysics Data System (ADS)

    Geng, Yingnan

    2016-09-01

    Adaptive support-window algorithm is one of the simplest local algorithms for stereo matching. An important problem for adaptive support-window algorithm is to determine the appropriate support-window size, which is always hard to do and limits the validity of adaptive support-window algorithm. An appropriate support-window size must be selected adaptively based on image features. In this paper, information entropy of image is defined for stereo matching in the RGB vector space. Based on adaptive support-window, a new support-window selection algorithm, which uses information entropy of image to quantify image features such as illumination color and number of object contained in an image, is proposed. Experimental results evaluated on the Middlebury stereo benchmark show that our algorithm outperforms the conventional adaptive support-window algorithms.

  5. On entropy/information continuity in molecular electronic states

    NASA Astrophysics Data System (ADS)

    Nalewajski, Roman F.

    2016-04-01

    ARRAY(0x2421ba0) This article is dedicated to Prof. Andreas Savin on the occasion of his 65th birthday.Throughout the article x denotes a scalar quantity, x stands for the row- or column-vector, and x represents a square or rectangular matrix. The natural logarithm log = ln used in the Shannon entropy expresses the amount of information in nats (natural units): 1 nat = 1.44 bits.

  6. Skein theory and topological quantum registers: Braiding matrices and topological entanglement entropy of non-Abelian quantum Hall states

    SciTech Connect

    Hikami, Kazuhiro

    2008-07-15

    We study topological properties of quasi-particle states in the non-Abelian quantum Hall states. We apply a skein-theoretic method to the Read-Rezayi state whose effective theory is the SU(2){sub K} Chern-Simons theory. As a generalization of the Pfaffian (K = 2) and the Fibonacci (K = 3) anyon states, we compute the braiding matrices of quasi-particle states with arbitrary spins. Furthermore we propose a method to compute the entanglement entropy skein-theoretically. We find that the entanglement entropy has a nontrivial contribution called the topological entanglement entropy which depends on the quantum dimension of non-Abelian quasi-particle intertwining two subsystems.

  7. Min-entropy and quantum key distribution: Nonzero key rates for ''small'' numbers of signals

    SciTech Connect

    Bratzik, Sylvia; Mertz, Markus; Kampermann, Hermann; Bruss, Dagmar

    2011-02-15

    We calculate an achievable secret key rate for quantum key distribution with a finite number of signals by evaluating the quantum conditional min-entropy explicitly. The min-entropy for a classical random variable is the negative logarithm of the maximal value in its probability distribution. The quantum conditional min-entropy can be expressed in terms of the guessing probability, which we calculate for d-dimensional systems. We compare these key rates to previous approaches using the von Neumann entropy and find nonzero key rates for a smaller number of signals. Furthermore, we improve the secret key rates by modifying the parameter estimation step. Both improvements taken together lead to nonzero key rates for only 10{sup 4}-10{sup 5} signals. An interesting conclusion can also be drawn from the additivity of the min-entropy and its relation to the guessing probability: for a set of symmetric tensor product states, the optimal minimum-error discrimination (MED) measurement is the optimal MED measurement on each subsystem.

  8. Using the Renyi entropy to describe quantum dissipative systems in statistical mechanics

    NASA Astrophysics Data System (ADS)

    Kirchanov, V. S.

    2008-09-01

    We develop a formalism for describing quantum dissipative systems in statistical mechanics based on the quantum Renyi entropy. We derive the quantum Renyi distribution from the principle of maximum quantum Renyi entropy and differentiate this distribution (the temperature density matrix) with respect to the inverse temperature to obtain the Bloch equation. We then use the Feynman path integral with a modified Mensky functional to obtain a Lindblad-type equation. From this equation using projection operators, we derive the integro-differential equation for the reduced temperature statistical operator, an analogue of the Zwanzig equation in statistical mechanics, and find its formal solution in the form of a series in the class of summable functions.

  9. [Rapid identification of variable star spectrum based on information entropy].

    PubMed

    Cai, Jiang-hui; Meng, Wen-jun; Sun, Shi-wei; Zhao, Xu-jun; Zhang, Ji-fu

    2012-01-01

    Variable star is very important for mankind studying cosmic origin and evolution. For studying variable star, the chief difficulty results from the filtration and identification of variable star, that is how to validly identify variable star spectra from large high-dimensional star spectra data. The traditional outlier definition tries to find the difference between the outlier data and the general model by different ways, and then the result is quantitatively analyzed and filtrated. However, the time complexity of this method is over size and its results are inscrutable and unaccountable. Information entropy is a measure of the uncertainty associated with a random variable. In the present paper, information entropy is imported as the standard of dataset common mode. A novel method is proposed to identify the variable star spectrum rapidly based on information entropy. The time complexity of this method is observably reduced and the man-made impact is effectively overcome. The preliminary experimental results based on Sloan star spectrum data show that the method is workable for rapid identification of variable star spectrum. PMID:22497171

  10. Thermodynamical properties of triangular quantum wires: entropy, specific heat, and internal energy

    NASA Astrophysics Data System (ADS)

    Khordad, R.

    2016-07-01

    In the present work, thermodynamical properties of a GaAs quantum wire with equilateral triangle cross section are studied. First, the energy levels of the system are obtained by solving the Schrödinger equation. Second, the Tsallis formalism is applied to obtain entropy, internal energy, and specific heat of the system. We have found that the specific heat and entropy have certain physically meaningful values, which mean thermodynamic properties cannot take any continuous value, unlike classical thermodynamics in which they are considered as continuous quantities. Maximum of entropy increases with increasing the wire size. The specific heat is zero at special temperatures. Specific heat decreases with increasing temperature. There are several peaks in specific heat, and these are dependent on quantum wire size.

  11. Quantum Information: Opportunities and Challenges

    SciTech Connect

    Bennink, Ryan S

    2008-01-01

    Modern society is shaped by the ability to transmit, manipulate, and store large amounts of information. Although we tend to think of information as abstract, information is physical, and computing is a physical process. How then should we understand information in a quantum world, in which physical systems may exist in multiple states at once and are altered by the very act of observation? This question has evolved into an exciting new field of research called Quantum Information (QI). QI challenges many accepted rules and practices in computer science. For example, a quantum computer would turn certain hard problems into soft problems, and would render common computationally-secure encryption methods (such as RSA) insecure. At the same time, quantum communication would provide an unprecedented kind of intrinsic information security at the level of the smallest physical objects used to store or transmit the information. This talk provides a general introduction to the subject of quantum information and its relevance to cyber security. In the first part, two of the stranger aspects of quantum physics namely, superposition and uncertainty are explained, along with their relation to the concept of information. These ideas are illustrated with a few examples: quantum ID cards, quantum key distribution, and Grover s quantum search algorithm. The state-of-the-art in quantum computing and communication hardware is then discussed, along with the daunting technological challenges that must be overcome. Relevant experimental and theoretical efforts at ORNL are highlighted. The talk concludes with speculations on the short- and long-term impact of quantum information on cyber security.

  12. Maximum information entropy: a foundation for ecological theory.

    PubMed

    Harte, John; Newman, Erica A

    2014-07-01

    The maximum information entropy (MaxEnt) principle is a successful method of statistical inference that has recently been applied to ecology. Here, we show how MaxEnt can accurately predict patterns such as species-area relationships (SARs) and abundance distributions in macroecology and be a foundation for ecological theory. We discuss the conceptual foundation of the principle, why it often produces accurate predictions of probability distributions in science despite not incorporating explicit mechanisms, and how mismatches between predictions and data can shed light on driving mechanisms in ecology. We also review possible future extensions of the maximum entropy theory of ecology (METE), a potentially important foundation for future developments in ecological theory.

  13. Informational derivation of quantum theory

    NASA Astrophysics Data System (ADS)

    Chiribella, Giulio; D'Ariano, Giacomo Mauro; Perinotti, Paolo

    2011-07-01

    We derive quantum theory from purely informational principles. Five elementary axioms—causality, perfect distinguishability, ideal compression, local distinguishability, and pure conditioning—define a broad class of theories of information processing that can be regarded as standard. One postulate—purification—singles out quantum theory within this class.

  14. Informational derivation of quantum theory

    SciTech Connect

    Chiribella, Giulio; D'Ariano, Giacomo Mauro; Perinotti, Paolo

    2011-07-15

    We derive quantum theory from purely informational principles. Five elementary axioms - causality, perfect distinguishability, ideal compression, local distinguishability, and pure conditioning - define a broad class of theories of information processing that can be regarded as standard. One postulate - purification - singles out quantum theory within this class.

  15. Lateral Quantum Dots for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    House, Matthew Gregory

    The possibility of building a computer that takes advantage of the most subtle nature of quantum physics has been driving a lot of research in atomic and solid state physics for some time. It is still not clear what physical system or systems can be used for this purpose. One possibility that has been attracting significant attention from researchers is to use the spin state of an electron confined in a semiconductor quantum dot. The electron spin is magnetic in nature, so it naturally is well isolated from electrical fluctuations that can a loss of quantum coherence. It can also be manipulated electrically, by taking advantage of the exchange interaction. In this work we describe several experiments we have done to study the electron spin properties of lateral quantum dots. We have developed lateral quantum dot devices based on the silicon metal-oxide-semiconductor transistor, and studied the physics of electrons confined in these quantum dots. We measured the electron spin excited state lifetime, which was found to be as long as 30 ms at the lowest magnetic fields that we could measure. We fabricated and characterized a silicon double quantum dot. Using this double quantum dot design, we fabricated devices which combined a silicon double quantum dot with a superconducting microwave resonator. The microwave resonator was found to be sensitive to two-dimensional electrons in the transistor channel, which we measured and characterized. We developed a new method for extracting information from random telegraph signals, which are produced when we observe thermal fluctuations of electrons in quantum dots. The new statistical method, based on the hidden Markov model, allows us to detect spin-dependent effects in such fluctuations even though we are not able to directly observe the electron spin. We use this analysis technique on data from two experiments involving gallium arsenide quantum dots and use it to measure spin-dependent tunneling rates. Our results advance the

  16. Optical Hybrid Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Takeda, Shuntaro; Furusawa, Akira

    Historically, two complementary approaches to optical quantum information processing have been pursued: qubits and continuous-variables, each exploiting either particle or wave nature of light. However, both approaches have pros and cons. In recent years, there has been a significant progress in combining both approaches with a view to realizing hybrid protocols that overcome the current limitations. In this chapter, we first review the development of the two approaches with a special focus on quantum teleportation and its applications. We then introduce our recent research progress in realizing quantum teleportation by a hybrid scheme, and mention its future applications to universal and fault-tolerant quantum information processing.

  17. How an autonomous quantum Maxwell demon can harness correlated information

    NASA Astrophysics Data System (ADS)

    Chapman, Adrian; Miyake, Akimasa

    2015-12-01

    We study an autonomous quantum system which exhibits refrigeration under an information-work trade-off like a Maxwell demon. The system becomes correlated as a single "demon" qubit interacts sequentially with memory qubits while in contact with two heat reservoirs of different temperatures. Using strong subadditivity of the von Neumann entropy, we derive a global Clausius inequality to show thermodynamic advantages from access to correlated information. It is demonstrated, in a matrix product density operator formalism, that our demon can simultaneously realize refrigeration against a thermal gradient and erasure of information from its memory, which is impossible without correlations. The phenomenon can be even enhanced by the presence of quantum coherence.

  18. Creation of a low-entropy quantum gas of polar molecules in an optical lattice.

    PubMed

    Moses, Steven A; Covey, Jacob P; Miecnikowski, Matthew T; Yan, Bo; Gadway, Bryce; Ye, Jun; Jin, Deborah S

    2015-11-01

    Ultracold polar molecules, with their long-range electric dipolar interactions, offer a unique platform for studying correlated quantum many-body phenomena. However, realizing a highly degenerate quantum gas of molecules with a low entropy per particle is challenging. We report the synthesis of a low-entropy quantum gas of potassium-rubidium molecules (KRb) in a three-dimensional optical lattice. We simultaneously load into the optical lattice a Mott insulator of bosonic Rb atoms and a single-band insulator of fermionic K atoms. Then, using magnetoassociation and optical state transfer, we efficiently produce ground-state molecules in the lattice at those sites that contain one Rb and one K atom. The achieved filling fraction of 25% should enable future studies of transport and entanglement propagation in a many-body system with long-range dipolar interactions. PMID:26542566

  19. Vacuum viscosity and entropy generation in quantum gravitational processes in the early universe

    NASA Astrophysics Data System (ADS)

    Hu, B. L.

    Entropy generation in quantum gravitational processes due to vacuum polarization and particle production in the early universe is discussed. The quantum processes of spontaneous and induced particle production from the vacuum and n-particle state as well as the classical process of non-adiabatic frequency shifts of normal modes of the system are described in the context of an adiabatic formulation of finite temperature quantum field theory and the thermodynamics of relativistic imperfect fluids. Vacuum viscosity arising from the interaction of the field vacua with dynamical spacetimes and kinematic viscosity arising from the non-adiabatic expansion of relativistic gases are defined and calculated for a number of representative systems of fields and background spacetimes. Their use in the description of dissipative processes in the early universe and their role in the definition of gravitational entropy are explored.

  20. Stability theorem of depolarizing channels for the minimal output quantum Rényi entropies

    NASA Astrophysics Data System (ADS)

    Bae, Eunok; Gour, Gilad; Lee, Soojoon; Park, Jeonghoon; Sanders, Barry C.

    2016-03-01

    The stability theorem of the depolarizing channel states that if a state is close to achieving the minimal/maximal output value of a certain quantity through the channel, then it must be close to an input state giving the minimal/maximal value. We show that the stability theorem of the depolarizing channel holds for the output quantum p-Rényi entropy for p≥slant 2 or p = 1, which is an extension of the known case p = 2. As an application, we present a protocol in which Bob determines whether Alice prepares a pure quantum state close to a product state. In the protocol, Alice transmits to Bob multiple copies of a pure state through a depolarizing channel, and Bob estimates its output quantum p-Rényi entropy. By using our stability theorem, we show that Bob can determine whether her preparation is appropriate.

  1. Generalized information (entanglement) entropies depending on the probability (density matrix), (modified gravity)

    NASA Astrophysics Data System (ADS)

    Obregón, Octavio; Cabo Bizet, Nana Geraldine

    2016-03-01

    Generalized information (entanglement) entropy(ies) that depend only on the probability (the density matrix) will be exhibited. It will be shown that these generalized information entropy(ies) are obtained by means of the superstatistics proposal and they correspond to generalized entanglement entropy(ies) that are at the same time a consequence of generalizing the Replica trick. Following the entropic force formulation, these generalized entropy(ies) provide a modified Newtońs law of gravitation. We discuss the difficulties to get an associated theory of gravity. Moreover, our results show corrections to the von Neumann entropy S0 that are larger than the usual UV ones and also than the corrections to the length dependent AdS3 entropy which result comparable to the UV ones. The correction terms due to the new entropy would modify the Ryu-Takayanagi identification between the CFT and the gravitational AdS3 entropies.

  2. Universal corrections to the entanglement entropy in gapped quantum spin chains: A numerical study

    NASA Astrophysics Data System (ADS)

    Levi, Emanuele; Castro-Alvaredo, Olalla A.; Doyon, Benjamin

    2013-09-01

    We carry out a numerical study of the bipartite entanglement entropy in the gapped regime of two paradigmatic quantum spin chain models: the Ising chain in an external magnetic field and the antiferromagnetic XXZ model. The universal scaling limit of these models is described by the massive Ising field theory and the SU(2)-Thirring (sine-Gordon) model, respectively. We may therefore exploit quantum field theoretical results to predict the behavior of the entropy. We numerically confirm that in the scaling limit, corrections to the saturation of the entropy at large region size are proportional to a modified Bessel function of the first kind, K0(2mr), where m is a mass scale (the inverse correlation length) and r the length of the region under consideration. The proportionality constant is simply related to the number of particle types in the universal spectrum. This was originally predicted by J. L. Cardy, O. A. Castro-Alvaredo, and B. Doyon [J. Stat. Phys.JSTPBS0022-471510.1007/s10955-007-9422-x 130, 129 (2008)] and B. Doyon [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.031602 102, 031602 (2009)] for two-dimensional quantum field theories. Away from the universal region our numerics suggest an entropic behavior following quite closely the quantum field theory prediction, except for extra dependencies on the correlation length.

  3. Hybrid quantum information processing

    NASA Astrophysics Data System (ADS)

    Furusawa, Akira

    2013-03-01

    There are two types of schemes for quantum information processing (QIP). One is based on qubits, and the other is based on continuous variables (CVs), where the computational basis for qubit QIP is { | 0 > , | 1 > } and that for CV QIP is { | x > } (- ∞ < x < ∞). A universal gate set for qubit QIP is {`bit flip'σx, `phase flip'σz, `Hadamard gate'H, ` π / 8 gate', `controlled NOT (CNOT) gate'}. Similarly, a universal gate set for CV QIP is {` x-displacement' D& circ; (x) , ` p-displacement' D& circ; (ip) , `Fourier gate' F& circ;, `cubic phase gate'e ikxcirc;3, `quantum non-demolition (QND) gate'}. There is one-to-one correspondence between them. CV version of `bit flip'σx is ` x-displacement' D& circ; (x) , which changes the value of the computational basis. Similarly, CV version of `phase flip'σz is ` p-displacement' D& circ; (ip) , where `phase flip'σz switches the ``value'' of `conjugate basis' of qubit { | + > , | - > } (| +/- > = (| 0 > +/- | 1 >) / √{ 2}) and ` p-displacement' D& circ; (ip) changes the value of CV conjugate basis { | p > }. `Hadamard' and `Fourier' gates transform computational bases to respective conjugate bases. CV version of ` π / 8 gate' is a `cubic phase gate'e ikxcirc;3, and CV version of CNOT gate is a QND gate. However, the origin of nonlinearity for QIP is totally different, here the very basic nonlinear operation is calculation of multiplication and of course it is the heart of information processing. The nonlinearity of qubit QIP comes from a CNOT gate, while that of CV QIP comes from a cubic phase gate. Since nonlinear operations are harder to realize compared to linear operations, the most difficult operation for qubit is a CNOT gate, while the counter part, a QND gate, is not so difficult. CNOT and QND gates are both entangling gates, it follows that creating entanglement is easier for CV QIP compared to qubit QIP. Here, creating entanglement is the heart of QIP. So, it is a big advantage of CV QIP. On

  4. Quantum communication and information processing

    NASA Astrophysics Data System (ADS)

    Beals, Travis Roland

    Quantum computers enable dramatically more efficient algorithms for solving certain classes of computational problems, but, in doing so, they create new problems. In particular, Shor's Algorithm allows for efficient cryptanalysis of many public-key cryptosystems. As public key cryptography is a critical component of present-day electronic commerce, it is crucial that a working, secure replacement be found. Quantum key distribution (QKD), first developed by C.H. Bennett and G. Brassard, offers a partial solution, but many challenges remain, both in terms of hardware limitations and in designing cryptographic protocols for a viable large-scale quantum communication infrastructure. In Part I, I investigate optical lattice-based approaches to quantum information processing. I look at details of a proposal for an optical lattice-based quantum computer, which could potentially be used for both quantum communications and for more sophisticated quantum information processing. In Part III, I propose a method for converting and storing photonic quantum bits in the internal state of periodically-spaced neutral atoms by generating and manipulating a photonic band gap and associated defect states. In Part II, I present a cryptographic protocol which allows for the extension of present-day QKD networks over much longer distances without the development of new hardware. I also present a second, related protocol which effectively solves the authentication problem faced by a large QKD network, thus making QKD a viable, information-theoretic secure replacement for public key cryptosystems.

  5. Correlations in quantum thermodynamics: Heat, work, and entropy production

    PubMed Central

    Alipour, S.; Benatti, F.; Bakhshinezhad, F.; Afsary, M.; Marcantoni, S.; Rezakhani, A. T.

    2016-01-01

    We provide a characterization of energy in the form of exchanged heat and work between two interacting constituents of a closed, bipartite, correlated quantum system. By defining a binding energy we derive a consistent quantum formulation of the first law of thermodynamics, in which the role of correlations becomes evident, and this formulation reduces to the standard classical picture in relevant systems. We next discuss the emergence of the second law of thermodynamics under certain—but fairly general—conditions such as the Markovian assumption. We illustrate the role of correlations and interactions in thermodynamics through two examples. PMID:27767124

  6. Quantum Tomograms and Their Application in Quantum Information Science

    NASA Astrophysics Data System (ADS)

    Fedorov, Aleksey K.; Yurchenko, Stanislav O.

    2013-02-01

    This note is devoted to quantum tomograms application in quantum information science. Representation for quantum tomograms of continuous variables via Feynman path integrals is considered. Due to this construction quantum tomograms of harmonic oscillator are obtained. Application tomograms in causal analysis of quantum states is presented. Two qubit maximum entangled and "quantum-classical" states have been analyzed by tomographic causal analysis of quantum states.

  7. Note on a Family of Monotone Quantum Relative Entropies

    NASA Astrophysics Data System (ADS)

    Deuchert, Andreas; Hainzl, Christian; Seiringer, Robert

    2015-10-01

    Given a convex function and two hermitian matrices A and B, Lewin and Sabin study in (Lett Math Phys 104:691-705, 2014) the relative entropy defined by . Among other things, they prove that the so-defined quantity is monotone if and only if is operator monotone. The monotonicity is then used to properly define for bounded self-adjoint operators acting on an infinite-dimensional Hilbert space by a limiting procedure. More precisely, for an increasing sequence of finite-dimensional projections with strongly, the limit is shown to exist and to be independent of the sequence of projections . The question whether this sequence converges to its "obvious" limit, namely , has been left open. We answer this question in principle affirmatively and show that . If the operators A and B are regular enough, that is ( A - B), and are trace-class, the identity holds.

  8. Customized lifting multiwavelet packet information entropy for equipment condition identification

    NASA Astrophysics Data System (ADS)

    Chen, Jinglong; Zuo, Ming J.; Zi, Yanyang; He, Zhengjia; Yuan, Jing; Chen, Xuefeng

    2013-09-01

    Condition identification of mechanical equipment from vibration measurement data is significant to avoid economic loss caused by unscheduled breakdowns and catastrophic accidents. However, this task still faces challenges due to the complexity of equipment and the harsh environment. This paper provides a possibility for equipment condition identification by proposing a method called customized lifting multiwavelet packet information entropy. Benefiting from the properties of multi-resolution analysis and multiple wavelet basis functions, the multiwavelet method has advantages in characterizing non-stationary vibration signals. In order to realize the accurate detection and identification of the condition features, a customized lifting multiwavelet packet is constructed via a multiwavelet lifting scheme. Then the vibration signal from the mechanical equipment is processed by the customized lifting multiwavelet packet transform. The relative energy in each frequency band of the multiwavelet packet transform coefficients that equals a percentage of the whole signal energy is taken as the probability. The normalized information entropy is obtained based on the relative energy to describe the condition of a mechanical system. The proposed method is applied to the condition identification of a rolling mill and a demountable disk-drum aero-engine. The results support the feasibility of the proposed method in equipment condition identification.

  9. Minimal Rényi-Ingarden-Urbanik Entropy of Multipartite Quantum States

    NASA Astrophysics Data System (ADS)

    Enríquez, Marco; Puchała, Zbigniew; Życzkowski, Karol

    2015-07-01

    We study the entanglement of a pure state of a composite quantum system consisting of several subsystems with $d$ levels each. It can be described by the R\\'enyi-Ingarden-Urbanik entropy $S_q$ of a decomposition of the state in a product basis, minimized over all local unitary transformations. In the case $q=0$ this quantity becomes a function of the rank of the tensor representing the state, while in the limit $q \\to \\infty$ the entropy becomes related to the overlap with the closest separable state and the geometric measure of entanglement. For any bipartite system the entropy $S_1$ coincides with the standard entanglement entropy. We analyze the distribution of the minimal entropy for random states of three and four-qubit systems. In the former case the distributions of $3$-tangle is studied and some of its moments are evaluated, while in the latter case we analyze the distribution of the hyperdeterminant. The behavior of the maximum overlap of a three-qudit system with the closest separable state is also investigated in the asymptotic limit.

  10. First principle nonlinear quantum dynamics using a correlation-based von Neumann entropy

    NASA Astrophysics Data System (ADS)

    Westermann, Till; Manthe, Uwe

    2012-05-01

    A new concept to describe the quantum dynamics in complex systems is suggested. It extends established schemes based on the Dirac-Frenkel variation principle, e.g., the multi-configurational time-dependent Hartree (MCTDH) approach. The concept is based on a correlation-based von Neumann entropy (CvN-entropy) definition measuring the complexity of the wavefunction. Equations of motion are derived using a CvN-entropy constraint in the variational principle and result in a generally applicable effective Hamiltonian. It consists of the standard Hamilton operator and an additional nonlinear operator which limits the complexity of the wavefunction. Effectively, this nonlinear operator absorbs complex structures which are emerging in the wavefunction and allows one to introduce non-norm conserving equations of motion. Important aspects of the new concept are outlined studying the wave packet propagation on the diabatic B2 potential energy surfaces of NO2. First, it is demonstrated that during standard wave packet propagation the CvN-entropy increases strongly with time roughly independent of the coordinate systems employed. Second, one finds that employing CvN-entropy constrained MCTDH propagation yields improved wave function accuracy on longer time scales while compromising on the short time accuracy. Third, the loss of the wavefunction's norm is directly related to the overlap with the exact wavefunction. This provides an error estimate available without knowing an exact reference.

  11. First principle nonlinear quantum dynamics using a correlation-based von Neumann entropy.

    PubMed

    Westermann, Till; Manthe, Uwe

    2012-05-28

    A new concept to describe the quantum dynamics in complex systems is suggested. It extends established schemes based on the Dirac-Frenkel variation principle, e.g., the multi-configurational time-dependent Hartree (MCTDH) approach. The concept is based on a correlation-based von Neumann entropy (CvN-entropy) definition measuring the complexity of the wavefunction. Equations of motion are derived using a CvN-entropy constraint in the variational principle and result in a generally applicable effective Hamiltonian. It consists of the standard Hamilton operator and an additional nonlinear operator which limits the complexity of the wavefunction. Effectively, this nonlinear operator absorbs complex structures which are emerging in the wavefunction and allows one to introduce non-norm conserving equations of motion. Important aspects of the new concept are outlined studying the wave packet propagation on the diabatic B(2) potential energy surfaces of NO(2). First, it is demonstrated that during standard wave packet propagation the CvN-entropy increases strongly with time roughly independent of the coordinate systems employed. Second, one finds that employing CvN-entropy constrained MCTDH propagation yields improved wave function accuracy on longer time scales while compromising on the short time accuracy. Third, the loss of the wavefunction's norm is directly related to the overlap with the exact wavefunction. This provides an error estimate available without knowing an exact reference. PMID:22667549

  12. Reduced Density Matrix and Entanglement Entropy of Permutationally Invariant Quantum Many-Body Systems

    NASA Astrophysics Data System (ADS)

    Popkov, Vladislav; Salerno, Mario

    2013-06-01

    In this paper we discuss the properties of the reduced density matrix of quantum many body systems with permutational symmetry and present basic quantification of the entanglement in terms of the von Neumann (VNE), Renyi and Tsallis entropies. In particular, we show, on the specific example of the spin 1/2 Heisenberg model, how the RDM acquires a block diagonal form with respect to the quantum number k fixing the polarization in the subsystem conservation of Sz and with respect to the irreducible representations of the Sn group. Analytical expression for the RDM elements and for the RDM spectrum are derived for states of arbitrary permutational symmetry and for arbitrary polarizations. The temperature dependence and scaling of the VNE across a finite temperature phase transition is discussed and the RDM moments and the Rényi and Tsallis entropies calculated both for symmetric ground states of the Heisenberg chain and for maximally mixed states.

  13. Reduced Density Matrix and Entanglement Entropy of Permutationally Invariant Quantum Many-Body Systems

    NASA Astrophysics Data System (ADS)

    Popkov, Vladislav; Salerno, Mario

    2012-11-01

    In this paper we discuss the properties of the reduced density matrix of quantum many body systems with permutational symmetry and present basic quantification of the entanglement in terms of the von Neumann (VNE), Renyi and Tsallis entropies. In particular, we show, on the specific example of the spin 1/2 Heisenberg model, how the RDM acquires a block diagonal form with respect to the quantum number k fixing the polarization in the subsystem conservation of Sz and with respect to the irreducible representations of the Sn group. Analytical expression for the RDM elements and for the RDM spectrum are derived for states of arbitrary permutational symmetry and for arbitrary polarizations. The temperature dependence and scaling of the VNE across a finite temperature phase transition is discussed and the RDM moments and the Rényi and Tsallis entropies calculated both for symmetric ground states of the Heisenberg chain and for maximally mixed states.

  14. Entanglement entropy and mutual information in Bose-Einstein condensates

    SciTech Connect

    Ding Wenxin; Yang Kun

    2009-07-15

    In this paper we study the entanglement properties of free nonrelativistic Bose gases. At zero temperature, we calculate the bipartite block entanglement entropy of the system and find that it diverges logarithmically with the particle number in the subsystem. For finite temperatures, we study the mutual information between the two blocks. We first analytically study an infinite-range hopping model, then numerically study a set of long-range hopping models in one dimension that exhibit Bose-Einstein condensation. In both cases we find that a Bose-Einstein condensate, if present, makes a divergent contribution to the mutual information which is proportional to the logarithm of the number of particles in the condensate in the subsystem. The prefactor of the logarithmic divergent term is model dependent.

  15. Models, Entropy and Information of Temporal Social Networks

    NASA Astrophysics Data System (ADS)

    Zhao, Kun; Karsai, Márton; Bianconi, Ginestra

    Temporal social networks are characterized by heterogeneous duration of contacts, which can either follow a power-law distribution, such as in face-to-face interactions, or a Weibull distribution, such as in mobile-phone communication. Here we model the dynamics of face-to-face interaction and mobile phone communication by a reinforcement dynamics, which explains the data observed in these different types of social interactions. We quantify the information encoded in the dynamics of these networks by the entropy of temporal networks. Finally, we show evidence that human dynamics is able to modulate the information present in social network dynamics when it follows circadian rhythms and when it is interfacing with a new technology such as the mobile-phone communication technology.

  16. Finding the quantum thermoelectric with maximal efficiency and minimal entropy production at given power output

    NASA Astrophysics Data System (ADS)

    Whitney, Robert S.

    2015-03-01

    We investigate the nonlinear scattering theory for quantum systems with strong Seebeck and Peltier effects, and consider their use as heat engines and refrigerators with finite power outputs. This paper gives detailed derivations of the results summarized in a previous paper [R. S. Whitney, Phys. Rev. Lett. 112, 130601 (2014), 10.1103/PhysRevLett.112.130601]. It shows how to use the scattering theory to find (i) the quantum thermoelectric with maximum possible power output, and (ii) the quantum thermoelectric with maximum efficiency at given power output. The latter corresponds to a minimal entropy production at that power output. These quantities are of quantum origin since they depend on system size over electronic wavelength, and so have no analog in classical thermodynamics. The maximal efficiency coincides with Carnot efficiency at zero power output, but decreases with increasing power output. This gives a fundamental lower bound on entropy production, which means that reversibility (in the thermodynamic sense) is impossible for finite power output. The suppression of efficiency by (nonlinear) phonon and photon effects is addressed in detail; when these effects are strong, maximum efficiency coincides with maximum power. Finally, we show in particular limits (typically without magnetic fields) that relaxation within the quantum system does not allow the system to exceed the bounds derived for relaxation-free systems, however, a general proof of this remains elusive.

  17. The Role of the Total Entropy Production in the Dynamics of Open Quantum Systems in Detection of Non-Markovianity

    NASA Astrophysics Data System (ADS)

    Salimi, S.; Haseli, S.; Khorashad, A. S.; Adabi, F.

    2016-09-01

    The interaction between system and environment is a fundamental concept in the theory of open quantum systems. As a result of the interaction, an amount of correlation (both classical and quantum) emerges between the system and the environment. In this work, we recall the quantity that will be very useful to describe the emergence of the correlation between the system and the environment, namely, the total entropy production. Appearance of total entropy production is due to the entanglement production between the system and the environment. In this work, we discuss about the role of the total entropy production for detecting the non-Markovianity. By utilizing the relation between the total entropy production and total correlation between subsystems, one can see a temporary decrease of total entropy production is a signature of non-Markovianity. We apply our criterion for the special case, where the composite system has initial correlation with environment.

  18. Quantum information theory: classical communication over quantum channels

    NASA Astrophysics Data System (ADS)

    Cortese, John Anthony

    This thesis studies classical communication over quantum channels. Chapter 1 describes an algebraic technique which extends several previously known qubit channel capacity results to the qudit quantum channel case. Chapter 2 derives a formula for the relative entropy function of two qubit density matrices in terms of their Bloch vectors. The application of the Bloch vector relative entropy formula to the determination of Holevo-Schumacher-Westmoreland (HSW) capacities for qubit quantum channels is discussed. Chapter 3 outlines several numerical simulation results which support theoretical conclusions and conjectures discussed in Chapters 1 and 2. Chapter 4 closes the thesis with comments, examples and discussion on the additivity of Holevo Chi and the HSW channel capacity.

  19. Quantum Information Science: An Update

    NASA Astrophysics Data System (ADS)

    Kwek, L. C.; Zen, Freddy P.

    2016-08-01

    It is now roughly thirty years since the incipient ideas on quantum information science was concretely formalized. Over the last three decades, there has been much development in this field, and at least one technology, namely devices for quantum cryptography, is now commercialized. Yet, the holy grail of a workable quantum computing machine still lies faraway at the horizon. In any case, it took nearly several centuries before the vacuum tubes were invented after the first mechanical calculating were constructed, and several decades later, for the transistor to bring the current computer technology to fruition. In this review, we provide a short survey of the current development and progress in quantum information science. It clearly does not do justice to the amount of work in the past thirty years. Nevertheless, despite the modest attempt, this review hopes to induce younger researchers into this exciting field.

  20. Resource Letter QI-1: Quantum Information

    NASA Astrophysics Data System (ADS)

    Strauch, Frederick W.

    2016-07-01

    This Resource Letter surveys the history and modern developments in the field of quantum information. It is written to guide advanced undergraduates, beginning graduate students, and other new researchers to the theoretical and experimental aspects of this field. The topics covered include quantum states and processes, quantum coding and cryptography, quantum computation, the experimental implementation of quantum information processing, and the role of quantum information in the fundamental properties and foundations of physical theories.

  1. Generalized information and entanglement entropy, gravitation and holography

    NASA Astrophysics Data System (ADS)

    Obregón, O.

    2015-06-01

    A nonextensive statistical mechanics entropy that depends only on the probability distribution is proposed in the framework of superstatistics. It is based on a Γ(χ2) distribution that depends on β and also on pl. The corresponding modified von Neumann entropy is constructed; it is shown that it can also be obtained from a generalized Replica trick. We further demonstrate a generalized H-theorem. Considering the entropy as a function of the temperature and volume, it is possible to generalize the equation of state of an ideal gas. Moreover, following the entropic force formulation a generalized Newton's law is obtained, and following the proposal that the Einstein equations can be deduced from the Clausius law, we discuss on the structure that a generalized Einstein's theory would have. Lastly, we address the question whether the generalized entanglement entropy can play a role in the gauge/gravity duality. We pay attention to 2d CFT and their gravity duals. The correction terms to the von Neumann entropy result more relevant than the usual UV ones and also than those due to the area dependent AdS3 entropy which result comparable to the UV ones. Then the correction terms due to the new entropy would modify the Ryu-Takayanagi identification between the CFT entanglement entropy and the AdS entropy in a different manner than the UV ones or than the corrections to the AdS3 area dependent entropy.

  2. Information Entropy Analysis of the H1N1 Genetic Code

    NASA Astrophysics Data System (ADS)

    Martwick, Andy

    2010-03-01

    During the current H1N1 pandemic, viral samples are being obtained from large numbers of infected people world-wide and are being sequenced on the NCBI Influenza Virus Resource Database. The information entropy of the sequences was computed from the probability of occurrence of each nucleotide base at every position of each set of sequences using Shannon's definition of information entropy, [ H=∑bpb,2( 1pb ) ] where H is the observed information entropy at each nucleotide position and pb is the probability of the base pair of the nucleotides A, C, G, U. Information entropy of the current H1N1 pandemic is compared to reference human and swine H1N1 entropy. As expected, the current H1N1 entropy is in a low entropy state and has a very large mutation potential. Using the entropy method in mature genes we can identify low entropy regions of nucleotides that generally correlate to critical protein function.

  3. Quantum gravity of Kerr-Schild spacetimes and the logarithmic correction to Schwarzschild black hole entropy

    NASA Astrophysics Data System (ADS)

    El-Menoufi, Basem Kamal

    2016-05-01

    In the context of effective field theory, we consider quantum gravity with minimally coupled massless particles. Fixing the background geometry to be of the Kerr-Schild type, we fully determine the one-loop effective action of the theory whose finite non-local part is induced by the long-distance portion of quantum loops. This is accomplished using the non-local expansion of the heat kernel in addition to a non-linear completion technique through which the effective action is expanded in gravitational curvatures. Via Euclidean methods, we identify a logarithmic correction to the Bekenstein-Hawking entropy of Schwarzschild black hole. Using dimensional transmutation the result is shown to exhibit an interesting interplay between the UV and IR properties of quantum gravity.

  4. Structural information content of networks: graph entropy based on local vertex functionals.

    PubMed

    Dehmer, Matthias; Emmert-Streib, Frank

    2008-04-01

    In this paper we define the structural information content of graphs as their corresponding graph entropy. This definition is based on local vertex functionals obtained by calculating j-spheres via the algorithm of Dijkstra. We prove that the graph entropy and, hence, the local vertex functionals can be computed with polynomial time complexity enabling the application of our measure for large graphs. In this paper we present numerical results for the graph entropy of chemical graphs and discuss resulting properties. PMID:18243802

  5. Practicality of quantum information processing

    NASA Astrophysics Data System (ADS)

    Lau, Hoi-Kwan

    Quantum Information Processing (QIP) is expected to bring revolutionary enhancement to various technological areas. However, today's QIP applications are far from being practical. The problem involves both hardware issues, i.e., quantum devices are imperfect, and software issues, i.e., the functionality of some QIP applications is not fully understood. Aiming to improve the practicality of QIP, in my PhD research I have studied various topics in quantum cryptography and ion trap quantum computation. In quantum cryptography, I first studied the security of position-based quantum cryptography (PBQC). I discovered a wrong assumption in the previous literature that the cheaters are not allowed to share entangled resources. I proposed entanglement attacks that could cheat all known PBQC protocols. I also studied the practicality of continuous-variable (CV) quantum secret sharing (QSS). While the security of CV QSS was considered by the literature only in the limit of infinite squeezing, I found that finitely squeezed CV resources could also provide finite secret sharing rate. Our work relaxes the stringent resources requirement of implementing QSS. In ion trap quantum computation, I studied the phase error of quantum information induced by dc Stark effect during ion transportation. I found an optimized ion trajectory for which the phase error is the minimum. I also defined a threshold speed, above which ion transportation would induce significant error. In addition, I proposed a new application for ion trap systems as universal bosonic simulators (UBS). I introduced two architectures, and discussed their respective strength and weakness. I illustrated the implementations of bosonic state initialization, transformation, and measurement by applying radiation fields or by varying the trap potential. When comparing with conducting optical experiments, the ion trap UBS is advantageous in higher state initialization efficiency and higher measurement accuracy. Finally, I

  6. Efficient Quantum Information Processing via Quantum Compressions

    NASA Astrophysics Data System (ADS)

    Deng, Y.; Luo, M. X.; Ma, S. Y.

    2016-01-01

    Our purpose is to improve the quantum transmission efficiency and reduce the resource cost by quantum compressions. The lossless quantum compression is accomplished using invertible quantum transformations and applied to the quantum teleportation and the simultaneous transmission over quantum butterfly networks. New schemes can greatly reduce the entanglement cost, and partially solve transmission conflictions over common links. Moreover, the local compression scheme is useful for approximate entanglement creations from pre-shared entanglements. This special task has not been addressed because of the quantum no-cloning theorem. Our scheme depends on the local quantum compression and the bipartite entanglement transfer. Simulations show the success probability is greatly dependent of the minimal entanglement coefficient. These results may be useful in general quantum network communication.

