WorldWideScience

Sample records for quantum information encoding

  1. Abstract algebra, projective geometry and time encoding of quantum information

    Planat, M R P; Planat, Michel R. P.; Saniga, Metod

    2005-01-01

    Algebraic geometrical concepts are playing an increasing role in quantum applications such as coding, cryptography, tomography and computing. We point out here the prominent role played by Galois fields viewed as cyclotomic extensions of the integers modulo a prime characteristic $p$. They can be used to generate efficient cyclic encoding, for transmitting secrete quantum keys, for quantum state recovery and for error correction in quantum computing. Finite projective planes and their generalization are the geometric counterpart to cyclotomic concepts, their coordinatization involves Galois fields, and they have been used repetitively for enciphering and coding. Finally the characters over Galois fields are fundamental for generating complete sets of mutually unbiased bases, a generic concept of quantum information processing and quantum entanglement. Gauss sums over Galois fields ensure minimum uncertainty under such protocols. Some Galois rings which are cyclotomic extensions of the integers modulo 4 are al...

  2. Encoding quantum information in a stabilized manifold of a superconducting cavity

    Touzard, S.; Leghtas, Z.; Mundhada, S. O.; Axline, C.; Reagor, M.; Chou, K.; Blumoff, J.; Sliwa, K. M.; Shankar, S.; Frunzio, L.; Schoelkopf, R. J.; Mirrahimi, M.; Devoret, M. H.

    In a superconducting Josephson circuit architecture, we activate a multi-photon process between two modes by applying microwave drives at specific frequencies. This creates a pairwise exchange of photons between a high-Q cavity and the environment. The resulting open dynamical system develops a two-dimensional quasi-energy ground state manifold. Can we encode, protect and manipulate quantum information in this manifold? We experimentally investigate the convergence and escape rates in and out of this confined subspace. Finally, using quantum Zeno dynamics, we aim to perform gates which maintain the state in the protected manifold at all times. Work supported by: ARO, ONR, AFOSR and YINQE.

  3. Comment on "Secure quantum private information retrieval using phase-encoded queries"

    Shi, Run-hua; Mu, Yi; Zhong, Hong; Zhang, Shun

    2016-12-01

    In this Comment, we reexamine the security of phase-encoded quantum private query (QPQ). We find that the current phase-encoded QPQ protocols, including their applications, are vulnerable to a probabilistic entangle-and-measure attack performed by the owner of the database. Furthermore, we discuss how to overcome this security loophole and present an improved cheat-sensitive QPQ protocol without losing the good features of the original protocol.

  4. Quantum information

    Rodgers, P

    1998-03-01

    There is more to information than a string of ones and zeroes the ability of ''quantum bits'' to be in two states at the same time could revolutionize information technology. In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry one of the biggest industries in the world today. Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers? Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed. (author)

  5. Universal Quantum Computing with Arbitrary Continuous-Variable Encoding

    Lau, Hoi-Kwan; Plenio, Martin B.

    2016-09-01

    Implementing a qubit quantum computer in continuous-variable systems conventionally requires the engineering of specific interactions according to the encoding basis states. In this work, we present a unified formalism to conduct universal quantum computation with a fixed set of operations but arbitrary encoding. By storing a qubit in the parity of two or four qumodes, all computing processes can be implemented by basis state preparations, continuous-variable exponential-swap operations, and swap tests. Our formalism inherits the advantages that the quantum information is decoupled from collective noise, and logical qubits with different encodings can be brought to interact without decoding. We also propose a possible implementation of the required operations by using interactions that are available in a variety of continuous-variable systems. Our work separates the "hardware" problem of engineering quantum-computing-universal interactions, from the "software" problem of designing encodings for specific purposes. The development of quantum computer architecture could hence be simplified.

  6. Universal Quantum Computing with Arbitrary Continuous-Variable Encoding.

    Lau, Hoi-Kwan; Plenio, Martin B

    2016-09-02

    Implementing a qubit quantum computer in continuous-variable systems conventionally requires the engineering of specific interactions according to the encoding basis states. In this work, we present a unified formalism to conduct universal quantum computation with a fixed set of operations but arbitrary encoding. By storing a qubit in the parity of two or four qumodes, all computing processes can be implemented by basis state preparations, continuous-variable exponential-swap operations, and swap tests. Our formalism inherits the advantages that the quantum information is decoupled from collective noise, and logical qubits with different encodings can be brought to interact without decoding. We also propose a possible implementation of the required operations by using interactions that are available in a variety of continuous-variable systems. Our work separates the "hardware" problem of engineering quantum-computing-universal interactions, from the "software" problem of designing encodings for specific purposes. The development of quantum computer architecture could hence be simplified.

  7. Quantum algorithmic information theory

    Svozil, Karl

    1995-01-01

    The agenda of quantum algorithmic information theory, ordered `top-down,' is the quantum halting amplitude, followed by the quantum algorithmic information content, which in turn requires the theory of quantum computation. The fundamental atoms processed by quantum computation are the quantum bits which are dealt with in quantum information theory. The theory of quantum computation will be based upon a model of universal quantum computer whose elementary unit is a two-port interferometer capa...

  8. Quantum information density and network

    Qiao BI; Jin-qing FANG; Gui-ping LIU

    2009-01-01

    We present a quantum information network in which quantum information density is used for per- forming quantum computing or teleportation. The pho- tons are entangled in quantum channels and play a role of flying ebit to transmit interaction among the nodes. A particular quantum Gaussian channel is constructed; it permits photon-encoded information to transmit quan- tum signals with certain quantum parallelism. The cor- responding quantum dynamical mutual information is discussed, and the controlling nodes connectivity by driv- ing the network is studied. With regard to different driving functions, the connectivity distribution of the network is complicated. They obey positive or negative power law, and also influence the assortativity coefficient or the dynamical property of the network.

  9. Quantum biological information theory

    Djordjevic, Ivan B

    2016-01-01

    This book is a self-contained, tutorial-based introduction to quantum information theory and quantum biology. It serves as a single-source reference to the topic for researchers in bioengineering, communications engineering, electrical engineering, applied mathematics, biology, computer science, and physics. The book provides all the essential principles of the quantum biological information theory required to describe the quantum information transfer from DNA to proteins, the sources of genetic noise and genetic errors as well as their effects. Integrates quantum information and quantum biology concepts; Assumes only knowledge of basic concepts of vector algebra at undergraduate level; Provides a thorough introduction to basic concepts of quantum information processing, quantum information theory, and quantum biology; Includes in-depth discussion of the quantum biological channel modelling, quantum biological channel capacity calculation, quantum models of aging, quantum models of evolution, quantum models o...

  10. Continuous-variable quantum information processing

    Andersen, Ulrik Lund; Leuchs, G.; Silberhorn, C.

    2010-01-01

    the continuous degree of freedom of a quantum system for encoding, processing or detecting information, one enters the field of continuous-variable (CV) quantum information processing. In this paper we review the basic principles of CV quantum information processing with main focus on recent developments...... in the field. We will be addressing the three main stages of a quantum information system; the preparation stage where quantum information is encoded into CVs of coherent states and single-photon states, the processing stage where CV information is manipulated to carry out a specified protocol and a detection...

  11. Quantum Information Theory

    Nielsen, M. A.

    2000-01-01

    Quantum information theory is the study of the achievable limits of information processing within quantum mechanics. Many different types of information can be accommodated within quantum mechanics, including classical information, coherent quantum information, and entanglement. Exploring the rich variety of capabilities allowed by these types of information is the subject of quantum information theory, and of this Dissertation. In particular, I demonstrate several novel limits to the informa...

  12. Quantum information theory

    Nielsen, M A

    1998-01-01

    Quantum information theory is the study of the achievable limits of information processing within quantum mechanics. Many different types of information can be accommodated within quantum mechanics, including classical information, coherent quantum information, and entanglement. Exploring the rich variety of capabilities allowed by these types of information is the subject of quantum information theory, and of this Dissertation. In particular, I demonstrate several novel limits to the information processing ability of quantum mechanics. Results of especial interest include: the demonstration of limitations to the class of measurements which may be performed in quantum mechanics; a capacity theorem giving achievable limits to the transmission of classical information through a two-way noiseless quantum channel; resource bounds on distributed quantum computation; a new proof of the quantum noiseless channel coding theorem; an information-theoretic characterization of the conditions under which quantum error-cor...

  13. Quantum information to the home

    Choi, Iris; Young, Robert J.; Townsend, Paul D.

    2011-06-01

    Information encoded on individual quanta will play an important role in our future lives, much as classically encoded digital information does today. Combining quantum information carried by single photons with classical signals encoded on strong laser pulses in modern fibre-to-the-home (FTTH) networks is a significant challenge, the solution to which will facilitate the global distribution of quantum information to the home and with it a quantum internet [1]. In real-world networks, spontaneous Raman scattering in the optical fibre would induce crosstalk between the high-power classical channels and a single-photon quantum channel, such that the latter is unable to operate. Here, we show that the integration of quantum and classical information on an FTTH network is possible by performing quantum key distribution (QKD) on a network while simultaneously transferring realistic levels of classical data. Our novel scheme involves synchronously interleaving a channel of quantum data with the Raman scattered photons from a classical channel, exploiting the periodic minima in the instantaneous crosstalk and thereby enabling secure QKD to be performed.