  7. Entanglement Entropy and Topological Order in Resonating Valence-Bond Quantum Spin Liquids

    NASA Astrophysics Data System (ADS)

    Wildeboer, Julia; Seidel, Alexander; Melko, Roger

    On the triangular and kagome lattices, short-ranged resonating valence bond (RVB) wave functions can be sampled without the sign problem using a recently-developed Pfaffian Monte Carlo scheme. In this talk, we present a study of the Renyi entanglement entropy in these wave functions using a replica-trick method. Using various spatial bipartitions, including the Levin-Wen construction, our finite-size scaled Renyi entropy gives a topological contribution consistent with γ =ln (2) , as expected for a gapped ℤ2 quantum spin liquid. We prove that the mutual statistics are consistent with the toric code anyon model and rule out any other quasiparticle statistics such as the double semion model.

  8. Dynamics of energy transport and entropy production in ac-driven quantum electron systems

    NASA Astrophysics Data System (ADS)

    Ludovico, María Florencia; Moskalets, Michael; Sánchez, David; Arrachea, Liliana

    2016-07-01

    We analyze the time-resolved energy transport and the entropy production in ac-driven quantum coherent electron systems coupled to multiple reservoirs at finite temperature. At slow driving, we formulate the first and second laws of thermodynamics valid at each instant of time. We identify heat fluxes flowing through the different pieces of the device and emphasize the importance of the energy stored in the contact and central regions for the second law of thermodynamics to be instantaneously satisfied. In addition, we discuss conservative and dissipative contributions to the heat flux and to the entropy production as a function of time. We illustrate these ideas with a simple model corresponding to a driven level coupled to two reservoirs with different chemical potentials.

  9. Thermodynamics, Entropy, Information and the Efficiency of Solar Cells

    NASA Astrophysics Data System (ADS)

    Abrams, Zeev R.

    For well over 50 years, the limits to photovoltaic energy conversion have been known and codified, and have played a vital role in the push for technological breakthroughs to reach—and even attempt to surpass—those limits. This limit, known as the Shockley-Queisser detailed-balance limit, was found by using only the most basic of thermodynamic assumptions, and therefore provides an upper bound that is difficult to contest without violating the laws of thermodynamics. Many different schemes have been devised to improve a solar cell's efficiency beyond this limit, with various benefits and drawbacks for each method. Since the field of solar cell research has been analyzed and dissected for so long by a large variety of researchers, it is quite hard to say or discover anything new without repeating the work of the past. The approach taken in this work is to analyze solar cells from the joint perspective of thermodynamics and information theory. These two subjects have recently been appreciated to be highly interrelated, and using the formalism of Missing Information, we can differentiate between different novel technologies, as well as devise new limits for new and existing methodologies. In this dissertation, the fundamentals of photovoltaic conversion are analyzed from the most basic of principles, emphasizing the thermodynamic parameters of the photovoltaic process. In particular, an emphasis is made on the voltage of the device, as opposed to the current. This emphasis is made since there is a direct relation between the open-circuit voltage of a solar cell and the fundamental equations of thermodynamics and the Free Energy of the system. Moreover, this relation extends to the entropy of the system, which subsequently relates to the field of Information Theory. By focusing on the voltage instead of the current, realizations are made that are not obvious to the majority or researchers in the field, and in particular to efforts of surpassing the Shockley

  10. Eeg Transfer Entropy Tracks Changes in Information Transfer on the Onset of Vision

    NASA Astrophysics Data System (ADS)

    Madulara, M. D.; Francisco, P. A. B.; Nawang, S.; Arogancia, D. C.; Cellucci, C. J.; Rapp, P. E.; Albano, A. M.

    We investigate the pairwise mutual information and transfer entropy of ten-channel, free-running electroencephalographs measured from thirteen subjects under two behavioral conditions: eyes open resting and eyes closed resting. Mutual information measures nonlinear correlations; transfer entropy determines the directionality of information transfer. For all channel pairs, mutual information is generally lower with eyes open compared to eyes closed indicating that EEG signals at different scalp sites become more dissimilar as the visual system is engaged. On the other hand, transfer entropy increases on average by almost two-fold when the eyes are opened. The largest one-way transfer entropies are to and from the Oz site consistent with the involvement of the occipital lobe in vision. The largest net transfer entropies are from F3 and F4 to almost all the other scalp sites.

  11. Shannon information entropies for the three-dimensional Klein-Gordon problem with the Poschl-Teller potential

    NASA Astrophysics Data System (ADS)

    Ghafourian, M.; Hassanabadi, H.

    2016-06-01

    The Shannon information entropies for the Klein-Gordon equations are evaluated for the Poschl-Teller potential, and the position-space information entropies for the ground and the excited states are calculated.

  12. Informational basis of sensory adaptation: entropy and single-spike efficiency in rat barrel cortex.

    PubMed

    Adibi, Mehdi; Clifford, Colin W G; Arabzadeh, Ehsan

    2013-09-11

    We showed recently that exposure to whisker vibrations enhances coding efficiency in rat barrel cortex despite increasing correlations in variability (Adibi et al., 2013). Here, to understand how adaptation achieves this improvement in sensory representation, we decomposed the stimulus information carried in neuronal population activity into its fundamental components in the framework of information theory. In the context of sensory coding, these components are the entropy of the responses across the entire stimulus set (response entropy) and the entropy of the responses conditional on the stimulus (conditional response entropy). We found that adaptation decreased response entropy and conditional response entropy at both the level of single neurons and the pooled activity of neuronal populations. However, the net effect of adaptation was to increase the mutual information because the drop in the conditional entropy outweighed the drop in the response entropy. The information transmitted by a single spike also increased under adaptation. As population size increased, the information content of individual spikes declined but the relative improvement attributable to adaptation was maintained.

  13. Statistical entropy of a BTZ black hole from loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Frodden, Ernesto; Geiller, Marc; Noui, Karim; Perez, Alejandro

    2013-05-01

    We compute the statistical entropy of a BTZ black hole in the context of three-dimensional Euclidean loop quantum gravity with a cosmological constant Λ. As in the four-dimensional case, a quantum state of the black hole is characterized by a spin network state. Now however, the underlying colored graph Γ lives in a two-dimensional spacelike surface Σ, and some of its links cross the black hole horizon, which is viewed as a circular boundary of Σ. Each link ℓ crossing the horizon is colored by a spin j ℓ (at the kinematical level), and the length L of the horizon is given by the sum L = ∑ ℓ L ℓ of the fundamental length contributions L ℓ carried by the spins j ℓ of the links ℓ. We propose an estimation for the number N_{\\varGamma}^{BTZ}( {L,Λ} ) of the Euclidean BTZ black hole microstates (defined on a fixed graph Γ) based on an analytic continuation from the case Λ > 0 to the case Λ < 0. In our model, we show that N_{\\varGamma}^{BTZ}( {L,Λ} ) reproduces the Bekenstein-Hawking entropy in the classical limit. This asymptotic behavior is independent of the choice of the graph Γ provided that the condition L = ∑ ℓ L ℓ is satisfied, as it should be in three-dimensional quantum gravity.

  14. Quantum Information Processing with Trapped Ions

    NASA Astrophysics Data System (ADS)

    Roos, Christian

    Trapped ions constitute a well-isolated small quantum system that offers low decoherence rates and excellent opportunities for quantum control and measurement by laser-induced manipulation of the ions. These properties make trapped ions an attractive system for experimental investigations of quantum information processing. In the following, the basics of storing, manipulating and measuring quantum information encoded in a string of trapped ions will be discussed. Based on these techniques, entanglement can be created and simple quantum protocols like quantum teleportation be realized. This chapter concludes with a discussion of the use of entangling laser-ion interactions for quantum simulations and quantum logic spectroscopy.

  15. Measuring heart rate variability by means of information entropies based on Choi-Williams distribution.

    PubMed

    Vallverdú, Montserrat; Clariá, Francesc; Melia, Umberto; Bayés de Luna, Antonio; Caminal, Pere

    2015-08-01

    The Shannon entropy theory was applied to the Choi-Williams time-frequency distribution (CWD) of cardiac time series (RR series) in order to extract entropy information in both time and frequency domains. From this distribution, four indexes were defined: (1) instantaneous partial entropy; (2) spectral partial entropy; (3) instantaneous complete entropy; (4) spectral complete entropy. These indexes were used for analyzing the heart rate variability of ischemic cardiomyopathy patients (ICM) with different sudden cardiac death risk. The results have shown that the values of these indexes tend to decrease, with different proportion, when the severity of pathological condition increases. Statistical differences (p-value < 0.0005) of these indexes were found comparing low risk and high risk of cardiac death during night and between daytime and nighttime periods of ICM patients. Finally, these indexes have demonstrated to be useful tools to quantify the different complex components of the cardiac time series.

  16. Information entropy to measure the spatial and temporal complexity of solute transport in heterogeneous porous media

    NASA Astrophysics Data System (ADS)

    Li, Weiyao; Huang, Guanhua; Xiong, Yunwu

    2016-04-01

    The complexity of the spatial structure of porous media, randomness of groundwater recharge and discharge (rainfall, runoff, etc.) has led to groundwater movement complexity, physical and chemical interaction between groundwater and porous media cause solute transport in the medium more complicated. An appropriate method to describe the complexity of features is essential when study on solute transport and conversion in porous media. Information entropy could measure uncertainty and disorder, therefore we attempted to investigate complexity, explore the contact between the information entropy and complexity of solute transport in heterogeneous porous media using information entropy theory. Based on Markov theory, two-dimensional stochastic field of hydraulic conductivity (K) was generated by transition probability. Flow and solute transport model were established under four conditions (instantaneous point source, continuous point source, instantaneous line source and continuous line source). The spatial and temporal complexity of solute transport process was characterized and evaluated using spatial moment and information entropy. Results indicated that the entropy increased as the increase of complexity of solute transport process. For the point source, the one-dimensional entropy of solute concentration increased at first and then decreased along X and Y directions. As time increased, entropy peak value basically unchanged, peak position migrated along the flow direction (X direction) and approximately coincided with the centroid position. With the increase of time, spatial variability and complexity of solute concentration increase, which result in the increases of the second-order spatial moment and the two-dimensional entropy. Information entropy of line source was higher than point source. Solute entropy obtained from continuous input was higher than instantaneous input. Due to the increase of average length of lithoface, media continuity increased, flow and

  17. Quantum mechanical correlation functions, maximum entropy analytic continuation, and ring polymer molecular dynamics.

    PubMed

    Habershon, Scott; Braams, Bastiaan J; Manolopoulos, David E

    2007-11-01

    The maximum entropy analytic continuation (MEAC) and ring polymer molecular dynamics (RPMD) methods provide complementary approaches to the calculation of real time quantum correlation functions. RPMD becomes exact in the high temperature limit, where the thermal time betavariant Planck's over 2pi tends to zero and the ring polymer collapses to a single classical bead. MEAC becomes most reliable at low temperatures, where betavariant Planck's over 2pi exceeds the correlation time of interest and the numerical imaginary time correlation function contains essentially all of the information that is needed to recover the real time dynamics. We show here that this situation can be exploited by combining the two methods to give an improved approximation that is better than either of its parts. In particular, the MEAC method provides an ideal way to impose exact moment (or sum rule) constraints on a prior RPMD spectrum. The resulting scheme is shown to provide a practical solution to the "nonlinear operator problem" of RPMD, and to give good agreement with recent exact results for the short-time velocity autocorrelation function of liquid parahydrogen. Moreover these improvements are obtained with little extra effort, because the imaginary time correlation function that is used in the MEAC procedure can be computed at the same time as the RPMD approximation to the real time correlation function. However, there are still some problems involving long-time dynamics for which the RPMD+MEAC combination is inadequate, as we illustrate with an example application to the collective density fluctuations in liquid orthodeuterium. PMID:17994808

  18. Use of mutual information to decrease entropy: Implications for the second law of thermodynamics

    SciTech Connect

    Lloyd, S.

    1989-05-15

    Several theorems on the mechanics of gathering information are proved, and the possibility of violating the second law of thermodynamics by obtaining information is discussed in light of these theorems. Maxwell's demon can lower the entropy of his surroundings by an amount equal to the difference between the maximum entropy of his recording device and its initial entropy, without generating a compensating entropy increase. A demon with human-scale recording devices can reduce the entropy of a gas by a negligible amount only, but the proof of the demon's impracticability leaves open the possibility that systems highly correlated with their environment can reduce the environment's entropy by a substantial amount without increasing entropy elsewhere. In the event that a boundary condition for the universe requires it to be in a state of low entropy when small, the correlations induced between different particle modes during the expansion phase allow the modes to behave like Maxwell's demons during the contracting phase, reducing the entropy of the universe to a low value.

  19. Bipartite Entanglement Entropy in Massive Two-Dimensional Quantum Field Theory

    SciTech Connect

    Doyon, Benjamin

    2009-01-23

    Recently, Cardy, Castro Alvaredo, and the author obtained the first exponential correction to saturation of the bipartite entanglement entropy at large region lengths in massive two-dimensional integrable quantum field theory. It depends only on the particle content of the model, and not on the way particles scatter. Based on general analyticity arguments for form factors, we propose that this result is universal, and holds for any massive two-dimensional model (also out of integrability). We suggest a link of this result with counting pair creations far in the past.

  20. Bipartite entanglement entropy in massive two-dimensional quantum field theory.

    PubMed

    Doyon, Benjamin

    2009-01-23

    Recently, Cardy, Castro Alvaredo, and the author obtained the first exponential correction to saturation of the bipartite entanglement entropy at large region lengths in massive two-dimensional integrable quantum field theory. It depends only on the particle content of the model, and not on the way particles scatter. Based on general analyticity arguments for form factors, we propose that this result is universal, and holds for any massive two-dimensional model (also out of integrability). We suggest a link of this result with counting pair creations far in the past.

  1. Teleportation as a depolarizing quantum channel, relative entropy, and classical capacity.

    PubMed

    Bowen, G; Bose, S

    2001-12-24

    We show that standard teleportation with an arbitrary mixed state resource is equivalent to a generalized depolarizing channel with probabilities given by the maximally entangled components of the resource. This enables the usage of any quantum channel as a generalized depolarizing channel without additional twirling operations. It also provides a nontrivial upper bound on the entanglement of a class of mixed states. Our result allows a consistent and statistically motivated quantification of teleportation success in terms of the relative entropy and this quantification can be related to a classical capacity.

  2. [Index of stability and its mechanisms of aerobic granular system using volume-based information entropy].

    PubMed

    Li, Zhi-Hua; Ji, Xiao-Qin; Li, Sheng; Xie, Lei; Zhao, Hai-Long; Wang, Xiao-Chang

    2012-03-01

    Autotrophic nitrification granular sludge was cultivated in a sequencing batch reactor (SBR), the information entropy of volume distribution decreased from 2.05 (27 d, granules were firstly observed) to 1.85 (95 d) during granulation period. And the driving force for the decrease of information entropy could be ascribed to the washing out of flocs by means of the hydraulic selection pressure. After the granules formation stage finished, the median settling velocity of the granules system was 6.27 m x h(-1) and the information entropy of volume distribution would not be controlled by the settling velocity selection pressure (6 m x h(-1)). It was found that the size, settling velocity and the volume-based information entropy periodically changed. The mean, minimum and maximum of information entropy were 2.16, 1.79 and 2.63, respectively, during the period from 122 d to 579 d. The mean size varied by the pattern of increase and decrease periodically. The driving force for the fluctuation of the information entropy was the smashing of the larger granular and the volume fragmentation growth, and the volume distribution of the information entropy could well indicate the stability of granular sludge systems.

  3. Entropy is conserved in Hawking radiation as tunneling: A revisit of the black hole information loss paradox

    SciTech Connect

    Zhang Baocheng; Cai Qingyu; Zhan Mingsheng; You Li

    2011-02-15

    Research Highlights: > Information is found to be encoded and carried away by Hawking radiations. > Entropy is conserved in Hawking radiation. > We thus conclude no information is lost. > The dynamics of black hole may be unitary. - Abstract: We revisit in detail the paradox of black hole information loss due to Hawking radiation as tunneling. We compute the amount of information encoded in correlations among Hawking radiations for a variety of black holes, including the Schwarzchild black hole, the Reissner-Nordstroem black hole, the Kerr black hole, and the Kerr-Newman black hole. The special case of tunneling through a quantum horizon is also considered. Within a phenomenological treatment based on the accepted emission probability spectrum from a black hole, we find that information is leaked out hidden in the correlations of Hawking radiation. The recovery of this previously unaccounted for information helps to conserve the total entropy of a system composed of a black hole plus its radiations. We thus conclude, irrespective of the microscopic picture for black hole collapsing, the associated radiation process: Hawking radiation as tunneling, is consistent with unitarity as required by quantum mechanics.

  4. Shannon information entropy for assessing space-time variability of rainfall and streamflow in semiarid region.

    PubMed

    Rodrigues da Silva, Vicente de P; Belo Filho, Adelgcio F; Rodrigues Almeida, Rafaela S; de Holanda, Romildo Morant; da Cunha Campos, João Hugo Baracuy

    2016-02-15

    The principle of maximum entropy can provide consistent basis to analyze water resources and geophysical processes in general. In this paper, we propose to assess the space-time variability of rainfall and streamflow in northeastern region of Brazil using the Shannon entropy. Mean values of marginal and relative entropies were computed for a 10-year period from 189 stations in the study area and entropy maps were then constructed for delineating annual and seasonal characteristics of rainfall and streamflow. The Mann-Kendall test was used to evaluate the long-term trend in marginal entropy as well as relative entropy for two sample stations. High degree of similarity was found between rainfall and streamflow, particularly during dry season. Both rainfall and streamflow variability can satisfactorily be obtained in terms of marginal entropy as a comprehensive measure of the regional uncertainty of these hydrological events. The Shannon entropy produced spatial patterns which led to a better understanding of rainfall and streamflow characteristics throughout the northeastern region of Brazil. The total relative entropy indicated that rainfall and streamflow carried the same information content at annual and rainy season time scales. PMID:26657379

  5. Efficient calculation of molecular configurational entropies using an information theoretic approximation

    PubMed Central

    King, Bracken M.; Silver, Nathaniel W.; Tidor, Bruce

    2012-01-01

    Accurate computation of free energy changes upon molecular binding remains a challenging problem, and changes in configurational entropy are especially difficult due both to the potentially large numbers of local minima, anharmonicity, and high-order coupling among degrees of freedom. Here we propose a new method to compute molecular entropies based on the maximum information spanning tree (MIST) approximation that we have previously developed. Estimates of high-order couplings using only low-order terms provide excellent convergence properties, and the theory is also guaranteed to bound the entropy. The theory is presented together with applications to the calculation of the entropies of a variety of small molecules and the binding entropy change for a series of HIV protease inhibitors. The MIST framework developed here is demonstrated to compare favorably with results computed using the related mutual information expansion (MIE) approach, and an analysis of similarities between the methods is presented. PMID:22229789

  6. How much a quantum measurement is informative?

    SciTech Connect

    Dall'Arno, Michele; D'Ariano, Giacomo Mauro; Sacchi, Massimiliano F.

    2014-12-04

    The informational power of a quantum measurement is the maximum amount of classical information that the measurement can extract from any ensemble of quantum states. We discuss its main properties. Informational power is an additive quantity, being equivalent to the classical capacity of a quantum-classical channel. The informational power of a quantum measurement is the maximum of the accessible information of a quantum ensemble that depends on the measurement. We present some examples where the symmetry of the measurement allows to analytically derive its informational power.

  7. Local, nonlocal quantumness and information theoretic measures

    NASA Astrophysics Data System (ADS)

    Agrawal, Pankaj; Sazim, Sk; Chakrabarty, Indranil; Pati, Arun K.

    2016-08-01

    It has been suggested that there may exist quantum correlations that go beyond entanglement. The existence of such correlations can be revealed by information theoretic quantities such as quantum discord, but not by the conventional measures of entanglement. We argue that a state displays quantumness, that can be of local and nonlocal origin. Information theoretic measures not only characterize the nonlocal quantumness, but also the local quantumness, such as the “local superposition”. This can be a reason, why such measures are nonzero, when there is no entanglement. We consider a generalized version of the Werner state to demonstrate the interplay of local quantumness, nonlocal quantumness and classical mixedness of a state.

  8. Quantum States as Objective Informational Bridges

    NASA Astrophysics Data System (ADS)

    Healey, Richard

    2015-09-01

    A quantum state represents neither properties of a physical system nor anyone's knowledge of its properties. The important question is not what quantum states represent but how they are used—as informational bridges. Knowing about some physical situations (its backing conditions), an agent may assign a quantum state to form expectations about other possible physical situations (its advice conditions). Quantum states are objective: only expectations based on correct state assignments are generally reliable. If a quantum state represents anything, it is the objective probabilistic relations between its backing conditions and its advice conditions. This paper offers an account of quantum states and their function as informational bridges, in quantum teleportation and elsewhere.

  9. The Holographic Entropy Cone

    SciTech Connect

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael

    2015-09-21

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phase space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.

  10. The Holographic Entropy Cone

    DOE PAGES

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael

    2015-09-21

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phasemore » space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.« less

  11. How can an autonomous quantum Maxwell demon harness correlated information?

    NASA Astrophysics Data System (ADS)

    Chapman, Adrian; Miyake, Akimasa; CQuIC Thermodynamics Team

    We study an autonomous quantum system, which exhibits refrigeration under an information-work tradeoff like a Maxwell demon. The system becomes correlated as a single ``demon'' qubit interacts sequentially with memory qubits while in contact with two heat reservoirs of different temperatures. Using strong subadditivity of the von Neumann entropy, we derive a global Clausius inequality to show thermodynamical advantages from access to correlated information. It is demonstrated, in a matrix product density operator formalism, that our demon can simultaneously realize refrigeration against a thermal gradient and erasure of information from its memory, which is impossible without correlations. The phenomenon can be even enhanced by the presence of quantum coherence. The work was supported in part by National Science Foundation Grants PHY-1212445 and PHY-1521016.

  12. Shock waves, increase of entropy and loss of information

    SciTech Connect

    Lax, P.D.

    1984-10-01

    We discuss, for the simplified model of a single conservation law, the concepts of genuine nonlinearity, breakdown of classical solutions, solutions in the distribution sense and their nonuniqueness, the viscosity method, finite difference methods, and the shock condition. We then discuss, for the scalar model, the compactness of solutions constructed by the viscosity and difference methods, and derive the entropy inequality for such solutions. We derive Glimm's estimate for the total variation of solutions of scalar equations that satisfy the shock condition, and show that a discontinuous solution that satisfies the shock condition also satisfies the entropy condition. Scattered remarks are given about the equations of compressible flow: the increase of entropy, some consequences of Carnot's theorem, and the equipartition of energy in the wake of strong shocks.

  13. Information Theoretic Approach Based on Entropy for Classification of Bioacoustics Signals

    NASA Astrophysics Data System (ADS)

    Han, Ng Chee; Muniandy, Sithi V.; Dayou, Jedol; Mun, Ho Chong; Ahmad, Abdul Hamid; Dalimin, Mohd. Noh

    2010-07-01

    A new hybrid method for automated frog sound identification by incorporating entropy and spectral centroid concept is proposed. Entropy has important physical implications as the amount of "disorder" of a system. This study explores the use of various definitions of entropies such as the Shannon entropy, Kolmogorov-Rényi entropy and Tsallis entropy as measure of information contents or complexity for the purpose of the pattern recognition of bioacoustics signal. Each of these definitions of entropies characterizes different aspects of the signal. The entropies are combined with other standard pattern recognition tools such as the Fourier spectral analysis to form a hybrid spectral-entropic classification scheme. The efficiency of the system is tested using a database of sound syllables are obtained from a number of species of Microhylidae frogs. Nonparametric k-NN classifier is used to recognize the frog species based on the spectral-entropic features. The result showed that the k-NN classifier based on the selected features is able to identify the species of the frogs with relativity good accuracy compared to features relying on spectral contents alone. The robustness of the developed system is also tested for different noise levels.

  14. Quantum information processing with atoms and photons.

    PubMed

    Monroe, C

    2002-03-14

    Quantum information processors exploit the quantum features of superposition and entanglement for applications not possible in classical devices, offering the potential for significant improvements in the communication and processing of information. Experimental realization of large-scale quantum information processors remains a long-term vision, as the required nearly pure quantum behaviour is observed only in exotic hardware such as individual laser-cooled atoms and isolated photons. But recent theoretical and experimental advances suggest that cold atoms and individual photons may lead the way towards bigger and better quantum information processors, effectively building mesoscopic versions of 'Schrödinger's cat' from the bottom up.

  15. Measurement and control in quantum information science

    NASA Astrophysics Data System (ADS)

    Mabuchi, Hideo

    2005-03-01

    Quantum information science has a broad interface with control theory. In the region of overlap between these two thriving fields, one finds compelling problems ranging from robust and time-optimal control of quantum dynamics to the analysis and design of concatenated coding schemes. In this talk I will begin with a brief overview of recent work on applications of control theory in quantum information science, and then provide a more detailed review of my own group's research on quantum feedback control, quantum state preparation and quantum metrology.

  16. Entropy excess in strongly correlated Fermi systems near a quantum critical point

    SciTech Connect

    Clark, J.W.; Zverev, M.V.; Khodel, V.A.

    2012-12-15

    A system of interacting, identical fermions described by standard Landau Fermi-liquid (FL) theory can experience a rearrangement of its Fermi surface if the correlations grow sufficiently strong, as occurs at a quantum critical point where the effective mass diverges. As yet, this phenomenon defies full understanding, but salient aspects of the non-Fermi-liquid (NFL) behavior observed beyond the quantum critical point are still accessible within the general framework of the Landau quasiparticle picture. Self-consistent solutions of the coupled Landau equations for the quasiparticle momentum distribution n(p) and quasiparticle energy spectrum {epsilon}(p) are shown to exist in two distinct classes, depending on coupling strength and on whether the quasiparticle interaction is regular or singular at zero momentum transfer. One class of solutions maintains the idempotency condition n{sup 2}(p)=n(p) of standard FL theory at zero temperature T while adding pockets to the Fermi surface. The other solutions are characterized by a swelling of the Fermi surface and a flattening of the spectrum {epsilon}(p) over a range of momenta in which the quasiparticle occupancies lie between 0 and 1 even at T=0. The latter, non-idempotent solution is revealed by analysis of a Poincare mapping associated with the fundamental Landau equation connecting n(p) and {epsilon}(p) and validated by solution of a variational condition that yields the symmetry-preserving ground state. Significantly, this extraordinary solution carries the burden of a large temperature-dependent excess entropy down to very low temperatures, threatening violation of the Nernst Theorem. It is argued that certain low-temperature phase transitions, notably those involving Cooper-pair formation, offer effective mechanisms for shedding the entropy excess. Available measurements in heavy-fermion compounds provide concrete support for such a scenario. - Highlights: Black-Right-Pointing-Pointer Extension of Landau

  17. Correlation lengths and topological entanglement entropies of unitary and nonunitary fractional quantum Hall wave functions.

    PubMed

    Estienne, B; Regnault, N; Bernevig, B A

    2015-05-01

    Using the newly developed matrix product state formalism for non-Abelian fractional quantum Hall (FQH) states, we address the question of whether a FQH trial wave function written as a correlation function in a nonunitary conformal field theory (CFT) can describe the bulk of a gapped FQH phase. We show that the nonunitary Gaffnian state exhibits clear signatures of a pathological behavior. As a benchmark we compute the correlation length of a Moore-Read state and find it to be finite in the thermodynamic limit. By contrast, the Gaffnian state has an infinite correlation length in (at least) the non-Abelian sector, and is therefore gapless. We also compute the topological entanglement entropy of several non-Abelian states with and without quasiholes. For the first time in the FQH effect the results are in excellent agreement in all topological sectors with the CFT prediction for unitary states. For the nonunitary Gaffnian state in finite size systems, the topological entanglement entropy seems to behave like that of the composite fermion Jain state at equal filling.

  18. Origin of microbial life: Nano- and molecular events, thermodynamics/entropy, quantum mechanisms and genetic instructions.

    PubMed

    Trevors, J T

    2011-03-01

    Currently, there are no agreed upon mechanisms and supporting evidence for the origin of the first microbial cells on the Earth. However, some hypotheses have been proposed with minimal supporting evidence and experimentation/observations. The approach taken in this article is that life originated at the nano- and molecular levels of biological organization, using quantum mechanic principles that became manifested as classical microbial cell(s), allowing the origin of microbial life on the Earth with a core or minimal, organic, genetic code containing the correct instructions for cell(s) for growth and division, in a micron dimension environment, with a local entropy range conducive to life (present about 4 billion years ago), and obeying the laws of thermodynamics. An integrated approach that explores all encompassing factors necessary for the origin of life, may bring forth plausible hypotheses (and mechanisms) with much needed supporting experimentation and observations for an origin of life theory.

  19. Measuring entanglement entropies in many-body systems

    SciTech Connect

    Klich, Israel; Refael, Gil; Silva, Alessandro

    2006-09-15

    We explore the relation between entanglement entropy of quantum many-body systems and the distribution of corresponding, properly selected, observables. Such a relation is necessary to actually measure the entanglement entropy. We show that, in general, the Shannon entropy of the probability distribution of certain symmetry observables gives a lower bound to the entropy. In some cases this bound is saturated and directly gives the entropy. We also show other cases in which the probability distribution contains enough information to extract the entropy: we show how this is done in several examples including BEC wave functions, the Dicke model, XY spin chain, and chains with strong randomness.

  20. Amplification, Redundancy, and Quantum Chernoff Information

    NASA Astrophysics Data System (ADS)

    Zwolak, Michael; Riedel, C. Jess; Zurek, Wojciech H.

    2014-04-01

    Amplification was regarded, since the early days of quantum theory, as a mysterious ingredient that endows quantum microstates with macroscopic consequences, key to the "collapse of the wave packet," and a way to avoid embarrassing problems exemplified by Schrödinger's cat. Such a bridge between the quantum microworld and the classical world of our experience was postulated ad hoc in the Copenhagen interpretation. Quantum Darwinism views amplification as replication, in many copies, of the information about quantum states. We show that such amplification is a natural consequence of a broad class of models of decoherence, including the photon environment we use to obtain most of our information. This leads to objective reality via the presence of robust and widely accessible records of selected quantum states. The resulting redundancy (the number of copies deposited in the environment) follows from the quantum Chernoff information that quantifies the information transmitted by a typical elementary subsystem of the environment.

  1. Amplification, redundancy, and quantum Chernoff information.

    PubMed

    Zwolak, Michael; Riedel, C Jess; Zurek, Wojciech H

    2014-04-11

    Amplification was regarded, since the early days of quantum theory, as a mysterious ingredient that endows quantum microstates with macroscopic consequences, key to the "collapse of the wave packet," and a way to avoid embarrassing problems exemplified by Schrödinger's cat. Such a bridge between the quantum microworld and the classical world of our experience was postulated ad hoc in the Copenhagen interpretation. Quantum Darwinism views amplification as replication, in many copies, of the information about quantum states. We show that such amplification is a natural consequence of a broad class of models of decoherence, including the photon environment we use to obtain most of our information. This leads to objective reality via the presence of robust and widely accessible records of selected quantum states. The resulting redundancy (the number of copies deposited in the environment) follows from the quantum Chernoff information that quantifies the information transmitted by a typical elementary subsystem of the environment.

  2. Entropy excess in strongly correlated Fermi systems near a quantum critical point

    NASA Astrophysics Data System (ADS)

    Clark, J. W.; Zverev, M. V.; Khodel, V. A.

    2012-12-01

    A system of interacting, identical fermions described by standard Landau Fermi-liquid (FL) theory can experience a rearrangement of its Fermi surface if the correlations grow sufficiently strong, as occurs at a quantum critical point where the effective mass diverges. As yet, this phenomenon defies full understanding, but salient aspects of the non-Fermi-liquid (NFL) behavior observed beyond the quantum critical point are still accessible within the general framework of the Landau quasiparticle picture. Self-consistent solutions of the coupled Landau equations for the quasiparticle momentum distribution n(p) and quasiparticle energy spectrum ɛ(p) are shown to exist in two distinct classes, depending on coupling strength and on whether the quasiparticle interaction is regular or singular at zero momentum transfer. One class of solutions maintains the idempotency condition n2(p)=n(p) of standard FL theory at zero temperature T while adding pockets to the Fermi surface. The other solutions are characterized by a swelling of the Fermi surface and a flattening of the spectrum ɛ(p) over a range of momenta in which the quasiparticle occupancies lie between 0 and 1 even at T=0. The latter, non-idempotent solution is revealed by analysis of a Poincaré mapping associated with the fundamental Landau equation connecting n(p) and ɛ(p) and validated by solution of a variational condition that yields the symmetry-preserving ground state. Significantly, this extraordinary solution carries the burden of a large temperature-dependent excess entropy down to very low temperatures, threatening violation of the Nernst Theorem. It is argued that certain low-temperature phase transitions, notably those involving Cooper-pair formation, offer effective mechanisms for shedding the entropy excess. Available measurements in heavy-fermion compounds provide concrete support for such a scenario.

  3. Matrix Techniques in Quantum Information Science

    NASA Astrophysics Data System (ADS)

    Li, Chi-Kwong

    2013-09-01

    Mathematical techniques in quantum information science will be discussed. The focus will be on two specific topics. The first one concerns the study of quantum operations (channels) using the theory of completely positive linear maps. The second one concerns the study of quantum error correction using the theory of generalized numerical ranges. The discussion includes material from some recent research papers.

  4. A cloud detection algorithm using edge detection and information entropy over urban area

    NASA Astrophysics Data System (ADS)

    Zheng, Hong; Wen, Tianxiao; Li, Zhen

    2013-10-01

    Aiming at detecting cloud interference over urban area, an algorithm in this research is proposed to detect urban cloud area combining extracting edge information with information entropy, focusing on distinguishing complex surface features accurately to retain intact surface information. Firstly, image edge sharpening is used. Secondly, Canny edge detector and closing operation are applied to extract and strengthen edge features. Thirdly, information entropy extraction is adopted to ensure cloud positional accuracy. Compared with traditional cloud detection methods, this algorithm protects the integrity of urban surface features efficiently, improving the segmentation accuracy. Test results prove the effectiveness of this algorithm.

  5. Photonic qubits for remote quantum information processing

    NASA Astrophysics Data System (ADS)

    Maunz, P.; Olmschenk, S.; Hayes, D.; Matsukevich, D. N.; Duan, L.-M.; Monroe, C.

    2009-05-01

    Quantum information processing between remote quantum memories relies on a fast and faithful quantum channel. Recent experiments employed both, the photonic polarization and frequency qubits, in order to entangle remote atoms [1, 2], to teleport quantum information [3] and to operate a quantum gate between distant atoms. Here, we compare the dierent schemes used in these experiments and analyze the advantages of the dierent choices of atomic and photonic qubits and their coherence properties. [4pt] [1] D. L. Moehring et al. Nature 449, 68 (2007).[0pt] [2] D. N. Matsukevich et al. Phys. Rev. Lett. 100, 150404 2008).[0pt] [3] S. Olmschenk et al. Science, 323, 486 (2009).

  6. Information causality in the quantum and post-quantum regime.

    PubMed

    Ringbauer, Martin; Fedrizzi, Alessandro; Berry, Dominic W; White, Andrew G

    2014-01-01

    Quantum correlations can be stronger than anything achieved by classical systems, yet they are not reaching the limit imposed by relativity. The principle of information causality offers a possible explanation for why the world is quantum and why there appear to be no even stronger correlations. Generalizing the no-signaling condition it suggests that the amount of accessible information must not be larger than the amount of transmitted information. Here we study this principle experimentally in the classical, quantum and post-quantum regimes. We simulate correlations that are stronger than allowed by quantum mechanics by exploiting the effect of polarization-dependent loss in a photonic Bell-test experiment. Our method also applies to other fundamental principles and our results highlight the special importance of anisotropic regions of the no-signalling polytope in the study of fundamental principles. PMID:25378182

  7. Information causality in the quantum and post-quantum regime.

    PubMed

    Ringbauer, Martin; Fedrizzi, Alessandro; Berry, Dominic W; White, Andrew G

    2014-11-07

    Quantum correlations can be stronger than anything achieved by classical systems, yet they are not reaching the limit imposed by relativity. The principle of information causality offers a possible explanation for why the world is quantum and why there appear to be no even stronger correlations. Generalizing the no-signaling condition it suggests that the amount of accessible information must not be larger than the amount of transmitted information. Here we study this principle experimentally in the classical, quantum and post-quantum regimes. We simulate correlations that are stronger than allowed by quantum mechanics by exploiting the effect of polarization-dependent loss in a photonic Bell-test experiment. Our method also applies to other fundamental principles and our results highlight the special importance of anisotropic regions of the no-signalling polytope in the study of fundamental principles.

  8. Quantum information, cognition, and music.

    PubMed

    Dalla Chiara, Maria L; Giuntini, Roberto; Leporini, Roberto; Negri, Eleonora; Sergioli, Giuseppe

    2015-01-01

    Parallelism represents an essential aspect of human mind/brain activities. One can recognize some common features between psychological parallelism and the characteristic parallel structures that arise in quantum theory and in quantum computation. The article is devoted to a discussion of the following questions: a comparison between classical probabilistic Turing machines and quantum Turing machines.possible applications of the quantum computational semantics to cognitive problems.parallelism in music. PMID:26539139

  9. Quantum information, cognition, and music.

    PubMed

    Dalla Chiara, Maria L; Giuntini, Roberto; Leporini, Roberto; Negri, Eleonora; Sergioli, Giuseppe

    2015-01-01

    Parallelism represents an essential aspect of human mind/brain activities. One can recognize some common features between psychological parallelism and the characteristic parallel structures that arise in quantum theory and in quantum computation. The article is devoted to a discussion of the following questions: a comparison between classical probabilistic Turing machines and quantum Turing machines.possible applications of the quantum computational semantics to cognitive problems.parallelism in music.

  10. Quantum information, cognition, and music

    PubMed Central

    Dalla Chiara, Maria L.; Giuntini, Roberto; Leporini, Roberto; Negri, Eleonora; Sergioli, Giuseppe

    2015-01-01

    Parallelism represents an essential aspect of human mind/brain activities. One can recognize some common features between psychological parallelism and the characteristic parallel structures that arise in quantum theory and in quantum computation. The article is devoted to a discussion of the following questions: a comparison between classical probabilistic Turing machines and quantum Turing machines.possible applications of the quantum computational semantics to cognitive problems.parallelism in music. PMID:26539139

  11. Quantum-coherence quantifiers based on the Tsallis relative α entropies

    NASA Astrophysics Data System (ADS)

    Rastegin, Alexey E.

    2016-03-01

    The concept of coherence is one of cornerstones in physics. The development of quantum information science has lead to renewed interest in properly approaching the coherence at the quantum level. Various measures could be proposed to quantify coherence of a quantum state with respect to the prescribed orthonormal basis. To be a proper measure of coherence, each candidate should enjoy certain properties. It seems that the monotonicity property plays a crucial role here. Indeed, there is known an intuitive measure of coherence that does not share this condition. We study coherence measures induced by quantum divergences of the Tsallis type. Basic properties of the considered coherence quantifiers are derived. Tradeoff relations between coherence and mixedness are examined. The property of monotonicity under incoherent selective measurements has to be reformulated. The proposed formulation can naturally be treated as a parametric extension of its standard form. Finally, two coherence measures quadratic in moduli of matrix elements are compared from the monotonicity viewpoint.

  12. Photonic quantum information: science and technology.

    PubMed

    Takeuchi, Shigeki

    2016-01-01

    Recent technological progress in the generation, manipulation and detection of individual single photons has opened a new scientific field of photonic quantum information. This progress includes the realization of single photon switches, photonic quantum circuits with specific functions, and the application of novel photonic states to novel optical metrology beyond the limits of standard optics. In this review article, the recent developments and current status of photonic quantum information technology are overviewed based on the author's past and recent works.