  14. Quantum information to the home

    Choi, Iris; Young, Robert J; Townsend, Paul D, E-mail: paul.townsend@tyndall.ie [Photonic Systems Group, Tyndall National Institute and Department of Physics, University College Cork, Cork (Ireland)

    2011-06-15

    Information encoded on individual quanta will play an important role in our future lives, much as classically encoded digital information does today. Combining quantum information carried by single photons with classical signals encoded on strong laser pulses in modern fibre-to-the-home (FTTH) networks is a significant challenge, the solution to which will facilitate the global distribution of quantum information to the home and with it a quantum internet. In real-world networks, spontaneous Raman scattering in the optical fibre would induce crosstalk between the high-power classical channels and a single-photon quantum channel, such that the latter is unable to operate. Here, we show that the integration of quantum and classical information on an FTTH network is possible by performing quantum key distribution (QKD) on a network while simultaneously transferring realistic levels of classical data. Our novel scheme involves synchronously interleaving a channel of quantum data with the Raman scattered photons from a classical channel, exploiting the periodic minima in the instantaneous crosstalk and thereby enabling secure QKD to be performed.

  15. Dynamical Equations for Quantum Information and Application in Information Channel

    BI Qiao; XING Xiu-San; H. E. Ruda

    2005-01-01

    @@ We establish several dynamical equations for quantum information density. It is demonstrated that quantum information density shares the same formalism of the Liouville equation, subdynamics kinetic equation and Fokker-Planck equation as the density operator and also possesses the superposition property. These allow one to use quantum information density directly to model quantum information. The kinetic equations for quantum information density reveal that the dynamical process of quantum information may be related to dissipative,Markovian, or diffusional information flows, together causing irreversibility. Finally, we discuss superposition of quantum information density, which allows us to construct a quantum information channel in the coherent state representation using harmonic oscillator based encoded quantum information, and obtain a formula for quantum dynamical mutual information.

  16. Encoding information into precipitation structures

    Martens, Kirsten; Bena, Ioana; Droz, Michel; Rácz, Zoltan

    2008-12-01

    Material design at submicron scales would be profoundly affected if the formation of precipitation patterns could be easily controlled. It would allow the direct building of bulk structures, in contrast to traditional techniques which consist of removing material in order to create patterns. Here, we discuss an extension of our recent proposal of using electrical currents to control precipitation bands which emerge in the wake of reaction fronts in A+ + B- → C reaction-diffusion processes. Our main result, based on simulating the reaction-diffusion-precipitation equations, is that the dynamics of the charged agents can be guided by an appropriately designed time-dependent electric current so that, in addition to the control of the band spacing, the width of the precipitation bands can also be tuned. This makes straightforward the encoding of information into precipitation patterns and, as an amusing example, we demonstrate the feasibility by showing how to encode a musical rhythm.

  17. Quantum information causality

    Pitalúa-García, Damián

    2012-01-01

    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 combin...

  18. Quantum information with Rydberg atoms

    Saffman, Mark; Walker, T.G.; Mølmer, Klaus

    2010-01-01

    qubits. The availability of a strong long-range interaction that can be coherently turned on and off is an enabling resource for a wide range of quantum information tasks stretching far beyond the original gate proposal. Rydberg enabled capabilities include long-range two-qubit gates, collective encoding...... of multiqubit registers, implementation of robust light-atom quantum interfaces, and the potential for simulating quantum many-body physics. The advances of the last decade are reviewed, covering both theoretical and experimental aspects of Rydberg-mediated quantum information processing.......Rydberg atoms with principal quantum number n»1 have exaggerated atomic properties including dipole-dipole interactions that scale as n4 and radiative lifetimes that scale as n3. It was proposed a decade ago to take advantage of these properties to implement quantum gates between neutral atom...

  19. Repeated quantum error correction on a continuously encoded qubit by real-time feedback

    Cramer, J.; Kalb, N.; Rol, M. A.; Hensen, B.; Blok, M. S.; Markham, M.; Twitchen, D. J.; Hanson, R.; Taminiau, T. H.

    2016-05-01

    Reliable quantum information processing in the face of errors is a major fundamental and technological challenge. Quantum error correction protects quantum states by encoding a logical quantum bit (qubit) in multiple physical qubits. To be compatible with universal fault-tolerant computations, it is essential that states remain encoded at all times and that errors are actively corrected. Here we demonstrate such active error correction on a continuously protected logical qubit using a diamond quantum processor. We encode the logical qubit in three long-lived nuclear spins, repeatedly detect phase errors by non-destructive measurements, and apply corrections by real-time feedback. The actively error-corrected qubit is robust against errors and encoded quantum superposition states are preserved beyond the natural dephasing time of the best physical qubit in the encoding. These results establish a powerful platform to investigate error correction under different types of noise and mark an important step towards fault-tolerant quantum information processing.

  20. Repeated quantum error correction on a continuously encoded qubit by real-time feedback.

    Cramer, J; Kalb, N; Rol, M A; Hensen, B; Blok, M S; Markham, M; Twitchen, D J; Hanson, R; Taminiau, T H

    2016-05-05

    Reliable quantum information processing in the face of errors is a major fundamental and technological challenge. Quantum error correction protects quantum states by encoding a logical quantum bit (qubit) in multiple physical qubits. To be compatible with universal fault-tolerant computations, it is essential that states remain encoded at all times and that errors are actively corrected. Here we demonstrate such active error correction on a continuously protected logical qubit using a diamond quantum processor. We encode the logical qubit in three long-lived nuclear spins, repeatedly detect phase errors by non-destructive measurements, and apply corrections by real-time feedback. The actively error-corrected qubit is robust against errors and encoded quantum superposition states are preserved beyond the natural dephasing time of the best physical qubit in the encoding. These results establish a powerful platform to investigate error correction under different types of noise and mark an important step towards fault-tolerant quantum information processing.

  1. Quantum information causality.

    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.

  2. Controlling Quantum Information

    Landahl, A J

    2002-01-01

    Quantum information science explores ways in which quantum physical laws can be harnessed to control the acquisition, transmission, protection, and processing of information. This field has seen explosive growth in the past several years from progress on both theoretical and experimental fronts. Essential to this endeavor are methods for controlling quantum information. In this thesis, I present three new approaches for controlling quantum information. First, I present a new protocol for continuously protecting unknown quantum states from noise. This protocol combines and expands ideas from the theories of quantum error correction and quantum feedback control. The result can outperform either approach by itself. I generalize this protocol to all known quantum stabilizer codes, and study its application to the three-qubit repetition code in detail via Monte Carlo simulations. Next, I present several new protocols for controlling quantum information that are fault-tolerant. These protocols require only local qu...

  3. Quantum Information An Introduction

    Hayashi, Masahito

    2006-01-01

    Recently, quantum information theory has been developing through a fusion of results from various research fields. This requires that understanding of basic results on diverse topics, and derived from different disciplinary perspectives, is required for appreciating the overall picture. Intended to merge key topics from both the information-theoretic and quantum- mechanical viewpoints, this graduate-level textbook provides a unified viewpoint of quantum information theory and lucid explanations of those basic results, so that the reader fundamentally grasps advances and challenges. For example, advanced topics in quantum communication such as quantum teleportation, superdense coding, quantum state transmission (quantum error-correction), and quantum encryption especially benefit from this unified approach. Unlike earlier treatments, the text requires knowledge of only linear algebra, probability theory, and quantum mechanics, while it treats the topics of quantum hypothesis testing and the discrimination of q...

  4. Quantum information and coherence

    Öhberg, Patrik

    2014-01-01

    This book offers an introduction to ten key topics in quantum information science and quantum coherent phenomena, aimed at graduate-student level. The chapters cover some of the most recent developments in this dynamic research field where theoretical and experimental physics, combined with computer science, provide a fascinating arena for groundbreaking new concepts in information processing. The book addresses both the theoretical and experimental aspects of the subject, and clearly demonstrates how progress in experimental techniques has stimulated a great deal of theoretical effort and vice versa. Experiments are shifting from simply preparing and measuring quantum states to controlling and manipulating them, and the book outlines how the first real applications, notably quantum key distribution for secure communication, are starting to emerge. The chapters cover quantum retrodiction, ultracold quantum gases in optical lattices, optomechanics, quantum algorithms, quantum key distribution, quantum cont...

  5. Quantum information theory

    Wilde, Mark M

    2017-01-01

    Developing many of the major, exciting, pre- and post-millennium developments from the ground up, this book is an ideal entry point for graduate students into quantum information theory. Significant attention is given to quantum mechanics for quantum information theory, and careful studies of the important protocols of teleportation, superdense coding, and entanglement distribution are presented. In this new edition, readers can expect to find over 100 pages of new material, including detailed discussions of Bell's theorem, the CHSH game, Tsirelson's theorem, the axiomatic approach to quantum channels, the definition of the diamond norm and its interpretation, and a proof of the Choi–Kraus theorem. Discussion of the importance of the quantum dynamic capacity formula has been completely revised, and many new exercises and references have been added. This new edition will be welcomed by the upcoming generation of quantum information theorists and the already established community of classical information theo...