  13. Assessing Bayesian model averaging uncertainty of groundwater modeling based on information entropy method

    NASA Astrophysics Data System (ADS)

    Zeng, Xiankui; Wu, Jichun; Wang, Dong; Zhu, Xiaobin; Long, Yuqiao

    2016-07-01

    Because of groundwater conceptualization uncertainty, multi-model methods are usually used and the corresponding uncertainties are estimated by integrating Markov Chain Monte Carlo (MCMC) and Bayesian model averaging (BMA) methods. Generally, the variance method is used to measure the uncertainties of BMA prediction. The total variance of ensemble prediction is decomposed into within-model and between-model variances, which represent the uncertainties derived from parameter and conceptual model, respectively. However, the uncertainty of a probability distribution couldn't be comprehensively quantified by variance solely. A new measuring method based on information entropy theory is proposed in this study. Due to actual BMA process hard to meet the ideal mutually exclusive collectively exhaustive condition, BMA predictive uncertainty could be decomposed into parameter, conceptual model, and overlapped uncertainties, respectively. Overlapped uncertainty is induced by the combination of predictions from correlated model structures. In this paper, five simple analytical functions are firstly used to illustrate the feasibility of the variance and information entropy methods. A discrete distribution example shows that information entropy could be more appropriate to describe between-model uncertainty than variance. Two continuous distribution examples show that the two methods are consistent in measuring normal distribution, and information entropy is more appropriate to describe bimodal distribution than variance. The two examples of BMA uncertainty decomposition demonstrate that the two methods are relatively consistent in assessing the uncertainty of unimodal BMA prediction. Information entropy is more informative in describing the uncertainty decomposition of bimodal BMA prediction. Then, based on a synthetical groundwater model, the variance and information entropy methods are used to assess the BMA uncertainty of groundwater modeling. The uncertainty assessments of

  14. Scaling of entanglement entropy in a quantum phase transition in the transverse Ising model induced by a quench

    SciTech Connect

    Majumdar, Priyadarshi; Bandyopadhyay, Pratul

    2010-01-15

    It is known that at the critical point of a zero-temperature quantum phase transition in a one-dimensional spin system the entanglement entropy of a block of L spins with the rest of the system scales logarithmically with L with a prefactor determined by the central charge of the relevant conformal field theory. When we introduce critical slowing down incorporating the Kibble-Zurek mechanism of defect formation induced by a quench, the implicit nonadiabatic transition disturbs the scaling behavior. We have shown that in this case the entanglement entropy also obeys a scaling law such that it increases logarithmically with L but the prefactor depends on the quench time. This puts a constraint on the block size L so that we cannot arbitrarily choose it. Thus, the entanglement entropy obeys the scaling law only in a restrictive sense due to the formation of defects.

  15. Fisher Information, Entropy, and the Second and Third Laws of Thermodynamics

    EPA Science Inventory

    We propose Fisher Information as a new calculable thermodynamic property that can be shown to follow the Second and the Third Laws of Thermodynamics. Fisher Information is, however, qualitatively different from entropy and potentially possessing a great deal more structure. Hence...

  16. Infrared image non-rigid registration based on regional information entropy demons algorithm

    NASA Astrophysics Data System (ADS)

    Lu, Chaoliang; Ma, Lihua; Yu, Ming; Cui, Shumin; Wu, Qingrong

    2015-02-01

    Infrared imaging fault detection which is treated as an ideal, non-contact, non-destructive testing method is applied to the circuit board fault detection. Since Infrared images obtained by handheld infrared camera with wide-angle lens have both rigid and non-rigid deformations. To solve this problem, a new demons algorithm based on regional information entropy was proposed. The new method overcame the shortcomings of traditional demons algorithm that was sensitive to the intensity. First, the information entropy image was gotten by computing regional information entropy of the image. Then, the deformation between the two images was calculated that was the same as demons algorithm. Experimental results demonstrated that the proposed algorithm has better robustness in intensity inconsistent images registration compared with the traditional demons algorithm. Achieving accurate registration between intensity inconsistent infrared images provided strong support for the temperature contrast.

  17. Spacetime replication of continuous variable quantum information

    NASA Astrophysics Data System (ADS)

    Hayden, Patrick; Nezami, Sepehr; Salton, Grant; Sanders, Barry C.

    2016-08-01

    The theory of relativity requires that no information travel faster than light, whereas the unitarity of quantum mechanics ensures that quantum information cannot be cloned. These conditions provide the basic constraints that appear in information replication tasks, which formalize aspects of the behavior of information in relativistic quantum mechanics. In this article, we provide continuous variable (CV) strategies for spacetime quantum information replication that are directly amenable to optical or mechanical implementation. We use a new class of homologically constructed CV quantum error correcting codes to provide efficient solutions for the general case of information replication. As compared to schemes encoding qubits, our CV solution requires half as many shares per encoded system. We also provide an optimized five-mode strategy for replicating quantum information in a particular configuration of four spacetime regions designed not to be reducible to previously performed experiments. For this optimized strategy, we provide detailed encoding and decoding procedures using standard optical apparatus and calculate the recovery fidelity when finite squeezing is used. As such we provide a scheme for experimentally realizing quantum information replication using quantum optics.

  18. The decoupling approach to quantum information theory

    NASA Astrophysics Data System (ADS)

    Dupuis, Frédéric

    2010-04-01

    Quantum information theory studies the fundamental limits that physical laws impose on information processing tasks such as data compression and data transmission on noisy channels. This thesis presents general techniques that allow one to solve many fundamental problems of quantum information theory in a unified framework. The central theorem of this thesis proves the existence of a protocol that transmits quantum data that is partially known to the receiver through a single use of an arbitrary noisy quantum channel. In addition to the intrinsic interest of this problem, this theorem has as immediate corollaries several central theorems of quantum information theory. The following chapters use this theorem to prove the existence of new protocols for two other types of quantum channels, namely quantum broadcast channels and quantum channels with side information at the transmitter. These protocols also involve sending quantum information partially known by the receiver with a single use of the channel, and have as corollaries entanglement-assisted and unassisted asymptotic coding theorems. The entanglement-assisted asymptotic versions can, in both cases, be considered as quantum versions of the best coding theorems known for the classical versions of these problems. The last chapter deals with a purely quantum phenomenon called locking. We demonstrate that it is possible to encode a classical message into a quantum state such that, by removing a subsystem of logarithmic size with respect to its total size, no measurement can have significant correlations with the message. The message is therefore "locked" by a logarithmic-size key. This thesis presents the first locking protocol for which the success criterion is that the trace distance between the joint distribution of the message and the measurement result and the product of their marginals be sufficiently small.

  19. Colloquium: Protecting quantum information against environmental noise

    NASA Astrophysics Data System (ADS)

    Suter, Dieter; Álvarez, Gonzalo A.

    2016-10-01

    Quantum technologies represent a rapidly evolving field in which the specific properties of quantum mechanical systems are exploited to enhance the performance of various applications such as sensing, transmission, and processing of information. Such devices can be useful only if the quantum systems also interact with their environment. However, the interactions with the environment can degrade the specific quantum properties of these systems, such as coherence and entanglement. It is therefore essential that the interaction between a quantum system and the environment is controlled in such a way that the unwanted effects of the environment are suppressed while the necessary interactions are retained. This Colloquium gives an overview, aimed at newcomers to this field, of some of the challenges that need to be overcome to achieve this goal. A number of techniques have been developed for this purpose in different areas of physics including magnetic resonance, optics, and quantum information. They include the application of static or time-dependent fields to the quantum system, which are designed to average the effect of the environmental interactions to zero. Quantum error correction schemes were developed to detect and eliminate certain errors that occur during the storage and processing of quantum information. In many physical systems, it is useful to use specific quantum states that are intrinsically less susceptible to environmental noise for encoding the quantum information. The dominant contribution to the loss of information is pure dephasing, i.e., through the loss of coherence in quantum mechanical superposition states. Accordingly, most schemes for reducing loss of information focus on dephasing processes. This is also the focus of this Colloquium.

  20. Relating information entropy and mass variance to measure bias and non-Gaussianity

    NASA Astrophysics Data System (ADS)

    Pandey, Biswajit

    2016-09-01

    We relate the information entropy and the mass variance of any distribution in the regime of small fluctuations. We use a set of Monte Carlo simulations of different homogeneous and inhomogeneous distributions to verify the relation and also test it in a set of cosmological N-body simulations. We find that the relation is in excellent agreement with the simulations and is independent of number density and the nature of the distributions. We show that the relation between information entropy and mass variance can be used to determine the linear bias on large scales and detect the signatures of non-Gaussianity on small scales in galaxy distributions.

  1. Quantum metrology from a quantum information science perspective

    NASA Astrophysics Data System (ADS)

    Tóth, Géza; Apellaniz, Iagoba

    2014-10-01

    We summarize important recent advances in quantum metrology, in connection to experiments in cold gases, trapped cold atoms and photons. First we review simple metrological setups, such as quantum metrology with spin squeezed states, with Greenberger-Horne-Zeilinger states, Dicke states and singlet states. We calculate the highest precision achievable in these schemes. Then, we present the fundamental notions of quantum metrology, such as shot-noise scaling, Heisenberg scaling, the quantum Fisher information and the Cramér-Rao bound. Using these, we demonstrate that entanglement is needed to surpass the shot-noise scaling in very general metrological tasks with a linear interferometer. We discuss some applications of the quantum Fisher information, such as how it can be used to obtain a criterion for a quantum state to be a macroscopic superposition. We show how it is related to the speed of a quantum evolution, and how it appears in the theory of the quantum Zeno effect. Finally, we explain how uncorrelated noise limits the highest achievable precision in very general metrological tasks. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘50 years of Bell’s theorem’.

  2. Entropy uncertainty relations and stability of phase-temporal quantum cryptography with finite-length transmitted strings

    SciTech Connect

    Molotkov, S. N.

    2012-12-15

    Any key-generation session contains a finite number of quantum-state messages, and it is there-fore important to understand the fundamental restrictions imposed on the minimal length of a string required to obtain a secret key with a specified length. The entropy uncertainty relations for smooth min and max entropies considerably simplify and shorten the proof of security. A proof of security of quantum key distribution with phase-temporal encryption is presented. This protocol provides the maximum critical error compared to other protocols up to which secure key distribution is guaranteed. In addition, unlike other basic protocols (of the BB84 type), which are vulnerable with respect to an attack by 'blinding' of avalanche photodetectors, this protocol is stable with respect to such an attack and guarantees key security.

  3. Quantum information and gravity cutoff in theories with species

    NASA Astrophysics Data System (ADS)

    Dvali, Gia; Gomez, Cesar

    2009-04-01

    We show that lowering of the gravitational cutoff relative to the Planck mass, imposed by black hole physics in theories with N species, has an independent justification from quantum information theory. First, this scale marks the limiting capacity of any information processor. Secondly, by taking into the account the limitations of the quantum information storage in any system with species, the bound on the gravity cutoff becomes equivalent to the holographic bound, and this equivalence automatically implies the equality of entanglement and Bekenstein-Hawking entropies. Next, the same bound follows from quantum cloning theorem. Finally, we point out that by identifying the UV and IR threshold scales of the black hole quasi-classicality in four-dimensional field and high dimensional gravity theories, the bound translates as the correspondence between the two theories. In case when the high dimensional background is AdS, this reproduces the well-known AdS/CFT relation, but also suggests a generalization of the correspondence beyond AdS spaces. In particular, it reproduces a recently suggested duality between a four-dimensional CFT and a flat five-dimensional theory, in which gravity crosses over from four to five dimensional regime in far infrared.

  4. Algorithmic information content, Church-Turing thesis, physical entropy, and Maxwell's demon

    SciTech Connect

    Zurek, W.H.

    1990-01-01

    Measurements convert alternative possibilities of its potential outcomes into the definiteness of the record'' -- data describing the actual outcome. The resulting decrease of statistical entropy has been, since the inception of the Maxwell's demon, regarded as a threat to the second law of thermodynamics. For, when the statistical entropy is employed as the measure of the useful work which can be extracted from the system, its decrease by the information gathering actions of the observer would lead one to believe that, at least from the observer's viewpoint, the second law can be violated. I show that the decrease of ignorance does not necessarily lead to the lowering of disorder of the measured physical system. Measurements can only convert uncertainty (quantified by the statistical entropy) into randomness of the outcome (given by the algorithmic information content of the data). The ability to extract useful work is measured by physical entropy, which is equal to the sum of these two measures of disorder. So defined physical entropy is, on the average, constant in course of the measurements carried out by the observer on an equilibrium system. 27 refs., 6 figs.

  5. Eigensolution techniques, their applications and Fisherʼs information entropy of the Tietz-Wei diatomic molecular model

    NASA Astrophysics Data System (ADS)

    Falaye, B. J.; Oyewumi, K. J.; Ikhdair, S. M.; Hamzavi, M.

    2014-11-01

    In this study, the approximate analytical solutions of Schrödinger, Klein-Gordon and Dirac equations under the Tietz-Wei (TW) diatomic molecular potential are represented by using an approximation for the centrifugal term. We have applied three types of eigensolution techniques: the functional analysis approach, supersymmetry quantum mechanics and the asymptotic iteration method to solve the Klein-Gordon, Dirac and Schrödinger equations, respectively. The energy eigenvalues and the corresponding eigenfunctions for these three wave equations are obtained, and some numerical results and figures are reported. It has been shown that these techniques yielded exactly the same results. some expectation values of the TW diatomic molecular potential within the framework of the Hellmann-Feynman theorem have been presented. The probability distributions that characterize the quantum mechanical states of TW diatomic molecular potential are analyzed by means of complementary information measures of a probability distribution called Fisher's information entropy. This distribution has been described in terms of Jacobi polynomials, whose characteristics are controlled by quantum numbers.

  6. Can Nonprivate Channels Transmit Quantum Information?

    NASA Astrophysics Data System (ADS)

    Smith, Graeme; Smolin, John A.

    2009-01-01

    We study the power of quantum channels with little or no capacity for private communication. Because privacy is a necessary condition for quantum communication, one might expect that such channels would be of little use for transmitting quantum states. Nevertheless, we find strong evidence that there are pairs of such channels that, when used together, can transmit far more quantum information than the sum of their individual private capacities. Because quantum transmissions are necessarily private, this would imply a large violation of additivity for the private capacity. Specifically, we present channels which display either (1) a large joint quantum capacity but very small individual private capacities or (2) a severe violation of additivity for the Holevo information.

  7. Quantum-information processing in disordered and complex quantum systems

    SciTech Connect

    Sen, Aditi; Sen, Ujjwal; Ahufinger, Veronica; Briegel, Hans J.; Sanpera, Anna; Lewenstein, Maciej

    2006-12-15

    We study quantum information processing in complex disordered many body systems that can be implemented by using lattices of ultracold atomic gases and trapped ions. We demonstrate, first in the short range case, the generation of entanglement and the local realization of quantum gates in a disordered magnetic model describing a quantum spin glass. We show that in this case it is possible to achieve fidelities of quantum gates higher than in the classical case. Complex systems with long range interactions, such as ions chains or dipolar atomic gases, can be used to model neural network Hamiltonians. For such systems, where both long range interactions and disorder appear, it is possible to generate long range bipartite entanglement. We provide an efficient analytical method to calculate the time evolution of a given initial state, which in turn allows us to calculate its quantum correlations.

  8. Negative Entropy of Life

    NASA Astrophysics Data System (ADS)

    Goradia, Shantilal

    2015-10-01

    We modify Newtonian gravity to probabilistic quantum mechanical gravity to derive strong coupling. If this approach is valid, we should be able to extend it to the physical body (life) as follows. Using Boltzmann equation, we get the entropy of the universe (137) as if its reciprocal, the fine structure constant (ALPHA), is the hidden candidate representing the negative entropy of the universe which is indicative of the binary information as its basis (http://www.arXiv.org/pdf/physics0210040v5). Since ALPHA relates to cosmology, it must relate to molecular biology too, with the binary system as the fundamental source of information for the nucleotides of the DNA as implicit in the book by the author: ``Quantum Consciousness - The Road to Reality.'' We debate claims of anthropic principle based on the negligible variation of ALPHA and throw light on thermodynamics. We question constancy of G in multiple ways.

  9. Fault Detection and Diagnosis for Gas Turbines Based on a Kernelized Information Entropy Model

    PubMed Central

    Wang, Weiying; Xu, Zhiqiang; Tang, Rui; Li, Shuying; Wu, Wei

    2014-01-01

    Gas turbines are considered as one kind of the most important devices in power engineering and have been widely used in power generation, airplanes, and naval ships and also in oil drilling platforms. However, they are monitored without man on duty in the most cases. It is highly desirable to develop techniques and systems to remotely monitor their conditions and analyze their faults. In this work, we introduce a remote system for online condition monitoring and fault diagnosis of gas turbine on offshore oil well drilling platforms based on a kernelized information entropy model. Shannon information entropy is generalized for measuring the uniformity of exhaust temperatures, which reflect the overall states of the gas paths of gas turbine. In addition, we also extend the entropy to compute the information quantity of features in kernel spaces, which help to select the informative features for a certain recognition task. Finally, we introduce the information entropy based decision tree algorithm to extract rules from fault samples. The experiments on some real-world data show the effectiveness of the proposed algorithms. PMID:25258726

  10. Fault detection and diagnosis for gas turbines based on a kernelized information entropy model.

    PubMed

    Wang, Weiying; Xu, Zhiqiang; Tang, Rui; Li, Shuying; Wu, Wei

    2014-01-01

    Gas turbines are considered as one kind of the most important devices in power engineering and have been widely used in power generation, airplanes, and naval ships and also in oil drilling platforms. However, they are monitored without man on duty in the most cases. It is highly desirable to develop techniques and systems to remotely monitor their conditions and analyze their faults. In this work, we introduce a remote system for online condition monitoring and fault diagnosis of gas turbine on offshore oil well drilling platforms based on a kernelized information entropy model. Shannon information entropy is generalized for measuring the uniformity of exhaust temperatures, which reflect the overall states of the gas paths of gas turbine. In addition, we also extend the entropy to compute the information quantity of features in kernel spaces, which help to select the informative features for a certain recognition task. Finally, we introduce the information entropy based decision tree algorithm to extract rules from fault samples. The experiments on some real-world data show the effectiveness of the proposed algorithms. PMID:25258726

  11. Fault detection and diagnosis for gas turbines based on a kernelized information entropy model.

    PubMed

    Wang, Weiying; Xu, Zhiqiang; Tang, Rui; Li, Shuying; Wu, Wei

    2014-01-01

    Gas turbines are considered as one kind of the most important devices in power engineering and have been widely used in power generation, airplanes, and naval ships and also in oil drilling platforms. However, they are monitored without man on duty in the most cases. It is highly desirable to develop techniques and systems to remotely monitor their conditions and analyze their faults. In this work, we introduce a remote system for online condition monitoring and fault diagnosis of gas turbine on offshore oil well drilling platforms based on a kernelized information entropy model. Shannon information entropy is generalized for measuring the uniformity of exhaust temperatures, which reflect the overall states of the gas paths of gas turbine. In addition, we also extend the entropy to compute the information quantity of features in kernel spaces, which help to select the informative features for a certain recognition task. Finally, we introduce the information entropy based decision tree algorithm to extract rules from fault samples. The experiments on some real-world data show the effectiveness of the proposed algorithms.

  12. Random subspaces in quantum information theory

    NASA Astrophysics Data System (ADS)

    Hayden, Patrick

    2005-03-01

    The selection of random unitary transformations plays a role in quantum information theory analogous to the role of random hash functions in classical information theory. Recent applications have included protocols achieving the quantum channel capacity and methods for extending superdense coding from bits to qubits. In addition, the corresponding random subspaces have proved useful for studying the structure of bipartite and multipartite entanglement. In quantum information theory, we're fond of saying that Hilbert space is a big place, the implication being that there's room for the unexpected to occur. The goal of this talk is to further bolster this homespun wisdowm. I'm going to present a number of results in quantum information theory that stem from the initially counterintuitive geometry of high-dimensional vector spaces, where subspaces with highly extremal properties are the norm rather than the exception. Peter Shor has shown, for example, that randomly selected subspaces can be used to send quantum information through a noisy quantum channel at the highest possible rate, that is, the quantum channel capacity. More recently, Debbie Leung, Andreas Winter and I demonstrated that a randomly chosen subspace of a bipartite quantum system will likely contain nothing but nearly maximally entangled states, even if the subspace is nearly as large as the original system in qubit terms. This observation has implications for communication, especially superdense coding.

  13. Microstrip Superconducting Quantum Interference Devices for Quantum Information Science

    NASA Astrophysics Data System (ADS)

    De Feo, Michael P.

    Quantum-limited amplification in the microwave frequency range is of both practical and fundamental importance. The weak signals corresponding to single microwave photons require substantial amplification to resolve. When probing quantum excitations of the electromagnetic field, the substantial noise produced by standard amplifiers dominates the signal, therefore, several averages must be accumulated to achieve even a modest signal-to-noise ratio. Even worse, the back-action on the system due to amplifier noise can hasten the decay of the quantum state. In recent years, low-noise microwave-frequency amplification has been advancing rapidly and one field that would benefit greatly from this is circuit quantum electrodynamics (cQED). The development of circuit quantum electrodynamics—which implements techniques of quantum optics at microwave frequencies—has led to revolutionary progress in the field of quantum information science. cQED employs quantum bits (qubits) and superconducting microwave resonators in place of the atoms and cavities used in quantum optics permitting preparation and control of low energy photon states in macroscopic superconducting circuits at millikelvin temperatures. We have developed a microstrip superconducting quantum interference device (SQUID) amplifier (MSA) to provide the first stage of amplification for these systems. Employing sub-micron Josephson tunnel junctions for enhanced gain, these MSAs operate at microwave frequencies and are optimized to perform with near quantum-limited noise characteristics. Our MSA is utilized as the first stage of amplification to probe the dynamics of a SQUID oscillator. The SQUID oscillator is a flux-tunable microwave resonator formed by a capacitively shunted dc SQUID. Josephson plasma oscillations are induced by pulsed microwave excitations at the resonant frequency of the oscillator. Once pulsed, decaying plasma oscillations are observed in the time domain. By measuring with pulse amplitudes

  14. Quantum information processing : science & technology.

    SciTech Connect

    Horton, Rebecca; Carroll, Malcolm S.; Tarman, Thomas David

    2010-09-01

    Qubits demonstrated using GaAs double quantum dots (DQD). The qubit basis states are the (1) singlet and (2) triplet stationary states. Long spin decoherence times in silicon spurs translation of GaAs qubit in to silicon. In the near term the goals are: (1) Develop surface gate enhancement mode double quantum dots (MOS & strained-Si/SiGe) to demonstrate few electrons and spin read-out and to examine impurity doped quantum-dots as an alternative architecture; (2) Use mobility, C-V, ESR, quantum dot performance & modeling to feedback and improve upon processing, this includes development of atomic precision fabrication at SNL; (3) Examine integrated electronics approaches to RF-SET; (4) Use combinations of numerical packages for multi-scale simulation of quantum dot systems (NEMO3D, EMT, TCAD, SPICE); and (5) Continue micro-architecture evaluation for different device and transport architectures.

  15. Relativistic quantum information and time machines

    NASA Astrophysics Data System (ADS)

    Ralph, Timothy C.; Downes, Tony G.

    2012-01-01

    Relativistic quantum information combines the informational approach to understanding and using quantum mechanical systems - quantum information - with the relativistic view of the Universe. In this introductory review we examine key results to emerge from this new field of research in physics and discuss future directions. A particularly active area recently has been the question of what happens when quantum systems interact with general relativistic closed timelike curves - effectively time machines. We discuss two different approaches that have been suggested for modelling such situations. It is argued that the approach based on matching the density operator of the quantum state between the future and past most consistently avoids the paradoxes usually associated with time travel.

  16. The smooth entropy formalism for von Neumann algebras

    NASA Astrophysics Data System (ADS)

    Berta, Mario; Furrer, Fabian; Scholz, Volkher B.

    2016-01-01

    We discuss information-theoretic concepts on infinite-dimensional quantum systems. In particular, we lift the smooth entropy formalism as introduced by Renner and collaborators for finite-dimensional systems to von Neumann algebras. For the smooth conditional min- and max-entropy, we recover similar characterizing properties and information-theoretic operational interpretations as in the finite-dimensional case. We generalize the entropic uncertainty relation with quantum side information of Tomamichel and Renner and discuss applications to quantum cryptography. In particular, we prove the possibility to perform privacy amplification and classical data compression with quantum side information modeled by a von Neumann algebra.

  17. The Entropy Estimation of the Physics’ Course Content on the Basis of Intradisciplinary Connections’ Information Model

    NASA Astrophysics Data System (ADS)

    Tatyana, Gnitetskaya

    2016-08-01

    In this paper the information model of intradisciplinary connections and semantic structures method are described. The information parameters, which we use in information model, are introduced. The question we would like to answer in this paper is - how to optimize the Physics Course’ content. As an example, the differences between entropy values in the contents of physics lecture with one topic but different logics of explanations are showed.

  18. Entropy in Postmerger and Acquisition Integration from an Information Technology Perspective

    ERIC Educational Resources Information Center

    Williams, Gloria S.

    2012-01-01

    Mergers and acquisitions have historically experienced failure rates from 50% to more than 80%. Successful integration of information technology (IT) systems can be the difference between postmerger success or failure. The purpose of this phenomenological study was to explore the entropy phenomenon during postmerger IT integration. To that end, a…

  19. Generalized entanglement entropy

    NASA Astrophysics Data System (ADS)

    Taylor, Marika

    2016-07-01

    We discuss two measures of entanglement in quantum field theory and their holographic realizations. For field theories admitting a global symmetry, we introduce a global symmetry entanglement entropy, associated with the partitioning of the symmetry group. This quantity is proposed to be related to the generalized holographic entanglement entropy defined via the partitioning of the internal space of the bulk geometry. Thesecond measure of quantum field theory entanglement is the field space entanglement entropy, obtained by integrating out a subset of the quantum fields. We argue that field space entanglement entropy cannot be precisely realised geometrically in a holographic dual. However, for holographic geometries with interior decoupling regions, the differential entropy provides a close analogue to the field space entanglement entropy. We derive generic descriptions of such inner throat regions in terms of gravity coupled to massive scalars and show how the differential entropy in the throat captures features of the field space entanglement entropy.

  20. Quantum correlations require multipartite information principles.

    PubMed

    Gallego, Rodrigo; Würflinger, Lars Erik; Acín, Antonio; Navascués, Miguel

    2011-11-18

    Identifying which correlations among distant observers are possible within our current description of nature, based on quantum mechanics, is a fundamental problem in physics. Recently, information concepts have been proposed as the key ingredient to characterize the set of quantum correlations. Novel information principles, such as information causality or nontrivial communication complexity, have been introduced in this context and successfully applied to some concrete scenarios. We show in this work a fundamental limitation of this approach: no principle based on bipartite information concepts is able to singleout the set of quantum correlations for an arbitrary number of parties. Our results reflect the intricate structure of quantum correlations and imply that new and intrinsically multipartite information concepts are needed for their full understanding.

  1. Entropy algebras and Birkhoff factorization

    NASA Astrophysics Data System (ADS)

    Marcolli, Matilde; Tedeschi, Nicolas

    2015-11-01

    We develop notions of Rota-Baxter structures and associated Birkhoff factorizations, in the context of min-plus semirings and their thermodynamic deformations, including deformations arising from quantum information measures such as the von Neumann entropy. We consider examples related to Manin's renormalization and computation program, to Markov random fields and to counting functions and zeta functions of algebraic varieties.

  2. Efficient compression of quantum information

    SciTech Connect

    Plesch, Martin; Buzek, Vladimir

    2010-03-15

    We propose a scheme for an exact efficient transformation of a tensor product state of many identically prepared qubits into a state of a logarithmically small number of qubits. Using a quadratic number of elementary quantum gates we transform N identically prepared qubits into a state, which is nontrivial only on the first [log{sub 2}(N+1)] qubits. This procedure might be useful for quantum memories, as only a small portion of the original qubits has to be stored. Another possible application is in communicating a direction encoded in a set of quantum states, as the compressed state provides a high-effective method for such an encoding.

  3. Optical technologies for quantum information science

    NASA Astrophysics Data System (ADS)

    Kwiat, Paul G.; Altepeter, Joseph; Barreiro, Julio; Branning, David A.; Jeffrey, Evan R.; Peters, Nicholas; VanDevender, Aaron P.

    2004-02-01

    A number of optical technologies remain to be developed and optimized for various applications in quantum information processing, especially quantum communication. We will give an overview of our approach to some of these, including periodic heralded single-photon sources based on spontaneous parametric down-conversion, ultrabright sources of tunable entangled photons, near unit efficiency single- and multi-photon detectors based on an atomic vapor interaction, quantum state transducers based on high efficiency frequency up-conversion, and low-loss optical quantum memories.

  4. Upper entropy axioms and lower entropy axioms

    NASA Astrophysics Data System (ADS)

    Guo, Jin-Li; Suo, Qi

    2015-04-01

    The paper suggests the concepts of an upper entropy and a lower entropy. We propose a new axiomatic definition, namely, upper entropy axioms, inspired by axioms of metric spaces, and also formulate lower entropy axioms. We also develop weak upper entropy axioms and weak lower entropy axioms. Their conditions are weaker than those of Shannon-Khinchin axioms and Tsallis axioms, while these conditions are stronger than those of the axiomatics based on the first three Shannon-Khinchin axioms. The subadditivity and strong subadditivity of entropy are obtained in the new axiomatics. Tsallis statistics is a special case of satisfying our axioms. Moreover, different forms of information measures, such as Shannon entropy, Daroczy entropy, Tsallis entropy and other entropies, can be unified under the same axiomatics.

  5. Upper entropy axioms and lower entropy axioms

    SciTech Connect

    Guo, Jin-Li Suo, Qi

    2015-04-15

    The paper suggests the concepts of an upper entropy and a lower entropy. We propose a new axiomatic definition, namely, upper entropy axioms, inspired by axioms of metric spaces, and also formulate lower entropy axioms. We also develop weak upper entropy axioms and weak lower entropy axioms. Their conditions are weaker than those of Shannon–Khinchin axioms and Tsallis axioms, while these conditions are stronger than those of the axiomatics based on the first three Shannon–Khinchin axioms. The subadditivity and strong subadditivity of entropy are obtained in the new axiomatics. Tsallis statistics is a special case of satisfying our axioms. Moreover, different forms of information measures, such as Shannon entropy, Daroczy entropy, Tsallis entropy and other entropies, can be unified under the same axiomatics.

  6. Steady and optimal entropy squeezing of a two-level atom with quantum-jump-based feedback and classical driving in a dissipative cavity

    NASA Astrophysics Data System (ADS)

    Yu, Min; Fang, Mao-Fa

    2016-10-01

    We investigate the entropy squeezing of a two-level atom coupled to a dissipative cavity under two different controls: In the first case, quantum-jump-based feedback is alone applied, whereas in the second case we consider the combined effect of quantum-jump-based feedback and classical driving, in which we provide a scheme to generate and protect steady and optimal entropy squeezing of the two-level atom. The results show that the entropy squeezing of atomic polarization components greatly depends on the control of quantum-jump-based feedback and classical driving. Under the condition of designing proper quantum-jump-based feedback parameters, the entropy squeezing can be generated and protected. Furthermore, when both quantum-jump-based feedback and classical driving are simultaneously applied, steady and optimal entropy squeezing of the two-level atom can be obtained even though there is initially no entropy squeezing, which is explained by making use of the steady-state solution of the atom.

  7. Steady and optimal entropy squeezing of a two-level atom with quantum-jump-based feedback and classical driving in a dissipative cavity

    NASA Astrophysics Data System (ADS)

    Yu, Min; Fang, Mao-Fa

    2016-07-01

    We investigate the entropy squeezing of a two-level atom coupled to a dissipative cavity under two different controls: In the first case, quantum-jump-based feedback is alone applied, whereas in the second case we consider the combined effect of quantum-jump-based feedback and classical driving, in which we provide a scheme to generate and protect steady and optimal entropy squeezing of the two-level atom. The results show that the entropy squeezing of atomic polarization components greatly depends on the control of quantum-jump-based feedback and classical driving. Under the condition of designing proper quantum-jump-based feedback parameters, the entropy squeezing can be generated and protected. Furthermore, when both quantum-jump-based feedback and classical driving are simultaneously applied, steady and optimal entropy squeezing of the two-level atom can be obtained even though there is initially no entropy squeezing, which is explained by making use of the steady-state solution of the atom.

  8. Quantum correlations and distinguishability of quantum states

    SciTech Connect

    Spehner, Dominique

    2014-07-15

    A survey of various concepts in quantum information is given, with a main emphasis on the distinguishability of quantum states and quantum correlations. Covered topics include generalized and least square measurements, state discrimination, quantum relative entropies, the Bures distance on the set of quantum states, the quantum Fisher information, the quantum Chernoff bound, bipartite entanglement, the quantum discord, and geometrical measures of quantum correlations. The article is intended both for physicists interested not only by collections of results but also by the mathematical methods justifying them, and for mathematicians looking for an up-to-date introductory course on these subjects, which are mainly developed in the physics literature.

  9. Hilbert's projective metric in quantum information theory

    NASA Astrophysics Data System (ADS)

    Reeb, David; Kastoryano, Michael J.; Wolf, Michael M.

    2011-08-01

    We introduce and apply Hilbert's projective metric in the context of quantum information theory. The metric is induced by convex cones such as the sets of positive, separable or positive partial transpose operators. It provides bounds on measures for statistical distinguishability of quantum states and on the decrease of entanglement under protocols involving local quantum operations and classical communication or under other cone-preserving operations. The results are formulated in terms of general cones and base norms and lead to contractivity bounds for quantum channels, for instance, improving Ruskai's trace-norm contraction inequality. A new duality between distinguishability measures and base norms is provided. For two given pairs of quantum states we show that the contraction of Hilbert's projective metric is necessary and sufficient for the existence of a probabilistic quantum operation that maps one pair onto the other. Inequalities between Hilbert's projective metric and the Chernoff bound, the fidelity and various norms are proven.

  10. Minimising the heat dissipation of quantum information erasure

    NASA Astrophysics Data System (ADS)

    Hamed Mohammady, M.; Mohseni, Masoud; Omar, Yasser

    2016-01-01

    Quantum state engineering and quantum computation rely on information erasure procedures that, up to some fidelity, prepare a quantum object in a pure state. Such processes occur within Landauer's framework if they rely on an interaction between the object and a thermal reservoir. Landauer's principle dictates that this must dissipate a minimum quantity of heat, proportional to the entropy reduction that is incurred by the object, to the thermal reservoir. However, this lower bound is only reachable for some specific physical situations, and it is not necessarily achievable for any given reservoir. The main task of our work can be stated as the minimisation of heat dissipation given probabilistic information erasure, i.e., minimising the amount of energy transferred to the thermal reservoir as heat if we require that the probability of preparing the object in a specific pure state ≤ft|{\\varphi }1\\right.> be no smaller than {p}{\\varphi 1}{max}-δ . Here {p}{\\varphi 1}{max} is the maximum probability of information erasure that is permissible by the physical context, and δ ≥slant 0 the error. To determine the achievable minimal heat dissipation of quantum information erasure within a given physical context, we explicitly optimise over all possible unitary operators that act on the composite system of object and reservoir. Specifically, we characterise the equivalence class of such optimal unitary operators, using tools from majorisation theory, when we are restricted to finite-dimensional Hilbert spaces. Furthermore, we discuss how pure state preparation processes could be achieved with a smaller heat cost than Landauer's limit, by operating outside of Landauer's framework.

  11. Entropy of nonrotating isolated horizons in Lovelock theory from loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Wang, Jing-Bo; Huang, Chao-Guang; Li, Lin

    2016-08-01

    In this paper, the BF theory method is applied to the nonrotating isolated horizons in Lovelock theory. The final entropy matches the Wald entropy formula for this theory. We also confirm the conclusion obtained by Bodendorfer et al. that the entropy is related to the flux operator rather than the area operator in general diffeomorphic-invariant theory. Supported by National Natural Science Foundation of China (11275207)

  12. Photonic quantum information: science and technology

    PubMed Central

    TAKEUCHI, Shigeki

    2016-01-01

    Recent technological progress in the generation, manipulation and detection of individual single photons has opened a new scientific field of photonic quantum information. This progress includes the realization of single photon switches, photonic quantum circuits with specific functions, and the application of novel photonic states to novel optical metrology beyond the limits of standard optics. In this review article, the recent developments and current status of photonic quantum information technology are overviewed based on the author’s past and recent works. PMID:26755398

  13. Thermodynamics of information exchange between two coupled quantum dots.

    PubMed

    Kutvonen, Aki; Sagawa, Takahiro; Ala-Nissila, Tapio

    2016-03-01

    We propose a setup based on two coupled quantum dots where thermodynamics of a measurement can be quantitatively characterized. The information obtained in the measurement can be utilized by performing feedback in a manner apparently breaking the second law of thermodynamics. In this way the setup can be operated as a Maxwell's demon, where both the measurement and feedback are performed separately by controlling an external parameter. This is analogous to the case of the original Szilard engine. Since the setup contains both the microscopic demon and the engine itself, the operation of the whole measurement-feedback cycle can be explained in detail at the level of single realizations. In addition, we derive integral fluctuation relations for both the bare and coarse-grained entropy productions in the setup. PMID:27078332

  14. Thermodynamics of information exchange between two coupled quantum dots

    NASA Astrophysics Data System (ADS)

    Kutvonen, Aki; Sagawa, Takahiro; Ala-Nissila, Tapio

    2016-03-01

    We propose a setup based on two coupled quantum dots where thermodynamics of a measurement can be quantitatively characterized. The information obtained in the measurement can be utilized by performing feedback in a manner apparently breaking the second law of thermodynamics. In this way the setup can be operated as a Maxwell's demon, where both the measurement and feedback are performed separately by controlling an external parameter. This is analogous to the case of the original Szilard engine. Since the setup contains both the microscopic demon and the engine itself, the operation of the whole measurement-feedback cycle can be explained in detail at the level of single realizations. In addition, we derive integral fluctuation relations for both the bare and coarse-grained entropy productions in the setup.

  15. Entropy Is Simple, Qualitatively.

    ERIC Educational Resources Information Center

    Lambert, Frank L.

    2002-01-01

    Suggests that qualitatively, entropy is simple. Entropy increase from a macro viewpoint is a measure of the dispersal of energy from localized to spread out at a temperature T. Fundamentally based on statistical and quantum mechanics, this approach is superior to the non-fundamental "disorder" as a descriptor of entropy change. (MM)

  16. Quantum information. Unconditional quantum teleportation between distant solid-state quantum bits.

    PubMed

    Pfaff, W; Hensen, B J; Bernien, H; van Dam, S B; Blok, M S; Taminiau, T H; Tiggelman, M J; Schouten, R N; Markham, M; Twitchen, D J; Hanson, R

    2014-08-01

    Realizing robust quantum information transfer between long-lived qubit registers is a key challenge for quantum information science and technology. Here we demonstrate unconditional teleportation of arbitrary quantum states between diamond spin qubits separated by 3 meters. We prepare the teleporter through photon-mediated heralded entanglement between two distant electron spins and subsequently encode the source qubit in a single nuclear spin. By realizing a fully deterministic Bell-state measurement combined with real-time feed-forward, quantum teleportation is achieved upon each attempt with an average state fidelity exceeding the classical limit. These results establish diamond spin qubits as a prime candidate for the realization of quantum networks for quantum communication and network-based quantum computing. PMID:25082696

  17. Quantum information. Unconditional quantum teleportation between distant solid-state quantum bits.

    PubMed

    Pfaff, W; Hensen, B J; Bernien, H; van Dam, S B; Blok, M S; Taminiau, T H; Tiggelman, M J; Schouten, R N; Markham, M; Twitchen, D J; Hanson, R

    2014-08-01

    Realizing robust quantum information transfer between long-lived qubit registers is a key challenge for quantum information science and technology. Here we demonstrate unconditional teleportation of arbitrary quantum states between diamond spin qubits separated by 3 meters. We prepare the teleporter through photon-mediated heralded entanglement between two distant electron spins and subsequently encode the source qubit in a single nuclear spin. By realizing a fully deterministic Bell-state measurement combined with real-time feed-forward, quantum teleportation is achieved upon each attempt with an average state fidelity exceeding the classical limit. These results establish diamond spin qubits as a prime candidate for the realization of quantum networks for quantum communication and network-based quantum computing.