  6. Quantum Information with Structured Light

    Mirhosseini, Mohammad

    Quantum information science promises dramatic progress in a variety of fields such as cryptography, computation, and metrology. Although the proof-of-principle attempts for implementing quantum protocols have often relied on only a few qubits, the utilization of more sophisticated quantum systems is required for practical applications. In this thesis, we investigate the emerging role of high-dimensional optical states as a resource for encoding quantum information. We begin the first chapter with a review of orbital angular momentum (OAM) as a prime candidate for realizing multilevel quantum states and follow with a brief introduction to the quantum measurement theory. The second and the third chapters are dedicated to the application of OAM modes in quantum cryptography. In the second chapter, we discuss the challenges of projective measurement of OAM at the single-photon level, a crucial task required for quantum information processing. We then present our development of an efficient and accurate mode-sorting device that is capable of projectively measuring the orbital angular momentum of single photons. In the third chapter, we discuss the role of OAM modes in increasing the information capacity of quantum cryptography. We start this chapter by establishing the merits of encoding information on the quantum index of OAM modes in a free-space link. We then generalizing the BB-84 QKD protocol to the Hilbert space spanned by a finite number of OAM modes and outline our experimental realization. The last two chapters are dedicated to the tomography of structured light fields. We start the fourth chapter by applying the recently found method of direct measurement to the characterization of OAM superpositions. We find the quantum state in the Hilbert space spanned by 27 OAM modes by performing a weak measurement of orbital angular momentum (OAM) followed by a strong measurement of azimuthal angle. We then introduce the concept of compressive direct measurement (CDM

  7. Introduction to quantum information science

    Hayashi, Masahito; Kawachi, Akinori; Kimura, Gen; Ogawa, Tomohiro

    2015-01-01

    This book presents the basics of quantum information, e.g., foundation of quantum theory, quantum algorithms, quantum entanglement, quantum entropies, quantum coding, quantum error correction and quantum cryptography. The required knowledge is only elementary calculus and linear algebra. This way the book can be understood by undergraduate students. In order to study quantum information, one usually has to study the foundation of quantum theory. This book describes it from more an operational viewpoint which is suitable for quantum information while traditional textbooks of quantum theory lack this viewpoint. The current  book bases on Shor's algorithm, Grover's algorithm, Deutsch-Jozsa's algorithm as basic algorithms. To treat several topics in quantum information, this book covers several kinds of information quantities in quantum systems including von Neumann entropy. The limits of several kinds of quantum information processing are given. As important quantum protocols,this book contains quantum teleport...

  8. Hybrid quantum information processing

    Furusawa, Akira [Department of Applied Physics, School of Engineering, The University of Tokyo (Japan)

    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.

  9. Spacetime replication of continuous variable quantum information

    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.

  10. Types of quantum information

    Griffiths, Robert B.

    2007-01-01

    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...

  11. Pattern recognition of quantum information based on pattern-distance

    Dong Daoyi; Chen Zonghai; Jiang Shengxiang

    2005-01-01

    Looking upon every encoding state of quantum information systems as a quantum information pattern, A kind of pattern-distance between different patterns as a measurement of comparability of quantum information patterns is defined, and two kinds of recognition algorithms based on pattern-distance for quantum information are proposed. They can respectively recognize quantum information with known objective pattern and unknown objective pattern. In the two algorithms, the phases and occurrence probabilities of different eigenpatterns of quantum information are sufficiently considered. Two examples demonstrate the feasibility and effectiveness of the two recognition methods. These algorithms point out a new and important path for applications of quantum information and pattern recognition.

  12. Relativistic quantum information

    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

  13. Hiding Quantum Information in the Perfect Code

    Shaw, Bilal A

    2010-01-01

    We present and analyze a protocol for quantum steganography where the sender (Alice) encodes her steganographic information into the error syndromes of the perfect (five-qubit) quantum error-correcting code, and sends it to the receiver (Bob) over a depolarizing channel. Alice and Bob share a classical secret key, and hide quantum information in such a way that to an eavesdropper (Eve) without access to the secret key, the quantum message looks like an innocent codeword with a typical sequence of quantum errors. We calculate the average rate of key consumption, and show how the protocol improves in performance as information is spread over multiple codeword blocks. Alice and Bob utilize different encodings to optimize the average number of steganographic bits that they can send to each other while matching the error statistics of the depolarizing channel.

  14. Introduction to quantum information science

    Hayashi, Masahito [Nagoya Univ. (Japan). Graduate School of Mathematics; Ishizaka, Satoshi [Hiroshima Univ., Higashi-Hiroshima (Japan). Graduate School of Integrated Arts and Sciences; Kawachi, Akinori [Tokyo Institute of Technology (Japan). Dept. of Mathematical and Computing Sciences; Kimura, Gen [Shibaura Institute of Technology, Saitama (Japan). College of Systems Engineering and Science; Ogawa, Tomohiro [Univ. of Electro-Communications, Tokyo (Japan). Graduate School of Information Systems

    2015-04-01

    Presents the mathematical foundation for quantum information in a very didactic way. Summarizes all required mathematical knowledge in linear algebra. Supports teaching and learning with more than 100 exercises with solutions. Includes brief descriptions to recent results with references. This book presents the basics of quantum information, e.g., foundation of quantum theory, quantum algorithms, quantum entanglement, quantum entropies, quantum coding, quantum error correction and quantum cryptography. The required knowledge is only elementary calculus and linear algebra. This way the book can be understood by undergraduate students. In order to study quantum information, one usually has to study the foundation of quantum theory. This book describes it from more an operational viewpoint which is suitable for quantum information while traditional textbooks of quantum theory lack this viewpoint. The current book bases on Shor's algorithm, Grover's algorithm, Deutsch-Jozsa's algorithm as basic algorithms. To treat several topics in quantum information, this book covers several kinds of information quantities in quantum systems including von Neumann entropy. The limits of several kinds of quantum information processing are given. As important quantum protocols,this book contains quantum teleportation, quantum dense coding, quantum data compression. In particular conversion theory of entanglement via local operation and classical communication are treated too. This theory provides the quantification of entanglement, which coincides with von Neumann entropy. The next part treats the quantum hypothesis testing. The decision problem of two candidates of the unknown state are given. The asymptotic performance of this problem is characterized by information quantities. Using this result, the optimal performance of classical information transmission via noisy quantum channel is derived. Quantum information transmission via noisy quantum channel by quantum error

  15. From Bell's inequalities to quantum information: a new quantum revolution

    CERN. Geneva

    2015-01-01

    In 1964, John Stuart Bell discovered that it is possible to settle the debate experimentally, by testing the famous "Bell's inequalities", and to show directly that the revolutionary concept of entanglement is indeed a reality. 

A long series of experiments closer and closer to the ideal scheme presented by Bell has confirmed that entanglement is indeed "a great quantum mystery", to use the words of Feynman. Based on that concept, a new field of research has emerged, quantum information, where one uses quantum bits, the so-called “qubits”, to encode the information and process it. Entanglement ...

  16. Quantum holographic encoding in a two-dimensional electron gas

    Moon, Christopher

    2010-05-26

    The advent of bottom-up atomic manipulation heralded a new horizon for attainable information density, as it allowed a bit of information to be represented by a single atom. The discrete spacing between atoms in condensed matter has thus set a rigid limit on the maximum possible information density. While modern technologies are still far from this scale, all theoretical downscaling of devices terminates at this spatial limit. Here, however, we break this barrier with electronic quantum encoding scaled to subatomic densities. We use atomic manipulation to first construct open nanostructures - 'molecular holograms' - which in turn concentrate information into a medium free of lattice constraints: the quantum states of a two-dimensional degenerate Fermi gas of electrons. The information embedded in the holograms is transcoded at even smaller length scales into an atomically uniform area of a copper surface, where it is densely projected into both two spatial degrees of freedom and a third holographic dimension mapped to energy. In analogy to optical volume holography, this requires precise amplitude and phase engineering of electron wavefunctions to assemble pages of information volumetrically. This data is read out by mapping the energy-resolved electron density of states with a scanning tunnelling microscope. As the projection and readout are both extremely near-field, and because we use native quantum states rather than an external beam, we are not limited by lensing or collimation and can create electronically projected objects with features as small as {approx}0.3 nm. These techniques reach unprecedented densities exceeding 20 bits/nm{sup 2} and place tens of bits into a single fermionic state.

  17. Quantum information theory mathematical foundation

    Hayashi, Masahito

    2017-01-01

    This graduate textbook provides a unified view of quantum information theory. Clearly explaining the necessary mathematical basis, it merges key topics from both information-theoretic and quantum- mechanical viewpoints and provides lucid explanations of the basic results. Thanks to this unified approach, it makes accessible such advanced topics in quantum communication as quantum teleportation, superdense coding, quantum state transmission (quantum error-correction) and quantum encryption. Since the publication of the preceding book Quantum Information: An Introduction, there have been tremendous strides in the field of quantum information. In particular, the following topics – all of which are addressed here – made seen major advances: quantum state discrimination, quantum channel capacity, bipartite and multipartite entanglement, security analysis on quantum communication, reverse Shannon theorem and uncertainty relation. With regard to the analysis of quantum security, the present book employs an impro...