  18. Quantum statistical entropy and minimal length of 5D Ricci-flat black string with generalized uncertainty principle

    SciTech Connect

    Liu Molin; Gui Yuanxing; Liu Hongya

    2008-12-15

    In this paper, we study the quantum statistical entropy in a 5D Ricci-flat black string solution, which contains a 4D Schwarzschild-de Sitter black hole on the brane, by using the improved thin-layer method with the generalized uncertainty principle. The entropy is the linear sum of the areas of the event horizon and the cosmological horizon without any cutoff and any constraint on the bulk's configuration rather than the usual uncertainty principle. The system's density of state and free energy are convergent in the neighborhood of horizon. The small-mass approximation is determined by the asymptotic behavior of metric function near horizons. Meanwhile, we obtain the minimal length of the position {delta}x, which is restrained by the surface gravities and the thickness of layer near horizons.

  19. MIDER: network inference with mutual information distance and entropy reduction.

    PubMed

    Villaverde, Alejandro F; Ross, John; Morán, Federico; Banga, Julio R

    2014-01-01

    The prediction of links among variables from a given dataset is a task referred to as network inference or reverse engineering. It is an open problem in bioinformatics and systems biology, as well as in other areas of science. Information theory, which uses concepts such as mutual information, provides a rigorous framework for addressing it. While a number of information-theoretic methods are already available, most of them focus on a particular type of problem, introducing assumptions that limit their generality. Furthermore, many of these methods lack a publicly available implementation. Here we present MIDER, a method for inferring network structures with information theoretic concepts. It consists of two steps: first, it provides a representation of the network in which the distance among nodes indicates their statistical closeness. Second, it refines the prediction of the existing links to distinguish between direct and indirect interactions and to assign directionality. The method accepts as input time-series data related to some quantitative features of the network nodes (such as e.g. concentrations, if the nodes are chemical species). It takes into account time delays between variables, and allows choosing among several definitions and normalizations of mutual information. It is general purpose: it may be applied to any type of network, cellular or otherwise. A Matlab implementation including source code and data is freely available (http://www.iim.csic.es/~gingproc/mider.html). The performance of MIDER has been evaluated on seven different benchmark problems that cover the main types of cellular networks, including metabolic, gene regulatory, and signaling. Comparisons with state of the art information-theoretic methods have demonstrated the competitive performance of MIDER, as well as its versatility. Its use does not demand any a priori knowledge from the user; the default settings and the adaptive nature of the method provide good results for a wide

  20. MIDER: network inference with mutual information distance and entropy reduction.

    PubMed

    Villaverde, Alejandro F; Ross, John; Morán, Federico; Banga, Julio R

    2014-01-01

    The prediction of links among variables from a given dataset is a task referred to as network inference or reverse engineering. It is an open problem in bioinformatics and systems biology, as well as in other areas of science. Information theory, which uses concepts such as mutual information, provides a rigorous framework for addressing it. While a number of information-theoretic methods are already available, most of them focus on a particular type of problem, introducing assumptions that limit their generality. Furthermore, many of these methods lack a publicly available implementation. Here we present MIDER, a method for inferring network structures with information theoretic concepts. It consists of two steps: first, it provides a representation of the network in which the distance among nodes indicates their statistical closeness. Second, it refines the prediction of the existing links to distinguish between direct and indirect interactions and to assign directionality. The method accepts as input time-series data related to some quantitative features of the network nodes (such as e.g. concentrations, if the nodes are chemical species). It takes into account time delays between variables, and allows choosing among several definitions and normalizations of mutual information. It is general purpose: it may be applied to any type of network, cellular or otherwise. A Matlab implementation including source code and data is freely available (http://www.iim.csic.es/~gingproc/mider.html). The performance of MIDER has been evaluated on seven different benchmark problems that cover the main types of cellular networks, including metabolic, gene regulatory, and signaling. Comparisons with state of the art information-theoretic methods have demonstrated the competitive performance of MIDER, as well as its versatility. Its use does not demand any a priori knowledge from the user; the default settings and the adaptive nature of the method provide good results for a wide

  1. Trapped Atomic Ions and Quantum Information Processing

    SciTech Connect

    Wineland, D. J.; Leibfried, D.; Bergquist, J. C.; Blakestad, R. B.; Bollinger, J. J.; Britton, J.; Chiaverini, J.; Epstein, R. J.; Hume, D. B.; Itano, W. M.; Jost, J. D.; Koelemeij, J. C. J.; Langer, C.; Ozeri, R.; Reichle, R.; Rosenband, T.; Schaetz, T.; Schmidt, P. O.; Seidelin, S.; Shiga, N.

    2006-11-07

    The basic requirements for quantum computing and quantum simulation (single- and multi-qubit gates, long memory times, etc.) have been demonstrated in separate experiments on trapped ions. Construction of a large-scale information processor will require synthesis of these elements and implementation of high-fidelity operations on a very large number of qubits. This is still well in the future. NIST and other groups are addressing part of the scaling issue by trying to fabricate multi-zone arrays of traps that would allow highly-parallel and scalable processing. In the near term, some simple quantum processing protocols are being used to aid in quantum metrology, such as in atomic clocks. As the number of qubits increases, Schroedinger's cat paradox and the measurement problem in quantum mechanics become more apparent; with luck, trapped ion systems might be able to shed light on these fundamental issues.

  2. Universal behavior of the Shannon mutual information in nonintegrable self-dual quantum chains

    NASA Astrophysics Data System (ADS)

    Alcaraz, F. C.

    2016-09-01

    An existing conjecture states that the Shannon mutual information contained in the ground-state wave function of conformally invariant quantum chains, on periodic lattices, has a leading finite-size scaling behavior that, similarly as the von Neumann entanglement entropy, depends on the value of the central charge of the underlying conformal field theory describing the physical properties. This conjecture applies whenever the ground-state wave function is expressed in some special basis (conformal basis). Its formulation comes mainly from numerical evidences on exactly integrable quantum chains. In this paper, the above conjecture was tested for several general nonintegrable quantum chains. We introduce new families of self-dual Z (Q ) symmetric quantum chains (Q =2 ,3 ,... ). These quantum chains contain nearest-neighbor as well next-nearest-neighbor interactions (coupling constant p ). In the cases Q =2 and Q =3 , they are extensions of the standard quantum Ising and three-state Potts chains, respectively. For Q =4 and Q ≥5 , they are extensions of the Ashkin-Teller and Z (Q ) parafermionic quantum chains. Our studies indicate that these models are interesting on their own. They are critical, conformally invariant, and share the same universality class in a continuous critical line. Moreover, our numerical analysis for Q =2 -8 indicate that the Shannon mutual information exhibits the conjectured behavior irrespective if the conformally invariant quantum chain is exactly integrable or not. For completeness we also calculated, for these new families of quantum chains, the two existing generalizations of the Shannon mutual information, which are based on the Rényi entropy and on the Rényi divergence.

  3. MIDER: Network Inference with Mutual Information Distance and Entropy Reduction

    PubMed Central

    Villaverde, Alejandro F.; Ross, John; Morán, Federico; Banga, Julio R.

    2014-01-01

    The prediction of links among variables from a given dataset is a task referred to as network inference or reverse engineering. It is an open problem in bioinformatics and systems biology, as well as in other areas of science. Information theory, which uses concepts such as mutual information, provides a rigorous framework for addressing it. While a number of information-theoretic methods are already available, most of them focus on a particular type of problem, introducing assumptions that limit their generality. Furthermore, many of these methods lack a publicly available implementation. Here we present MIDER, a method for inferring network structures with information theoretic concepts. It consists of two steps: first, it provides a representation of the network in which the distance among nodes indicates their statistical closeness. Second, it refines the prediction of the existing links to distinguish between direct and indirect interactions and to assign directionality. The method accepts as input time-series data related to some quantitative features of the network nodes (such as e.g. concentrations, if the nodes are chemical species). It takes into account time delays between variables, and allows choosing among several definitions and normalizations of mutual information. It is general purpose: it may be applied to any type of network, cellular or otherwise. A Matlab implementation including source code and data is freely available (http://www.iim.csic.es/~gingproc/mider.html). The performance of MIDER has been evaluated on seven different benchmark problems that cover the main types of cellular networks, including metabolic, gene regulatory, and signaling. Comparisons with state of the art information–theoretic methods have demonstrated the competitive performance of MIDER, as well as its versatility. Its use does not demand any a priori knowledge from the user; the default settings and the adaptive nature of the method provide good results for a wide

  4. Limitation on the Accessible Information for Quantum Channels with Inefficient Measurements

    NASA Astrophysics Data System (ADS)

    Jacobs, Kurt

    2005-10-01

    To transmit classical information using a quantum system, the sender prepares the system in one of a set of possible states and sends it to the receiver. The receiver then makes a measurement on the system to obtain information about the senders choice of state. The amount of information which is accessible to the receiver depends upon the encoding and the measurement. Here we derive a bound on this information which generalizes the bound derived by Schumacher, Westmoreland and Wootters [Schumacher, Westmoreland and Wootters, Phys. Rev. Lett. 76, 3452 (1996)] to include inefficient measurements, and thus all quantum operations. This also allows us to obtain a generalization of a bound derived by Hall [Hall, Phys. Rev. A 55, 100 (1997)], and to show that the average reduction in the von Neumann entropy which accompanies a measurement is concave in the initial state, for all quantum operations.

  5. Experimental demonstration of information to energy conversion in a quantum system at the Landauer limit

    NASA Astrophysics Data System (ADS)

    Peterson, J. P. S.; Sarthour, R. S.; Souza, A. M.; Oliveira, I. S.; Goold, J.; Modi, K.; Soares-Pinto, D. O.; Céleri, L. C.

    2016-04-01

    Landauer's principle sets fundamental thermodynamical constraints for classical and quantum information processing, thus affecting not only various branches of physics, but also of computer science and engineering. Despite its importance, this principle was only recently experimentally considered for classical systems. Here we employ a nuclear magnetic resonance set-up to experimentally address the information to energy conversion in a quantum system. Specifically, we consider a three nuclear spins S =1/2 (qubits) molecule-the system, the reservoir and the ancilla-to measure the heat dissipated during the implementation of a global system-reservoir unitary interaction that changes the information content of the system. By employing an interferometric technique, we were able to reconstruct the heat distribution associated with the unitary interaction. Then, through quantum state tomography, we measured the relative change in the entropy of the system. In this way, we were able to verify that an operation that changes the information content of the system must necessarily generate heat in the reservoir, exactly as predicted by Landauer's principle. The scheme presented here allows for the detailed study of irreversible entropy production in quantum information processors.

  6. Band target entropy minimization for retrieving the information of individual components from overlapping chromatographic data.

    PubMed

    Xia, Zhenzhen; Liu, Yan; Cai, Wensheng; Shao, Xueguang

    2015-09-11

    Band target entropy minimization (BTEM) is a self-modeling curve resolution (SMCR) approach relying on non-negative criterion and minimization of Shannon entropy. In this study, BTEM algorithm was applied to retrieving the information of individual components from overlapping gas chromatography-mass spectrometry (GC-MS) data. The algorithm starts with dividing the whole data into bands along the retention time. In each band, singular value decomposition (SVD) is used to decompose the data into scores and loadings. Because the pure chromatographic signal possesses the lowest Shannon entropy, the chromatographic signal of each component can be constructed by optimizing the combination of the loadings with minimal Shannon entropy under non-negative criterion. To show the efficiency of the algorithm, a simulated four-component overlapping GC-MS data and an experimental GC-MS data of 18 organophosphorus pesticide mixture are investigated. The results show that both the chromatographic profiles and mass spectra of the components can be successfully extracted from the overlapping signals.

  7. Black holes, information, and Hilbert space for quantum gravity

    NASA Astrophysics Data System (ADS)

    Nomura, Yasunori; Varela, Jaime; Weinberg, Sean J.

    2013-04-01

    A coarse-grained description for the formation and evaporation of a black hole is given within the framework of a unitary theory of quantum gravity preserving locality, without dropping the information that manifests as macroscopic properties of the state at late times. The resulting picture depends strongly on the reference frame one chooses to describe the process. In one description based on a reference frame in which the reference point stays outside the black hole horizon for sufficiently long time, a late black hole state becomes a superposition of black holes in different locations and with different spins, even if the back hole is formed from collapsing matter that had a well-defined classical configuration with no angular momentum. The information about the initial state is partly encoded in relative coefficients—especially phases—of the terms representing macroscopically different geometries. In another description in which the reference point enters into the black hole horizon at late times, an S-matrix description in the asymptotically Minkowski spacetime is not applicable, but it still allows for an “S-matrix” description in the full quantum gravitational Hilbert space including singularity states. Relations between different descriptions are given by unitary transformations acting on the full Hilbert space, and they in general involve superpositions of “distant” and “infalling” descriptions. Despite the intrinsically quantum mechanical nature of the black hole state, measurements performed by a classical physical observer are consistent with those implied by general relativity. In particular, the recently-considered firewall phenomenon can occur only for an exponentially fine-tuned (and intrinsically quantum mechanical) initial state, analogous to an entropy decreasing process in a system with large degrees of freedom.

  8. Fisher information, nonclassicality and quantum revivals

    NASA Astrophysics Data System (ADS)

    Romera, Elvira; de los Santos, Francisco

    2013-11-01

    Wave packet revivals and fractional revivals are studied by means of a measure of nonclassicality based on the Fisher information. In particular, we show that the spreading and the regeneration of initially Gaussian wave packets in a quantum bouncer and in the infinite square-well correspond, respectively, to high and low nonclassicality values. This result is in accordance with the physical expectations that at a quantum revival wave packets almost recover their initial shape and the classical motion revives temporarily afterward.

  9. Nuclear magnetic resonance quantum information processing

    PubMed Central

    Serra, R. M.; Oliveira, I. S.

    2012-01-01

    For the past decade, nuclear magnetic resonance (NMR) has been established as a main experimental technique for testing quantum protocols in small systems. This Theme Issue presents recent advances and major challenges of NMR quantum information possessing (QIP), including contributions by researchers from 10 different countries. In this introduction, after a short comment on NMR-QIP basics, we briefly anticipate the contents of this issue. PMID:22946031

  10. Maximum information entropy principle and the interpretation of probabilities in statistical mechanics - a short review

    NASA Astrophysics Data System (ADS)

    Kuić, Domagoj

    2016-05-01

    In this paper an alternative approach to statistical mechanics based on the maximum information entropy principle (MaxEnt) is examined, specifically its close relation with the Gibbs method of ensembles. It is shown that the MaxEnt formalism is the logical extension of the Gibbs formalism of equilibrium statistical mechanics that is entirely independent of the frequentist interpretation of probabilities only as factual (i.e. experimentally verifiable) properties of the real world. Furthermore, we show that, consistently with the law of large numbers, the relative frequencies of the ensemble of systems prepared under identical conditions (i.e. identical constraints) actually correspond to the MaxEnt probabilites in the limit of a large number of systems in the ensemble. This result implies that the probabilities in statistical mechanics can be interpreted, independently of the frequency interpretation, on the basis of the maximum information entropy principle.

  11. A ranking procedure by incomplete pairwise comparisons using information entropy and Dempster-Shafer evidence theory.

    PubMed

    Pan, Dongbo; Lu, Xi; Liu, Juan; Deng, Yong

    2014-01-01

    Decision-making, as a way to discover the preference of ranking, has been used in various fields. However, owing to the uncertainty in group decision-making, how to rank alternatives by incomplete pairwise comparisons has become an open issue. In this paper, an improved method is proposed for ranking of alternatives by incomplete pairwise comparisons using Dempster-Shafer evidence theory and information entropy. Firstly, taking the probability assignment of the chosen preference into consideration, the comparison of alternatives to each group is addressed. Experiments verified that the information entropy of the data itself can determine the different weight of each group's choices objectively. Numerical examples in group decision-making environments are used to test the effectiveness of the proposed method. Moreover, the divergence of ranking mechanism is analyzed briefly in conclusion section. PMID:25250393

  12. Quantum information-geometry of dissipative quantum phase transitions.

    PubMed

    Banchi, Leonardo; Giorda, Paolo; Zanardi, Paolo

    2014-02-01

    A general framework for analyzing the recently discovered phase transitions in the steady state of dissipation-driven open quantum systems is still lacking. To fill this gap, we extend the so-called fidelity approach to quantum phase transitions to open systems whose steady state is a Gaussian fermionic state. We endow the manifold of correlation matrices of steady states with a metric tensor g measuring the distinguishability distance between solutions corresponding to a different set of control parameters. The phase diagram can then be mapped out in terms of the scaling behavior of g and connections with the Liouvillean gap and the model correlation functions unveiled. We argue that the fidelity approach, thanks to its differential-geometric and information-theoretic nature, provides insights into dissipative quantum critical phenomena as well as a general and powerful strategy to explore them. PMID:25353417

  13. Quantum information-geometry of dissipative quantum phase transitions.

    PubMed

    Banchi, Leonardo; Giorda, Paolo; Zanardi, Paolo

    2014-02-01

    A general framework for analyzing the recently discovered phase transitions in the steady state of dissipation-driven open quantum systems is still lacking. To fill this gap, we extend the so-called fidelity approach to quantum phase transitions to open systems whose steady state is a Gaussian fermionic state. We endow the manifold of correlation matrices of steady states with a metric tensor g measuring the distinguishability distance between solutions corresponding to a different set of control parameters. The phase diagram can then be mapped out in terms of the scaling behavior of g and connections with the Liouvillean gap and the model correlation functions unveiled. We argue that the fidelity approach, thanks to its differential-geometric and information-theoretic nature, provides insights into dissipative quantum critical phenomena as well as a general and powerful strategy to explore them.

  14. Quantum distillation: Dynamical generation of low-entropy states of strongly correlated fermions in an optical lattice

    SciTech Connect

    Heidrich-Meisner, F.; Manmana, S. R.; Rigol, M.; Muramatsu, A.; Feiguin, A. E.; Dagotto, Elbio R

    2009-01-01

    Correlations between particles can lead to subtle and sometimes counterintuitive phenomena. We analyze one such case, occurring during the sudden expansion of fermions in a lattice when the initial state has a strong admixture of double occupancies. We promote the notion of quantum distillation: during the expansion and in the case of strongly repulsive interactions, doublons group together, forming a nearly ideal band insulator, which is metastable with low entropy. We propose that this effect could be used for cooling purposes in experiments with two-component Fermi gases.

  15. Wigner distribution function and entropy of the damped harmonic oscillator within the theory of the open quantum systems

    NASA Technical Reports Server (NTRS)

    Isar, Aurelian

    1995-01-01

    The harmonic oscillator with dissipation is studied within the framework of the Lindblad theory for open quantum systems. By using the Wang-Uhlenbeck method, the Fokker-Planck equation, obtained from the master equation for the density operator, is solved for the Wigner distribution function, subject to either the Gaussian type or the delta-function type of initial conditions. The obtained Wigner functions are two-dimensional Gaussians with different widths. Then a closed expression for the density operator is extracted. The entropy of the system is subsequently calculated and its temporal behavior shows that this quantity relaxes to its equilibrium value.

  16. Structural modelling and control design under incomplete parameter information: The maximum-entropy approach

    NASA Technical Reports Server (NTRS)

    Hyland, D. C.

    1983-01-01

    A stochastic structural control model is described. In contrast to the customary deterministic model, the stochastic minimum data/maximum entropy model directly incorporates the least possible a priori parameter information. The approach is to adopt this model as the basic design model, thus incorporating the effects of parameter uncertainty at a fundamental level, and design mean-square optimal controls (that is, choose the control law to minimize the average of a quadratic performance index over the parameter ensemble).

  17. Engineering Photonic Switches for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Oza, Neal N.

    In this dissertation, we describe, characterize, and demonstrate the operation of a dual-in, dual-out, all-optical, fiber-based quantum switch. This "cross-bar" switch is particularly useful for applications in quantum information processing because of its low-loss, high-speed, low-noise, and quantum-state-retention properties. Building upon on our lab's prior development of an ultrafast demultiplexer [1-3] , the new cross-bar switch can be used as a tunable multiplexer and demultiplexer. In addition to this more functional geometry, we present results demonstrating faster performance with a switching window of ≈45 ps, corresponding to >20-GHz switching rates. We show a switching fidelity of >98%, i. e., switched polarization-encoded photonic qubits are virtually identical to unswitched photonic qubits. We also demonstrate the ability to select one channel from a two-channel quantum data stream with the state of the measured (recovered) quantum channel having >96% relative fidelity with the state of that channel transmitted alone. We separate the two channels of the quantum data stream by 155 ps, corresponding to a 6.5-GHz datastream. Finally, we describe, develop, and demonstrate an application that utilizes the switch's higher-speed, lower-loss, and spatio-temporal-encoding features to perform quantum state tomographies on entangled states in higher-dimensional Hilbert spaces. Since many previous demonstrations show bipartite entanglement of two-level systems, we define "higher" as d > 2 where d represents the dimensionality of a photon. We show that we can generate and measure time-bin-entangled, two-photon, qutrit (d = 3) and ququat (d = 4) states with >85% and >64% fidelity to an ideal maximally entangled state, respectively. Such higher-dimensional states have applications in dense coding [4] , loophole-free tests of nonlocality [5] , simplifying quantum logic gates [6] , and increasing tolerance to noise and loss for quantum information processing [7] .

  18. Non-classical light for quantum information

    NASA Astrophysics Data System (ADS)

    Goldschmidt, Elizabeth Anne

    Non-classical light is both easily encoded with quantum information and robust against decoherence, making it a key resource that enables many quantum information applications including quantum computing, quantum communication, and quantum metrology. We present a wide range of experimental and theoretical research toward the generation, detection, characterization, and storage of non-classical states of light with an eye toward quantum information applications. To provide a basis for the rest of the work, we begin by discussing theoretically the role of photon number statistics in optical quantum information and the use of second-order optical coherence to characterize non-classical light. Building on that, we present an original tool for the difficult problem of reconstructing the underlying mode distribution of multi-mode optical fields using simple measurements of higher-order optical coherence. We then move on to the problem of generating and storing single photons. We do this in a solid-state medium, a rare-earth ion-doped crystal, with a long-lived spin transition ideal for storing quantum information. We experimentally demonstrate the feasibility of this concept by showing correlations between the optical fields that herald storage and retrieval of collective excitations. This scheme can be used for the two important and distinct applications of generating single photons on-demand and storing quantum information and entanglement. The detection of non-classical light is a task as important as its generation. To this end, we study detectors with near unity detection efficiency and photon number resolution for use in quantum-enabled metrology. We use such a detector to experimentally demonstrate compression of spatial fringes and investigate the possibility of improving measurement resolution with classical and non-classical light. Finally, we report a set of experiments using photon number statistics to characterize classical and non-classical light. We

  19. Life, Information, Entropy, and Time: Vehicles for Semantic Inheritance.

    PubMed

    Crofts, Antony R

    2007-01-01

    Attempts to understand how information content can be included in an accounting of the energy flux of the biosphere have led to the conclusion that, in information transmission, one component, the semantic content, or "the meaning of the message," adds no thermodynamic burden over and above costs arising from coding, transmission and translation. In biology, semantic content has two major roles. For all life forms, the message of the genotype encoded in DNA specifies the phenotype, and hence the organism that is tested against the real world through the mechanisms of Darwinian evolution. For human beings, communication through language and similar abstractions provides an additional supra-phenotypic vehicle for semantic inheritance, which supports the cultural heritages around which civilizations revolve. The following three postulates provide the basis for discussion of a number of themes that demonstrate some important consequences. (i) Information transmission through either pathway has thermodynamic components associated with data storage and transmission. (ii) The semantic content adds no additional thermodynamic cost. (iii) For all semantic exchange, meaning is accessible only through translation and interpretation, and has a value only in context. (1) For both pathways of semantic inheritance, translational and copying machineries are imperfect. As a consequence both pathways are subject to mutation and to evolutionary pressure by selection. Recognition of semantic content as a common component allows an understanding of the relationship between genes and memes, and a reformulation of Universal Darwinism. (2) The emergent properties of life are dependent on a processing of semantic content. The translational steps allow amplification in complexity through combinatorial possibilities in space and time. Amplification depends on the increased potential for complexity opened by 3D interaction specificity of proteins, and on the selection of useful variants by

  20. Life, Information, Entropy, and Time: Vehicles for Semantic Inheritance.

    PubMed

    Crofts, Antony R

    2007-01-01

    Attempts to understand how information content can be included in an accounting of the energy flux of the biosphere have led to the conclusion that, in information transmission, one component, the semantic content, or "the meaning of the message," adds no thermodynamic burden over and above costs arising from coding, transmission and translation. In biology, semantic content has two major roles. For all life forms, the message of the genotype encoded in DNA specifies the phenotype, and hence the organism that is tested against the real world through the mechanisms of Darwinian evolution. For human beings, communication through language and similar abstractions provides an additional supra-phenotypic vehicle for semantic inheritance, which supports the cultural heritages around which civilizations revolve. The following three postulates provide the basis for discussion of a number of themes that demonstrate some important consequences. (i) Information transmission through either pathway has thermodynamic components associated with data storage and transmission. (ii) The semantic content adds no additional thermodynamic cost. (iii) For all semantic exchange, meaning is accessible only through translation and interpretation, and has a value only in context. (1) For both pathways of semantic inheritance, translational and copying machineries are imperfect. As a consequence both pathways are subject to mutation and to evolutionary pressure by selection. Recognition of semantic content as a common component allows an understanding of the relationship between genes and memes, and a reformulation of Universal Darwinism. (2) The emergent properties of life are dependent on a processing of semantic content. The translational steps allow amplification in complexity through combinatorial possibilities in space and time. Amplification depends on the increased potential for complexity opened by 3D interaction specificity of proteins, and on the selection of useful variants by

  1. Combinatorics of the SU(2) black hole entropy in loop quantum gravity

    SciTech Connect

    Agullo, Ivan; Barbero G, J. Fernando; Borja, Enrique F.; Diaz-Polo, Jacobo; Villasenor, Eduardo J. S.

    2009-10-15

    We use the combinatorial and number-theoretical methods developed in previous works by the authors to study black hole entropy in the new proposal put forth by Engle, Noui, and Perez. Specifically, we give the generating functions relevant for the computation of the entropy and use them to derive its asymptotic behavior, including the value of the Immirzi parameter and the coefficient of the logarithmic correction.

  2. Preface of the special issue quantum foundations: information approach.

    PubMed

    D'Ariano, Giacomo Mauro; Khrennikov, Andrei

    2016-05-28

    This special issue is based on the contributions of a group of top experts in quantum foundations and quantum information and probability. It enlightens a number of interpretational, mathematical and experimental problems of quantum theory. PMID:27091161

  3. Preface of the special issue quantum foundations: information approach

    PubMed Central

    2016-01-01

    This special issue is based on the contributions of a group of top experts in quantum foundations and quantum information and probability. It enlightens a number of interpretational, mathematical and experimental problems of quantum theory. PMID:27091161

  4. Quantum metrology from an information theory perspective

    SciTech Connect

    Boixo, Sergio; Datta, Animesh; Davis, Matthew J.; Flammia, Steven T.; Shaji, Anil; Tacla, Alexandre B.; Caves, Carlton M.

    2009-04-13

    Questions about quantum limits on measurement precision were once viewed from the perspective of how to reduce or avoid the effects of quantum noise. With the advent of quantum information science came a paradigm shift to proving rigorous bounds on measurement precision. These bounds have been interpreted as saying, first, that the best achievable sensitivity scales as 1/n, where n is the number of particles one has available for a measurement and, second, that the only way to achieve this Heisenberg-limited sensitivity is to use quantum entanglement. We review these results and show that using quadratic couplings of n particles to a parameter to be estimated, one can achieve sensitivities that scale as 1/n{sup 2} if one uses entanglement, but even in the absence of any entanglement at any time during the measurement protocol, one can achieve a super-Heisenberg scaling of 1/n{sup 3/2}.

  5. Retrieving and routing quantum information in a quantum network

    NASA Astrophysics Data System (ADS)

    Sazim, S.; Chiranjeevi, V.; Chakrabarty, I.; Srinathan, K.

    2015-12-01

    In extant quantum secret sharing protocols, once the secret is shared in a quantum network ( qnet) it cannot be retrieved, even if the dealer wishes that his/her secret no longer be available in the network. For instance, if the dealer is part of the two qnets, say {{Q}}_1 and {{Q}}_2 and he/she subsequently finds that {{Q}}_2 is more reliable than {{Q}}_1, he/she may wish to transfer all her secrets from {{Q}}_1 to {{Q}}_2. Known protocols are inadequate to address such a revocation. In this work we address this problem by designing a protocol that enables the source/dealer to bring back the information shared in the network, if desired. Unlike classical revocation, the no-cloning theorem automatically ensures that the secret is no longer shared in the network. The implications of our results are multi-fold. One interesting implication of our technique is the possibility of routing qubits in asynchronous qnets. By asynchrony we mean that the requisite data/resources are intermittently available (but not necessarily simultaneously) in the qnet. For example, we show that a source S can send quantum information to a destination R even though (a) S and R share no quantum resource, (b) R's identity is unknown to S at the time of sending the message, but is subsequently decided, (c) S herself can be R at a later date and/or in a different location to bequeath her information (`backed-up' in the qnet) and (d) importantly, the path chosen for routing the secret may hit a dead end due to resource constraints, congestion, etc., (therefore the information needs to be back-tracked and sent along an alternate path). Another implication of our technique is the possibility of using insecure resources. For instance, if the quantum memory within an organization is insufficient, it may safely store (using our protocol) its private information with a neighboring organization without (a) revealing critical data to the host and (b) losing control over retrieving the data. Putting the

  6. Information theory, spectral geometry, and quantum gravity.

    PubMed

    Kempf, Achim; Martin, Robert

    2008-01-18

    We show that there exists a deep link between the two disciplines of information theory and spectral geometry. This allows us to obtain new results on a well-known quantum gravity motivated natural ultraviolet cutoff which describes an upper bound on the spatial density of information. Concretely, we show that, together with an infrared cutoff, this natural ultraviolet cutoff beautifully reduces the path integral of quantum field theory on curved space to a finite number of ordinary integrations. We then show, in particular, that the subsequent removal of the infrared cutoff is safe.

  7. Restricted numerical range: A versatile tool in the theory of quantum information

    NASA Astrophysics Data System (ADS)

    Gawron, Piotr; Puchała, Zbigniew; Miszczak, Jarosław Adam; Skowronek, Łukasz; Życzkowski, Karol

    2010-10-01

    Numerical range of a Hermitian operator X is defined as the set of all possible expectation values of this observable among a normalized quantum state. We analyze a modification of this definition in which the expectation value is taken among a certain subset of the set of all quantum states. One considers, for instance, the set of real states, the set of product states, separable states, or the set of maximally entangled states. We show exemplary applications of these algebraic tools in the theory of quantum information: analysis of k-positive maps and entanglement witnesses, as well as study of the minimal output entropy of a quantum channel. Product numerical range of a unitary operator is used to solve the problem of local distinguishability of a family of two unitary gates.

  8. The relation between majorization theory and quantum information from entanglement monotones perspective

    NASA Astrophysics Data System (ADS)

    Erol, V.

    2016-04-01

    Entanglement has been studied extensively for understanding the mysteries of non-classical correlations between quantum systems. In the bipartite case, there are well known monotones for quantifying entanglement such as concurrence, relative entropy of entanglement (REE) and negativity, which cannot be increased via local operations. The study on these monotones has been a hot topic in quantum information [1-7] in order to understand the role of entanglement in this discipline. It can be observed that from any arbitrary quantum pure state a mixed state can obtained. A natural generalization of this observation would be to consider local operations classical communication (LOCC) transformations between general pure states of two parties. Although this question is a little more difficult, a complete solution has been developed using the mathematical framework of the majorization theory [8]. In this work, we analyze the relation between entanglement monotones concurrence and negativity with respect to majorization for general two-level quantum systems of two particles.

  9. Dependence of information entropy of uniform Fermi systems on correlations and thermal effects

    NASA Astrophysics Data System (ADS)

    Moustakidis, Ch. C.; Massen, S. E.

    2005-01-01

    The influence of correlations of uniform Fermi systems (nuclear matter, electron gas, and liquid He3 ) on Shannon’s information entropy, S , is studied. S is the sum of the information entropies in position and momentum spaces. It is found that, for three different Fermi systems with different particle interactions, the correlated part of S (Scor) depends on the correlation parameter of the systems or on the discontinuity gap of the momentum distribution through two parameter expressions. The values of the parameters characterize the strength of the correlations. A two parameter expression also holds between Scor and the mean kinetic energy (K) of the Fermi system. The study of thermal effects on the uncorrelated electron gas leads to a relation between the thermal part of S (Sthermal) and the fundamental quantities of temperature, thermodynamical entropy, and the mean kinetic energy. It is found that, in the case of low temperature limit, the expression connecting Sthermal with K is the same to the one which connects Scor with K . There are only some small differences on the values of the parameters. Thus, regardless of the reason (correlations or thermal) that changes K , S takes almost the same value.

  10. Analysing the information flow between financial time series . An improved estimator for transfer entropy

    NASA Astrophysics Data System (ADS)

    Marschinski, R.; Kantz, H.

    2002-11-01

    Following the recently introduced concept of transfer entropy, we attempt to measure the information flow between two financial time series, the Dow Jones and DAX stock index. Being based on Shannon entropies, this model-free approach in principle allows us to detect statistical dependencies of all types, i.e. linear and nonlinear temporal correlations. However, when available data is limited and the expected effect is rather small, a straightforward implementation suffers badly from misestimation due to finite sample effects, making it basically impossible to assess the significance of the obtained values. We therefore introduce a modified estimator, called effective transfer entropy, which leads to improved results in such conditions. In the application, we then manage to confirm an information transfer on a time scale of one minute between the two financial time series. The different economic impact of the two indices is also recovered from the data. Numerical results are then interpreted on one hand as capability of one index to explain future observations of the other, and on the other hand within terms of coupling strengths in the framework of a bivariate autoregressive stochastic model. Evidence is given for a nonlinear character of the coupling between Dow Jones and DAX.

  11. Markov and non-Markov processes in complex systems by the dynamical information entropy

    NASA Astrophysics Data System (ADS)

    Yulmetyev, R. M.; Gafarov, F. M.

    1999-12-01

    We consider the Markov and non-Markov processes in complex systems by the dynamical information Shannon entropy (DISE) method. The influence and important role of the two mutually dependent channels of entropy alternation (creation or generation of correlation) and anti-correlation (destroying or annihilation of correlation) have been discussed. The developed method has been used for the analysis of the complex systems of various natures: slow neutron scattering in liquid cesium, psychology (short-time numeral and pattern human memory and effect of stress on the dynamical taping-test), random dynamics of RR-intervals in human ECG (problem of diagnosis of various disease of the human cardio-vascular systems), chaotic dynamics of the parameters of financial markets and ecological systems.

  12. Parallel information transfer in a multinode quantum information processor.

    PubMed

    Borneman, T W; Granade, C E; Cory, D G

    2012-04-01

    We describe a method for coupling disjoint quantum bits (qubits) in different local processing nodes of a distributed node quantum information processor. An effective channel for information transfer between nodes is obtained by moving the system into an interaction frame where all pairs of cross-node qubits are effectively coupled via an exchange interaction between actuator elements of each node. All control is achieved via actuator-only modulation, leading to fast implementations of a universal set of internode quantum gates. The method is expected to be nearly independent of actuator decoherence and may be made insensitive to experimental variations of system parameters by appropriate design of control sequences. We show, in particular, how the induced cross-node coupling channel may be used to swap the complete quantum states of the local processors in parallel.

  13. Quantum information processing by weaving quantum Talbot carpets

    NASA Astrophysics Data System (ADS)

    Farías, Osvaldo Jiménez; de Melo, Fernando; Milman, Pérola; Walborn, Stephen P.

    2015-06-01

    Single-photon interference due to passage through a periodic grating is considered in a novel proposal for processing D -dimensional quantum systems (quDits) encoded in the spatial degrees of freedom of light. We show that free-space propagation naturally implements basic single-quDit gates by means of the Talbot effect: an intricate time-space carpet of light in the near-field diffraction regime. By adding a diagonal phase gate, we show that a complete set of single-quDit gates can be implemented. We then introduce a spatially dependent beam splitter that allows for projective measurements in the computational basis and can be used for the implementation of controlled operations between two quDits. Universal quantum information processing can then be implemented with linear optics and ancilla photons via postselection and feed-forward following the original proposal of Knill-Laflamme and Milburn. Although we consider photons, our scheme should be directly applicable to a number of other physical systems. Interpretation of the Talbot effect as a quantum logic operation provides a beautiful and interesting way to visualize quantum computation through wave propagation and interference.

  14. Photonic Crystal Microcavities for Quantum Information Science

    NASA Astrophysics Data System (ADS)

    Hagemeier, Jenna Nicole

    Quantum information science and technology is a broad and fascinating field, encompassing diverse research areas such as materials science, atomic physics, superconductors, solid-state physics, and photonics. A goal of this field is to demonstrate the basic functions of information initialization, manipulation, and read-out in systems that take advantage of quantum physics to greatly enhance computing performance capabilities. In a hybrid quantum information network, different systems are used to perform different functions, to best exploit the advantageous properties of each system. For example, matter quantum bits (qubits) can be used for local data storage and manipulation while photonic qubits can be used for long-distance communication between storage points of the network. Our research focuses on the following two solid-state realizations of a matter qubit for the purpose of building such a hybrid quantum network: the electronic spin of a self-assembled indium arsenide quantum dot and the electronic spin of a nitrogen-vacancy defect center in diamond. Light--matter interactions are necessary to transfer the information from the matter qubit to the photonic qubit, and this interaction can be enhanced by embedding the spin system in an optical cavity. We focus on photonic crystal microcavities for this purpose, and we study interactions between the optical cavity modes and incorporated spin systems. To improve the performance of this spin--photon interface, it is important to maximize the coupling strength between the spin and photonic systems and to increase the read-out efficiency of information stored in the cavity. In this thesis, we present our work to deterministically couple a nitrogen-vacancy center in diamond to a photonic crystal microcavity in gallium phosphide. This is achieved by nanopositioning a pre-selected diamond nanocrystal in the intensity maximum of the optical cavity mode. We also present an optimized design of a photonic crystal

  15. Quantum Information with Continuous Variable systems

    NASA Astrophysics Data System (ADS)

    Rodó, Carles

    2010-05-01

    This thesis deals with the study of quantum communication protocols with Continuous Variable (CV) systems. Continuous Variable systems are those described by canonical conjugated coordinates x and p endowed with infinite dimensional Hilbert spaces, thus involving a complex mathematical structure. A special class of CV states, are the so-called Gaussian states. With them, it has been possible to implement certain quantum tasks as quantum teleportation, quantum cryptography and quantum computation with fantastic experimental success. The importance of Gaussian states is two-fold; firstly, its structural mathematical description makes them much more amenable than any other CV system. Secondly, its production, manipulation and detection with current optical technology can be done with a very high degree of accuracy and control. Nevertheless, it is known that in spite of their exceptional role within the space of all Continuous Variable states, in fact, Gaussian states are not always the best candidates to perform quantum information tasks. Thus non-Gaussian states emerge as potentially good candidates for communication and computation purposes.

  16. Quantum information, oscillations and the psyche

    NASA Astrophysics Data System (ADS)

    Martin, F.; Carminati, F.; Galli Carminati, G.

    2010-05-01

    In this paper, taking the theory of quantum information as a model, we consider the human unconscious, pre-consciousness and consciousness as sets of quantum bits (qubits). We view how there can be communication between these various qubit sets. In doing this we are inspired by the theory of nuclear magnetic resonance. In this way we build a model of handling a mental qubit with the help of pulses of a mental field. Starting with an elementary interaction between two qubits we build two-qubit quantum logic gates that allow information to be transferred from one qubit to the other. In this manner we build a quantum process that permits consciousness to "read" the unconscious and vice versa. The elementary interaction, e.g. between a pre-consciousness qubit and a consciousness one, allows us to predict the time evolution of the pre-consciousness + consciousness system in which pre-consciousness and consciousness are quantum entangled. This time evolution exhibits Rabi oscillations that we name mental Rabi oscillations. This time evolution shows how for example the unconscious can influence consciousness. In a process like mourning the influence of the unconscious on consciousness, as the influence of consciousness on the unconscious, are in agreement with what is observed in psychiatry.

  17. Entropy of higher dimensional nonrotating isolated horizons from loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Wang, Jingbo; Huang, Chao-Guang

    2015-02-01

    In this paper, we extend the calculation of the entropy of nonrotating isolated horizons in four-dimensional spacetime to that in a higher-dimensional spacetime. We show that the boundary degrees of freedom on an isolated horizon can be described effectively by an SO(1,1) BF theory. Then the entropy of the nonrotating isolated horizon can be calculated by counting the number of microstates. It satisfies the Bekenstein-Hawking law in its leading term and has a ‘zero-point entropy’ correction.