  18. Secret key rates for an encoded quantum repeater

    Bratzik, Sylvia; Kampermann, Hermann; Bruß, Dagmar

    2014-03-01

    We investigate secret key rates for the quantum repeater using encoding [L. Jiang et al., Phys. Rev. A 79, 032325 (2009), 10.1103/PhysRevA.79.032325] and compare them to the standard repeater scheme by Briegel, Dür, Cirac, and Zoller. The former scheme has the advantage of a minimal consumption of classical communication. We analyze the trade-off in the secret key rate between the communication time and the required resources. For this purpose we introduce an error model for the repeater using encoding which allows for input Bell states with a fidelity smaller than one, in contrast to the model given by L. Jiang et al. [Phys. Rev. A 79, 032325 (2009), 10.1103/PhysRevA.79.032325]. We show that one can correct additional errors in the encoded connection procedure of this repeater and develop a suitable decoding algorithm. Furthermore, we derive the rate of producing entangled pairs for the quantum repeater using encoding and give the minimal parameter values (gate quality and initial fidelity) for establishing a nonzero secret key. We find that the generic quantum repeater is optimal regarding the secret key rate per memory per second and show that the encoded quantum repeater using the simple three-qubit repetition code can even have an advantage with respect to the resources compared to other recent quantum repeater schemes with encoding.

  19. Quantum criticality from Fisher information

    Song, Hongting; Luo, Shunlong; Fu, Shuangshuang

    2017-04-01

    Quantum phase transition is primarily characterized by a qualitative sudden change in the ground state of a quantum system when an external or internal parameter of the Hamiltonian is continuously varied. Investigating quantum criticality using information-theoretic methods has generated fruitful results. Quantum correlations and fidelity have been exploited to characterize the quantum critical phenomena. In this work, we employ quantum Fisher information to study quantum criticality. The singular or extremal point of the quantum Fisher information is adopted as the estimated thermal critical point. By a significant model constructed in Quan et al. (Phys Rev Lett 96: 140604, 2006), the effectiveness of this method is illustrated explicitly.

  20. Tools for Multimode Quantum Information: Modulation, Detection, and Spatial Quantum Correlations

    Lassen, Mikael Østergaard; Delaubert, Vincent; Janousek, Jirí

    2007-01-01

    We present here all the tools required for continuous variable parallel quantum information protocols based on spatial multi-mode quantum correlations and entanglement. We describe techniques for encoding and detecting this quantum information with high efficiency in the individual modes. We use ...

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

    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.

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

    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

  3. The decoupling approach to quantum information theory

    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.

  4. Colloquium: Protecting quantum information against environmental noise

    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.

  5. A secure quantum key distribution scheme based on variable quantum encoding algorithms

    Zhiwen Zhao; Yi Luo; Zhangji Zhao; Haiming Long

    2011-01-01

    The security of the quantum secret key plays a critical role in quantum communications. Thus far, one problem that still exists in existing protocols is the leakage of the length of the secret key. In this letter, based on variable quantum encoding algorithms, we propose a secure quantum key distribution scheme, which can overcome the security problem involving the leakage of the secret key. Security analysis shows that the proposed scheme is both secure and effective.%@@ The security of the quantum secret key plays a critical role in quantum communications.Thus far, one problem that still exists in existing protocols is the leakage of the length of the secret key.In this letter,based on variable quantum encoding algorithms, we propose a secure quantum key distribution scheme,which can overcome the security problem involving the leakage of the secret key.Security analysis shows that the proposed scheme is both secure and effective.

  6. Quantum information processing in nanostructures Quantum optics; Quantum computing

    Reina-Estupinan, J H

    2002-01-01

    Since information has been regarded os a physical entity, the field of quantum information theory has blossomed. This brings novel applications, such as quantum computation. This field has attracted the attention of numerous researchers with backgrounds ranging from computer science, mathematics and engineering, to the physical sciences. Thus, we now have an interdisciplinary field where great efforts are being made in order to build devices that should allow for the processing of information at a quantum level, and also in the understanding of the complex structure of some physical processes at a more basic level. This thesis is devoted to the theoretical study of structures at the nanometer-scale, 'nanostructures', through physical processes that mainly involve the solid-state and quantum optics, in order to propose reliable schemes for the processing of quantum information. Initially, the main results of quantum information theory and quantum computation are briefly reviewed. Next, the state-of-the-art of ...

  7. Quantum Information and Nepal

    Brady, Adam; Chapagain, Nirdosh; Simkhada, Prashanna

    2011-10-01

    Quantum Information (QI) is a relatively young science with exciting research opportunities. Nepal has an untapped reserve of motivated students with scientific research potential. Based on our educational experience in Nepal and in the US and based on our exposure to QI, we explore the possibility of developing QI research in Nepal. In this poster we lay out basic facts on physics and physics education in Nepal, report on an introductory QI class experiment at BYU, and use what we have learned to envision a QI future in Nepal.

  8. Recoverability in quantum information theory

    Wilde, Mark M

    2015-01-01

    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...

  9. Spin flips and quantum information for anti-parallel spins

    Gisin, Nicolas

    1999-01-01

    We consider two different ways to encode quantum information, by parallel or anti-parallel pairs of spins. We find that there is more information in the anti-parallel ones. This purely quantum mechanical effect is due to entanglement, not of the states but occuring in the course of the measuring process. We also introduce a range of quantum information processing machines, such as spin-flip and anti-cloning.

  10. Quantum information does not exist

    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.

  11. Inequalities for quantum skew information

    Audenaert, Koenraad; Cai, Liang; Hansen, Frank

    2008-01-01

    We study quantum information inequalities and show that the basic inequality between the quantum variance and the metric adjusted skew information generates all the multi-operator matrix inequalities or Robertson type determinant inequalities studied by a number of authors. We introduce an order...... relation on the set of functions representing quantum Fisher information that renders the set into a lattice with an involution. This order structure generates new inequalities for the metric adjusted skew informations. In particular, the Wigner-Yanase skew information is the maximal skew information...... with respect to this order structure in the set of Wigner-Yanase-Dyson skew informations....

  12. Quantum information theory and quantum statistics

    Petz, D. [Alfred Renyi Institute of Mathematics, Budapest (Hungary)

    2008-07-01

    Based on lectures given by the author, this book focuses on providing reliable introductory explanations of key concepts of quantum information theory and quantum statistics - rather than on results. The mathematically rigorous presentation is supported by numerous examples and exercises and by an appendix summarizing the relevant aspects of linear analysis. Assuming that the reader is familiar with the content of standard undergraduate courses in quantum mechanics, probability theory, linear algebra and functional analysis, the book addresses graduate students of mathematics and physics as well as theoretical and mathematical physicists. Conceived as a primer to bridge the gap between statistical physics and quantum information, a field to which the author has contributed significantly himself, it emphasizes concepts and thorough discussions of the fundamental notions to prepare the reader for deeper studies, not least through the selection of well chosen exercises. (orig.)

  13. BRICS and Quantum Information Processing

    Schmidt, Erik Meineche

    1998-01-01

    BRICS is a research centre and international PhD school in theoretical computer science, based at the University of Aarhus, Denmark. The centre has recently become engaged in quantum information processing in cooperation with the Department of Physics, also University of Aarhus. This extended...... abstract surveys activities at BRICS with special emphasis on the activities in quantum information processing....

  14. Unified approach to topological quantum computation with anyons: From qubit encoding to Toffoli gate

    Xu, Haitan; Taylor, J. M.

    2011-07-01

    Topological quantum computation may provide a robust approach for encoding and manipulating information utilizing the topological properties of anyonic quasiparticle excitations. We develop an efficient means to map between dense and sparse representations of quantum information (qubits) and a simple construction of multiqubit gates, for all anyon models from Chern-Simons-Witten SU(2)k theory that support universal quantum computation by braiding (k⩾3,k≠4). In the process, we show how the constructions of topological quantum memory and gates for k=2,4 connect naturally to those for k⩾3,k≠4, unifying these concepts in a simple framework. Furthermore, we illustrate potential extensions of these ideas to other anyon models outside of Chern-Simons-Witten field theory.

  15. Catalytic Decoupling of Quantum Information

    Majenz, Christian; Berta, Mario; Dupuis, Frédéric

    2017-01-01

    The decoupling technique is a fundamental tool in quantum information theory with applications ranging from quantum thermodynamics to quantum many body physics to the study of black hole radiation. In this work we introduce the notion of catalytic decoupling, that is, decoupling in the presence...... of an uncorrelated ancilla system. This removes a restriction on the standard notion of decoupling, which becomes important for structureless resources, and yields a tight characterization in terms of the max-mutual information. Catalytic decoupling naturally unifies various tasks like the erasure of correlations...... and quantum state merging, and leads to a resource theory of decoupling....

  16. Studies in quantum information theory

    Menicucci, Nicolas C.

    Quantum information theory started as the backdrop for quantum computing and is often considered only in relation to this technology, which is still in its infancy. But quantum information theory is only partly about quantum computing. While much of the interest in this field is spurred by the possible use of quantum computers for code breaking using fast factoring algorithms, to a physicist interested in deeper issues, it presents an entirely new set of questions based on an entirely different way of looking at the quantum world. This thesis is an exploration of several topics in quantum information theory. But it is also more than this. This thesis explores the new paradigm brought about by quantum information theory---that of physics as the flow of information. The thesis consists of three main parts. The first part describes my work on continuous-variable cluster states, a new platform for quantum computation. This begins with background material discussing classical and quantum computation and emphasizing the physical underpinnings of each, followed by a discussion of two recent unorthodox models of quantum computation. These models are combined into an original proposal for quantum computation using continuous-variable cluster states, including a proposed optical implementation. These are followed by a mathematical result radically simplifying the optical construction. Subsequent work simplifies this connection even further and provides a constructive proposal for scalable generation of large-scale cluster states---necessary if there is to be any hope of using this method in practical quantum computation. Experimental implementation is currently underway by my collaborators at The University of Virginia. The second part describes my work related to the physics of trapped ions, starting with an overview of the basic theory of linear ion traps. Although ion traps are often discussed in terms of their potential use for quantum computation, my work looks at their

  17. High Information Capacity Quantum Imaging

    2014-09-19

    the quantum nature of light), and detector reset time. Algorithmic : We provide a method for spatiotemporally-regularized estimation of intensity and...High Information Capacity Quantum Imaging This is the final report for the DARPA InPho program. In reality, we finished this program in early 2013...Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 Quantum Imaging, Photon Counting, LIDAR REPORT DOCUMENTATION PAGE 11

  18. Time, Quantum and Information

    Turner, Leaf [Los Alamos, New Mexico (United States)

    2004-04-09

    Time, Quantum and Information, a paean to Professor Carl Friedrich von Weizsaecker, commemorates his 90th birthday. The range of Professor Weizsaecker'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 Weizsaecker?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 Weizsaecker?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 Weizsaecker?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 Weizsaecker?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 Weizsaecker--Williams technique of calculating the bremsstrahlung of relativistic electrons. But how many of us know of Weizsaecker'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

  19. Quantum information processing in phase space: A modular variables approach

    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.

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

    Sabuncu, Metin; Filip, R.; Leuchs, G.

    2010-01-01

    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...

  1. Experimental measurement-device-independent quantum key distribution with uncharacterized encoding.

    Wang, Chao; Wang, Shuang; Yin, Zhen-Qiang; Chen, Wei; Li, Hong-Wei; Zhang, Chun-Mei; Ding, Yu-Yang; Guo, Guang-Can; Han, Zheng-Fu

    2016-12-01

    Measurement-device-independent quantum key distribution (MDI QKD) is an efficient way to share secrets using untrusted measurement devices. However, the assumption on the characterizations of encoding states is still necessary in this promising protocol, which may lead to unnecessary complexity and potential loopholes in realistic implementations. Here, by using the mismatched-basis statistics, we present the first proof-of-principle experiment of MDI QKD with uncharacterized encoding sources. In this demonstration, the encoded states are only required to be constrained in a two-dimensional Hilbert space, and two distant parties (Alice and Bob) are resistant to state preparation flaws even if they have no idea about the detailed information of their encoding states. The positive final secure key rates of our system exhibit the feasibility of this novel protocol, and demonstrate its value for the application of secure communication with uncharacterized devices.

  2. Quantum information sharing between topologically distinct platforms

    Hou, Chang-Yu; Refael, Gil; Shtengel, Kirill

    2016-12-01

    Can topological quantum entanglement between anyons in one topological medium "stray" into a different, topologically distinct medium? In other words, can quantum information encoded nonlocally in the combined state of non-Abelian anyons be shared between two distinct topological media? For one-dimensional topological superconductors with Majorana bound states at the end of system, the quantum information store in those Majorana bound states can be transfered by directly coupling nearby Majorana bound states. However, coupling of two one-dimensional Majorana states will produce a gap, indicating that distinct topological regions of one-dimensional wires unite into a single topological region through the information transfer process. In this paper, we consider a setup with two two-dimensional p -wave superconductors of opposite chirality adjacent to each other. Even two comoving chiral modes at the domain wall between them cannot be gapped through interactions; we demonstrate that information encoded in the fermionic parity of two Majorana zero modes, originally within the same superconducting domain, can be shared between the domains or moved entirely from one domain to another provided that vortices can tunnel between them in a controlled fashion.

  3. Quantum information and convex optimization

    Reimpell, Michael

    2008-07-01

    This thesis is concerned with convex optimization problems in quantum information theory. It features an iterative algorithm for optimal quantum error correcting codes, a postprocessing method for incomplete tomography data, a method to estimate the amount of entanglement in witness experiments, and it gives necessary and sufficient criteria for the existence of retrodiction strategies for a generalized mean king problem. (orig.)

  4. Universal quantum computation using all-optical hybrid encoding

    郭奇; 程留永; 王洪福; 张寿

    2015-01-01

    By employing displacement operations, single-photon subtractions, and weak cross-Kerr nonlinearity, we propose an alternative way of implementing several universal quantum logical gates for all-optical hybrid qubits encoded in both single-photon polarization state and coherent state. Since these schemes can be straightforwardly implemented only using local operations without teleportation procedure, therefore, less physical resources and simpler operations are required than the existing schemes. With the help of displacement operations, a large phase shift of the coherent state can be obtained via currently available tiny cross-Kerr nonlinearity. Thus, all of these schemes are nearly deterministic and feasible under current technology conditions, which makes them suitable for large-scale quantum computing.

  5. Quantum key distribution based on phase encoding and polarization measurement

    Ma, H Q; Zhao, J L; Ma, Hai-Qiang; Wu, Ling-An; Zhao, Jian-Ling

    2007-01-01

    A one-way quantum key distribution scheme based on intrinsically stable Faraday-mirror type Michelson interferometers with four-port polarizing beampslitters has been demonstrated which can compensate for birefringence effects automatically. The encoding is performed with phase modulators, but decoding is accomplished through measurement of the polarization state of Bob's photons. An extinction ratio of about 30dB was maintained for several hours over 50km of fiber at 1310nm without any adjustment to the setup, which shows its good potential for practical systems

  6. Minimal memory requirements for pearl necklace encoders of quantum convolutional codes

    Houshmand, Monireh; Wilde, Mark M

    2010-01-01

    One of the major goals in quantum computer science is to reduce the overhead associated with the implementation of quantum computers, and inevitably, routines for quantum error correction will account for most of this overhead. A particular technique for quantum error correction that may be useful in the outer layers of a concatenated scheme for fault tolerance is quantum convolutional coding. The encoder for a quantum convolutional code has a representation as a convolutional encoder or as a "pearl necklace" encoder. In the pearl necklace representation, it has not been particularly clear in the research literature how much quantum memory such an encoder would require for implementation. Here, we offer an algorithm that answers this question. The algorithm first constructs a weighted, directed acyclic graph where each vertex of the graph corresponds to a gate string in the pearl necklace encoder, and each path through the graph represents a non-commutative path through gates in the encoder. We show that the ...

  7. Experimental implementation of encoded logical qubit operations in a perfect quantum error correcting code.

    Zhang, Jingfu; Laflamme, Raymond; Suter, Dieter

    2012-09-07

    Large-scale universal quantum computing requires the implementation of quantum error correction (QEC). While the implementation of QEC has already been demonstrated for quantum memories, reliable quantum computing requires also the application of nontrivial logical gate operations to the encoded qubits. Here, we present examples of such operations by implementing, in addition to the identity operation, the NOT and the Hadamard gate to a logical qubit encoded in a five qubit system that allows correction of arbitrary single-qubit errors. We perform quantum process tomography of the encoded gate operations, demonstrate the successful correction of all possible single-qubit errors, and measure the fidelity of the encoded logical gate operations.

  8. Quantum communication and information processing

    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.

  9. Recoverability in quantum information theory

    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. Quantum States as Ordinary Information

    Ken Wharton

    2014-03-01

    Full Text Available Despite various parallels between quantum states and ordinary information, quantum no-go-theorems have convinced many that there is no realistic framework that might underly quantum theory, no reality that quantum states can represent knowledge about. This paper develops the case that there is a plausible underlying reality: one actual spacetime-based history, although with behavior that appears strange when analyzed dynamically (one time-slice at a time. By using a simple model with no dynamical laws, it becomes evident that this behavior is actually quite natural when analyzed “all-at-once” (as in classical action principles. From this perspective, traditional quantum states would represent incomplete information about possible spacetime histories, conditional on the future measurement geometry. Without dynamical laws imposing additional restrictions, those histories can have a classical probability distribution, where exactly one history can be said to represent an underlying reality.

  11. Isotope-based quantum information

    G Plekhanov, Vladimir

    2012-01-01

    The present book provides to the main ideas and techniques of the rapid progressing field of quantum information and quantum computation using isotope - mixed materials. It starts with an introduction to the isotope physics and then describes of the isotope - based quantum information and quantum computation. The ability to manipulate and control electron and/or nucleus spin in semiconductor devices provides a new route to expand the capabilities of inorganic semiconductor-based electronics and to design innovative devices with potential application in quantum computing. One of the major challenges towards these objectives is to develop semiconductor-based systems and architectures in which the spatial distribution of spins and their properties can be controlled. For instance, to eliminate electron spin decoherence resulting from hyperfine interaction due to nuclear spin background, isotopically controlled devices are needed (i.e., nuclear spin-depleted). In other emerging concepts, the control of the spatial...