  18. Non-Markovianity and reservoir memory of quantum channels: a quantum information theory perspective.

    PubMed

    Bylicka, B; Chruściński, D; Maniscalco, S

    2014-07-21

    Quantum technologies rely on the ability to coherently transfer information encoded in quantum states along quantum channels. Decoherence induced by the environment sets limits on the efficiency of any quantum-enhanced protocol. Generally, the longer a quantum channel is the worse its capacity is. We show that for non-Markovian quantum channels this is not always true: surprisingly the capacity of a longer channel can be greater than of a shorter one. We introduce a general theoretical framework linking non-Markovianity to the capacities of quantum channels and demonstrate how harnessing non-Markovianity may improve the efficiency of quantum information processing and communication.

  19. Non-Markovianity and reservoir memory of quantum channels: a quantum information theory perspective

    PubMed Central

    Bylicka, B.; Chruściński, D.; Maniscalco, S.

    2014-01-01

    Quantum technologies rely on the ability to coherently transfer information encoded in quantum states along quantum channels. Decoherence induced by the environment sets limits on the efficiency of any quantum-enhanced protocol. Generally, the longer a quantum channel is the worse its capacity is. We show that for non-Markovian quantum channels this is not always true: surprisingly the capacity of a longer channel can be greater than of a shorter one. We introduce a general theoretical framework linking non-Markovianity to the capacities of quantum channels and demonstrate how harnessing non-Markovianity may improve the efficiency of quantum information processing and communication. PMID:25043763

  20. Entropy and the Shelf Model: A Quantum Physical Approach to a Physical Property

    ERIC Educational Resources Information Center

    Jungermann, Arnd H.

    2006-01-01

    In contrast to most other thermodynamic data, entropy values are not given in relation to a certain--more or less arbitrarily defined--zero level. They are listed in standard thermodynamic tables as absolute values of specific substances. Therefore these values describe a physical property of the listed substances. One of the main tasks of…

  1. Definition of a time variable with entropy of a perfect fluid in canonical quantum gravity

    NASA Astrophysics Data System (ADS)

    Cianfrani, Francesco; Montani, Giovanni; Zonetti, Simone

    2009-06-01

    The Brown-Kuchař mechanism is applied in the case of general relativity coupled with Schutz' model for a perfect fluid. Using the canonical formalism and manipulating the set of modified constraints one is able to recover the definition of a time-evolution operator, i.e. a physical Hamiltonian, expressed as a functional of gravitational variables and the entropy.

  2. A Formal Derivation of the Gibbs Entropy for Classical Systems Following the Schrodinger Quantum Mechanical Approach

    ERIC Educational Resources Information Center

    Santillan, M.; Zeron, E. S.; Del Rio-Correa, J. L.

    2008-01-01

    In the traditional statistical mechanics textbooks, the entropy concept is first introduced for the microcanonical ensemble and then extended to the canonical and grand-canonical cases. However, in the authors' experience, this procedure makes it difficult for the student to see the bigger picture and, although quite ingenuous, the subtleness of…

  3. Energetic loads and informational entropy during insect metamorphosis: measuring structural variability and self-organization.

    PubMed

    Damos, Petros T; Papadopoulos, Nikos T; Rigas, Alexandros; Savopoulou-Soultani, Matilda

    2011-10-01

    In this work an information theory approach is presented for measuring structural variability during insect metamorphosis. Following a self-organizational perspective, the underlying assumption is that an insect pupa is a cybernetic bio-system, which displays a homeostatic control during its metamorphosis. The description of structural variability was based on biochemical data (lipids, glycogen, carbohydrates and proteins) analysed at different time intervals during the metamorphosis of Anarsia lineatella Zeller (Lepidoptera: Gelechiidae). Probabilities of biochemical variables were further treated by considering a finite countable set of progressive metamorphosis states having Markov properties at isothermal conditions (25 °C, 16:8h L:D, 65 ± 5%RH). The probabilities of the biochemical variables, as well as the related informational entropies, are affected when the system moves one step forward for each successive state. In most cases, but protein, there is some observable evidence that histolysis could be related to a decrease in informational entropy H ('disorganization of the system'), followed by a 'stable balance period' during the middle stages of metamorphosis. An initial increase in H is measured at the last stages of metamorphosis, which theoretically correspond to histogenesis ('reorganization of the system'). In this context, the temporal evolution of pupal structural variability was probabilistically quantified according to the classical information theory. The principles of the proposed holistic system are independent of its detailed dynamics and the proposed model can potentially describe part of the observable experimental data during metamorphosis of a holometabolous insect.

  4. Quantum information erasure inside black holes

    NASA Astrophysics Data System (ADS)

    Lowe, David A.; Thorlacius, Larus

    2015-12-01

    An effective field theory for infalling observers in the vicinity of a quasi-static black hole is given in terms of a freely falling lattice discretization. The lattice model successfully reproduces the thermal spectrum of outgoing Hawking radiation, as was shown by Corley and Jacobson, but can also be used to model observations made by a typical low-energy observer who enters the black hole in free fall at a prescribed time. The explicit short distance cutoff ensures that, from the viewpoint of the infalling observer, any quantum information that entered the black hole more than a scrambling time earlier has been erased by the black hole singularity. This property, combined with the requirement that outside observers need at least of order the scrambling time to extract quantum information from the black hole, ensures that a typical infalling observer does not encounter drama upon crossing the black hole horizon in a theory where black hole information is preserved for asymptotic observers.

  5. A measure of Quantum Unspeakable Information

    NASA Astrophysics Data System (ADS)

    Girolami, Davide

    2014-03-01

    A piece of information is said unspeakable if it cannot be encoded into a sequence of bits. For example, the transformation law between the coordinates of two distant laboratories cannot be specified without a shared reference frame. This condition has been proven to be equivalent to constrain local operations in the two labs by means of a superselection rule [Rev. Mod. Phys. 79, 555 (2007)]. I introduce a measure of unspeakable information based on the skew information [PNAS 49, 910 (1963)], which evaluates the ability of a quantum state to act as a reference frame under a specific superselection rule. Then, I show that evaluating unspeakable information is equivalent to measuring the amount of quantum coherence of a state with respect to a given basis. I propose a proof of concept experiment in optical set-up to evaluate the amount of unspeakable information, i.e. of relative coherence, of a quantum state without fully reconstructing its density matrix. This work is supported by the Singapore National Research Foundation under NRF Grant No. NRF-NRFF2011-07.

  6. Information entropy-based classification of triterpenoids and steroids from Ganoderma.

    PubMed

    Castellano, Gloria; Torrens, Francisco

    2015-08-01

    A set of 71 triterpenoid and steroid compounds from Ganoderma were periodically classified using a procedure based on information entropy with artificial intelligence. Six features were used in hierarchical order to classify the triterpenoids and steroids structurally. The phytochemicals belonging to the same group in the periodic table present similar antioxidant activity, and those compounds belonging to the same period exhibit maximum resemblance. The periodic classification is related to the experimental bioactivity and antioxidant potency data that are available in the literature: a steroid with a three-ketone group conjugated with two carbon-carbon double bonds in the right side of the periodic table exhibits the greatest antioxidant activity. PMID:26024957

  7. Information entropy-based classification of triterpenoids and steroids from Ganoderma.

    PubMed

    Castellano, Gloria; Torrens, Francisco

    2015-08-01

    A set of 71 triterpenoid and steroid compounds from Ganoderma were periodically classified using a procedure based on information entropy with artificial intelligence. Six features were used in hierarchical order to classify the triterpenoids and steroids structurally. The phytochemicals belonging to the same group in the periodic table present similar antioxidant activity, and those compounds belonging to the same period exhibit maximum resemblance. The periodic classification is related to the experimental bioactivity and antioxidant potency data that are available in the literature: a steroid with a three-ketone group conjugated with two carbon-carbon double bonds in the right side of the periodic table exhibits the greatest antioxidant activity.

  8. Steepest-entropy-ascent quantum thermodynamic modeling of the relaxation process of isolated chemically reactive systems using density of states and the concept of hypoequilibrium state

    NASA Astrophysics Data System (ADS)

    Li, Guanchen; von Spakovsky, Michael R.

    2016-01-01

    This paper presents a study of the nonequilibrium relaxation process of chemically reactive systems using steepest-entropy-ascent quantum thermodynamics (SEAQT). The trajectory of the chemical reaction, i.e., the accessible intermediate states, is predicted and discussed. The prediction is made using a thermodynamic-ensemble approach, which does not require detailed information about the particle mechanics involved (e.g., the collision of particles). Instead, modeling the kinetics and dynamics of the relaxation process is based on the principle of steepest-entropy ascent (SEA) or maximum-entropy production, which suggests a constrained gradient dynamics in state space. The SEAQT framework is based on general definitions for energy and entropy and at least theoretically enables the prediction of the nonequilibrium relaxation of system state at all temporal and spatial scales. However, to make this not just theoretically but computationally possible, the concept of density of states is introduced to simplify the application of the relaxation model, which in effect extends the application of the SEAQT framework even to infinite energy eigenlevel systems. The energy eigenstructure of the reactive system considered here consists of an extremely large number of such levels (on the order of 10130) and yields to the quasicontinuous assumption. The principle of SEA results in a unique trajectory of system thermodynamic state evolution in Hilbert space in the nonequilibrium realm, even far from equilibrium. To describe this trajectory, the concepts of subsystem hypoequilibrium state and temperature are introduced and used to characterize each system-level, nonequilibrium state. This definition of temperature is fundamental rather than phenomenological and is a generalization of the temperature defined at stable equilibrium. In addition, to deal with the large number of energy eigenlevels, the equation of motion is formulated on the basis of the density of states and a set of

  9. Sharing the Quantum State and the Classical Information Simultaneously

    NASA Astrophysics Data System (ADS)

    Qin, Huawang; Dai, Yuewei

    2016-08-01

    An efficient quantum secret sharing scheme is proposed, in which the quantum state and the classical information can be shared simultaneously through only one distribution. The dealer uses the operations of quantum-controlled-not and Hadamard gate to encode the secret quantum state and classical information, and the participants use the single-particle measurements to recover the original quantum state and classical information. Compared to the existing schemes, our scheme is more efficient when the quantum state and the classical information need to be shared simultaneously.

  10. Complementarity of quantum discord and classically accessible information

    SciTech Connect

    Zwolak, Michael P.; Zurek, Wojciech H.

    2013-05-20

    The sum of the Holevo quantity (that bounds the capacity of quantum channels to transmit classical information about an observable) and the quantum discord (a measure of the quantumness of correlations of that observable) yields an observable-independent total given by the quantum mutual information. This split naturally delineates information about quantum systems accessible to observers – information that is redundantly transmitted by the environment – while showing that it is maximized for the quasi-classical pointer observable. Other observables are accessible only via correlations with the pointer observable. In addition, we prove an anti-symmetry property relating accessible information and discord. It shows that information becomes objective – accessible to many observers – only as quantum information is relegated to correlations with the global environment, and, therefore, locally inaccessible. Lastly, the resulting complementarity explains why, in a quantum Universe, we perceive objective classical reality while flagrantly quantum superpositions are out of reach.

  11. Complementarity of quantum discord and classically accessible information

    DOE PAGES

    Zwolak, Michael P.; Zurek, Wojciech H.

    2013-05-20

    The sum of the Holevo quantity (that bounds the capacity of quantum channels to transmit classical information about an observable) and the quantum discord (a measure of the quantumness of correlations of that observable) yields an observable-independent total given by the quantum mutual information. This split naturally delineates information about quantum systems accessible to observers – information that is redundantly transmitted by the environment – while showing that it is maximized for the quasi-classical pointer observable. Other observables are accessible only via correlations with the pointer observable. In addition, we prove an anti-symmetry property relating accessible information and discord. Itmore » shows that information becomes objective – accessible to many observers – only as quantum information is relegated to correlations with the global environment, and, therefore, locally inaccessible. Lastly, the resulting complementarity explains why, in a quantum Universe, we perceive objective classical reality while flagrantly quantum superpositions are out of reach.« less

  12. Complementarity of quantum discord and classically accessible information

    PubMed Central

    Zwolak, Michael; Zurek, Wojciech H.

    2013-01-01

    The sum of the Holevo quantity (that bounds the capacity of quantum channels to transmit classical information about an observable) and the quantum discord (a measure of the quantumness of correlations of that observable) yields an observable-independent total given by the quantum mutual information. This split naturally delineates information about quantum systems accessible to observers – information that is redundantly transmitted by the environment – while showing that it is maximized for the quasi-classical pointer observable. Other observables are accessible only via correlations with the pointer observable. We also prove an anti-symmetry property relating accessible information and discord. It shows that information becomes objective – accessible to many observers – only as quantum information is relegated to correlations with the global environment, and, therefore, locally inaccessible. The resulting complementarity explains why, in a quantum Universe, we perceive objective classical reality while flagrantly quantum superpositions are out of reach.

  13. PREFACE: International Conference on Quantum Optics and Quantum Information (icQoQi) 2013

    NASA Astrophysics Data System (ADS)

    2014-11-01

    Quantum Information can be understood as being naturally derived from a new understanding of information theory when quantum systems become information carriers and quantum effects become non negligible. Experiments and the realization of various interesting phenomena in quantum information within the established field of quantum optics have been reported, which has provided a very convenient framework for the former. Together, quantum optics and quantum information are among the most exciting areas of interdisciplinary research in modern day science which cover a broad spectrum of topics, from the foundations of quantum mechanics and quantum information science to the introduction of new types of quantum technologies and metrology. The International Conference on Quantum Optics and Quantum Information (icQoQi) 2013 was organized by the Faculty of Science, International Islamic University Malaysia with the objective of bringing together leading academic scientists, researchers and scholars in the domain of interest from around the world to share their experiences and research results about all aspects of quantum optics and quantum information. While the event was organized on a somewhat modest scale, it was in fact a rather fruitful meeting for established researchers and students as well, especially for the local scene where the field is relatively new. We would therefore, like to thank the organizing committee, our advisors and all parties for having made this event successful and last but not least would extend our sincerest gratitude to IOP for publishing these selected papers from icQoQi2013 in Journal of Physics: Conference Series.

  14. Information-theoretic temporal Bell inequality and quantum computation

    SciTech Connect

    Morikoshi, Fumiaki

    2006-05-15

    An information-theoretic temporal Bell inequality is formulated to contrast classical and quantum computations. Any classical algorithm satisfies the inequality, while quantum ones can violate it. Therefore, the violation of the inequality is an immediate consequence of the quantumness in the computation. Furthermore, this approach suggests a notion of temporal nonlocality in quantum computation.

  15. Generalized isotropic Lipkin-Meshkov-Glick models: ground state entanglement and quantum entropies

    NASA Astrophysics Data System (ADS)

    Carrasco, José A.; Finkel, Federico; González-López, Artemio; Rodríguez, Miguel A.; Tempesta, Piergiulio

    2016-03-01

    We introduce a new class of generalized isotropic Lipkin-Meshkov-Glick models with \\text{su}(m+1) spin and long-range non-constant interactions, whose non-degenerate ground state is a Dicke state of \\text{su}(m+1) type. We evaluate in closed form the reduced density matrix of a block of L spins when the whole system is in its ground state, and study the corresponding von Neumann and Rényi entanglement entropies in the thermodynamic limit. We show that both of these entropies scale as alog L when L tends to infinity, where the coefficient a is equal to (m  -  k)/2 in the ground state phase with k vanishing \\text{su}(m+1) magnon densities. In particular, our results show that none of these generalized Lipkin-Meshkov-Glick models are critical, since when L\\to ∞ their Rényi entropy R q becomes independent of the parameter q. We have also computed the Tsallis entanglement entropy of the ground state of these generalized \\text{su}(m+1) Lipkin-Meshkov-Glick models, finding that it can be made extensive by an appropriate choice of its parameter only when m-k≥slant 3 . Finally, in the \\text{su}(3) case we construct in detail the phase diagram of the ground state in parameter space, showing that it is determined in a simple way by the weights of the fundamental representation of \\text{su}(3) . This is also true in the \\text{su}(m+1) case; for instance, we prove that the region for which all the magnon densities are non-vanishing is an (m  +  1)-simplex in {{{R}}m} whose vertices are the weights of the fundamental representation of \\text{su}(m+1) .

  16. Another short and elementary proof of strong subadditivity of quantum entropy

    NASA Astrophysics Data System (ADS)

    Ruskai, Mary Beth

    2007-08-01

    A short and elementary proof of the joint convexity of relative entropy is presented, using nothing beyond linear algebra. The key ingredients are an easily verified integral representation and the strategy used to prove the Cauchy-Schwarz inequality in elementary courses. Several consequences are proved in a way which allows an elementary proof of strong subadditivity in a few more lines. Some expository material on Schwarz inequalities for operators and the Holevo bound for partial measurements is also included.

  17. PREFACE: Quantum Information, Communication, Computation and Cryptography

    NASA Astrophysics Data System (ADS)

    Benatti, F.; Fannes, M.; Floreanini, R.; Petritis, D.

    2007-07-01

    The application of quantum mechanics to information related fields such as communication, computation and cryptography is a fast growing line of research that has been witnessing an outburst of theoretical and experimental results, with possible practical applications. On the one hand, quantum cryptography with its impact on secrecy of transmission is having its first important actual implementations; on the other hand, the recent advances in quantum optics, ion trapping, BEC manipulation, spin and quantum dot technologies allow us to put to direct test a great deal of theoretical ideas and results. These achievements have stimulated a reborn interest in various aspects of quantum mechanics, creating a unique interplay between physics, both theoretical and experimental, mathematics, information theory and computer science. In view of all these developments, it appeared timely to organize a meeting where graduate students and young researchers could be exposed to the fundamentals of the theory, while senior experts could exchange their latest results. The activity was structured as a school followed by a workshop, and took place at The Abdus Salam International Center for Theoretical Physics (ICTP) and The International School for Advanced Studies (SISSA) in Trieste, Italy, from 12-23 June 2006. The meeting was part of the activity of the Joint European Master Curriculum Development Programme in Quantum Information, Communication, Cryptography and Computation, involving the Universities of Cergy-Pontoise (France), Chania (Greece), Leuven (Belgium), Rennes1 (France) and Trieste (Italy). This special issue of Journal of Physics A: Mathematical and Theoretical collects 22 contributions from well known experts who took part in the workshop. They summarize the present day status of the research in the manifold aspects of quantum information. The issue is opened by two review articles, the first by G Adesso and F Illuminati discussing entanglement in continuous variable

  18. Quantum Theory is an Information Theory

    NASA Astrophysics Data System (ADS)

    D'Ariano, Giacomo M.; Perinotti, Paolo

    2016-03-01

    In this paper we review the general framework of operational probabilistic theories (OPT), along with the six axioms from which quantum theory can be derived. We argue that the OPT framework along with a relaxed version of five of the axioms, define a general information theory. We close the paper with considerations about the role of the observer in an OPT, and the interpretation of the von Neumann postulate and the Schrödinger-cat paradox.

  19. An investigation of the information propagation and entropy transport aspects of Stirling machine numerical simulation

    NASA Technical Reports Server (NTRS)

    Goldberg, Louis F.

    1992-01-01

    Aspects of the information propagation modeling behavior of integral machine computer simulation programs are investigated in terms of a transmission line. In particular, the effects of pressure-linking and temporal integration algorithms on the amplitude ratio and phase angle predictions are compared against experimental and closed-form analytic data. It is concluded that the discretized, first order conservation balances may not be adequate for modeling information propagation effects at characteristic numbers less than about 24. An entropy transport equation suitable for generalized use in Stirling machine simulation is developed. The equation is evaluated by including it in a simulation of an incompressible oscillating flow apparatus designed to demonstrate the effect of flow oscillations on the enhancement of thermal diffusion. Numerical false diffusion is found to be a major factor inhibiting validation of the simulation predictions with experimental and closed-form analytic data. A generalized false diffusion correction algorithm is developed which allows the numerical results to match their analytic counterparts. Under these conditions, the simulation yields entropy predictions which satisfy Clausius' inequality.

  20. Identifying changes in EEG information transfer during drowsy driving by transfer entropy

    PubMed Central

    Huang, Chih-Sheng; Pal, Nikhil R.; Chuang, Chun-Hsiang; Lin, Chin-Teng

    2015-01-01

    Drowsy driving is a major cause of automobile accidents. Previous studies used neuroimaging based approaches such as analysis of electroencephalogram (EEG) activities to understand the brain dynamics of different cortical regions during drowsy driving. However, the coupling between brain regions responding to this vigilance change is still unclear. To have a comprehensive understanding of neural mechanisms underlying drowsy driving, in this study we use transfer entropy, a model-free measure of effective connectivity based on information theory. We investigate the pattern of information transfer between brain regions when the vigilance level, which is derived from the driving performance, changes from alertness to drowsiness. Results show that the couplings between pairs of frontal, central, and parietal areas increased at the intermediate level of vigilance, which suggests that an enhancement of the cortico-cortical interaction is necessary to maintain the task performance and prevent behavioral lapses. Additionally, the occipital-related connectivity magnitudes monotonically decreases as the vigilance level declines, which further supports the cortical gating of sensory stimuli during drowsiness. Neurophysiological evidence of mutual relationships between brain regions measured by transfer entropy might enhance the understanding of cortico-cortical communication during drowsy driving. PMID:26557069

  1. Automatic Segmentation of Myocardium from Black-Blood MR Images Using Entropy and Local Neighborhood Information

    PubMed Central

    Zheng, Qian; Lu, Zhentai; Zhang, Minghui; Xu, Lin; Ma, Huan; Song, Shengli; Feng, Qianjin; Feng, Yanqiu; Chen, Wufan; He, Taigang

    2015-01-01

    By using entropy and local neighborhood information, we present in this study a robust adaptive Gaussian regularizing Chan–Vese (CV) model to segment the myocardium from magnetic resonance images with intensity inhomogeneity. By utilizing the circular Hough transformation (CHT) our model is able to detect epicardial and endocardial contours of the left ventricle (LV) as circles automatically, and the circles are used as the initialization. In the cost functional of our model, the interior and exterior energies are weighted by the entropy to improve the robustness of the evolving curve. Local neighborhood information is used to evolve the level set function to reduce the impact of the heterogeneity inside the regions and to improve the segmentation accuracy. An adaptive window is utilized to reduce the sensitivity to initialization. The Gaussian kernel is used to regularize the level set function, which can not only ensure the smoothness and stability of the level set function, but also eliminate the traditional Euclidean length term and re-initialization. Extensive validation of the proposed method on patient data demonstrates its superior performance over other state-of-the-art methods. PMID:25811976

  2. A Generalized Information Theoretical Model for Quantum Secret Sharing

    NASA Astrophysics Data System (ADS)

    Bai, Chen-Ming; Li, Zhi-Hui; Xu, Ting-Ting; Li, Yong-Ming

    2016-07-01

    An information theoretical model for quantum secret sharing was introduced by H. Imai et al. (Quantum Inf. Comput. 5(1), 69-80 2005), which was analyzed by quantum information theory. In this paper, we analyze this information theoretical model using the properties of the quantum access structure. By the analysis we propose a generalized model definition for the quantum secret sharing schemes. In our model, there are more quantum access structures which can be realized by our generalized quantum secret sharing schemes than those of the previous one. In addition, we also analyse two kinds of important quantum access structures to illustrate the existence and rationality for the generalized quantum secret sharing schemes and consider the security of the scheme by simple examples.

  3. Quantum corrections to holographic mutual information

    NASA Astrophysics Data System (ADS)

    Agón, Cesar A.; Faulkner, Thomas

    2016-08-01

    We compute the leading contribution to the mutual information (MI) of two disjoint spheres in the large distance regime for arbitrary conformal field theories (CFT) in any dimension. This is achieved by refining the operator product expansion method introduced by Cardy [1]. For CFTs with holographic duals the leading contribution to the MI at long distances comes from bulk quantum corrections to the Ryu-Takayanagi area formula. According to the FLM proposal [2] this equals the bulk MI between the two disjoint regions spanned by the boundary spheres and their corresponding minimal area surfaces. We compute this quantum correction and provide in this way a non-trivial check of the FLM proposal.

  4. Nonconvexity of the relative entropy for Markov dynamics: A Fisher information approach

    NASA Astrophysics Data System (ADS)

    Polettini, Matteo; Esposito, Massimiliano

    2013-07-01

    We show via counterexamples that relative entropy between the solution of a Markovian master equation and the steady state is not a convex function of time. We thus disprove the hypotheses that a general evolution principle of thermodynamics based on the decrease of the nonadiabatic entropy production could hold. However, we argue that a large separation of typical decay times is necessary for nonconvex solutions to occur, making concave transients extremely short lived with respect to the main relaxation modes. We describe a general method based on the Fisher information matrix to discriminate between generators that admit nonconvex solutions and those that do not. While initial conditions leading to concave transients are shown to be extremely fine-tuned, by our method we are able to select nonconvex initial conditions that are arbitrarily close to the steady state. Convexity does occur when the system is close to satisfying detailed balance or, more generally, when certain normality conditions of the decay modes are satisfied. Our results circumscribe the range of validity of a conjecture by Maes [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.010601 107, 010601 (2011)] regarding monotonicity of the large deviation rate functional for the occupation probability, showing that while the conjecture might hold in the long-time limit, the conditions for Lyapunov's second criterion for stability are not met.

  5. Yang-Baxter matrices associated with quantum information based on the topological basis

    NASA Astrophysics Data System (ADS)

    Yu, Li-Wei; Xue, Kang; Ge, Mo-Lin

    2016-07-01

    The solutions of Yang-Baxter equation (YBE) associated with quantum information have been reviewed with new progress. The additivity rule for two particles is shown to obey Lorentzian type other than the Gallilean. Acting the braiding operations on the topological basis, it turns out that the N-dimensional representations obeying YBE are nothing but the Wigner’s D-functions. The connection between the extremization of ℓ1-norm as well as of von Neumann entropy and the reduction of YBE to braid relation is also discussed.

  6. Standard Quantum Teleportation and Controlled Quantum Teleportation of an Arbitrary N-Qubit Information State

    NASA Astrophysics Data System (ADS)

    Verma, Vikram; Prakash, Hari

    2016-04-01

    We explicitly present precise and simple protocols for standard quantum teleportation and controlled quantum teleportation of an arbitrary N-qubit information state and analyse the case of perfect teleportation using general quantum channels and measurement bases. We find condition on resource quantum channel and Bell states for achieving perfect quantum teleportation. We also find the unitary transformation required to be done by Bob for perfect quantum teleportation and discuss the connection with others related works. We also discuss how perfect controlled quantum teleportation demands a correct choice of the measurement basis of additional party.

  7. Quantum information approach to the azurite mineral frustrated quantum magnet

    NASA Astrophysics Data System (ADS)

    Batle, J.; Ooi, C. H. Raymond; Abutalib, M.; Farouk, Ahmed; Abdalla, S.

    2016-07-01

    Quantum correlations are almost impossible to address in bulk systems. Quantum measures extended only to a few number of parties can be discussed in practice. In the present work, we study nonlocality for a cluster of spins belonging to a mineral whose structure is that of a quantum magnet. We reproduce at a much smaller scale the experimental outcomes, and then, we study the role of quantum correlations there. A macroscopic entanglement witness has been introduced in order to reveal nonlocal quantum correlations between individual constituents of the azurite mineral at nonzero temperatures. The critical point beyond which entanglement is zero is found at T_c < 1 K.

  8. Measurement and Information Extraction in Complex Dynamics Quantum Computation

    NASA Astrophysics Data System (ADS)

    Casati, Giulio; Montangero, Simone

    Quantum Information processing has several di.erent applications: some of them can be performed controlling only few qubits simultaneously (e.g. quantum teleportation or quantum cryptography) [1]. Usually, the transmission of large amount of information is performed repeating several times the scheme implemented for few qubits. However, to exploit the advantages of quantum computation, the simultaneous control of many qubits is unavoidable [2]. This situation increases the experimental di.culties of quantum computing: maintaining quantum coherence in a large quantum system is a di.cult task. Indeed a quantum computer is a many-body complex system and decoherence, due to the interaction with the external world, will eventually corrupt any quantum computation. Moreover, internal static imperfections can lead to quantum chaos in the quantum register thus destroying computer operability [3]. Indeed, as it has been shown in [4], a critical imperfection strength exists above which the quantum register thermalizes and quantum computation becomes impossible. We showed such e.ects on a quantum computer performing an e.cient algorithm to simulate complex quantum dynamics [5,6].

  9. Quantum Information Processing using Scalable Techniques

    NASA Astrophysics Data System (ADS)

    Hanneke, D.; Bowler, R.; Jost, J. D.; Home, J. P.; Lin, Y.; Tan, T.-R.; Leibfried, D.; Wineland, D. J.

    2011-05-01

    We report progress towards improving our previous demonstrations that combined all the fundamental building blocks required for scalable quantum information processing using trapped atomic ions. Included elements are long-lived qubits; a laser-induced universal gate set; state initialization and readout; and information transport, including co-trapping a second ion species to reinitialize motion without qubit decoherence. Recent efforts have focused on reducing experimental overhead and increasing gate fidelity. Most of the experimental duty cycle was previously used for transport, separation, and recombination of ion chains as well as re-cooling of motional excitation. We have addressed these issues by developing and implementing an arbitrary waveform generator with an update rate far above the ions' motional frequencies. To reduce gate errors, we actively stabilize the position of several UV (313 nm) laser beams. We have also switched the two-qubit entangling gate to one that acts directly on 9Be+ hyperfine qubit states whose energy separation is magnetic-fluctuation insensitive. This work is supported by DARPA, NSA, ONR, IARPA, Sandia, and the NIST Quantum Information Program.

  10. Superconducting circuits for quantum information: an outlook.

    PubMed

    Devoret, M H; Schoelkopf, R J

    2013-03-01

    The performance of superconducting qubits has improved by several orders of magnitude in the past decade. These circuits benefit from the robustness of superconductivity and the Josephson effect, and at present they have not encountered any hard physical limits. However, building an error-corrected information processor with many such qubits will require solving specific architecture problems that constitute a new field of research. For the first time, physicists will have to master quantum error correction to design and operate complex active systems that are dissipative in nature, yet remain coherent indefinitely. We offer a view on some directions for the field and speculate on its future. PMID:23471399

  11. Comment on "Similarity between quantum mechanics and thermodynamics: Entropy, temperature, and Carnot cycle".

    PubMed

    González-Díaz, L A; Díaz-Solórzano, S

    2015-05-01

    In the paper by Abe and Okuyama [Phys. Rev. E 83, 021121 (2011)], the quantum Carnot cycle of a simple two-state model of a particle confined in a one-dimensional infinite potential well is discussed. It is claimed that the state at the beginning of the quantum Carnot cycle is pure. After that, it is apparently transmuted to a mixed state if Clausius equality is imposed. We prove that this statement is incorrect. In particular, we prove that the state at the beginning of the cycle is mixed due to the process of measuring energy. PMID:26066282

  12. Comment on "Similarity between quantum mechanics and thermodynamics: Entropy, temperature, and Carnot cycle".

    PubMed

    González-Díaz, L A; Díaz-Solórzano, S

    2015-05-01

    In the paper by Abe and Okuyama [Phys. Rev. E 83, 021121 (2011)], the quantum Carnot cycle of a simple two-state model of a particle confined in a one-dimensional infinite potential well is discussed. It is claimed that the state at the beginning of the quantum Carnot cycle is pure. After that, it is apparently transmuted to a mixed state if Clausius equality is imposed. We prove that this statement is incorrect. In particular, we prove that the state at the beginning of the cycle is mixed due to the process of measuring energy.

  13. Attractor reconstruction from the time series of information entropy of seismic kinetics process

    NASA Astrophysics Data System (ADS)

    Stakhovsky, I. R.

    2016-09-01

    The attractor is reconstructed from the time series of the information entropy of the seismic kinetics process. It is shown that the seismic kinetics process is governed by three order parameters and is characterized by a strange attractor in the three-dimensional phase space. The D q-spectrum of the multifractal measure induced by the attractor, which describes the topological structure of the latter, is obtained. The monofractal dimension of the attractor is D q(0) = 2.31…, and the correlation dimension is D q(2) = 2.16…. The estimate of the largest Lyapunov exponent of the attractor λ1 = 0.331…. The positive signature of the largest Lyapunov exponent suggests that the attractor is chaotic and the behavior of the phase trajectory is unpredictable.

  14. Digital focusing of OCT images based on scalar diffraction theory and information entropy.

    PubMed

    Liu, Guozhong; Zhi, Zhongwei; Wang, Ruikang K

    2012-11-01

    This paper describes a digital method that is capable of automatically focusing optical coherence tomography (OCT) en face images without prior knowledge of the point spread function of the imaging system. The method utilizes a scalar diffraction model to simulate wave propagation from out-of-focus scatter to the focal plane, from which the propagation distance between the out-of-focus plane and the focal plane is determined automatically via an image-definition-evaluation criterion based on information entropy theory. By use of the proposed approach, we demonstrate that the lateral resolution close to that at the focal plane can be recovered from the imaging planes outside the depth of field region with minimal loss of resolution. Fresh onion tissues and mouse fat tissues are used in the experiments to show the performance of the proposed method.

  15. Negative Casimir entropies

    NASA Astrophysics Data System (ADS)

    Li, Yang; Milton, Kimball

    In the last decade, various results on the entropy related to the Casimir interactions between two bodies have been obtained and the striking feature that negative values of Casimir entropy frequently appear. The origin of this effect lies in many factors, such as the dissipation of the materials, the geometry of the configuration and so on. We recently investigated the entropies of one body systems. Although the self-free energy of one body systems are always divergent, the self-entropy could be finite in many cases. These phenomenon may throw more light on thermal dynamical behavior of quantum field systems.

  16. Entropy-based analysis and bioinformatics-inspired integration of global economic information transfer.

    PubMed

    Kim, Jinkyu; Kim, Gunn; An, Sungbae; Kwon, Young-Kyun; Yoon, Sungroh

    2013-01-01

    The assessment of information transfer in the global economic network helps to understand the current environment and the outlook of an economy. Most approaches on global networks extract information transfer based mainly on a single variable. This paper establishes an entirely new bioinformatics-inspired approach to integrating information transfer derived from multiple variables and develops an international economic network accordingly. In the proposed methodology, we first construct the transfer entropies (TEs) between various intra- and inter-country pairs of economic time series variables, test their significances, and then use a weighted sum approach to aggregate information captured in each TE. Through a simulation study, the new method is shown to deliver better information integration compared to existing integration methods in that it can be applied even when intra-country variables are correlated. Empirical investigation with the real world data reveals that Western countries are more influential in the global economic network and that Japan has become less influential following the Asian currency crisis.

  17. The impact of resolution upon entropy and information in coarse-grained models

    NASA Astrophysics Data System (ADS)

    Foley, Thomas T.; Shell, M. Scott; Noid, W. G.

    2015-12-01

    By eliminating unnecessary degrees of freedom, coarse-grained (CG) models tremendously facilitate numerical calculations and theoretical analyses of complex phenomena. However, their success critically depends upon the representation of the system and the effective potential that governs the CG degrees of freedom. This work investigates the relationship between the CG representation and the many-body potential of mean force (PMF), W, which is the appropriate effective potential for a CG model that exactly preserves the structural and thermodynamic properties of a given high resolution model. In particular, we investigate the entropic component of the PMF and its dependence upon the CG resolution. This entropic component, SW, is a configuration-dependent relative entropy that determines the temperature dependence of W. As a direct consequence of eliminating high resolution details from the CG model, the coarsening process transfers configurational entropy and information from the configuration space into SW. In order to further investigate these general results, we consider the popular Gaussian Network Model (GNM) for protein conformational fluctuations. We analytically derive the exact PMF for the GNM as a function of the CG representation. In the case of the GNM, -TSW is a positive, configuration-independent term that depends upon the temperature, the complexity of the protein interaction network, and the details of the CG representation. This entropic term demonstrates similar behavior for seven model proteins and also suggests, in each case, that certain resolutions provide a more efficient description of protein fluctuations. These results may provide general insight into the role of resolution for determining the information content, thermodynamic properties, and transferability of CG models. Ultimately, they may lead to a rigorous and systematic framework for optimizing the representation of CG models.

  18. The impact of resolution upon entropy and information in coarse-grained models

    SciTech Connect

    Foley, Thomas T.; Shell, M. Scott; Noid, W. G.

    2015-12-28

    By eliminating unnecessary degrees of freedom, coarse-grained (CG) models tremendously facilitate numerical calculations and theoretical analyses of complex phenomena. However, their success critically depends upon the representation of the system and the effective potential that governs the CG degrees of freedom. This work investigates the relationship between the CG representation and the many-body potential of mean force (PMF), W, which is the appropriate effective potential for a CG model that exactly preserves the structural and thermodynamic properties of a given high resolution model. In particular, we investigate the entropic component of the PMF and its dependence upon the CG resolution. This entropic component, S{sub W}, is a configuration-dependent relative entropy that determines the temperature dependence of W. As a direct consequence of eliminating high resolution details from the CG model, the coarsening process transfers configurational entropy and information from the configuration space into S{sub W}. In order to further investigate these general results, we consider the popular Gaussian Network Model (GNM) for protein conformational fluctuations. We analytically derive the exact PMF for the GNM as a function of the CG representation. In the case of the GNM, −TS{sub W} is a positive, configuration-independent term that depends upon the temperature, the complexity of the protein interaction network, and the details of the CG representation. This entropic term demonstrates similar behavior for seven model proteins and also suggests, in each case, that certain resolutions provide a more efficient description of protein fluctuations. These results may provide general insight into the role of resolution for determining the information content, thermodynamic properties, and transferability of CG models. Ultimately, they may lead to a rigorous and systematic framework for optimizing the representation of CG models.

  19. Environment-assisted quantum-information correction for continuous variables

    SciTech Connect

    Sabuncu, Metin; Filip, Radim; Leuchs, Gerd

    2010-01-15

    Quantum-information protocols are inevitably affected by decoherence which is associated with the leakage of quantum information into an environment. In this article we address the possibility of recovering the quantum information from an environmental measurement. We investigate continuous-variable quantum information, and we propose a simple environmental measurement that under certain circumstances fully restores the quantum information of the signal state although the state is not reconstructed with unit fidelity. We implement the protocol for which information is encoded into conjugate quadratures of coherent states of light and the noise added under the decoherence process is of Gaussian nature. The correction protocol is tested using both a deterministic as well as a probabilistic strategy. The potential use of the protocol in a continuous-variable quantum-key distribution scheme as a means to combat excess noise is also investigated.

  20. The dynamics of information-driven coordination phenomena: A transfer entropy analysis

    PubMed Central

    Borge-Holthoefer, Javier; Perra, Nicola; Gonçalves, Bruno; González-Bailón, Sandra; Arenas, Alex; Moreno, Yamir; Vespignani, Alessandro

    2016-01-01

    Data from social media provide unprecedented opportunities to investigate the processes that govern the dynamics of collective social phenomena. We consider an information theoretical approach to define and measure the temporal and structural signatures typical of collective social events as they arise and gain prominence. We use the symbolic transfer entropy analysis of microblogging time series to extract directed networks of influence among geolocalized subunits in social systems. This methodology captures the emergence of system-level dynamics close to the onset of socially relevant collective phenomena. The framework is validated against a detailed empirical analysis of five case studies. In particular, we identify a change in the characteristic time scale of the information transfer that flags the onset of information-driven collective phenomena. Furthermore, our approach identifies an order-disorder transition in the directed network of influence between social subunits. In the absence of clear exogenous driving, social collective phenomena can be represented as endogenously driven structural transitions of the information transfer network. This study provides results that can help define models and predictive algorithms for the analysis of societal events based on open source data. PMID:27051875

  1. Lag-specific transfer entropy as a tool to assess cardiovascular and cardiorespiratory information transfer.

    PubMed

    Faes, Luca; Marinazzo, Daniele; Montalto, Alessandro; Nollo, Giandomenico

    2014-10-01

    In the study of interacting physiological systems, model-free tools for time series analysis are fundamental to provide a proper description of how the coupling among systems arises from the multiple involved regulatory mechanisms. This study presents an approach which evaluates direction, magnitude, and exact timing of the information transfer between two time series belonging to a multivariate dataset. The approach performs a decomposition of the well-known transfer entropy (TE) which achieves 1) identifying, according to a lag-specific information-theoretic formulation of the concept of Granger causality, the set of time lags associated with significant information transfer, and 2) assigning to these delays an amount of information transfer such that the total contribution yields the aggregate TE. The approach is first validated on realizations of simulated linear and nonlinear multivariate processes interacting at different time lags and with different strength, reporting a high accuracy in the detection of imposed delays, and showing that the estimated lag-specific TE follows the imposed coupling strength. The subsequent application to heart period, systolic arterial pressure and respiration variability series measured from healthy subjects during a tilt test protocol illustrated how the proposed approach quantifies the modifications in the involvement and latency of important mechanisms of short-term physiological regulation, like the baroreflex and the respiratory sinus arrhythmia, induced by the orthostatic stress.