  12. Foundations of quantum theory and quantum information applications

    Galvão, E F

    2002-01-01

    This thesis establishes a number of connections between foundational issues in quantum theory, and some quantum information applications. It starts with a review of quantum contextuality and non-locality, multipartite entanglement characterisation, and of a few quantum information protocols. Quantum non-locality and contextuality are shown to be essential for different implementations of quantum information protocols known as quantum random access codes and quantum communication complexity protocols. I derive sufficient experimental conditions for tests of these quantum properties. I also discuss how the distribution of quantum information through quantum cloning processes can be useful in quantum computing. Regarding entanglement characterisation, some results are obtained relating two problems, that of additivity of the relative entropy of entanglement, and that of identifying different types of tripartite entanglement in the asymptotic regime of manipulations of many copies of a given state. The thesis end...

  13. Chaos and quantum Fisher information in the quantum kicked top

    Wang Xiao-Qian; Ma Jian; Zhang Xi-He; Wang Xiao-Guang

    2011-01-01

    Quantum Fisher information is related to the problem of parameter estimation. Recently, a criterion has been proposed for entanglement in multipartite systems based on quantum Fisher information. This paper studies the behaviours of quantum Fisher information in the quantum kicked top model, whose classical correspondence can be chaotic. It finds that, first, detected by quantum Fisher information, the quantum kicked top is entangled whether the system is in chaotic or in regular case. Secondly, the quantum Fisher information is larger in chaotic case than that in regular case, which means, the system is more sensitive in the chaotic case.

  14. Quantum Tomograms and Their Application in Quantum Information Science

    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.

  15. Information transfer through quantum channels

    Kretschmann, D.

    2007-03-12

    This PhD thesis represents work done between Aug. 2003 and Dec. 2006 in Reinhard F. Werner's quantum information theory group at Technische Universitaet Braunschweig, and Artur Ekert's Centre for Quantum Computation at the University of Cambridge. My thesis falls into the field of abstract quantum information theory. This work investigates both fundamental properties of quantum channels and their asymptotic capacities for classical as well as quantum information transfer. Stinespring's theorem is the basic structure theorem for quantum channels. It implies that every quantum channel can be represented as a unitary evolution on an enlarged system. In Ch. 3 we present a continuity theorem for Stinespring's representation: two quantum channels are similar if and only if it is possible to find unitary implementations that are likewise similar, with dimension-independent norm bounds. The continuity theorem allows to derive a formulation of the information-disturbance tradeoff in terms of quantum channels, and a continuity estimate for the no-broadcasting principle. In Ch. 4 we then apply the continuity theorem to give a strengthened no-go proof for quantum bit commitment, an important cryptographic primitive. This result also provides a natural characterization of those protocols that fall outside the standard setting of unconditional security, and thus may allow secure bit commitment. We present a new such protocol whose security relies on decoherence in the receiver's lab. Ch. 5 reviews the capacities of quantum channels for the transfer of both classical and quantum information, and investigates several variations in the notion of channel capacity. Memory effects are then investigated in detail in Ch. 6. We advertise a model which is sufficiently general to encompass all causal automata: every quantum process in which the outputs up to any given time t do not depend on the inputs at times t'>t can be represented as a concatenated memory

  16. Interference Phenomena in Quantum Information

    Stefanak, Martin

    2010-01-01

    One of the key features of quantum mechanics is the interference of probability amplitudes. The reason for the appearance of interference is mathematically very simple. It is the linear structure of the Hilbert space which is used for the description of quantum systems. In terms of physics we usually talk about the superposition principle valid for individual and composed quantum objects. So, while the source of interference is understandable it leads in fact to many counter-intuitive physical phenomena which puzzle physicists for almost hundred years. The present thesis studies interference in two seemingly disjoint fields of physics. However, both have strong links to quantum information processing and hence are related. In the first part we study the intriguing properties of quantum walks. In the second part we analyze a sophisticated application of wave packet dynamics in atoms and molecules for factorization of integers. The main body of the thesis is based on the original contributions listed separately...

  17. Quantum Information Science: An Update

    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.

  18. Contract Signature Using Quantum Information

    De Sousa, P B M; Ramos, Rubens Viana; Sousa, Paulo Benicio Melo de

    2006-01-01

    This paper describes how to perform contract signature in a fair way using quantum information. The protocol proposed permits two partners, users of a communication network, to exchange their signatures with non-repudiation. For this, we assume that there is a trustable arbitrator, responsible for the authentication of the signers and that performs a central task in a quantum teleportation protocol of the XOR function between two classical bits.

  19. Quantum information processing by weaving quantum Talbot carpets

    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.

  20. Resource Letter QI-1: Quantum Information

    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. Quantum information science as an approach to complex quantum systems

    Nielsen, M A

    2003-01-01

    What makes quantum information science a science? These notes explore the idea that quantum information science may offer a powerful approach to the study of complex quantum systems. We discuss how to quantify complexity in quantum systems, and argue that there are two qualitatively different types of complex quantum system. We also explore ways of understanding complex quantum dynamics by quantifying the strength of a quantum dynamical operation as a physical resource. This is the text for a talk at the ``Sixth International Conference on Quantum Communication, Measurement and Computing'', held at MIT, July 2002. Viewgraphs for the talk may be found at http://www.qinfo.org/talks/.

  2. Encoding simplicial quantum geometry in group field theories

    Oriti, D [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Muehlenberg 1, D-14476 Golm (Germany); Tlas, T, E-mail: daniele.oriti@aei.mpg.d, E-mail: tamer.tlas@aub.edu.l [Department of Mathematics, American Univeristy of Beirut, Bliss Street, Beirut, PO Box 11-0236 (Lebanon)

    2010-07-07

    An extended group field theory formalism for quantum gravity, based on a field that is a function of both group variables, interpreted as discretized connection, and Lie algebra variables, interpreted as discretized triads, has been proposed recently as an attempt to define models with a clearer link with simplicial geometry. In the context of such a formalism, we introduce a new symmetry requirement on the field. This leads, in 3D, to Feynman amplitudes interpreted as simplicial path integrals based on the Regge action, to a proper relation between the discrete connection and the triad vectors appearing in the Regge action, and to a much more satisfactory and transparent encoding of simplicial geometry already at the level of the group field theory action.

  3. Quantum information and general relativity

    Peres, A

    2004-01-01

    The Einstein-Podolsky-Rosen paradox (1935) is reexamined in the light of Shannon's information theory (1948). The EPR argument did not take into account that the observers' information was localized, like any other physical object. General relativity introduces new problems: there are horizons which act as one-way membranes for the propagation of quantum information, in particular black holes which act like sinks.

  4. On the Automation of Encoding Processes in the Quantum IO Monad

    James Barratt

    2012-10-01

    Full Text Available It is now clear that the use of resilient encoding schemes will be required for any quantum computing device to be realised. However, quantum programmers of the future will not wish to be tied up in the particulars of such encoding schemes. Quantum programming languages and libraries are already being developed, one of which is the Quantum IO Monad. QIO, as it is often abbreviated to, provides an interface to define and simulate quantum computations via a library of functions written in Haskell, a purely functional programming language. A solution is presented that takes an arbitrary QIO program and returns an equivalent program incorporating some specified quantum error correction techniques.

  5. Problems and solutions in quantum computing and quantum information

    Steeb, Willi-Hans

    2012-01-01

    Quantum computing and quantum information are two of the fastest growing and most exciting research fields in physics. Entanglement, teleportation and the possibility of using the non-local behavior of quantum mechanics to factor integers in random polynomial time have also added to this new interest. This book supplies a huge collection of problems in quantum computing and quantum information together with their detailed solutions, which will prove to be invaluable to students as well as researchers in these fields. All the important concepts and topics such as quantum gates and quantum circuits, product Hilbert spaces, entanglement and entanglement measures, deportation, Bell states, Bell inequality, Schmidt decomposition, quantum Fourier transform, magic gate, von Neumann entropy, quantum cryptography, quantum error corrections, number states and Bose operators, coherent states, squeezed states, Gaussian states, POVM measurement, quantum optics networks, beam splitter, phase shifter and Kerr Hamilton opera...

  6. Quantum Information Processing and Quantum Error Correction An Engineering Approach

    Djordjevic, Ivan

    2012-01-01

    Quantum Information Processing and Quantum Error Correction is a self-contained, tutorial-based introduction to quantum information, quantum computation, and quantum error-correction. Assuming no knowledge of quantum mechanics and written at an intuitive level suitable for the engineer, the book gives all the essential principles needed to design and implement quantum electronic and photonic circuits. Numerous examples from a wide area of application are given to show how the principles can be implemented in practice. This book is ideal for the electronics, photonics and computer engineer

  7. A group theoretic approach to quantum information

    Hayashi, Masahito

    2017-01-01

    This textbook is the first one addressing quantum information from the viewpoint of group symmetry. Quantum systems have a group symmetrical structure. This structure enables to handle systematically quantum information processing. However, there is no other textbook focusing on group symmetry for quantum information although there exist many textbooks for group representation. After the mathematical preparation of quantum information, this book discusses quantum entanglement and its quantification by using group symmetry. Group symmetry drastically simplifies the calculation of several entanglement measures although their calculations are usually very difficult to handle. This book treats optimal information processes including quantum state estimation, quantum state cloning, estimation of group action and quantum channel etc. Usually it is very difficult to derive the optimal quantum information processes without asymptotic setting of these topics. However, group symmetry allows to derive these optimal solu...

  8. A hybrid quantum encoding algorithm of vector quantization for image compression

    Pang Chao-Yang; Zhou Zheng-Wei; Guo Guang-Can

    2006-01-01

    Many classical encoding algorithms of vector quantization (VQ) of image compression that can obtain global optimal solution have computational complexity O(N). A pure quantum VQ encoding algorithm with probability of success near 100% has been proposed, that performs operations 45√N times approximately. In this paper, a hybrid quantum VQ encoding algorithm between the classical method and the quantum algorithm is presented. The number of its operations is less than √N for most images, and it is more efficient than the pure quantum algorithm.

  9. Negative entropy and information in quantum mechanics

    Cerf, N. J.; Adami, C.

    1995-01-01

    A framework for a quantum mechanical information theory is introduced that is based entirely on density operators, and gives rise to a unified description of classical correlation and quantum entanglement. Unlike in classical (Shannon) information theory, quantum (von Neumann) conditional entropies can be negative when considering quantum entangled systems, a fact related to quantum non-separability. The possibility that negative (virtual) information can be carried by entangled particles sug...

  10. Information Encoding on a Pseudo Random Noise Radar Waveform

    2013-03-01

    PSEUDO RANDOM NOISE RADAR WAVEFORM THESIS Joshua A. Hardin, Captain, USAF AFIT-ENG-13-M-22 DEPARTMENT OF THE AIR FORCE AIR...protection in the United States. AFIT-ENG-13-M-22 INFORMATION ENCODING ON A PSEUDO RANDOM NOISE RADAR WAVEFORM THESIS Presented to the Faculty...INFORMATION ENCODING ON A PSEUDO RANDOM NOISE RADAR WAVEFORM I. Introduction 1.1 Problem Description Navigation requires knowledge of current

  11. Ion trapping for quantum information processing

    WAN Jin-yin; WANG Yu-zhu; LIU Liang

    2007-01-01

    In this paper we have reviewed the recent pro-gresses on the ion trapping for quantum information process-ing and quantum computation. We have first discussed the basic principle of quantum information theory and then fo-cused on ion trapping for quantum information processing.Many variations, especially the techniques of ion chips, have been investigated since the original ion trap quantum compu-tation scheme was proposed. Full two-dimensional control of multiple ions on an ion chip is promising for the realization of scalable ion trap quantum computation and the implemen-tation of quantum networks.

  12. Minimum-cost quantum measurements for quantum information

    Wallden, Petros; Dunjko, Vedran; Andersson, Erika

    2014-01-01

    Knowing about optimal quantum measurements is important for many applications in quantum information and quantum communication. However, deriving optimal quantum measurements is often difficult. We present a collection of results for minimum-cost quantum measurements, and give examples of how they can be used. Among other results, we show that a minimum-cost measurement for a set of given pure states is formally equivalent to a minimum-error measurement for certain mixed states of those same ...

  13. The decoupling approach to quantum information theory

    Dupuis, Frédéric

    2010-01-01

    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 ha...

  14. Information Processing Structure of Quantum Gravity

    Gyongyosi, Laszlo; Imre, Sandor

    2014-05-01

    The theory of quantum gravity is aimed to fuse general relativity with quantum theory into a more fundamental framework. Quantum gravity provides both the non-fixed causality of general relativity and the quantum uncertainty of quantum mechanics. In a quantum gravity scenario, the causal structure is indefinite and the processes are causally non-separable. We provide a model for the information processing structure of quantum gravity. We show that the quantum gravity environment is an information resource-pool from which valuable information can be extracted. We analyze the structure of the quantum gravity space and the entanglement of the space-time geometry. We study the information transfer capabilities of quantum gravity space and define the quantum gravity channel. We characterize the information transfer of the gravity space and the correlation measure functions of the gravity channel. We investigate the process of stimulated storage for quantum gravity memories, a phenomenon that exploits the information resource-pool property of quantum gravity. The results confirm that the benefits of the quantum gravity space can be exploited in quantum computations, particularly in the development of quantum computers. The results are supported by the grant COST Action MP1006.

  15. Encoding Frequency Information in Lexicalized Grammars

    Carroll, J; Carroll, John; Weir, David

    1997-01-01

    We address the issue of how to associate frequency information with lexicalized grammar formalisms, using Lexicalized Tree Adjoining Grammar as a representative framework. We consider systematically a number of alternative probabilistic frameworks, evaluating their adequacy from both a theoretical and empirical perspective using data from existing large treebanks. We also propose three orthogonal approaches for backing off probability estimates to cope with the large number of parameters involved.

  16. Quantum information and physics: Some future directions

    Preskill, John

    2000-01-01

    I consider some promising future directions for quantum information theory that could influence the development of 21st century physics. Advances in the theory of the distinguishability of superoperators may lead to new strategies for improving the precision of quantum-limited measurements. A better grasp of the properties of multi-partite quantum entanglement may lead to deeper understanding of strongly-coupled dynamics in quantum many-body systems, quantum field theory, and quantum gravity.

  17. The role of quantum discord in quantum information theory

    Streltsov, Alexander [ICFO - The Institute of Photonic Sciences, Castelldefels (Spain)

    2014-07-01

    Quantum correlations beyond entanglement - in particular represented by quantum discord - have become a major research field in the last few years. In this talk we report on the role of quantum discord in several fundamental tasks in quantum information theory. Starting with the role of quantum discord in the quantum measurement process, we also discuss its role in the tasks of information sharing and entanglement distribution. Finally, we also show the limits of these results and present possible ways to go beyond these limits.

  18. Single logical qubit information encoding scheme with the minimal optical decoherence-free subsystem.

    Dong, Li; Wang, Jun-Xi; Li, Qing-Yang; Shen, Hong-Zhi; Dong, Hai-Kuan; Xiu, Xiao-Ming; Gao, Ya-Jun

    2016-03-01

    We present a scheme for encoding single logical qubit information, which is immune to collective decoherence acting on Hilbert space spanned by the corresponding states. The scheme needs a spatial entanglement gate and a polarization entanglement gate, which are realized with the assistance of weak cross-Kerr nonlinear interaction between photons and coherent states via Kerr media. Under the condition of sufficient large phase shifts, single logical qubit information can be encoded into this minimal optical decoherence-free subsystem with near-unity fidelity. Together with the mature techniques of measurement and classical feed forward, simple linear optical elements are applied to complete the encoding task, which offers the feasibility of this scheme for protecting quantum information against decoherence.

  19. How much a quantum measurement is informative?

    Dall' Arno, Michele [Graduate School of Information Science, Nagoya University, Nagoya, 464-8601 (Japan); ICFO-Institut de Ciencies Fotoniques, E-08860 Castelldefels, Barcelona (Spain); Quit Group, Dipartimento di Fisica, via Bassi 6, I-27100 Pavia (Italy); D' Ariano, Giacomo Mauro [Quit Group, Dipartimento di Fisica, via Bassi 6, I-27100 Pavia, Italy and Istituto Nazionale di Fisica Nucleare, Gruppo IV, via Bassi 6, I-27100 Pavia (Italy); Sacchi, Massimiliano F. [Quit Group, Dipartimento di Fisica, via Bassi 6, I-27100 Pavia, Italy and Istituto di Fotonica e Nanotecnologie (INF-CNR), P.zza L. da Vinci 32, I-20133, Milano (Italy)

    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.

  20. Local, nonlocal quantumness and information theoretic measures

    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.

  1. The operational meaning of quantum conditional information

    Devetak, I; Devetak, Igor; Yard, Jon

    2006-01-01

    With a statistical view towards information and noise, information theory derives ultimate limitations on information processing tasks. These limits are generally expressed in terms of entropic measures of information and correlations. Here we answer the quantum information-theoretic question: ``How correlated are two quantum systems from the perspective of a third?" by solving the following `quantum state redistribution' problem. Given an arbitrary quantum state of three systems, where Alice holds two and Bob holds one, what is the cost, in terms of quantum communication and entanglement, for Alice to give one of her parts to Bob? The communication cost gives the first operational interpretation to quantum conditional mutual information. The optimal procedure is self-dual under time reversal and is perfectly composable. This generalizes known protocols such as the state merging and fully quantum Slepian-Wolf protocols, from which almost every known protocol in quantum Shannon theory can be derived.

  2. Pragmatic Information in Quantum Mechanics

    Roederer, Juan G

    2015-01-01

    An objective definition of pragmatic information and the consideration of recent results about information processing in the human brain can help overcome some traditional difficulties with the interpretation of quantum mechanics. Rather than attempting to define information ab initio, I introduce the concept of interaction between material bodies as a primary concept. Two distinct categories can be identified: 1) Interactions which can always be reduced to a superposition of physical interactions (forces) between elementary constituents; 2) Interactions between complex bodies which cannot be reduced to a superposition of interactions between parts, and in which patterns and forms (in space and/or time) play the determining role. Pragmatic information is then defined as the correspondence between a given pattern and the ensuing pattern-specific change. I will show that pragmatic information is a biological concept that plays no active role in the purely physical domain; it only does so when a living organism ...