  2. The dynamics of information-driven coordination phenomena: A transfer entropy analysis.

    PubMed

    Borge-Holthoefer, Javier; Perra, Nicola; Gonçalves, Bruno; González-Bailón, Sandra; Arenas, Alex; Moreno, Yamir; Vespignani, Alessandro

    2016-04-01

    Data from social media provide unprecedented opportunities to investigate the processes that govern the dynamics of collective social phenomena. We consider an information theoretical approach to define and measure the temporal and structural signatures typical of collective social events as they arise and gain prominence. We use the symbolic transfer entropy analysis of microblogging time series to extract directed networks of influence among geolocalized subunits in social systems. This methodology captures the emergence of system-level dynamics close to the onset of socially relevant collective phenomena. The framework is validated against a detailed empirical analysis of five case studies. In particular, we identify a change in the characteristic time scale of the information transfer that flags the onset of information-driven collective phenomena. Furthermore, our approach identifies an order-disorder transition in the directed network of influence between social subunits. In the absence of clear exogenous driving, social collective phenomena can be represented as endogenously driven structural transitions of the information transfer network. This study provides results that can help define models and predictive algorithms for the analysis of societal events based on open source data. PMID:27051875

  3. Information-Technology Approach to Quantum Feedback Control

    NASA Astrophysics Data System (ADS)

    Dong, Dao-Yi; Zhang, Chen-Bin; Chen, Zong-Hai; Chen, Chun-Lin

    Quantum control theory is profitably reexamined from the perspective of quantum information, two results on the role of quantum information technology in quantum feedback control are presented and two quantum feedback control schemes, teleportation-based distant quantum feedback control and quantum feedback control with quantum cloning, are proposed. In the first feedback scheme, the output from the quantum system to be controlled is fed back into the distant actuator via teleportation to alter the dynamics of system. The result theoretically shows that it can accomplish some tasks such as distant feedback quantum control that Markovian or Bayesian quantum feedback can not complete. In the second feedback strategy, the design of quantum feedback control algorithms is separated into a state recognition step, which gives "on-off" signal to the actuator through recognizing some copies from the cloning machine, and a feedback (control) step using another copies of cloning machine. A compromise between information acquisition and measurement disturbance is established, and this strategy can perform some quantum control tasks with coherent feedback.

  4. PREFACE Quantum Groups, Quantum Foundations and Quantum Information: a Festschrift for Tony Sudbery

    NASA Astrophysics Data System (ADS)

    Weigert, Stefan

    2010-11-01

    On 29 July 2008, Professor Anthony Thomas Sudbery - known as Tony to his friends and colleagues - celebrated his 65th birthday. To mark this occasion and to honour Tony's scientific achievements, a 2-day Symposion was held at the University of York on 29-30 September 2008 under the sponsorship of the Institute of Physics and the London Mathematical Society. The breadth of Tony's research interests was reflected in the twelve invited lectures by A Beige, I Bengtsson, K Brown, N Cerf, E Corrigan, J Ladyman, A J Macfarlane, S Majid, C Manogue, S Popescu, J Ryan and R W Tucker. This Festschrift, also made possible by the generosity of the IOP and the LMS, reproduces the majority of these contributions together with other invited papers. Tony obtained his PhD from the University of Cambridge in 1970. His thesis, written under the guidance of Alan Macfarlane, is entitled Some aspects of chiral su(3) × su(3) symmetry in hadron dynamics. He arrived in York in 1971 with his wife Rodie, two young daughters, a lively mind and a very contemporary shock of hair. He was at that stage interested in mathematical physics and so was classed as an applied mathematician in the departmental division in place at that time. But luckily Tony did not fit into this category. His curiosity is combined with a good nose for problems and his capacity for knocking off conjectures impressed us all. Within a short time of his arrival he was writing papers on group theory, complex analysis and combinatorics, while continuing to work on quantum mechanics. His important paper on quaternionic analysis is an example of the imagination and elegance of his ideas. By developing a derivative, he replaced the relatively obscure analytical theory of quaternions by one informed by modern complex analysis. Other interests emerged, centred round the quantum: quantum mechanics and its foundations, quantum groups and quantum information. He didn't just dabble in these areas but mastered them, gaining a national

  5. Interpreting quantum discord through quantum state merging

    SciTech Connect

    Madhok, Vaibhav; Datta, Animesh

    2011-03-15

    We present an operational interpretation of quantum discord based on the quantum state merging protocol. Quantum discord is the markup in the cost of quantum communication in the process of quantum state merging, if one discards relevant prior information. Our interpretation has an intuitive explanation based on the strong subadditivity of von Neumann entropy. We use our result to provide operational interpretations of other quantities like the local purity and quantum deficit. Finally, we discuss in brief some instances where our interpretation is valid in the single-copy scenario.

  6. Modeling loop entropy.

    PubMed

    Chirikjian, Gregory S

    2011-01-01

    Proteins fold from a highly disordered state into a highly ordered one. Traditionally, the folding problem has been stated as one of predicting "the" tertiary structure from sequential information. However, new evidence suggests that the ensemble of unfolded forms may not be as disordered as once believed, and that the native form of many proteins may not be described by a single conformation, but rather an ensemble of its own. Quantifying the relative disorder in the folded and unfolded ensembles as an entropy difference may therefore shed light on the folding process. One issue that clouds discussions of "entropy" is that many different kinds of entropy can be defined: entropy associated with overall translational and rotational Brownian motion, configurational entropy, vibrational entropy, conformational entropy computed in internal or Cartesian coordinates (which can even be different from each other), conformational entropy computed on a lattice, each of the above with different solvation and solvent models, thermodynamic entropy measured experimentally, etc. The focus of this work is the conformational entropy of coil/loop regions in proteins. New mathematical modeling tools for the approximation of changes in conformational entropy during transition from unfolded to folded ensembles are introduced. In particular, models for computing lower and upper bounds on entropy for polymer models of polypeptide coils both with and without end constraints are presented. The methods reviewed here include kinematics (the mathematics of rigid-body motions), classical statistical mechanics, and information theory.

  7. Quantum fog and the degradation of information by the gravitational field

    SciTech Connect

    Sciffer, M. )

    1993-07-01

    In this paper the authors discuss how information transferred optically through a gravitational field is degraded as the quanta interact with the medium (vacuum state). The authors quantify information by means of Shannon's entropy, and consider information carriers that are quanta of some field. Next, the authors obtain the quantum noise ([open quote]quantum fog[close quote]) produced by the gravitational field and derive the appropriate [open quote]channel capacity[close quote] formula, which quantifies the maximum amount of information that can be transmitted per pulse, in the face of this noise. It is shown that the channel capacity formula vanishes if the source of information is a space-time singularity because a very intense noise is produced in the vicinity of the singularity. In other words, space-time singularities are hidden behind a very intense [open quote]quantum fog[close quote] and cannot be optically observed. A second consequence is that information is degraded as anisotropies (lumpiness) develop in the universe. 32 refs., 9 figs., 5 figs.

  8. Glassiness and exotic entropy scaling induced by quantum fluctuations in a disorder-free frustrated magnet

    PubMed Central

    Klich, I.; Lee, S.-H.; Iida, K.

    2014-01-01

    When spins are arranged in a lattice of triangular motif, the phenomenon of frustration leads to numerous energetically equivalent ground states, and results in exotic states such as spin liquid and spin ice. Here we report an alternative situation: a system, classically a liquid, freezes in the clean limit into a glassy state induced by quantum fluctuations. We call such glassy state a spin jam. The case in point is a frustrated magnet, where spins are arranged in a triangular network of bipyramids. Quantum corrections break the classical degeneracy into a set of aperiodic spin configurations forming local minima in a rugged energy landscape. This is established by mapping the problem into tiling with hexagonal tiles. The number of tessellations scales with the boundary length rather than its volume, showing the absence of local zero-energy modes. Low-temperature thermodynamics is discussed to compare it with other glassy materials. PMID:24686398

  9. Generalized second law in cosmology from causal boundary entropy

    PubMed

    Brustein

    2000-03-01

    A classical and quantum mechanical generalized second law of thermodynamics in cosmology implies constraints on the effective equation of state of the universe in the form of energy conditions, obeyed by many known cosmological solutions, forbids certain cosmological singularities, and is compatible with entropy bounds. This second law is based on the conjecture that causal boundaries and not only event horizons have geometric entropies proportional to their area. In string cosmology the second law provides new information about nonsingular solutions.

  10. Quantum Information Biology: From Information Interpretation of Quantum Mechanics to Applications in Molecular Biology and Cognitive Psychology

    NASA Astrophysics Data System (ADS)

    Asano, Masanari; Basieva, Irina; Khrennikov, Andrei; Ohya, Masanori; Tanaka, Yoshiharu; Yamato, Ichiro

    2015-10-01

    We discuss foundational issues of quantum information biology (QIB)—one of the most successful applications of the quantum formalism outside of physics. QIB provides a multi-scale model of information processing in bio-systems: from proteins and cells to cognitive and social systems. This theory has to be sharply distinguished from "traditional quantum biophysics". The latter is about quantum bio-physical processes, e.g., in cells or brains. QIB models the dynamics of information states of bio-systems. We argue that the information interpretation of quantum mechanics (its various forms were elaborated by Zeilinger and Brukner, Fuchs and Mermin, and D' Ariano) is the most natural interpretation of QIB. Biologically QIB is based on two principles: (a) adaptivity; (b) openness (bio-systems are fundamentally open). These principles are mathematically represented in the framework of a novel formalism— quantum adaptive dynamics which, in particular, contains the standard theory of open quantum systems.

  11. Fisher information in a quantum-critical environment

    SciTech Connect

    Sun Zhe; Ma Jian; Lu Xiaoming; Wang Xiaoguang

    2010-08-15

    We consider a process of parameter estimation in a spin-j system surrounded by a quantum-critical spin chain. Quantum Fisher information lies at the heart of the estimation task. We employ Ising spin chain in a transverse field as the environment which exhibits a quantum phase transition. Fisher information decays with time almost monotonously when the environment reaches the critical point. By choosing a fixed time or taking the time average, one can see the quantum Fisher information presents a sudden drop at the critical point. Different initial states of the environment are considered. The phenomenon that the quantum Fisher information, namely, the precision of estimation, changes dramatically can be used to detect the quantum criticality of the environment. We also introduce a general method to obtain the maximal Fisher information for a given state.

  12. Monitoring the informational efficiency of European corporate bond markets with dynamical permutation min-entropy

    NASA Astrophysics Data System (ADS)

    Zunino, Luciano; Bariviera, Aurelio F.; Guercio, M. Belén; Martinez, Lisana B.; Rosso, Osvaldo A.

    2016-08-01

    In this paper the permutation min-entropy has been implemented to unveil the presence of temporal structures in the daily values of European corporate bond indices from April 2001 to August 2015. More precisely, the informational efficiency evolution of the prices of fifteen sectorial indices has been carefully studied by estimating this information-theory-derived symbolic tool over a sliding time window. Such a dynamical analysis makes possible to obtain relevant conclusions about the effect that the 2008 credit crisis has had on the different European corporate bond sectors. It is found that the informational efficiency of some sectors, namely banks, financial services, insurance, and basic resources, has been strongly reduced due to the financial crisis whereas another set of sectors, integrated by chemicals, automobiles, media, energy, construction, industrial goods & services, technology, and telecommunications has only suffered a transitory loss of efficiency. Last but not least, the food & beverage, healthcare, and utilities sectors show a behavior close to a random walk practically along all the period of analysis, confirming a remarkable immunity against the 2008 financial crisis.

  13. Power of one bit of quantum information in quantum metrology

    NASA Astrophysics Data System (ADS)

    Cable, Hugo; Gu, Mile; Modi, Kavan

    2016-04-01

    We present a model of quantum metrology inspired by the computational model known as deterministic quantum computation with one quantum bit (DQC1). Using only one pure qubit together with l fully mixed qubits we obtain measurement precision (defined as root-mean-square error for the parameter being estimated) at the standard quantum limit, which is typically obtained using the same number of uncorrelated qubits in fully pure states. In principle, the standard quantum limit can be exceeded using an additional qubit which adds only a small amount of purity. We show that the discord in the final state vanishes only in the limit of attaining infinite precision for the parameter being estimated.

  14. Coupled-Double-Quantum-Dot Environmental Information Engines: A Numerical Analysis

    NASA Astrophysics Data System (ADS)

    Tanabe, Katsuaki

    2016-06-01

    We conduct numerical simulations for an autonomous information engine comprising a set of coupled double quantum dots using a simple model. The steady-state entropy production rate in each component, heat and electron transfer rates are calculated via the probability distribution of the four electronic states from the master transition-rate equations. We define an information-engine efficiency based on the entropy change of the reservoir, implicating power generators that employ the environmental order as a new energy resource. We acquire device-design principles, toward the realization of corresponding practical energy converters, including that (1) higher energy levels of the detector-side reservoir than those of the detector dot provide significantly higher work production rates by faster states' circulation, (2) the efficiency is strongly dependent on the relative temperatures of the detector and system sides and becomes high in a particular Coulomb-interaction strength region between the quantum dots, and (3) the efficiency depends little on the system dot's energy level relative to its reservoir but largely on the antisymmetric relative amplitudes of the electronic tunneling rates.

  15. Robust quantum metrological schemes based on protection of quantum Fisher information.

    PubMed

    Lu, Xiao-Ming; Yu, Sixia; Oh, C H

    2015-06-08

    Fragile quantum features such as entanglement are employed to improve the precision of parameter estimation and as a consequence the quantum gain becomes vulnerable to noise. As an established tool to subdue noise, quantum error correction is unfortunately overprotective because the quantum enhancement can still be achieved even if the states are irrecoverably affected, provided that the quantum Fisher information, which sets the ultimate limit to the precision of metrological schemes, is preserved and attained. Here we develop a theory of robust metrological schemes that preserve the quantum Fisher information instead of the quantum states themselves against noise. After deriving a minimal set of testable conditions on this kind of robustness, we construct a family of 2t+1 qubits metrological schemes being immune to t-qubit errors after the signal sensing. In comparison, at least five qubits are required for correcting arbitrary 1-qubit errors in standard quantum error correction.

  16. Robust quantum metrological schemes based on protection of quantum Fisher information.

    PubMed

    Lu, Xiao-Ming; Yu, Sixia; Oh, C H

    2015-01-01

    Fragile quantum features such as entanglement are employed to improve the precision of parameter estimation and as a consequence the quantum gain becomes vulnerable to noise. As an established tool to subdue noise, quantum error correction is unfortunately overprotective because the quantum enhancement can still be achieved even if the states are irrecoverably affected, provided that the quantum Fisher information, which sets the ultimate limit to the precision of metrological schemes, is preserved and attained. Here we develop a theory of robust metrological schemes that preserve the quantum Fisher information instead of the quantum states themselves against noise. After deriving a minimal set of testable conditions on this kind of robustness, we construct a family of 2t+1 qubits metrological schemes being immune to t-qubit errors after the signal sensing. In comparison, at least five qubits are required for correcting arbitrary 1-qubit errors in standard quantum error correction. PMID:26051453

  17. Robust quantum metrological schemes based on protection of quantum Fisher information

    NASA Astrophysics Data System (ADS)

    Lu, Xiao-Ming; Yu, Sixia; Oh, C. H.

    2015-06-01

    Fragile quantum features such as entanglement are employed to improve the precision of parameter estimation and as a consequence the quantum gain becomes vulnerable to noise. As an established tool to subdue noise, quantum error correction is unfortunately overprotective because the quantum enhancement can still be achieved even if the states are irrecoverably affected, provided that the quantum Fisher information, which sets the ultimate limit to the precision of metrological schemes, is preserved and attained. Here we develop a theory of robust metrological schemes that preserve the quantum Fisher information instead of the quantum states themselves against noise. After deriving a minimal set of testable conditions on this kind of robustness, we construct a family of 2t+1 qubits metrological schemes being immune to t-qubit errors after the signal sensing. In comparison, at least five qubits are required for correcting arbitrary 1-qubit errors in standard quantum error correction.

  18. Domain theoretic structures in quantum information theory

    NASA Astrophysics Data System (ADS)

    Feng, Johnny

    2011-12-01

    In this thesis, we continue the study of domain theoretic structures in quantum information theory initiated by Keye Martin and Bob Coecke in 2002. The first part of the thesis is focused on exploring the domain theoretic properties of qubit channels. We discover that the Scott continuous qubit channels are exactly those that are unital or constant. We then prove that the unital qubit channels form a continuous dcpo, and identify various measurements on them. We show that Holevo capacity is a measurement on unital qubit channels, and discover the natural measurement in this setting. We find that qubit channels also form a continuous dcpo, but capacity fails to be a measurement. In the second part we focus on the study of exact dcpos, a domain theoretic structure, closely related to continuous dcpos, possessed by quantum states. Exact dcpos admit a topology, called the exact topology, and we show that the exact topology has an order theoretic characterization similar to the characterization of the Scott topology on continuous dcpos. We then explore the connection between exact and continuous dcpos; first, by identifying an important set of points, called the split points, that distinguishes between exact and continuous structures; second, by exploring a continuous completion of exact dcpos, and showing that we can recover the exact topology from the Scott topology of the completion.

  19. Quantum-Classical Hybrid for Information Processing

    NASA Technical Reports Server (NTRS)

    Zak, Michail

    2011-01-01

    Based upon quantum-inspired entanglement in quantum-classical hybrids, a simple algorithm for instantaneous transmissions of non-intentional messages (chosen at random) to remote distances is proposed. The idea is to implement instantaneous transmission of conditional information on remote distances via a quantum-classical hybrid that preserves superposition of random solutions, while allowing one to measure its state variables using classical methods. Such a hybrid system reinforces the advantages, and minimizes the limitations, of both quantum and classical characteristics. Consider n observers, and assume that each of them gets a copy of the system and runs it separately. Although they run identical systems, the outcomes of even synchronized runs may be different because the solutions of these systems are random. However, the global constrain must be satisfied. Therefore, if the observer #1 (the sender) made a measurement of the acceleration v(sub 1) at t =T, then the receiver, by measuring the corresponding acceleration v(sub 1) at t =T, may get a wrong value because the accelerations are random, and only their ratios are deterministic. Obviously, the transmission of this knowledge is instantaneous as soon as the measurements have been performed. In addition to that, the distance between the observers is irrelevant because the x-coordinate does not enter the governing equations. However, the Shannon information transmitted is zero. None of the senders can control the outcomes of their measurements because they are random. The senders cannot transmit intentional messages. Nevertheless, based on the transmitted knowledge, they can coordinate their actions based on conditional information. If the observer #1 knows his own measurements, the measurements of the others can be fully determined. It is important to emphasize that the origin of entanglement of all the observers is the joint probability density that couples their actions. There is no centralized source

  20. Nonadiabatic approach to quantum optical information storage

    NASA Astrophysics Data System (ADS)

    Matsko, A. B.; Rostovtsev, Y. V.; Kocharovskaya, O.; Zibrov, A. S.; Scully, M. O.

    2001-10-01

    We show that there is no need for adiabatic passage in the storage and retrieval of information in the optically thick vapor of Lambda-type atoms. This information can be mapped into and retrieved out of long-lived atomic coherence with nearly perfect efficiency by strong writing and reading pulses with steep rising and falling edges. We elucidate similarities and differences between the ``adiabatic'' and ``instant'' light storage techniques, and conclude that for any switching time, an almost perfect information storage is possible if the group velocity of the signal pulse is much less than the speed of light in the vacuum c and the bandwidth of the signal pulse is much less then the width of the two-photon resonance. The maximum loss of the information appears in the case of instantaneous switching of the writing and reading fields compared with adiabatic switching, and is determined by the ratio of the initial group velocity of the signal pulse in the medium and speed of light in the vacuum c, which can be very small. Quantum restrictions to the storage efficiency are also discussed.

  1. Reply to "Comment on 'Similarity between quantum mechanics and thermodynamics: Entropy, temperature, and Carnot cycle' ''.

    PubMed

    Abe, Sumiyoshi

    2015-05-01

    In their Comment on the paper [Abe and Okuyama, Phys. Rev. E 83, 021121 (2011)], González-Díaz and Díaz-Solórzano discuss that the initial state of the quantum-mechanical analog of the Carnot cycle should be not in a pure state but in a mixed state due to a projective measurement of the system energy. Here, first the Comment is shown to miss the point. Then, second, multiple projective measurements are discussed as a generalization of the Comment, although they are not relevant to the work commented.

  2. A universal quantum information processor for scalable quantum communication and networks.

    PubMed

    Yang, Xihua; Xue, Bolin; Zhang, Junxiang; Zhu, Shiyao

    2014-10-15

    Entanglement provides an essential resource for quantum computation, quantum communication, and quantum networks. How to conveniently and efficiently realize the generation, distribution, storage, retrieval, and control of multipartite entanglement is the basic requirement for realistic quantum information processing. Here, we present a theoretical proposal to efficiently and conveniently achieve a universal quantum information processor (QIP) via atomic coherence in an atomic ensemble. The atomic coherence, produced through electromagnetically induced transparency (EIT) in the Λ-type configuration, acts as the QIP and has full functions of quantum beam splitter, quantum frequency converter, quantum entangler, and quantum repeater. By employing EIT-based nondegenerate four-wave mixing processes, the generation, exchange, distribution, and manipulation of light-light, atom-light, and atom-atom multipartite entanglement can be efficiently and flexibly achieved in a deterministic way with only coherent light fields. This method greatly facilitates the operations in quantum information processing, and holds promising applications in realistic scalable quantum communication and quantum networks.

  3. A universal quantum information processor for scalable quantum communication and networks

    PubMed Central

    Yang, Xihua; Xue, Bolin; Zhang, Junxiang; Zhu, Shiyao

    2014-01-01

    Entanglement provides an essential resource for quantum computation, quantum communication, and quantum networks. How to conveniently and efficiently realize the generation, distribution, storage, retrieval, and control of multipartite entanglement is the basic requirement for realistic quantum information processing. Here, we present a theoretical proposal to efficiently and conveniently achieve a universal quantum information processor (QIP) via atomic coherence in an atomic ensemble. The atomic coherence, produced through electromagnetically induced transparency (EIT) in the Λ-type configuration, acts as the QIP and has full functions of quantum beam splitter, quantum frequency converter, quantum entangler, and quantum repeater. By employing EIT-based nondegenerate four-wave mixing processes, the generation, exchange, distribution, and manipulation of light-light, atom-light, and atom-atom multipartite entanglement can be efficiently and flexibly achieved in a deterministic way with only coherent light fields. This method greatly facilitates the operations in quantum information processing, and holds promising applications in realistic scalable quantum communication and quantum networks. PMID:25316514

  4. Conservation of information and the foundations of quantum mechanics

    NASA Astrophysics Data System (ADS)

    Chiribella, Giulio; Scandolo, Carlo Maria

    2015-05-01

    We review a recent approach to the foundations of quantum mechanics inspired by quantum information theory [1, 2]. The approach is based on a general framework, which allows one to address a large class of physical theories which share basic information-theoretic features. We first illustrate two very primitive features, expressed by the axioms of causality and purity-preservation, which are satisfied by both classical and quantum theory. We then discuss the axiom of purification, which expresses a strong version of the Conservation of Information and captures the core of a vast number of protocols in quantum information. Purification is a highly non-classical feature and leads directly to the emergence of entanglement at the purely conceptual level, without any reference to the superposition principle. Supplemented by a few additional requirements, satisfied by classical and quantum theory, it provides a complete axiomatic characterization of quantum theory for finite dimensional systems.

  5. General impossible operations in quantum information

    SciTech Connect

    Pati, Arun K.

    2002-12-01

    We prove a general limitation in quantum information that unifies the impossibility principles such as no-cloning and no-anticloning. Further, we show that for an unknown qubit one cannot design a universal Hadamard gate for creating equal superposition of the original and its complement state. Surprisingly, we find that Hadamard transformations exist for an unknown qubit chosen either from the polar or equatorial great circles. Also, we show that for an unknown qubit one cannot design a universal unitary gate for creating unequal superpositions of the original and its complement state. We discuss why it is impossible to design a controlled-NOT gate for two unknown qubits and discuss the implications of these limitations. 03.67.Hk, 03.65.Ta.

  6. Enhanced atom interferometry through quantum information science

    NASA Astrophysics Data System (ADS)

    Edwards, Mark; Benton, Brandon; Krygier, Michael; Clark, Charles W.

    2011-03-01

    New designs for atom interferometers can be inspired by quantum information science (QIS). QIS--inspired atom interferometer (AI) designs have the potential for producing AIs with enhanced sensitivity and robustness. We compare the sensitivity of a standard Mach--Zehnder (M--Z) Bragg AI with an AI whose design is based on the idea of decoherence--free subspaces (DFS). We studied the performance of both atom interferometers using an enhanced version of a previously developed Bragg interferometer prototyping model. This model approximates the effect on the condensate of multiple Bragg pulses separated by time delays using two elements: the effect of a single pulse and condensate evolution between pulses. The overall effect is rapidly approximated by following the steps of the interferometric process. We describe this model and then present the comparison of the performance of the M--Z interferometer with that of the DFS--inspired interferometer. Support provided by NSF grant number PHY-0758111.

  7. Enhanced atom interferometry through quantum information science

    NASA Astrophysics Data System (ADS)

    Edwards, Mark; Benton, Brandon; Krygier, Michael; Clark, Charles

    2011-05-01

    New designs for atom interferometers can be inspired by quantum information science (QIS). QIS-inspired atom interferometer (AI) designs have the potential for producing AIs with enhanced sensitivity and robustness. We compare the sensitivity of a standard Mach-Zehnder (M-Z) Bragg AI with an AI whose design is based on the idea of decoherence-free subspaces (DFS). We studied the performance of both atom interferometers using an enhanced version of a previously developed Bragg interferometer prototyping model. This model approximates the effect on the condensate of multiple Bragg pulses separated by time delays using two elements: the effect of a single pulse and condensate evolution between pulses. The overall effect is rapidly approximated by following the steps of the interferometric process. We describe this model and then present the comparison of the performance of the M-Z interferometer with that of the DFS-inspired interferometer. Support provided by NSF grant number PHY-0758111.

  8. Spiking Cortical Model Based Multimodal Medical Image Fusion by Combining Entropy Information with Weber Local Descriptor

    PubMed Central

    Zhang, Xuming; Ren, Jinxia; Huang, Zhiwen; Zhu, Fei

    2016-01-01

    Multimodal medical image fusion (MIF) plays an important role in clinical diagnosis and therapy. Existing MIF methods tend to introduce artifacts, lead to loss of image details or produce low-contrast fused images. To address these problems, a novel spiking cortical model (SCM) based MIF method has been proposed in this paper. The proposed method can generate high-quality fused images using the weighting fusion strategy based on the firing times of the SCM. In the weighting fusion scheme, the weight is determined by combining the entropy information of pulse outputs of the SCM with the Weber local descriptor operating on the firing mapping images produced from the pulse outputs. The extensive experiments on multimodal medical images show that compared with the numerous state-of-the-art MIF methods, the proposed method can preserve image details very well and avoid the introduction of artifacts effectively, and thus it significantly improves the quality of fused images in terms of human vision and objective evaluation criteria such as mutual information, edge preservation index, structural similarity based metric, fusion quality index, fusion similarity metric and standard deviation. PMID:27649190

  9. Spiking Cortical Model Based Multimodal Medical Image Fusion by Combining Entropy Information with Weber Local Descriptor.

    PubMed

    Zhang, Xuming; Ren, Jinxia; Huang, Zhiwen; Zhu, Fei

    2016-01-01

    Multimodal medical image fusion (MIF) plays an important role in clinical diagnosis and therapy. Existing MIF methods tend to introduce artifacts, lead to loss of image details or produce low-contrast fused images. To address these problems, a novel spiking cortical model (SCM) based MIF method has been proposed in this paper. The proposed method can generate high-quality fused images using the weighting fusion strategy based on the firing times of the SCM. In the weighting fusion scheme, the weight is determined by combining the entropy information of pulse outputs of the SCM with the Weber local descriptor operating on the firing mapping images produced from the pulse outputs. The extensive experiments on multimodal medical images show that compared with the numerous state-of-the-art MIF methods, the proposed method can preserve image details very well and avoid the introduction of artifacts effectively, and thus it significantly improves the quality of fused images in terms of human vision and objective evaluation criteria such as mutual information, edge preservation index, structural similarity based metric, fusion quality index, fusion similarity metric and standard deviation. PMID:27649190

  10. Long-range entanglement is necessary for a topological storage of quantum information.

    PubMed

    Kim, Isaac H

    2013-08-23

    A general inequality between entanglement entropy and a number of topologically ordered states is derived, even without using the properties of the parent Hamiltonian or the formalism of topological quantum field theory. Given a quantum state |ψ], we obtain an upper bound on the number of distinct states that are locally indistinguishable from |ψ]. The upper bound is determined only by the entanglement entropy of some local subsystems. As an example, we show that log N≤2γ for a large class of topologically ordered systems on a torus, where N is the number of topologically protected states and γ is the constant subcorrection term of the entanglement entropy. We discuss applications to quantum many-body systems that do not have any low-energy topological quantum field theory description, as well as tradeoff bounds for general quantum error correcting codes.

  11. Symmetrically private information retrieval based on blind quantum computing

    NASA Astrophysics Data System (ADS)

    Sun, Zhiwei; Yu, Jianping; Wang, Ping; Xu, Lingling

    2015-05-01

    Universal blind quantum computation (UBQC) is a new secure quantum computing protocol which allows a user Alice who does not have any sophisticated quantum technology to delegate her computing to a server Bob without leaking any privacy. Using the features of UBQC, we propose a protocol to achieve symmetrically private information retrieval, which allows a quantum limited Alice to query an item from Bob with a fully fledged quantum computer; meanwhile, the privacy of both parties is preserved. The security of our protocol is based on the assumption that malicious Alice has no quantum computer, which avoids the impossibility proof of Lo. For the honest Alice, she is almost classical and only requires minimal quantum resources to carry out the proposed protocol. Therefore, she does not need any expensive laboratory which can maintain the coherence of complicated quantum experimental setups.

  12. Quantum Information Biology: From Theory of Open Quantum Systems to Adaptive Dynamics

    NASA Astrophysics Data System (ADS)

    Asano, Masanari; Basieva, Irina; Khrennikov, Andrei; Ohya, Masanori; Tanaka, Yoshiharu; Yamato, Ichiro

    This chapter reviews quantum(-like) information biology (QIB). Here biology is treated widely as even covering cognition and its derivatives: psychology and decision making, sociology, and behavioral economics and finances. QIB provides an integrative description of information processing by bio-systems at all scales of life: from proteins and cells to cognition, ecological and social systems. Mathematically QIB is based on the theory of adaptive quantum systems (which covers also open quantum systems). Ideologically QIB is based on the quantum-like (QL) paradigm: complex bio-systems process information in accordance with the laws of quantum information and probability. This paradigm is supported by plenty of statistical bio-data collected at all bio-scales. QIB re ects the two fundamental principles: a) adaptivity; and, b) openness (bio-systems are fundamentally open). In addition, quantum adaptive dynamics provides the most generally possible mathematical representation of these principles.

  13. Secure self-calibrating quantum random-bit generator

    SciTech Connect

    Fiorentino, M.; Santori, C.; Spillane, S. M.; Beausoleil, R. G.; Munro, W. J.

    2007-03-15

    Random-bit generators (RBGs) are key components of a variety of information processing applications ranging from simulations to cryptography. In particular, cryptographic systems require 'strong' RBGs that produce high-entropy bit sequences, but traditional software pseudo-RBGs have very low entropy content and therefore are relatively weak for cryptography. Hardware RBGs yield entropy from chaotic or quantum physical systems and therefore are expected to exhibit high entropy, but in current implementations their exact entropy content is unknown. Here we report a quantum random-bit generator (QRBG) that harvests entropy by measuring single-photon and entangled two-photon polarization states. We introduce and implement a quantum tomographic method to measure a lower bound on the 'min-entropy' of the system, and we employ this value to distill a truly random-bit sequence. This approach is secure: even if an attacker takes control of the source of optical states, a secure random sequence can be distilled.

  14. Jerusalem lectures on black holes and quantum information

    NASA Astrophysics Data System (ADS)

    Harlow, D.

    2016-01-01

    These lectures give an introduction to the quantum physics of black holes, including recent developments based on quantum information theory such as the firewall paradox and its various cousins. An introduction is also given to holography and the anti-de Sitter/conformal field theory (AdS/CFT) correspondence, focusing on those aspects which are relevant for the black hole information problem.

  15. Quantum mutual information and the one-time pad

    SciTech Connect

    Schumacher, Benjamin; Westmoreland, Michael D.

    2006-10-15

    Alice and Bob share a correlated composite quantum system AB. If AB is used as the key for a one-time pad cryptographic system, we show that the maximum amount of information that Alice can send securely to Bob is the quantum mutual information of AB.

  16. Geometric phase, quantum Fisher information, geometric quantum correlation and quantum phase transition in the cavity-Bose-Einstein-condensate system

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Xu, Jing-Bo

    2016-09-01

    We investigate the quantum phase transition of an atomic ensemble trapped in a single-mode optical cavity via the geometric phase and quantum Fisher information of an extra probe atom which is injected into the optical cavity and interacts with the cavity field. We also find that the geometric quantum correlation between two probe atoms exhibits a double sudden transition phenomenon and show this double sudden transition phenomenon is closely associated with the quantum phase transition of the atomic ensemble. Furthermore, we propose a theoretical scheme to prolong the frozen time during which the geometric quantum correlation remains constant by applying time-dependent electromagnetic field.

  17. The future (and past) of quantum theory after the Higgs boson: a quantum-informational viewpoint.

    PubMed

    Plotnitsky, Arkady

    2016-05-28

    Taking as its point of departure the discovery of the Higgs boson, this article considers quantum theory, including quantum field theory, which predicted the Higgs boson, through the combined perspective of quantum information theory and the idea of technology, while also adopting anon-realistinterpretation, in 'the spirit of Copenhagen', of quantum theory and quantum phenomena themselves. The article argues that the 'events' in question in fundamental physics, such as the discovery of the Higgs boson (a particularly complex and dramatic, but not essentially different, case), are made possible by the joint workings of three technologies: experimental technology, mathematical technology and, more recently, digital computer technology. The article will consider the role of and the relationships among these technologies, focusing on experimental and mathematical technologies, in quantum mechanics (QM), quantum field theory (QFT) and finite-dimensional quantum theory, with which quantum information theory has been primarily concerned thus far. It will do so, in part, by reassessing the history of quantum theory, beginning with Heisenberg's discovery of QM, in quantum-informational and technological terms. This history, the article argues, is defined by the discoveries of increasingly complex configurations of observed phenomena and the emergence of the increasingly complex mathematical formalism accounting for these phenomena, culminating in the standard model of elementary-particle physics, defining the current state of QFT. PMID:27091170

  18. The future (and past) of quantum theory after the Higgs boson: a quantum-informational viewpoint.

    PubMed

    Plotnitsky, Arkady

    2016-05-28

    Taking as its point of departure the discovery of the Higgs boson, this article considers quantum theory, including quantum field theory, which predicted the Higgs boson, through the combined perspective of quantum information theory and the idea of technology, while also adopting anon-realistinterpretation, in 'the spirit of Copenhagen', of quantum theory and quantum phenomena themselves. The article argues that the 'events' in question in fundamental physics, such as the discovery of the Higgs boson (a particularly complex and dramatic, but not essentially different, case), are made possible by the joint workings of three technologies: experimental technology, mathematical technology and, more recently, digital computer technology. The article will consider the role of and the relationships among these technologies, focusing on experimental and mathematical technologies, in quantum mechanics (QM), quantum field theory (QFT) and finite-dimensional quantum theory, with which quantum information theory has been primarily concerned thus far. It will do so, in part, by reassessing the history of quantum theory, beginning with Heisenberg's discovery of QM, in quantum-informational and technological terms. This history, the article argues, is defined by the discoveries of increasingly complex configurations of observed phenomena and the emergence of the increasingly complex mathematical formalism accounting for these phenomena, culminating in the standard model of elementary-particle physics, defining the current state of QFT.

  19. Enhancing teleportation of quantum Fisher information by partial measurements

    NASA Astrophysics Data System (ADS)

    Xiao, Xing; Yao, Yao; Zhong, Wo-Jun; Li, Yan-Ling; Xie, Ying-Mao

    2016-01-01

    The purport of quantum teleportation is to completely transfer information from one party to another distant partner. However, from the perspective of parameter estimation, it is the information carried by a particular parameter, not the information of total quantum state that needs to be teleported. Due to the inevitable noise in environments, we propose two schemes to enhance quantum Fisher information (QFI) teleportation under amplitude damping noise with the technique of partial measurements. We find that post-partial measurement can greatly enhance the teleported QFI, while the combination of prior partial measurement and post-partial measurement reversal could completely eliminate the effect of decoherence. We show that, somewhat consequentially, enhancing QFI teleportation is more economic than that of improving fidelity teleportation. Our work extends the ability of partial measurements as a quantum technique to battle decoherence in quantum information processing.

  20. Quantum of area {Delta}A=8{pi}l{sub P}{sup 2} and a statistical interpretation of black hole entropy

    SciTech Connect

    Ropotenko, Kostiantyn

    2010-08-15

    In contrast to alternative values, the quantum of area {Delta}A=8{pi}l{sub P}{sup 2} does not follow from the usual statistical interpretation of black hole entropy; on the contrary, a statistical interpretation follows from it. This interpretation is based on the two concepts: nonadditivity of black hole entropy and Landau quantization. Using nonadditivity a microcanonical distribution for a black hole is found and it is shown that the statistical weight of a black hole should be proportional to its area. By analogy with conventional Landau quantization, it is shown that quantization of a black hole is nothing but the Landau quantization. The Landau levels of a black hole and their degeneracy are found. The degree of degeneracy is equal to the number of ways to distribute a patch of area 8{pi}l{sub P}{sup 2} over the horizon. Taking into account these results, it is argued that the black hole entropy should be of the form S{sub bh}=2{pi}{center_dot}{Delta}{Gamma}, where the number of microstates is {Delta}{Gamma}=A/8{pi}l{sub P}{sup 2}. The nature of the degrees of freedom responsible for black hole entropy is elucidated. The applications of the new interpretation are presented. The effect of noncommuting coordinates is discussed.

  1. Generalized Cross Entropy Method for estimating joint distribution from incomplete information

    NASA Astrophysics Data System (ADS)

    Xu, Hai-Yan; Kuo, Shyh-Hao; Li, Guoqi; Legara, Erika Fille T.; Zhao, Daxuan; Monterola, Christopher P.

    2016-07-01

    Obtaining a full joint distribution from individual marginal distributions with incomplete information is a non-trivial task that continues to challenge researchers from various domains including economics, demography, and statistics. In this work, we develop a new methodology referred to as "Generalized Cross Entropy Method" (GCEM) that is aimed at addressing the issue. The objective function is proposed to be a weighted sum of divergences between joint distributions and various references. We show that the solution of the GCEM is unique and global optimal. Furthermore, we illustrate the applicability and validity of the method by utilizing it to recover the joint distribution of a household profile of a given administrative region. In particular, we estimate the joint distribution of the household size, household dwelling type, and household home ownership in Singapore. Results show a high-accuracy estimation of the full joint distribution of the household profile under study. Finally, the impact of constraints and weight on the estimation of joint distribution is explored.

  2. A novel approach for urbanization level evaluation based on information entropy principle: A case of Beijing

    NASA Astrophysics Data System (ADS)

    Zhao, Jingjing; Chai, Lihe

    2015-07-01

    Urbanization level evaluation (ULE) is an important scientific basis for guiding urban managers to make decisions. By introducing information entropy to describe the interactions between all indicators, a holistic structural parameter ξ, its dynamic equation and self-organizing feature map simulation technique are derived to describe the structural evolution of the indicator network. In this way, a novel ULE model is universally proposed. Then, we use the model to assess the evolutionary urbanization level of Beijing during 2005-2012. We calculate structural parameter ξ values of the indicator network with 35 microscopic indicators as nodes. The results show Beijing's urbanization level has ever kept increasing. Large increase of ξ values in 2008 and 2012 represented significant improvements of urbanization level in these two years, while a rapid adjustment of urbanization development occurred in 2010. Five meso-scopic subsystems as urban construction, economic development, social development, ecological environment and urban-rural development affected Beijing's urbanization level in different ways. The radar chart of the model shows the contributions of economic development and urban-rural development to Beijing's urbanization changed most, while poor coordination of urban-rural development largely existed. By showing Beijing's ULE based on two analytical ways, we further discuss the objectivity and flexibility in choosing indicator network. Finally, beyond the application case, we discuss the universality and superiority of the new model.

  3. Colloquium: Area laws for the entanglement entropy

    NASA Astrophysics Data System (ADS)

    Eisert, J.; Cramer, M.; Plenio, M. B.

    2010-01-01

    Physical interactions in quantum many-body systems are typically local: Individual constituents interact mainly with their few nearest neighbors. This locality of interactions is inherited by a decay of correlation functions, but also reflected by scaling laws of a quite profound quantity: the entanglement entropy of ground states. This entropy of the reduced state of a subregion often merely grows like the boundary area of the subregion, and not like its volume, in sharp contrast with an expected extensive behavior. Such “area laws” for the entanglement entropy and related quantities have received considerable attention in recent years. They emerge in several seemingly unrelated fields, in the context of black hole physics, quantum information science, and quantum many-body physics where they have important implications on the numerical simulation of lattice models. In this Colloquium the current status of area laws in these fields is reviewed. Center stage is taken by rigorous results on lattice models in one and higher spatial dimensions. The differences and similarities between bosonic and fermionic models are stressed, area laws are related to the velocity of information propagation in quantum lattice models, and disordered systems, nonequilibrium situations, and topological entanglement entropies are discussed. These questions are considered in classical and quantum systems, in their ground and thermal states, for a variety of correlation measures. A significant proportion is devoted to the clear and quantitative connection between the entanglement content of states and the possibility of their efficient numerical simulation. Matrix-product states, higher-dimensional analogs, and variational sets from entanglement renormalization are also discussed and the paper is concluded by highlighting the implications of area laws on quantifying the effective degrees of freedom that need to be considered in simulations of quantum states.

  4. Information driven current in a quantum Maxwell demon

    NASA Astrophysics Data System (ADS)

    Deffner, Sebastian

    2014-03-01

    We describe a minimal model of a quantum Maxwell demon obeying Hamiltonian dynamics. The model is solved exactly, and we analyze its steady-state behavior. We find that writing information to a quantum memory induces a probability current through the demon, which is the quantum analog of the classical Maxwell demon's action. Our model offers a simple and pedagogical paradigm for investigating the thermodynamics of quantum information processing. We acknowledge financial support by a fellowship within the postdoc-program of the German Academic Exchange Service (DAAD, contract No D/11/40955) and from the National Science Foundation (USA) under grant DMR-1206971.

  5. Temporal compression of quantum-information-carrying photons using a photon-echo quantum memory approach

    SciTech Connect

    Moiseev, S. A.; Tittel, W.

    2010-07-15

    We study quantum compression and decompression of light pulses that carry quantum information using a photon-echo quantum memory technique with controllable inhomogeneous broadening of an isolated atomic absorption line. We investigate media with differently broadened absorption profiles, transverse and longitudinal, finding that the recall efficiency can be as large as unity and that the quantum information encoded into the photonic qubits can remain unperturbed. Our results provide insight into reversible light-atom interaction and are interesting in view of future quantum communication networks, where pulse compression and decompression may play an important role in increasing the qubit rate or in mapping quantum information from photonic carriers with large optical bandwidth into atomic memories with smaller bandwidth.

  6. Experimental quantum deletion in an NMR quantum information processor

    NASA Astrophysics Data System (ADS)

    Long, Yu; Feng, GuanRu; Pearson, Jasong; Long, GuiLu

    2014-07-01

    We report an NMR experimental realization of a rapid quantum deletion algorithm that deletes marked states in an unsorted database. Unlike classical deletion, where search and deletion are equivalent, quantum deletion can be implemented with only a single query, which achieves exponential speed-up compared to the optimal classical analog. In the experimental realization, the GRAPE algorithm was used to obtain an optimized NMR pulse sequence, and the efficient method of maximum-likelihood has been used to reconstruct the experimental output state.

  7. Charged topological entanglement entropy

    NASA Astrophysics Data System (ADS)

    Matsuura, Shunji; Wen, Xueda; Hung, Ling-Yan; Ryu, Shinsei

    2016-05-01

    A charged entanglement entropy is a new measure which probes quantum entanglement between different charge sectors. We study symmetry-protected topological (SPT) phases in (2+1)-dimensional space-time by using this charged entanglement entropy. SPT phases are short-range entangled states without topological order and hence cannot be detected by the topological entanglement entropy. We demonstrate that the universal part of the charged entanglement entropy is nonzero for nontrivial SPT phases and therefore it is a useful measure to detect short-range entangled topological phases. We also discuss that the classification of SPT phases based on the charged topological entanglement entropy is related to that of the braiding statistics of quasiparticles.

  8. Towards a geometrical interpretation of quantum-information compression

    NASA Astrophysics Data System (ADS)

    Mitchison, Graeme; Jozsa, Richard

    2004-03-01

    Let S be the von Neumann entropy of a finite ensemble E of pure quantum states. We show that S may be naturally viewed as a function of a set of geometrical volumes in Hilbert space defined by the states and that S is monotonically increasing in each of these variables. Since S is the Schumacher compression limit of E , this monotonicity property suggests a geometrical interpretation of the quantum redundancy involved in the compression process. It provides clarification of previous work in which it was shown that S may be increased while increasing the overlap of each pair of states in the ensemble. As a by-product, our mathematical techniques also provide an interpretation of the subentropy of E .

  9. Entropy and information in flagellar axoneme cybernetics: a radial spokes integrative function.

    PubMed

    Cibert, Christian

    2003-04-01

    Radial spokes and the consequences of their relationships with the central apparatus seem to play a very important role in the regulation of axonemal activity. We modeled their behavior and observed that it appears to differ in the cilium and the flagellum with respect to the development of bending as a function of time. Specifically, our calculation raises the question of the real function of the radial spokes in the regulation of the axoneme, because a given curvature of the flagellar axoneme may correspond to two opposite of their tilts. The stable nil/low amplitude shear points that we had characterized along the flagellum allowed us to describe their axoneme as a series of modules [Cibert, 2002: Cell Motil. Cytoskeleton 51:89-111]. We observed that a nil/low shearing point moves along each module during beating when a new bend is created at the base of the flagellum [Cibert, 2001: Cell Motil. Cytoskeleton 49:161-175]. We propose that the structural gradients of isoforms of tubulin could be basic verniers that act as structural references for the axonemal machinery during the beating. This allowed us to interpret the axonemal organization as a segmented structure, that could be analyzed according to the complexion(1) theory and Shannon's information theory, which associate entropy and probability in the creation of information. The important consequence of this interpretation is that regulation of the axonemal machinery appears to be due to the upstream and downstream cross-talk between the axonemal segments that do not involve any dedicated integrative structure but depend on the energy level of the entire length of each module.

  10. Some Novel Thought Experiments Involving Foundations of Quantum Mechanics and Quantum Information

    NASA Astrophysics Data System (ADS)

    Akhavan, Omid

    2004-02-01

    In this thesis, we have proposed some novel thought experiments involving foundations of quantum mechanics and quantum information theory, using quantum entanglement property. Concerning foundations of quantum mechanics, we have suggested some typical systems including two correlated particles which can distinguish between the two famous theories of quantum mechanics, i.e. the standard and Bohmian quantum mechanics, at the individual level of pair of particles. Meantime, the two theories present the same predictions at the ensemble level of particles. Regarding quantum information theory, two theoretical quantum communication schemes including quantum dense coding and quantum teleportation schemes have been proposed by using entangled spatial states of two EPR particles shared between two parties. It is shown that the rate of classical information gain in our dense coding scheme is greater than some previously proposed multi-qubit protocols by a logarithmic factor dependent on the dimension of Hilbert space. The proposed teleportation scheme can provide a complete wave function teleportation of an object having other degrees of freedom in our three-dimensional space, for the first time. All required unitary operators which are necessary in our state preparation and Bell state measurement processes are designed using symmetric normalized Hadamard matrix, some basic gates and one typical conditional gate, which are introduced here for the first time.

  11. Comparing quantum cloning: A Fisher-information perspective

    NASA Astrophysics Data System (ADS)

    Song, Hongting; Luo, Shunlong; Li, Nan; Chang, Lina

    2013-10-01

    Perfect cloning of an unknown quantum state is impossible. Approximate cloning, which is optimal in various senses, has been found in many cases. Paradigmatic examples are Wootters-Zurek cloning and universal cloning. These cloning machines aim at optimal cloning of the full quantum states. However, in practice, what is important and relevant may only involve partial information in quantum states, rather than quantum states themselves. For example, signals are often encoded as parameters in quantum states, whose information content is well synthesized by quantum Fisher information. This raises the basic issue of evaluating the information transferring capability (e.g., distributing quantum Fisher information) of quantum cloning. We assess and compare Wootters-Zurek cloning and universal cloning from this perspective and show that, on average, Wootters-Zurek cloning performs better than universal cloning for the phase (as well as amplitude) parameter, although they are incomparable individually, and universal cloning has many advantages over Wootters-Zurek cloning in other contexts. Physical insights and related issues are further discussed.

  12. Entropy and chemical change. 1: Characterization of product (and reactant) energy distributions in reactive molecular collisions: Information and enthropy deficiency

    NASA Technical Reports Server (NTRS)

    Bernstein, R. B.; Levine, R. D.

    1972-01-01

    Optimal means of characterizing the distribution of product energy states resulting from reactive collisions of molecules with restricted distributions of initial states are considered, along with those for characterizing the particular reactant state distribution which yields a given set of product states at a specified total energy. It is suggested to represent the energy-dependence of global-type results in the form of square-faced bar plots, and of data for specific-type experiments as triangular-faced prismatic plots. The essential parameters defining the internal state distribution are isolated, and the information content of such a distribution is put on a quantitative basis. The relationship between the information content, the surprisal, and the entropy of the continuous distribution is established. The concept of an entropy deficiency, which characterizes the specificity of product state formation, is suggested as a useful measure of the deviance from statistical behavior. The degradation of information by experimental averaging is considered, leading to bounds on the entropy deficiency.

  13. Quantum channel for the transmission of information

    DOEpatents

    Dress, William B.; Kisner, Roger A.; Richards, Roger K.

    2004-01-13

    Systems and methods are described for a quantum channel for the transmission of information. A method includes: down converting a beam of coherent energy to provide a beam of multi-color entangled photons; converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; changing a phase of at least a portion of the converged multi-color entangled photon beam to generate a first interferometric multi-color entangled photon beam; combining the first interferometric multi-color entangled photon beam with a second interferometric multi-color entangled photon beam within a single beam splitter; wherein combining includes erasing energy and momentum characteristics from both the first interferometric multi-color entangled photon beam and the second interferometric multi-color entangled photon beam; splitting the first interferometric multi-color entangled photon beam and the second interferometric multi-color entangled photon beam within the single beam splitter, wherein splitting yields a first output beam of multi-color entangled photons and a second output beam of multi-color entangled photons; and modulating the first output beam of multi-color entangled photons.

  14. Entropy information of heart rate variability and its power spectrum during day and night

    NASA Astrophysics Data System (ADS)

    Jin, Li; Jun, Wang

    2013-07-01

    Physiologic systems generate complex fluctuations in their output signals that reflect the underlying dynamics. We employed the base-scale entropy method and the power spectral analysis to study the 24 hours heart rate variability (HRV) signals. The results show that such profound circadian-, age- and pathologic-dependent changes are accompanied by changes in base-scale entropy and power spectral distribution. Moreover, the base-scale entropy changes reflect the corresponding changes in the autonomic nerve outflow. With the suppression of the vagal tone and dominance of the sympathetic tone in congestive heart failure (CHF) subjects, there is more variability in the date fluctuation mode. So the higher base-scale entropy belongs to CHF subjects. With the decrease of the sympathetic tone and the respiratory frequency (RSA) becoming more pronounced with slower breathing during sleeping, the base-scale entropy drops in CHF subjects. The HRV series of the two healthy groups have the same diurnal/nocturnal trend as the CHF series. The fluctuation dynamics trend of data in the three groups can be described as “HF effect”.

  15. Semi-quantum information splitting using GHZ-type states

    NASA Astrophysics Data System (ADS)

    Nie, Yi-you; Li, Yuan-hua; Wang, Zi-sheng

    2013-01-01

    By using a generalized Greenberger-Horne-Zeilinger (GHZ) state in which is locally unitarily connected with standard GHZ state as a communication channel, semi-quantum key distribution is extended to study semi-quantum information splitting protocols for secret sharing of quantum information. In our scheme, quantum Alice splits arbitrary two, three and N-qubit states with two classical parties, Bob and Charlie, in a way that both parties are sufficient to reconstruct Alice's original states only under the condition of which she/he obtains the help from another one, but one of them cannot. The presented protocols are helpful for both secure against certain eavesdropping attacks and economical in processing of quantum information.

  16. La Saturated Absorption Spectroscopy for Applications in Quantum Information

    NASA Astrophysics Data System (ADS)

    Becker, Patrick; Donoghue, Liz; Dungan, Kristina; Liu, Jackie; Olmschenk, Steven

    2015-05-01

    Quantum information may revolutionize computation and communication by utilizing quantum systems based on matter quantum bits and entangled light. Ions are excellent candidates for quantum bits as they can be well-isolated from unwanted external influences by trapping and laser cooling. Doubly-ionized lanthanum in particular shows promise for use in quantum information as it has infrared transitions in the telecom band, with low attenuation in standard optical fiber, potentially allowing for long distance information transfer. However, the hyperfine splittings of the lowest energy levels, required for laser cooling, have not been measured. We present progress and recent results towards measuring the hyperfine splittings of these levels in lanthanum by saturated absorption spectroscopy with a hollow cathode lamp. This research is supported by the Army Research Office, Research Corporation for Science Advancement, and Denison University.

  17. Quantum optical implementation of quantum information processing and classical simulation of many-body physics from quantum information perspective

    NASA Astrophysics Data System (ADS)

    Wang, Bin

    This thesis is composed of two parts. In the first part we summarize our study on implementation of quantum information processing (QIP) in optical cavity QED systems, while in the second part we present our numerical investigations on strongly interacting Fermi systems using a powerful numerical algorithm developed from the perspective of quantum information theory. We explore various possible applications of cavity QED in the strong coupling regime to quantum information processing tasks theoretically, including efficient preparation of Schrodinger-cat states for traveling photon pulses, robust implementation of conditional quantum gates on neutral atoms, as well as implementation of a hybrid controlled SWAP gate. We analyze the feasibility and performance of our schemes by solving corresponding physical models either numerically or analytically. We implement a novel numerical algorithm called Time Evolving Block Decimation (TEBD), which was proposed by Vidal from the perspective of quantum information science. With this algorithm, we numerically study the ground state properties of strongly interacting fermions in an anisotropic optical lattice across a wide Feshbach resonance. The interactions in this system can be described by a general Hubbard model with particle assisted tunneling. For systems with equal spin population, we find that the Luther-Emery phase, which has been known to exist only for attractive on-site interactions in the conventional Hubbard model, could also be found even in the case with repulsive on-site interactions in the general Hubbard model. Using the TEBD algorithm, we also study the effect of particle assisted tunneling in spin-polarized systems. Fermi systems with unequal spin population and attractive interaction could allow the existence of exotic superfluidity, such as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. In the general Hubbard model, such exotic FFLO pairing of fermions could be suppressed by high particle assisted

  18. The gravity dual of Rényi entropy.

    PubMed

    Dong, Xi

    2016-01-01

    A remarkable yet mysterious property of black holes is that their entropy is proportional to the horizon area. This area law inspired the holographic principle, which was later realized concretely in gauge-gravity duality. In this context, entanglement entropy is given by the area of a minimal surface in a dual spacetime. However, discussions of area laws have been constrained to entanglement entropy, whereas a full understanding of a quantum state requires Rényi entropies. Here we show that all Rényi entropies satisfy a similar area law in holographic theories and are given by the areas of dual cosmic branes. This geometric prescription is a one-parameter generalization of the minimal surface prescription for entanglement entropy. Applying this we provide the first holographic calculation of mutual Rényi information between two disks of arbitrary dimension. Our results provide a framework for efficiently studying Rényi entropies and understanding entanglement structures in strongly coupled systems and quantum gravity. PMID:27515122

  19. The gravity dual of Rényi entropy

    PubMed Central

    Dong, Xi

    2016-01-01

    A remarkable yet mysterious property of black holes is that their entropy is proportional to the horizon area. This area law inspired the holographic principle, which was later realized concretely in gauge-gravity duality. In this context, entanglement entropy is given by the area of a minimal surface in a dual spacetime. However, discussions of area laws have been constrained to entanglement entropy, whereas a full understanding of a quantum state requires Rényi entropies. Here we show that all Rényi entropies satisfy a similar area law in holographic theories and are given by the areas of dual cosmic branes. This geometric prescription is a one-parameter generalization of the minimal surface prescription for entanglement entropy. Applying this we provide the first holographic calculation of mutual Rényi information between two disks of arbitrary dimension. Our results provide a framework for efficiently studying Rényi entropies and understanding entanglement structures in strongly coupled systems and quantum gravity. PMID:27515122

  20. The gravity dual of Rényi entropy

    NASA Astrophysics Data System (ADS)

    Dong, Xi

    2016-08-01

    A remarkable yet mysterious property of black holes is that their entropy is proportional to the horizon area. This area law inspired the holographic principle, which was later realized concretely in gauge-gravity duality. In this context, entanglement entropy is given by the area of a minimal surface in a dual spacetime. However, discussions of area laws have been constrained to entanglement entropy, whereas a full understanding of a quantum state requires Rényi entropies. Here we show that all Rényi entropies satisfy a similar area law in holographic theories and are given by the areas of dual cosmic branes. This geometric prescription is a one-parameter generalization of the minimal surface prescription for entanglement entropy. Applying this we provide the first holographic calculation of mutual Rényi information between two disks of arbitrary dimension. Our results provide a framework for efficiently studying Rényi entropies and understanding entanglement structures in strongly coupled systems and quantum gravity.

  1. The gravity dual of Rényi entropy.

    PubMed

    Dong, Xi

    2016-08-12

    A remarkable yet mysterious property of black holes is that their entropy is proportional to the horizon area. This area law inspired the holographic principle, which was later realized concretely in gauge-gravity duality. In this context, entanglement entropy is given by the area of a minimal surface in a dual spacetime. However, discussions of area laws have been constrained to entanglement entropy, whereas a full understanding of a quantum state requires Rényi entropies. Here we show that all Rényi entropies satisfy a similar area law in holographic theories and are given by the areas of dual cosmic branes. This geometric prescription is a one-parameter generalization of the minimal surface prescription for entanglement entropy. Applying this we provide the first holographic calculation of mutual Rényi information between two disks of arbitrary dimension. Our results provide a framework for efficiently studying Rényi entropies and understanding entanglement structures in strongly coupled systems and quantum gravity.

  2. BOOK REVIEW: Time, Quantum and Information

    NASA Astrophysics Data System (ADS)

    Turner, Leaf

    2004-04-01

    Time, Quantum and Information, a paean to Professor Carl Friedrich von Weizsäcker, commemorates his 90th birthday. The range of Professor Weizsäcker’s endeavours is an exhilarating example of what can be accomplished by one freely-soaring human spirit, who is at the same time a physicist, a philosopher, and a humanitarian. The editors, Lutz Castell and Otfried Ischebeck, have assembled an admirable collection of essays and articles written by Weizsäcker’s past students, collaborators, colleagues and acquaintances. Time, Quantum and Information offers the reader a panoply of unique insights into twentieth century science and history. Entangled with the stories about Weizsäcker’s influence on the lives of some of the contributors are discussions of the activities of German scientists during and following World War II, emphasizing their reluctance to work on atomic weapons following the war. By outlining Weizsäcker’s role in the early development of numerous tributaries of physical science, the book gives us a new glimpse into the origins of some of its disparate domains, such as nuclear physics, the physics of stellar nucleosynthesis, cosmic ray physics, fluid turbulence, and the formation of the solar system. We physicists have all studied Weizsäcker’s semi-empirical mass formula describing the binding energy of nuclei. We are aware too that both he and Hans Bethe independently discovered the nuclear cycles that provide stars with their enduring energy output. We have studied the Weizsäcker--Williams technique of calculating the bremsstrahlung of relativistic electrons. But how many of us know of Weizsäcker’s work in fluid turbulence that he, like Werner Heisenberg under whom he had earned his doctorate, pursued while holed up in Farm Hall? And how many of us are aware of his introduction of turbulent viscosity to account for the origin of planetary orbits, involving the migration of mass inwards and angular momentum outwards? Moreover, before

  3. BOOK REVIEW: Time, Quantum and Information

    NASA Astrophysics Data System (ADS)

    Turner, Leaf

    2004-04-01

    Time, Quantum and Information, a paean to Professor Carl Friedrich von Weizsäcker, commemorates his 90th birthday. The range of Professor Weizsäcker’s endeavours is an exhilarating example of what can be accomplished by one freely-soaring human spirit, who is at the same time a physicist, a philosopher, and a humanitarian. The editors, Lutz Castell and Otfried Ischebeck, have assembled an admirable collection of essays and articles written by Weizsäcker’s past students, collaborators, colleagues and acquaintances. Time, Quantum and Information offers the reader a panoply of unique insights into twentieth century science and history. Entangled with the stories about Weizsäcker’s influence on the lives of some of the contributors are discussions of the activities of German scientists during and following World War II, emphasizing their reluctance to work on atomic weapons following the war. By outlining Weizsäcker’s role in the early development of numerous tributaries of physical science, the book gives us a new glimpse into the origins of some of its disparate domains, such as nuclear physics, the physics of stellar nucleosynthesis, cosmic ray physics, fluid turbulence, and the formation of the solar system. We physicists have all studied Weizsäcker’s semi-empirical mass formula describing the binding energy of nuclei. We are aware too that both he and Hans Bethe independently discovered the nuclear cycles that provide stars with their enduring energy output. We have studied the Weizsäcker--Williams technique of calculating the bremsstrahlung of relativistic electrons. But how many of us know of Weizsäcker’s work in fluid turbulence that he, like Werner Heisenberg under whom he had earned his doctorate, pursued while holed up in Farm Hall? And how many of us are aware of his introduction of turbulent viscosity to account for the origin of planetary orbits, involving the migration of mass inwards and angular momentum outwards? Moreover, before

  4. The biophysical basis of Benveniste experiments: Entropy, structure, and information in water

    NASA Astrophysics Data System (ADS)

    Widom, Allan; Srivastava, Yogendra; Valenzi, Vincenzo

    Benveniste had observed that highly dilute (and even in the absence of physical molecules) biological agents still triggered relevant biological systems. Some of these experiments were reproduced in three other laboratories who cosigned the article, (Davenas et al., Nature 1988, 333, 816). Further works, [(Medical Hypotheses 2000, 54, 33), (Rivista di Biologia/Biology Forum 97, 2004, 169)], showed that molecular activity in more than 50 biochemical systems and even in bacteria could be induced by electromagnetic signals transferred through water solutes. The sources of the electromagnetic signals were recordings of specific biological activities. These results suggest that electromagnetic transmission of biochemical information can be stored in the electric dipole moments of water in close analogy to the manner in which magnetic moments store information on a computer disk. The electromagnetic transmission would enable in vivo transmissions of the specific molecular information between two functional biomolecules. In the present work, the physical nature of such biological information storage and retrieval in ordered quantum electromagnetic domains of water will be discussed.

  5. Determination of the axial stiffness of an optical trap with information entropy signals

    NASA Astrophysics Data System (ADS)

    Zhong, Mincheng; Zhou, Jinhua; Wu, Jianguang; Li, Yinmei

    2009-11-01

    Optical tweezers has been used to manipulate micro-sized particles for many years, and has been widely used in various applications. The axial trapping stiffness is one of the most important parameters to evaluate the trapping ability of an optical tweezers. In this paper, we calibrated the axial optical stiffnesses for micro-sized polystyrene spheres. When an external force was applied to particle held by an optical trap, the particle was displaced from the trap center by an amount proportional to the applied force. We displaced the particle from the trap center by applying triangular waves of varying velocity, and the varying velocity was obtained by altering the frequency of the triangular waves. In this case the particle has two balance position distributed at two-side of the trap center. The calibration of the axial position was critical to the measurement of axial optical stiffness. In this paper, the axial displacement between the balance position and the trap center was calibrated with image information entropy signals. According to Stokes Law, when the axial displacement of the particle relative to the external force was known, the axial optical stiffness can be measured, and this method was known as viscous drag method. The stiffnesses for a 2μm-diameter at different trapped depth were measured. Typical values for axial optical stiffness of our optical tweezers were between 4.0 and 7.5 pN/μm when the laser power was 35mW. Dependence of axial optical trapping stiffness on the diameter of the particles was measured with viscous drag method. At last, the origin of the measurement error was discussed.

  6. Quantum Bio-Informatics II From Quantum Information to Bio-Informatics

    NASA Astrophysics Data System (ADS)

    Accardi, L.; Freudenberg, Wolfgang; Ohya, Masanori

    2009-02-01

    The problem of quantum-like representation in economy cognitive science, and genetics / L. Accardi, A. Khrennikov and M. Ohya -- Chaotic behavior observed in linea dynamics / M. Asano, T. Yamamoto and Y. Togawa -- Complete m-level quantum teleportation based on Kossakowski-Ohya scheme / M. Asano, M. Ohya and Y. Tanaka -- Towards quantum cybernetics: optimal feedback control in quantum bio informatics / V. P. Belavkin -- Quantum entanglement and circulant states / D. Chruściński -- The compound Fock space and its application in brain models / K. -H. Fichtner and W. Freudenberg -- Characterisation of beam splitters / L. Fichtner and M. Gäbler -- Application of entropic chaos degree to a combined quantum baker's map / K. Inoue, M. Ohya and I. V. Volovich -- On quantum algorithm for multiple alignment of amino acid sequences / S. Iriyama and M. Ohya --Quantum-like models for decision making in psychology and cognitive science / A. Khrennikov -- On completely positive non-Markovian evolution of a d-level system / A. Kossakowski and R. Rebolledo -- Measures of entanglement - a Hilbert space approach / W. A. Majewski -- Some characterizations of PPT states and their relation / T. Matsuoka -- On the dynamics of entanglement and characterization ofentangling properties of quantum evolutions / M. Michalski -- Perspective from micro-macro duality - towards non-perturbative renormalization scheme / I. Ojima -- A simple symmetric algorithm using a likeness with Introns behavior in RNA sequences / M. Regoli -- Some aspects of quadratic generalized white noise functionals / Si Si and T. Hida -- Analysis of several social mobility data using measure of departure from symmetry / K. Tahata ... [et al.] -- Time in physics and life science / I. V. Volovich -- Note on entropies in quantum processes / N. Watanabe -- Basics of molecular simulation and its application to biomolecules / T. Ando and I. Yamato -- Theory of proton-induced superionic conduction in hydrogen-bonded systems

  7. Information complementarity in multipartite quantum states and security in cryptography

    NASA Astrophysics Data System (ADS)

    Bera, Anindita; Kumar, Asutosh; Rakshit, Debraj; Prabhu, R.; SenDe, Aditi; Sen, Ujjwal

    2016-03-01

    We derive complementarity relations for arbitrary quantum states of multiparty systems of any number of parties and dimensions between the purity of a part of the system and several correlation quantities, including entanglement and other quantum correlations as well as classical and total correlations, of that part with the remainder of the system. We subsequently use such a complementarity relation between purity and quantum mutual information in the tripartite scenario to provide a bound on the secret key rate for individual attacks on a quantum key distribution protocol.

  8. Generalised squeezing and information theory approach to quantum entanglement

    NASA Technical Reports Server (NTRS)

    Vourdas, A.

    1993-01-01

    It is shown that the usual one- and two-mode squeezing are based on reducible representations of the SU(1,1) group. Generalized squeezing is introduced with the use of different SU(1,1) rotations on each irreducible sector. Two-mode squeezing entangles the modes and information theory methods are used to study this entanglement. The entanglement of three modes is also studied with the use of the strong subadditivity property of the entropy.

  9. Manipulation of Entangled States for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Bose, S.; Huelga, S. F.; Jonathan, D.; Knight, P. L.; Murao, M.; Plenio, M. B.; Vedral, V.

    Entanglement manipulation, and especially Entanglement Swapping is at the heart of current work on quantum information processing, purification and quantum teleportation. We will discuss how it may be generalized to multiparticle systems and how this enables multi-user quantum cryptographic protocols to be developed. Our scheme allows us to establish multiparticle entanglement between particles which belong to distant users in a communication network through a prior distribution of Bell state singlets followed by local measurements. We compare our method for generating entanglement with existing schemes using simple quantum networks, and highlight the advantages and applications in cryptographic conferencing and in reading messages from more than one source through a single quantum measurement. We also discuss how entanglement leads to the idea of `telecloning', in which a teleportation-like protocol can be found which reproduces the output of an optimal quantum cloning machine.

  10. Understanding Entanglement as a Resource for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Cohen, Scott M.

    2008-05-01

    Ever since Erwin Schrodinger shocked the physics world by killing (and not killing) his cat, entanglement has played a critical role in attempts to understand quantum mechanics. More recently, entanglement has been shown to be a valuable resource, of central importance for quantum computation and the processing of quantum information. In this talk, I will describe a new diagrammatic approach to understanding why entanglement is so valuable, the key idea being that entanglement between two systems ``creates'' multiple images of the state of a third. By way of example, I will show how to ``visualize'' teleportation of unknown quantum states, and how to use entanglement to implement an interaction between spatially separated (and therefore non-interacting!) systems. These ideas have also proven useful in quantum state discrimination, where the state of a quantum system is unknown and is to be determined.

  11. Shannon's, mutual, conditional and joint entropy information indices: generalization of global indices defined from local vertex invariants.

    PubMed

    Barigye, Stephen J; Marrero-Ponce, Yovani; Santiago, Oscar Martinez; López, Yoan Martinez; Pérez-Giménez, Facundo; Torrens, Francisco

    2013-06-01

    A new mathematical approach is proposed in the definition of molecular descriptors (MDs) based on the application of information theory concepts. This approach stems from a new matrix representation of a molecular graph (G) which is derived from the generalization of an incidence matrix whose row entries correspond to connected subgraphs of a given G, and the calculation of the Shannon's entropy, the negentropy and the standardized information content, plus for the first time, the mutual, conditional and joint entropy-based MDs associated with G. We also define strategies that generalize the definition of global or local invariants from atomic contributions (local vertex invariants, LOVIs), introducing related metrics (norms), means and statistical invariants. These invariants are applied to a vector whose components express the atomic information content calculated using the Shannon's, mutual, conditional and joint entropybased atomic information indices. The novel information indices (IFIs) are implemented in the program TOMOCOMDCARDD. A principal component analysis reveals that the novel IFIs are capable of capturing structural information not codified by IFIs implemented in the software DRAGON. A comparative study of the different parameters (e.g. subgraph orders and/or types, invariants and class of MDs) used in the definition of these IFIs reveals several interesting results. The mutual entropy-based indices give the best correlation results in modeling of a physicochemical property, namely the partition coefficient of the 34 derivatives of 2-furylethylenes, among the classes of indices investigated in this study. In a comparison with classical MDs it is demonstrated that the new IFIs give good results for various QSPR models.

  12. Quantum information processing with electronic and nuclear spins in semiconductors

    NASA Astrophysics Data System (ADS)

    Klimov, Paul Victor

    Traditional electronic and communication devices operate by processing binary information encoded as bits. Such digital devices have led to the most advanced technologies that we encounter in our everyday lives and they influence virtually every aspect of our society. Nonetheless, there exists a much richer way to encode and process information. By encoding information in quantum mechanical states as qubits, phenomena such as coherence and entanglement can be harnessed to execute tasks that are intractable to digital devices. Under this paradigm, it should be possible to realize quantum computers, quantum communication networks and quantum sensors that outperform their classical counterparts. The electronic spin states of color-center defects in the semiconductor silicon carbide have recently emerged as promising qubit candidates. They have long-lived quantum coherence up to room temperature, they can be controlled with mature magnetic resonance techniques, and they have a built-in optical interface operating near the telecommunication bands. In this thesis I will present two of our contributions to this field. The first is the electric-field control of electron spin qubits. This development lays foundation for quantum electronics that operate via electrical gating, much like traditional electronics. The second is the universal control and entanglement of electron and nuclear spin qubits in an ensemble under ambient conditions. This development lays foundation for quantum devices that have a built-in redundancy and can operate in real-world conditions. Both developments represent important steps towards practical quantum devices in an electronic grade material.

  13. Quasi-probability representations of quantum theory with applications to quantum information science

    NASA Astrophysics Data System (ADS)

    Ferrie, Christopher

    2011-11-01

    This paper comprises a review of both the quasi-probability representations of infinite-dimensional quantum theory (including the Wigner function) and the more recently defined quasi-probability representations of finite-dimensional quantum theory. We focus on both the characteristics and applications of these representations with an emphasis toward quantum information theory. We discuss the recently proposed unification of the set of possible quasi-probability representations via frame theory and then discuss the practical relevance of negativity in such representations as a criteria for quantumness.

  14. Scalable quantum information processing with photons and atoms

    NASA Astrophysics Data System (ADS)

    Pan, Jian-Wei

    Over the past three decades, the promises of super-fast quantum computing and secure quantum cryptography have spurred a world-wide interest in quantum information, generating fascinating quantum technologies for coherent manipulation of individual quantum systems. However, the distance of fiber-based quantum communications is limited due to intrinsic fiber loss and decreasing of entanglement quality. Moreover, probabilistic single-photon source and entanglement source demand exponentially increased overheads for scalable quantum information processing. To overcome these problems, we are taking two paths in parallel: quantum repeaters and through satellite. We used the decoy-state QKD protocol to close the loophole of imperfect photon source, and used the measurement-device-independent QKD protocol to close the loophole of imperfect photon detectors--two main loopholes in quantum cryptograph. Based on these techniques, we are now building world's biggest quantum secure communication backbone, from Beijing to Shanghai, with a distance exceeding 2000 km. Meanwhile, we are developing practically useful quantum repeaters that combine entanglement swapping, entanglement purification, and quantum memory for the ultra-long distance quantum communication. The second line is satellite-based global quantum communication, taking advantage of the negligible photon loss and decoherence in the atmosphere. We realized teleportation and entanglement distribution over 100 km, and later on a rapidly moving platform. We are also making efforts toward the generation of multiphoton entanglement and its use in teleportation of multiple properties of a single quantum particle, topological error correction, quantum algorithms for solving systems of linear equations and machine learning. Finally, I will talk about our recent experiments on quantum simulations on ultracold atoms. On the one hand, by applying an optical Raman lattice technique, we realized a two-dimensional spin-obit (SO

  15. The Quantum Information Revolution: 101 Uses for Schodinger's Cat

    SciTech Connect

    Kwait, Paul G.

    2007-09-05

    A century after Einstein's revolutionary suggestion that light is composed of particles, the quantum information revolution seeks to use the almost magical properties of non-classical physics to enable new feats in information processing. The critical quantum resource is entanglement, which can now be produced at high rates with exquisite precision, enabling such feats as quantum cryptography and teleportation. I will describe some of these "micracles," and our investigations into how the usual benefits can be further extended, by using more complex quantum states (e.g., "hyper-entanglement"), and by incorporating other elements of modern physics (e.g., special relativity). Time and appetites permitting, a brief lesson in quantum cooking may be forthcoming.

  16. Double electromagnetically induced transparency and its application in quantum information

    NASA Astrophysics Data System (ADS)

    Wang, Zeng-Bin; Marzlin, Karl-Peter; Sanders, Barry C.

    2006-08-01

    Strong optical cross-phase modulation (XPM) for weak fields is tremendously important for optical quantum information (QI) processing and for all-optical switches in classical communication. A sufficiently large XPM would allow the design of deterministic controlled quantum gates for photonic qubits and thus enable universal optical quantum computation. Recently, several proposals have been brought forward to create large XPM using double electromagnetically induced transparency (DEIT) in which two weak signal light pulses travel at equally slow group velocity, but creating DEIT still poses an experimental challenge. We give a brief overview about DEIT and discuss its applications and limitations. A scheme that combines the best features of previous proposals and optimizes the large XPM parameter for DEIT schemes is outlined. Finally we devise a scheme to perform universal quantum information processing, which respects the bound on the achievable nonlinearity and addresses the requirement of quantum error correction.

  17. Localization in the quantum sawtooth map emulated on a quantum-information processor

    SciTech Connect

    Henry, Michael K.; Cory, David G.; Emerson, Joseph; Martinez, Rudy

    2006-12-15

    Quantum computers will be unique tools for understanding complex quantum systems. We report an experimental implementation of a sensitive, quantum coherence-dependent localization phenomenon on a quantum information processor (QIP). The localization effect was studied by emulating the dynamics of the quantum sawtooth map in the perturbative regime on a three-qubit QIP. Our results show that the width of the probability distribution in momentum space remained essentially unchanged with successive iterations of the sawtooth map, a result that is consistent with localization. The height of the peak relative to the baseline of the probability distribution did change, a result that is consistent with our QIP being an ensemble of quantum systems with a distribution of errors over the ensemble. We further show that the previously measured distributions of control errors correctly account for the observed changes in the probability distribution.

  18. ALPHA, Mass Generation and Quantum Information

    NASA Astrophysics Data System (ADS)

    Goradia, Shantilal

    2008-05-01

    The generation of Planck energy 10E19 Gev/Planck time during the observable age of the universe (10E60 Planck times) would generate 10E79 Gev. 10E79 Gev approximates the energy of the baryon number, implying an increase of the baryon number by 10E19/Planck time. What is the source of energy for this mass generation? The ALPHA implicated as negative entropy in [1] must create vacuum energy. Vacuum energy is negative energy. Nature must balance negative energy by generating positive energy (mass), implying ALPHA balances the increasing entropy of the visible universe and generates baryonic mass. Additionally, the successful cloning of the sheep Dolly, and observed molecular blinking dots in biochemistry support the binary BITS of ON and OFF states in [1]. Vindicating Hermite's 1873 mathematical linkage of the base of natural logarithm to transcendentality will implicate natural log based ALPHA in [1] as connected to consciousness. [1] Goradia S: www.arXiv.org/pdf/physics/0210040v3.

  19. Realizing controllable depolarization in photonic quantum-information channels

    SciTech Connect

    Shaham, A.; Eisenberg, H. S.

    2011-02-15

    Controlling the depolarization of light is a long-standing open problem. In recent years, many demonstrations have used the polarization of single photons to encode quantum information. The depolarization of these photons is equivalent to the decoherence of the quantum information they encode. We present schemes for building various depolarizing channels with controlled properties using birefringent crystals. Three such schemes are demonstrated, and their effects on single photons are shown by quantum process tomography to be in good agreement with a theoretical model.

  20. Entropy in Rhetoric.

    ERIC Educational Resources Information Center

    Marder, Daniel

    The Second Law of Thermodynamics demonstrates the idea of entropy, the tendency of ordered energy to free itself and thus break apart the system that contains it and dissipate that system into chaos. When applied to communications theory, entropy increases not only with noise but with the density of information--particles of possible meaning…

  1. Quantum information processing in phase space: A modular variables approach

    NASA Astrophysics Data System (ADS)

    Ketterer, A.; Keller, A.; Walborn, S. P.; Coudreau, T.; Milman, P.

    2016-08-01

    Binary quantum information can be fault-tolerantly encoded in states defined in infinite-dimensional Hilbert spaces. Such states define a computational basis, and permit a perfect equivalence between continuous and discrete universal operations. The drawback of this encoding is that the corresponding logical states are unphysical, meaning infinitely localized in phase space. We use the modular variables formalism to show that, in a number of protocols relevant for quantum information and for the realization of fundamental tests of quantum mechanics, it is possible to loosen the requirements on the logical subspace without jeopardizing their usefulness or their successful implementation. Such protocols involve measurements of appropriately chosen modular variables that permit the readout of the encoded discrete quantum information from the corresponding logical states. Finally, we demonstrate the experimental feasibility of our approach by applying it to the transverse degrees of freedom of single photons.

  2. TRENTOOL: A Matlab open source toolbox to analyse information flow in time series data with transfer entropy

    PubMed Central

    2011-01-01

    Background Transfer entropy (TE) is a measure for the detection of directed interactions. Transfer entropy is an information theoretic implementation of Wiener's principle of observational causality. It offers an approach to the detection of neuronal interactions that is free of an explicit model of the interactions. Hence, it offers the power to analyze linear and nonlinear interactions alike. This allows for example the comprehensive analysis of directed interactions in neural networks at various levels of description. Here we present the open-source MATLAB toolbox TRENTOOL that allows the user to handle the considerable complexity of this measure and to validate the obtained results using non-parametrical statistical testing. We demonstrate the use of the toolbox and the performance of the algorithm on simulated data with nonlinear (quadratic) coupling and on local field potentials (LFP) recorded from the retina and the optic tectum of the turtle (Pseudemys scripta elegans) where a neuronal one-way connection is likely present. Results In simulated data TE detected information flow in the simulated direction reliably with false positives not exceeding the rates expected under the null hypothesis. In the LFP data we found directed interactions from the retina to the tectum, despite the complicated signal transformations between these stages. No false positive interactions in the reverse directions were detected. Conclusions TRENTOOL is an implementation of transfer entropy and mutual information analysis that aims to support the user in the application of this information theoretic measure. TRENTOOL is implemented as a MATLAB toolbox and available under an open source license (GPL v3). For the use with neural data TRENTOOL seamlessly integrates with the popular FieldTrip toolbox. PMID:22098775

  3. Analysis of entanglement measures and LOCC maximized quantum Fisher information of general two qubit systems.

    PubMed

    Erol, Volkan; Ozaydin, Fatih; Altintas, Azmi Ali

    2014-06-24

    Entanglement has been studied extensively for unveiling the mysteries of non-classical correlations between quantum systems. In the bipartite case, there are well known measures for quantifying entanglement such as concurrence, relative entropy of entanglement (REE) and negativity, which cannot be increased via local operations. It was found that for sets of non-maximally entangled states of two qubits, comparing these entanglement measures may lead to different entanglement orderings of the states. On the other hand, although it is not an entanglement measure and not monotonic under local operations, due to its ability of detecting multipartite entanglement, quantum Fisher information (QFI) has recently received an intense attraction generally with entanglement in the focus. In this work, we revisit the state ordering problem of general two qubit states. Generating a thousand random quantum states and performing an optimization based on local general rotations of each qubit, we calculate the maximal QFI for each state. We analyze the maximized QFI in comparison with concurrence, REE and negativity and obtain new state orderings. We show that there are pairs of states having equal maximized QFI but different values for concurrence, REE and negativity and vice versa.

  4. Amplification of Information by Photons and the Quantum Chernoff Bound

    NASA Astrophysics Data System (ADS)

    Zwolak, Michael; Riedel, C. Jess; Zurek, Wojciech H.

    2014-03-01

    Amplification was regarded, since the early days of quantum theory, as a mysterious ingredient that endows quantum microstates with macroscopic consequences, key to the ``collapse of the wavepacket,'' and a way to avoid embarrassing problems exemplified by Schrödinger's cat. This bridge between the quantum microworld and the classical world of our experience was postulated ad hoc in the Copenhagen Interpretation. Quantum Darwinism views amplification as replication, in many copies, of information about quantum states. We show that such amplification is a natural consequence of a broad class of models of decoherence, including the photon environment we use to obtain most of our information. The resultant amplification is huge, proportional to # ξQCB . Here, #  is the environment size and ξQCB is the ``typical'' Quantum Chernoff Information, which quantifies the efficiency of the amplification. The information communicated though the environment is imprinted in the states of individual environment subsystems, e.g., in single photons, which document the transfer of information into the environment and result in the emergence of the classical world. See, http://mike.zwolak.org

  5. Frames, designs, and spherical codes in quantum information theory

    NASA Astrophysics Data System (ADS)

    Renes, Joseph M.

    Frame theory offers a lens through which to view a large portion of quantum information theory, providing an organizational principle to those topics in its purview. In this thesis, I cut a trail from foundational questions to practical applications, from the origin of the quantum probability rule to quantum cryptography, by way of a standard quantum measurement helpful in quantum tomography and representation of quantum theory. Before embarking, preparations are undertaken by outlining the relevant aspects of frame theory, particularly the characterization of generalized orthonormal bases in terms of physical quantum measurements, as well as several aesthetically appealing families of measurements, each possessing a high degree of symmetry. Much more than just elegant, though, these quantum measurements are found to be useful in many aspects of quantum information theory. I first consider the foundational question of justifying the quantum probability rule, showing that putting a probability valuation on generalized quantum measurements leads directly to the Born rule. Moreover, for qubits, the case neglected in the traditional formulation of Gleason's theorem, a symmetric three-outcome measurement called the trine is sufficient to impel the desired form. Keeping with foundational questions, I then turn to the problem of establishing a symmetric measurement capable of effortlessly rendering quantum theory in terms of classical probability theory. Numerical results provide an almost utterly convincing amount of evidence for this, justifying the subsequent study of its use in quantum tomography and detailed account of the properties of the reduction to probabilistic terms. Saving perhaps the most exciting topic for last, I make use of these aesthetic ensembles in the applied field of quantum cryptography. A large class of streamlined key distribution protocols may be cut from the cloth of these ensembles, and their symmetry affords them improved tolerance to

  6. PREFACE: Nobel Symposium 141: Qubits for Future Quantum Information Nobel Symposium 141: Qubits for Future Quantum Information

    NASA Astrophysics Data System (ADS)

    Claeson, Tord; Delsing, Per; Wendin, Göran

    2009-12-01

    Quantum mechanics is the most ground-breaking and fascinating theoretical concept developed in physics during the past century. Much of our present understanding of the microscopic world and its extension into the macroscopic world, including modern technical applications, is based upon quantum mechanics. We have experienced a remarkable development of information and communication technology during the past two decades, to a large extent depending upon successful fabrication of smaller and smaller components and circuits. However, we are finally approaching the physical limits of component miniaturization as we enter a microscopic world ruled by quantum mechanics. Present technology is mainly based upon classical physics such as mechanics and electromagnetism. We now face a similar paradigm shift as was experienced two hundred years ago, at the time of the industrial revolution. Engineered construction of systems is currently increasingly based on quantum physics instead of classical physics, and quantum information is replacing much of classical communication. Quantum computing is one of the most exciting sub-fields of this revolution. Individual quantum systems can be used to store and process information. They are called quantum bits, or qubits for short. A quantum computer could eventually be constructed by combining a number of qubits that act coherently. Important computations can be performed much more quickly than by classical computers. However, while we control and measure a qubit, it must be sufficiently isolated from its environment to avoid noise that causes decoherence at the same time. Currently, low temperature is generally needed to obtain sufficiently long decoherence times. Single qubits of many different kinds can be built and manipulated; some research groups have managed to successfully couple qubits and perform rudimentary logic operations. However, the fundamental problems, such as decoherence, entanglement, quantum measurements and error

  7. Strong converse theorems using Rényi entropies

    NASA Astrophysics Data System (ADS)

    Leditzky, Felix; Wilde, Mark M.; Datta, Nilanjana

    2016-08-01

    We use a Rényi entropy method to prove strong converse theorems for certain information-theoretic tasks which involve local operations and quantum (or classical) communication between two parties. These include state redistribution, coherent state merging, quantum state splitting, measurement compression with quantum side information, randomness extraction against quantum side information, and data compression with quantum side information. The method we employ in proving these results extends ideas developed by Sharma [preprint arXiv:1404.5940 [quant-ph] (2014)], which he used to give a new proof of the strong converse theorem for state merging. For state redistribution, we prove the strong converse property for the boundary of the entire achievable rate region in the (e, q)-plane, where e and q denote the entanglement cost and quantum communication cost, respectively. In the case of measurement compression with quantum side information, we prove a strong converse theorem for the classical communication cost, which is a new result extending the previously known weak converse. For the remaining tasks, we provide new proofs for strong converse theorems previously established using smooth entropies. For each task, we obtain the strong converse theorem from explicit bounds on the figure of merit of the task in terms of a Rényi generalization of the optimal rate. Hence, we identify candidates for the strong converse exponents for each task discussed in this paper. To prove our results, we establish various new entropic inequalities, which might be of independent interest. These involve conditional entropies and mutual information derived from the sandwiched Rényi divergence. In particular, we obtain novel bounds relating these quantities, as well as the Rényi conditional mutual information, to the fidelity of two quantum states.

  8. Coherent control of diamond defects for quantum information science and quantum sensing

    NASA Astrophysics Data System (ADS)

    Maurer, Peter

    Quantum mechanics, arguably one of the greatest achievements of modern physics, has not only fundamentally changed our understanding of nature but is also taking an ever increasing role in engineering. Today, the control of quantum systems has already had a far-reaching impact on time and frequency metrology. By gaining further control over a large variety of different quantum systems, many potential applications are emerging. Those applications range from the development of quantum sensors and new quantum metrological approaches to the realization of quantum information processors and quantum networks. Unfortunately most quantum systems are very fragile objects that require tremendous experimental effort to avoid dephasing. Being able to control the interaction between a quantum system with its local environment embodies therefore an important aspect for application and hence is at the focus of this thesis. Nitrogen Vacancy (NV) color centers in diamond have recently attracted attention as a room temperature solid state spin system that expresses long coherence times. The electronic spin associated with NV centers can be efficiently manipulated, initialized and readout using microwave and optical techniques. Inspired by these extraordinary properties, much effort has been dedicated to use NV centers as a building block for scalable room temperature quantum information processing and quantum communication as well as a quantum sensing. In the first part of this thesis we demonstrate that by decoupling the spin from the local environment the coherence time of a NV quantum register can be extended by three order of magnitudes. Employing a novel dissipative mechanism in combination with dynamical decoupling, memory times exceeding one second are observed. The second part shows that, based on quantum control, NV centers in nano-diamonds provide a nanoscale temperature sensor with unprecedented accuracy enabling local temperature measurements in living biological cells

  9. Information-preserving structures: A general framework for quantum zero-error information

    SciTech Connect

    Blume-Kohout, Robin; Ng, Hui Khoon; Poulin, David; Viola, Lorenza

    2010-12-15

    Quantum systems carry information. Quantum theory supports at least two distinct kinds of information (classical and quantum), and a variety of different ways to encode and preserve information in physical systems. A system's ability to carry information is constrained and defined by the noise in its dynamics. This paper introduces an operational framework, using information-preserving structures, to classify all the kinds of information that can be perfectly (i.e., with zero error) preserved by quantum dynamics. We prove that every perfectly preserved code has the same structure as a matrix algebra, and that preserved information can always be corrected. We also classify distinct operational criteria for preservation (e.g., 'noiseless','unitarily correctible', etc.) and introduce two natural criteria for measurement-stabilized and unconditionally preserved codes. Finally, for several of these operational criteria, we present efficient (polynomial in the state-space dimension) algorithms to find all of a channel's information-preserving structures.

  10. Doubly infinite separation of quantum information and communication

    NASA Astrophysics Data System (ADS)

    Liu, Zi-Wen; Perry, Christopher; Zhu, Yechao; Koh, Dax Enshan; Aaronson, Scott

    2016-01-01

    We prove the existence of (one-way) communication tasks with a subconstant versus superconstant asymptotic gap, which we call "doubly infinite," between their quantum information and communication complexities. We do so by studying the exclusion game [C. Perry et al., Phys. Rev. Lett. 115, 030504 (2015), 10.1103/PhysRevLett.115.030504] for which there exist instances where the quantum information complexity tends to zero as the size of the input n increases. By showing that the quantum communication complexity of these games scales at least logarithmically in n , we obtain our result. We further show that the established lower bounds and gaps still hold even if we allow a small probability of error. However in this case, the n -qubit quantum message of the zero-error strategy can be compressed polynomially.

  11. Quantum informational model of 3+1 dimensional gravitational dynamics

    NASA Astrophysics Data System (ADS)

    Yepez, Jeffrey

    2010-04-01

    Quantum information theory is undergoing rapid development and recently there has been much progress in mapping out its relationship to low dimensional gravity, primarily through Chern-Simons topological quantum field theory and conformal field theory, with the prime application being topological quantum computation. Less attention has been paid to the relationship of quantum information theory to the long established and well tested theory of gravitational dynamics of 3+1 dimensional spacetime. Here we discuss this question in the weak field approximation of the 4-space metric tensor. The proposed approach considers a quantum algorithmic scheme suitable for simulating physical curved space dynamics that is traditionally described by the well known Einstein-Hilbert action. The quantum algorithmic approach builds upon Einstein's veirbein representation of gravity, which Einstein originally developed back in 1928 in his search for a unified field theory and, moreover, which is presently widely accepted as the preferred theoretical approach for representing dynamical relativistic Dirac fields in curved space. Although the proposed quantum algorithmic scheme is regular-lattice based it nevertheless recovers both the Einstein equation of motion as an effective field theory and invariance of the gravitational gauge field (i.e., the spin connection) with respect to Lorentz transformations as the local symmetry group in the low energy limit.

  12. Quantum Dots in H1 Photonic Crystal Microcavities for Quantum Information

    NASA Astrophysics Data System (ADS)

    Hagemeier, Jenna; Bonato, Cristian; Truong, Tuan-Anh; Kim, Hyochul; Bakker, Morten; Beirne, Gareth J.; van Exter, Martin P.; Petroff, Pierre; Bouwmeester, Dirk

    2013-03-01

    Coupling semiconductor quantum dots to optical microcavities is a promising technique for implementing quantum information processing protocols in the solid-state. By placing one or more emitters in a cavity, it is possible to create an efficient source of single photons or to explore collective interactions of few-emitter systems. Our devices consist of two layers of quantum dots, embedded in the cavity region of H1 photonic crystal microcavities. One of the quantum dot layers can be frequency-tuned deterministically, allowing two resonant quantum dots to be coupled to a single cavity mode. Because good mode-matching between the cavity mode and the input/output channel is necessary for many applications, we optimize the far-field profiles of our H1 cavities and demonstrate strong enhancement of the external mode matching properties. We will discuss our far-field optimization results as well as our ongoing work to study interactions of multiple emitters in a cavity.

  13. Topological Quantum Buses: Coherent Quantum Information Transfer between Topological and Conventional Qubits

    NASA Astrophysics Data System (ADS)

    Bonderson, Parsa; Lutchyn, Roman M.

    2011-04-01

    We propose computing bus devices that enable quantum information to be coherently transferred between topological and conventional qubits. We describe a concrete realization of such a topological quantum bus acting between a topological qubit in a Majorana wire network and a conventional semiconductor double quantum dot qubit. Specifically, this device measures the joint (fermion) parity of these two different qubits by using the Aharonov-Casher effect in conjunction with an ancilliary superconducting flux qubit that facilitates the measurement. Such a parity measurement, together with the ability to apply Hadamard gates to the two qubits, allows one to produce states in which the topological and conventional qubits are maximally entangled and to teleport quantum states between the topological and conventional quantum systems.

  14. Topological quantum buses: coherent quantum information transfer between topological and conventional qubits.

    PubMed

    Bonderson, Parsa; Lutchyn, Roman M

    2011-04-01

    We propose computing bus devices that enable quantum information to be coherently transferred between topological and conventional qubits. We describe a concrete realization of such a topological quantum bus acting between a topological qubit in a Majorana wire network and a conventional semiconductor double quantum dot qubit. Specifically, this device measures the joint (fermion) parity of these two different qubits by using the Aharonov-Casher effect in conjunction with an ancilliary superconducting flux qubit that facilitates the measurement. Such a parity measurement, together with the ability to apply Hadamard gates to the two qubits, allows one to produce states in which the topological and conventional qubits are maximally entangled and to teleport quantum states between the topological and conventional quantum systems. PMID:21517366

  15. Quantum tagging: Authenticating location via quantum information and relativistic signaling constraints

    SciTech Connect

    Kent, Adrian; Munro, William J.; Spiller, Timothy P.

    2011-07-15

    We define the task of quantum tagging, that is, authenticating the classical location of a classical tagging device by sending and receiving quantum signals from suitably located distant sites, in an environment controlled by an adversary whose quantum information processing and transmitting power is unbounded. We define simple security models for this task and briefly discuss alternatives. We illustrate the pitfalls of naive quantum cryptographic reasoning in this context by describing several protocols which at first sight appear unconditionally secure but which, as we show, can in fact be broken by teleportation-based attacks. We also describe some protocols which cannot be broken by these specific attacks, but do not prove they are unconditionally secure. We review the history of quantum tagging protocols, and show that protocols previously proposed by Malaney and Chandran et al. are provably insecure.

  16. Quantum origin of quantum jumps: Breaking of unitary symmetry induced by information transfer in the transition from quantum to classical

    NASA Astrophysics Data System (ADS)

    Zurek, Wojciech Hubert

    2007-11-01

    Measurements transfer information about a system to the apparatus and then, further on, to observers and (often inadvertently) to the environment. I show that even imperfect copying essential in such situations restricts possible unperturbed outcomes to an orthogonal subset of all possible states of the system, thus breaking the unitary symmetry of its Hilbert space implied by the quantum superposition principle. Preferred outcome states emerge as a result. They provide a framework for “wave-packet collapse,” designating terminal points of quantum jumps and defining the measured observable by specifying its eigenstates. In quantum Darwinism, they are the progenitors of multiple copies spread throughout the environment—the fittest quantum states that not only survive decoherence, but subvert the environment into carrying information about them—into becoming a witness.

  17. Controllable quantum information network with a superconducting system

    SciTech Connect

    Zhang, Feng-yang; Liu, Bao; Chen, Zi-hong; Wu, Song-lin; Song, He-shan

    2014-07-15

    We propose a controllable and scalable architecture for quantum information processing using a superconducting system network, which is composed of current-biased Josephson junctions (CBJJs) as tunable couplers between the two superconducting transmission line resonators (TLRs), each coupling to multiple superconducting qubits (SQs). We explicitly demonstrate that the entangled state, the phase gate, and the information transfer between any two selected SQs can be implemented, respectively. Lastly, numerical simulation shows that our scheme is robust against the decoherence of the system. -- Highlights: •An architecture for quantum information processing is proposed. •The quantum information transfer between any two selected SQs is implemented. •This proposal is robust against the decoherence of the system. •This architecture can be fabricated on a chip down to the micrometer scale.

  18. Redundant information from thermal illumination: quantum Darwinism in scattered photons

    NASA Astrophysics Data System (ADS)

    Jess Riedel, C.; Zurek, Wojciech H.

    2011-07-01

    We study quantum Darwinism, the redundant recording of information about the preferred states of a decohering system by its environment, for an object illuminated by a blackbody. We calculate the quantum mutual information between the object and its photon environment for blackbodies that cover an arbitrary section of the sky. In particular, we demonstrate that more extended sources have a reduced ability to create redundant information about the system, in agreement with previous evidence that initial mixedness of an environment slows—but does not stop—the production of records. We also show that the qualitative results are robust for more general initial states of the system.

  19. PT -symmetric Hamiltonians and their application in quantum information

    NASA Astrophysics Data System (ADS)

    Croke, Sarah

    2015-05-01

    We discuss the prospect of PT -symmetric Hamiltonians finding applications in quantum information science, and conclude that such evolution is unlikely to provide any benefit over existing techniques. Although it has been known for some time that PT -symmetric quantum theory, when viewed as a unitary theory, is exactly equivalent to standard quantum mechanics, proposals continue to be put forward for schemes in which PT -symmetric quantum theory can outperform standard quantum theory. The most recent of these is the suggestion to use PT -symmetric Hamiltonians to perform an exponentially fast database search, a task known to be impossible with a quantum computer. Further, such a scheme has been shown to apparently produce effects in conflict with fundamental information-theoretic principles, such as the impossibility of superluminal information transfer, and the invariance of entanglement under local operations. In this paper we propose three inequivalent experimental implementations of PT -symmetric Hamiltonians, with careful attention to the resources required to realize each such evolution. Such an operational approach allows us to resolve these apparent conflicts, and evaluate fully schemes proposed in the literature for faster time evolution and state discrimination.

  20. Quantum information transfer between topological and conventional charge qubits

    NASA Astrophysics Data System (ADS)

    Jun, Li; Yan, Zou

    2016-02-01

    We propose a scheme to realize coherent quantum information transfer between topological and conventional charge qubits. We first consider a hybrid system where a quantum dot (QD) is tunnel-coupled to a semiconductor Majorana-hosted nanowire (MNW) via using gated control as a switch, the information encoded in the superposition state of electron empty and occupied state can be transferred to each other through choosing the proper interaction time to make measurements. Then we consider another system including a double QDs and a pair of parallel MNWs, it is shown that the entanglement information transfer can be realized between the two kinds of systems. We also realize long distance quantum information transfer between two quantum dots separated by an MNW, by making use of the nonlocal fermionic level formed with the pared Majorana feimions (MFs) emerging at the two ends of the MNW. Furthermore, we analyze the teleportationlike electron transfer phenomenon predicted by Tewari et al. [Phys. Rev. Lett. 100, 027001 (2008)] in our considered system. Interestingly, we find that this phenomenon exactly corresponds to the case that the information encoded in one QD just returns back to its original place during the dynamical evolution of the combined system from the perspective of quantum state transfer. Project supported by the National Natural Science Foundation of China (Grant No. 11304031).

  1. A Matter of Principle: The Principles of Quantum Theory, Dirac's Equation, and Quantum Information

    NASA Astrophysics Data System (ADS)

    Plotnitsky, Arkady

    2015-10-01

    This article is concerned with the role of fundamental principles in theoretical physics, especially quantum theory. The fundamental principles of relativity will be addressed as well, in view of their role in quantum electrodynamics and quantum field theory, specifically Dirac's work, which, in particular Dirac's derivation of his relativistic equation of the electron from the principles of relativity and quantum theory, is the main focus of this article. I shall also consider Heisenberg's earlier work leading him to the discovery of quantum mechanics, which inspired Dirac's work. I argue that Heisenberg's and Dirac's work was guided by their adherence to and their confidence in the fundamental principles of quantum theory. The final section of the article discusses the recent work by D'Ariano and coworkers on the principles of quantum information theory, which extend quantum theory and its principles in a new direction. This extension enabled them to offer a new derivation of Dirac's equations from these principles alone, without using the principles of relativity.

  2. Beyond the Shannon-Khinchin formulation: The composability axiom and the universal-group entropy

    NASA Astrophysics Data System (ADS)

    Tempesta, Piergiulio

    2016-02-01

    The notion of entropy is ubiquitous both in natural and social sciences. In the last two decades, a considerable effort has been devoted to the study of new entropic forms, which generalize the standard Boltzmann-Gibbs (BG) entropy and could be applicable in thermodynamics, quantum mechanics and information theory. In Khinchin (1957), by extending previous ideas of Shannon (1948) and Shannon and Weaver (1949), Khinchin proposed a characterization of the BG entropy, based on four requirements, nowadays known as the Shannon-Khinchin (SK) axioms. The purpose of this paper is twofold. First, we show that there exists an intrinsic group-theoretical structure behind the notion of entropy. It comes from the requirement of composability of an entropy with respect to the union of two statistically independent systems, that we propose in an axiomatic formulation. Second, we show that there exists a simple universal family of trace-form entropies. This class contains many well known examples of entropies and infinitely many new ones, a priori multi-parametric. Due to its specific relation with Lazard's universal formal group of algebraic topology, the new general entropy introduced in this work will be called the universal-group entropy. A new example of multi-parametric entropy is explicitly constructed.

  3. Quantum Darwinism for mixed-state environment

    NASA Astrophysics Data System (ADS)

    Quan, Haitao; Zwolak, Michael; Zurek, Wojciech

    2009-03-01

    We exam quantum darwinism when a system is in the presence of a mixed environment, and we find a general relation between the mutual information for the mixed-state environment and the change of the entropy of the fraction of the environment. We then look at a particular solvable model, and we numerically exam the time evolution of the ``mutual information" for large environment. Finally we discuss about the exact expressions for all entropies and the mutual information at special time.

  4. Generalized Entropic Uncertainty Relations with Tsallis' Entropy

    NASA Technical Reports Server (NTRS)

    Portesi, M.; Plastino, A.

    1996-01-01

    A generalization of the entropic formulation of the Uncertainty Principle of Quantum Mechanics is considered with the introduction of the q-entropies recently proposed by Tsallis. The concomitant generalized measure is illustrated for the case of phase and number operators in quantum optics. Interesting results are obtained when making use of q-entropies as the basis for constructing generalized entropic uncertainty measures.

  5. Scalable quantum information transfer between nitrogen-vacancy-center ensembles

    SciTech Connect

    Zhang, Feng-yang; Yang, Chui-Ping; Song, He-Shan

    2015-04-15

    We propose an architecture for realizing quantum information transfer (QIT). In this architecture, a LC circuit is used to induce the necessary interaction between flux qubits, each magnetically coupling to a nitrogen-vacancy center ensemble (NVCE). We explicitly show that for resonant interaction and large detuning cases, high-fidelity QIT between two spatially-separated NVCEs can be implemented. Our proposal can be extended to achieve QIT between any two selected NVCEs in a large hybrid system by adjusting system parameters, which is important in large scale quantum information processing. - Highlights: • Quantum information transfer between any two selected NV ensembles is implemented. • This architecture is robust against the dissipation of the system. • We explicitly show that for resonant interaction and large detuning cases.

  6. Survey of control performance in quantum information processing

    NASA Astrophysics Data System (ADS)

    Hocker, David; Zheng, Yicong; Kosut, Robert; Brun, Todd; Rabitz, Herschel

    2016-08-01

    There is a rich variety of physics underlying the fundamental gating operations for quantum information processing (QIP). A key aspect of a QIP system is how noise may enter during quantum operations and how suppressing or correcting its effects can best be addressed. Quantum control techniques have been developed to specifically address this effort, although a detailed classification of the compatibility of controls schemes with noise sources found in common quantum systems has not yet been performed. This work numerically examines the performance of modern control methods for suppressing decoherence in the presence of noise forms found in viable quantum systems. The noise-averaged process matrix for controlled one-qubit and two-qubit operations are calculated across noise found in systems driven by Markovian open quantum dynamics. Rather than aiming to describe the absolute best control scheme for a given physical circumstance, this work serves instead to classify quantum control behavior across a large class of noise forms so that opportunities for improving QIP performance may be identified.

  7. Decision theory and information propagation in quantum physics

    NASA Astrophysics Data System (ADS)

    Forrester, Alan

    In recent papers, Zurek [(2005). Probabilities from entanglement, Born's rule p k =| ψ k | 2 from entanglement. Physical Review A, 71, 052105] has objected to the decision-theoretic approach of Deutsch [(1999) Quantum theory of probability and decisions. Proceedings of the Royal Society of London A, 455, 3129-3137] and Wallace [(2003). Everettian rationality: defending Deutsch's approach to probability in the Everett interpretation. Studies in History and Philosophy of Modern Physics, 34, 415-438] to deriving the Born rule for quantum probabilities on the grounds that it courts circularity. Deutsch and Wallace assume that the many worlds theory is true and that decoherence gives rise to a preferred basis. However, decoherence arguments use the reduced density matrix, which relies upon the partial trace and hence upon the Born rule for its validity. Using the Heisenberg picture and quantum Darwinism-the notion that classical information is quantum information that can proliferate in the environment pioneered in Ollivier et al. [(2004). Objective properties from subjective quantum states: Environment as a witness. Physical Review Letters, 93, 220401 and (2005). Environment as a witness: Selective proliferation of information and emergence of objectivity in a quantum universe. Physical Review A, 72, 042113]-I show that measurement interactions between two systems only create correlations between a specific set of commuting observables of system 1 and a specific set of commuting observables of system 2. This argument picks out a unique basis in which information flows in the correlations between those sets of commuting observables. I then derive the Born rule for both pure and mixed states and answer some other criticisms of the decision theoretic approach to quantum probability.

  8. Microstrip SQUID amplifiers for quantum information science

    NASA Astrophysics Data System (ADS)

    Defeo, M. P.; Plourde, B. L. T.

    2012-02-01

    Recent progress in SQUID amplifiers suggests that these devices might approach quantum-limited sensitivity in the microwave range, thus making them a viable option for measurement of superconducting quantum systems. In the microstrip SQUID amplifier configuration, gains of around 20dB are possible at frequencies of several hundred MHz, and the gain is limited by the maximum voltage modulation available from the SQUID. One route for increasing the voltage modulation involves using larger resistive shunts, however maintaining non-hysteretic device operation requires smaller junction capacitances than is possible with conventional photolithographically patterned junctions. Operating at higher frequencies requires a shorter input coil which reduces mutual inductance between the coil and washer and therefore gain. We have fabricated microstrip SQUID amplifiers using submicron Al-AlOx-Al junctions and large shunts. The input coil and SQUID washer are optimized for producing high gain at frequencies in the gigahertz range. Recent measurements of gain and noise temperature will be discussed as well as demonstrations of these devices as a first stage of amplification for a superconducting system

  9. Protection of quantum information and optimal singlet conversion through higher-dimensional quantum systems and environment monitoring

    SciTech Connect

    Mascarenhas, E.; Marques, B.; Santos, M. Franca; Cavalcanti, D.; Cunha, M. Terra

    2010-03-15

    We study how to protect quantum information in quantum systems subjected to local dissipation. We show that combining the use of three-level systems, environment monitoring, and local feedback can fully and deterministically protect any available quantum information, including entanglement initially shared by different parties. These results can represent a gain in resources and/or distances in quantum communication protocols such as quantum repeaters and teleportation as well as time for quantum memories. Finally, we show that monitoring local environments physically implements the optimum singlet conversion protocol, which is essential for classical entanglement percolation.

  10. Wigner-Yanase skew information as tests for quantum entanglement

    SciTech Connect

    Chen Zeqian

    2005-05-15

    A Bell-type inequality is proposed in terms of Wigner-Yanase skew information, which is quadratic and involves only one local spin observable at each site. This inequality presents a hierarchic classification of all states of multipartite quantum systems from separable to fully entangled states, which is more powerful than the one presented by quadratic Bell inequalities from two-entangled to fully entangled states. In particular, it is proved that the inequality provides an exact test to distinguish entangled from nonentangled pure states of two qubits. Our inequality sheds considerable light on relationships between quantum entanglement and information theory.

  11. The information-carrying capacity of certain quantum channels

    NASA Astrophysics Data System (ADS)

    Morgan, Ciara

    2010-07-01

    In this thesis we analyse the type of states and ensembles which achieve the capacity for certain quantum channels carrying classical information. We first concentrate on the product-state capacity of a particular quantum channel, that is, the capacity which is achieved by encoding the output states from a source into codewords comprised of states taken from ensembles of non-entangled states and sending them over copies of the quantum channel. Using the "single-letter" formula proved independently by Holevo and by Schumacher and Westmoreland we obtain the product-state capacity of the qubit quantum amplitude-damping channel, which is determined by a transcendental equation in a single real variable and can be solved numerically. We demonstrate that the product-state capacity of this channel can be achieved using a minimal ensemble of non-orthogonal pure states. Next we consider the classical capacity of two quantum channels with memory, namely a periodic channel with quantum depolarising channel branches and a convex combination of quantum channels. We prove that the classical capacity for each of the classical memory channels mentioned above is, in fact, equal to the respective product-state capacities. For those channels this means that the classical capacity is achieved without the use of entangled input-states. Next we introduce the channel coding theorem for memoryless quantum channels, providing a known proof by Winter for the strong converse of the theorem. We then consider the strong converse to the channel coding theorem for a periodic quantum channel.

  12. Density of defects and the scaling law of the entanglement entropy in quantum phase transition of one-dimensional spin systems induced by a quench

    SciTech Connect

    Basu, Banasri; Bandyopadhyay, Pratul; Majumdar, Priyadarshi

    2011-03-15

    We have studied quantum phase transition induced by a quench in different one-dimensional spin systems. Our analysis is based on the dynamical mechanism which envisages nonadiabaticity in the vicinity of the critical point. This causes spin fluctuation which leads to the random fluctuation of the Berry phase factor acquired by a spin state when the ground state of the system evolves in a closed path. The two-point correlation of this phase factor is associated with the probability of the formation of defects. In this framework, we have estimated the density of defects produced in several one-dimensional spin chains. At the critical region, the entanglement entropy of a block of L spins with the rest of the system is also estimated which is found to increase logarithmically with L. The dependence on the quench time puts a constraint on the block size L. It is also pointed out that the Lipkin-Meshkov-Glick model in point-splitting regularized form appears as a combination of the XXX model and Ising model with magnetic field in the negative z axis. This unveils the underlying conformal symmetry at criticality which is lost in the sharp point limit. Our analysis shows that the density of defects as well as the scaling behavior of the entanglement entropy follows a universal behavior in all these systems.

  13. Manipulating quantum information with spin torque

    PubMed Central

    Sutton, Brian; Datta, Supriyo

    2015-01-01

    The use of spin torque as a substitute for magnetic fields is now well established for classical operations like the switching of a nanomagnet. What we are describing here could be viewed as an application of spin torque like effects to quantum processes involving single qubit rotations as well as two qubit entanglement. A key ingredient of this scheme is the use of a large number of itinerant electrons whose cumulative effect is to produce the desired qubit operations on static spins. Each interaction involves entanglement and collapse of wavefunctions so that the operation is only approximately unitary. However, we show that the non-unitary component of the operations can be kept below tolerable limits with proper design. As a capstone example, we present the implementation of a complete CNOT gate using the proposed spin potential based architecture, and show that the fidelity under ideal conditions can be made acceptably close to one. PMID:26648524

  14. Edge theory approach to topological entanglement entropy, mutual information, and entanglement negativity in Chern-Simons theories

    NASA Astrophysics Data System (ADS)

    Wen, Xueda; Matsuura, Shunji; Ryu, Shinsei

    2016-06-01

    We develop an approach based on edge theories to calculate the entanglement entropy and related quantities in (2+1)-dimensional topologically ordered phases. Our approach is complementary to, e.g., the existing methods using replica trick and Witten's method of surgery, and applies to a generic spatial manifold of genus g , which can be bipartitioned in an arbitrary way. The effects of fusion and braiding of Wilson lines can be also straightforwardly studied within our framework. By considering a generic superposition of states with different Wilson line configurations, through an interference effect, we can detect, by the entanglement entropy, the topological data of Chern-Simons theories, e.g., the R symbols, monodromy, and topological spins of quasiparticles. Furthermore, by using our method, we calculate other entanglement/correlation measures such as the mutual information and the entanglement negativity. In particular, it is found that the entanglement negativity of two adjacent noncontractible regions on a torus provides a simple way to distinguish Abelian and non-Abelian topological orders.

  15. Entanglement entropy of a black hole and isolated horizon

    NASA Astrophysics Data System (ADS)

    Shi, Jianhua; Hu, Shuangqi; Zhao, Ren

    2013-02-01

    Using Unruh-Verlinde temperature obtained by entropic force, we directly calculate partition functions of quantum field in Schwarzschild spacetime via quantum statistical method and derive the expression of the black hole statistical entropy. In our calculation the lower limit of integral is the location of isolated horizon introduced in loop quantum gravity and the upper limit of integral is infinity. So the obtained entropy is the statistical entropy from isolated horizon to the infinite. In our calculation there are not the cutoff and approximation. The results showed that, as long as proper Immirzi parameters are selected, the entropy obtained by loop quantum gravity is consistent with the quantum statistical entropy outside the black hole horizon. Therefore the black hole entropy is a quantum entanglement entropy outside the isolated horizon.

  16. nSQUID arrays as conveyers of quantum information

    SciTech Connect

    Deng, Qiang; Averin, D. V.

    2014-12-15

    We have considered the quantum dynamics of an array of nSQUIDs—two-junction SQUIDs with negative mutual inductance between their two arms. Effective dual-rail structure of the array creates additional internal degree of freedom for the fluxons in the array, which can be used to encode and transport quantum information. Physically, this degree of freedom is represented by electromagnetic excitations localized on the fluxon. We have calculated the spatial profile and frequency spectrum of these excitations. Their dynamics can be reduced to two quantum states, so that each fluxon moving through the array carries with it a qubit of information. Coherence properties of such a propagating qubit in the nSQUID array are characterized by the dynamic suppression of the low-frequency decoherence due to the motion-induced spreading of the noise spectral density to a larger frequency interval.

  17. Reflections on Zeilinger-Brukner Information Interpretation of Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Khrennikov, Andrei

    2016-07-01

    In this short review I present my personal reflections on Zeilinger-Brukner information interpretation of quantum mechanics (QM).In general, this interpretation is very attractive for me. However, its rigid coupling to the notion of irreducible quantum randomness is a very complicated issue which I plan to address in more detail. This note may be useful for general public interested in quantum foundations, especially because I try to analyze essentials of the information interpretation critically (i.e., not just emphasizing its advantages as it is commonly done). This review is written in non-physicist friendly manner. Experts actively exploring this interpretation may be interested in the paper as well, as in the comments of "an external observer" who have been monitoring the development of this approach to QM during the last 18 years. The last part of this review is devoted to the general methodology of science with references to views of de Finetti, Wigner, and Peres.

  18. Expected behavior of quantum thermodynamic machines with prior information.

    PubMed

    Thomas, George; Johal, Ramandeep S

    2012-04-01

    We estimate the expected behavior of the quantum model of a heat engine when we have incomplete information about external macroscopic parameters such as the magnetic field controlling the intrinsic energy scales of the working medium. We explicitly derive the prior probability distribution for these unknown parameters ai (i=1,2). Based on a few simple assumptions, the prior probability distribution is found to be of the form Π(ai)∝1/ai. By calculating the expected values of various physical quantities related to this engine, we find that the expected behavior of the quantum model exhibits thermodynamiclike features. This leads us to a surprising proposal that incomplete information quantified as an appropriate prior distribution can lead us to expect classical thermodynamic behavior in quantum models.

  19. H1 photonic crystal cavities for hybrid quantum information protocols.

    PubMed

    Hagemeier, Jenna; Bonato, Cristian; Truong, Tuan-Anh; Kim, Hyochul; Beirne, Gareth J; Bakker, Morten; van Exter, Martin P; Luo, Yunqiu; Petroff, Pierre; Bouwmeester, Dirk

    2012-10-22

    Hybrid quantum information protocols are based on local qubits, such as trapped atoms, NV centers, and quantum dots, coupled to photons. The coupling is achieved through optical cavities. Here we demonstrate far-field optimized H1 photonic crystal membrane cavities combined with an additional back reflection mirror below the membrane that meet the optical requirements for implementing hybrid quantum information protocols. Using numerical optimization we find that 80% of the light can be radiated within an objective numerical aperture of 0.8, and the coupling to a single-mode fiber can be as high as 92%. We experimentally prove the unique external mode matching properties by resonant reflection spectroscopy with a cavity mode visibility above 50%. PMID:23187235

  20. H1 photonic crystal cavities for hybrid quantum information protocols

    NASA Astrophysics Data System (ADS)

    Hagemeier, Jenna; Bonato, Cristian; Truong, Tuan-Anh; Kim, Hyochul; Beirne, Gareth J.; Bakker, Morten; van Exter, Martin P.; Luo, Yunqiu; Petroff, Pierre; Bouwmeester, Dirk

    2012-10-01

    Hybrid quantum information protocols are based on local qubits, such as trapped atoms, NV centers, and quantum dots, coupled to photons. The coupling is achieved through optical cavities. Here we demonstrate far-field optimized H1 photonic crystal membrane cavities combined with an additional back reflection mirror below the membrane that meet the optical requirements for implementing hybrid quantum information protocols. Using numerical optimization we find that 80% of the light can be radiated within an objective numerical aperture of 0.8, and the coupling to a single-mode fiber can be as high as 92%. We experimentally prove the unique external mode matching properties by resonant reflection spectroscopy with a cavity mode visibility above 50%.