  3. Examples of minimal-memory, non-catastrophic quantum convolutional encoders

    Wilde, Mark M; Hosseini-Khayat, Saied

    2010-01-01

    One of the most important open questions in the theory of quantum convolutional coding is to determine a minimal-memory, non-catastrophic, polynomial-depth convolutional encoder for an arbitrary quantum convolutional code. Here, we present a technique that finds quantum convolutional encoders with such desirable properties for several example quantum convolutional codes (an exposition of our technique in full generality will appear elsewhere). We first show how to encode the well-studied Forney-Grassl-Guha (FGG) code with an encoder that exploits just one memory qubit (the former Grassl-Roetteler encoder requires 15 memory qubits). We then show how our technique can find an online decoder corresponding to this encoder, and we also detail the operation of our technique on a different example of a quantum convolutional code. Finally, the reduction in memory for the FGG encoder makes it feasible to simulate the performance of a quantum turbo code employing it, and we present the results of such simulations.

  4. Principles and methods of quantum information technologies

    Semba, Kouichi

    2016-01-01

    This book presents the research and development-related results of the “FIRST” Quantum Information Processing Project, which was conducted from 2010 to 2014 with the support of the Council for Science, Technology and Innovation of the Cabinet Office of the Government of Japan. The project supported 33 research groups and explored five areas: quantum communication, quantum metrology and sensing, coherent computing, quantum simulation, and quantum computing. The book is divided into seven main sections. Parts I through V, which consist of twenty chapters, focus on the system and architectural aspects of quantum information technologies, while Parts VI and VII, which consist of eight chapters, discuss the superconducting quantum circuit, semiconductor spin and molecular spin technologies.   Readers will be introduced to new quantum computing schemes such as quantum annealing machines and coherent Ising machines, which have now arisen as alternatives to standard quantum computers and are designed to successf...

  5. Encoding techniques for complex information structures in connectionist systems

    Barnden, John; Srinivas, Kankanahalli

    1990-01-01

    Two general information encoding techniques called relative position encoding and pattern similarity association are presented. They are claimed to be a convenient basis for the connectionist implementation of complex, short term information processing of the sort needed in common sense reasoning, semantic/pragmatic interpretation of natural language utterances, and other types of high level cognitive processing. The relationships of the techniques to other connectionist information-structuring methods, and also to methods used in computers, are discussed in detail. The rich inter-relationships of these other connectionist and computer methods are also clarified. The particular, simple forms are discussed that the relative position encoding and pattern similarity association techniques take in the author's own connectionist system, called Conposit, in order to clarify some issues and to provide evidence that the techniques are indeed useful in practice.

  6. Information quality measurement of medical encoding support based on usability.

    Puentes, John; Montagner, Julien; Lecornu, Laurent; Cauvin, Jean-Michel

    2013-12-01

    Medical encoding support systems for diagnoses and medical procedures are an emerging technology that begins to play a key role in billing, reimbursement, and health policies decisions. A significant problem to exploit these systems is how to measure the appropriateness of any automatically generated list of codes, in terms of fitness for use, i.e. their quality. Until now, only information retrieval performance measurements have been applied to estimate the accuracy of codes lists as quality indicator. Such measurements do not give the value of codes lists for practical medical encoding, and cannot be used to globally compare the quality of multiple codes lists. This paper defines and validates a new encoding information quality measure that addresses the problem of measuring medical codes lists quality. It is based on a usability study of how expert coders and physicians apply computer-assisted medical encoding. The proposed measure, named ADN, evaluates codes Accuracy, Dispersion and Noise, and is adapted to the variable length and content of generated codes lists, coping with limitations of previous measures. According to the ADN measure, the information quality of a codes list is fully represented by a single point, within a suitably constrained feature space. Using one scheme, our approach is reliable to measure and compare the information quality of hundreds of codes lists, showing their practical value for medical encoding. Its pertinence is demonstrated by simulation and application to real data corresponding to 502 inpatient stays in four clinic departments. Results are compared to the consensus of three expert coders who also coded this anonymized database of discharge summaries, and to five information retrieval measures. Information quality assessment applying the ADN measure showed the degree of encoding-support system variability from one clinic department to another, providing a global evaluation of quality measurement trends.

  7. Relativistic quantum information theory and quantum reference frames

    Palmer, Matthew C

    2013-01-01

    This thesis is a compilation of research in relativistic quantum information theory, and research in quantum reference frames. The research in the former category provides a fundamental construction of quantum information theory of localised qubits in curved spacetimes. For example, this concerns quantum experiments on free-space photons and electrons in the vicinity of the Earth. From field theory a description of localised qubits that traverse classical trajectories in curved spacetimes is obtained, for photons and massive spin-1/2 fermions. The equations governing the evolution of the two-dimensional quantum state and its absolute phase are determined. Quantum information theory of these qubits is then developed. The Stern-Gerlach measurement formalism for massive spin-1/2 fermions is also derived from field theory. In the latter category of research, the process of changing reference frames is considered for the case where the reference frames are quantum systems. As part of this process, it is shown that...

  8. Quantum information transfer between topological and conventional charge qubits

    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).

  9. Quantum Information in Space and Time

    Volovich, I V

    2001-01-01

    Many important results in modern quantum information theory have been obtained for an idealized situation when the spacetime dependence of quantum phenomena is neglected. However the transmission and processing of (quantum) information is a physical process in spacetime. Therefore such basic notions in quantum information theory as the notions of composite systems, entangled states and the channel should be formulated in space and time. We emphasize the importance of the investigation of quantum information in space and time. Entangled states in space and time are considered. A modification of Bell`s equation which includes the spacetime variables is suggested. A general relation between quantum theory and theory of classical stochastic processes is proposed. It expresses the condition of local realism in the form of a {\\it noncommutative spectral theorem}. Applications of this relation to the security of quantum key distribution in quantum cryptography are considered.

  10. Measurement and control in quantum information science

    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.

  11. Phase Information in Quantum Oracle Computing

    Machta, J.

    1998-01-01

    Computational devices may be supplied with external sources of information (oracles). Quantum oracles may transmit phase information which is available to a quantum computer but not a classical computer. One consequence of this observation is that there is an oracle which is of no assistance to a classical computer but which allows a quantum computer to solve undecidable problems. Thus useful relativized separations between quantum and classical complexity classes must exclude the transmissio...

  12. Information Processing Structure of Quantum Gravity

    Gyongyosi, Laszlo

    2014-01-01

    The theory of quantum gravity is aimed to fuse general relativity with quantum theory into a more fundamental framework. The space of quantum gravity provides both the non-fixed causality of general relativity and the quantum uncertainty of quantum mechanics. In a quantum gravity scenario, the causal structure is indefinite and the processes are causally non-separable. In this work, we provide a model for the information processing structure of quantum gravity. We show that the quantum gravity environment is an information resource-pool from which valuable information can be extracted. We analyze the structure of the quantum gravity space and the entanglement of the space-time geometry. We study the information transfer capabilities of quantum gravity space and define the quantum gravity channel. We reveal that the quantum gravity space acts as a background noise on the local environment states. We characterize the properties of the noise of the quantum gravity space and show that it allows the separate local...

  13. Introduction to quantum physics and information processing

    Vathsan, Radhika

    2016-01-01

    An Elementary Guide to the State of the Art in the Quantum Information FieldIntroduction to Quantum Physics and Information Processing guides beginners in understanding the current state of research in the novel, interdisciplinary area of quantum information. Suitable for undergraduate and beginning graduate students in physics, mathematics, or engineering, the book goes deep into issues of quantum theory without raising the technical level too much.The text begins with the basics of quantum mechanics required to understand how two-level systems are used as qubits. It goes on to show how quant

  14. Illustrating the concept of quantum information

    Jozsa, R

    2003-01-01

    Over the past decade quantum information theory has developed into a vigorous field of research despite the fact that quantum information, as a precise concept, is undefined. Indeed the very idea of viewing quantum states as carriers of some kind of information (albeit unknowable in classical terms), leads naturally to interesting questions that might otherwise never have been asked, and corresponding new insights. We will discuss some illustrative examples, including a strengthening of the well known no-cloning theorem leading to a property of permanence for quantum information, and considerations arising from information compression that reflect on fundamental issues.

  15. Fisher Information of Wavefunctions: Classical and Quantum

    LUO Shun-Long

    2006-01-01

    A parametric quantum mechanical wavefunction naturally induces parametric probability distributions by taking absolute square, and we can consider its classical Fisher information. On the other hand, it also induces parametric rank-one projections which may be viewed as density operators, and we can talk about its quantum Fisher information. Among many versions of quantum Fisher information, there are two prominent ones. The first,deiined via a quantum score function, was introduced by Helstrom in 1967 and is well known. The second,defined via the square root of the density operator, has its origin in the skew information introduced by Wigner and Yanase in 1963 and remains relatively unnoticed. This study is devoted to investigating the relationships between the classical Fisher information and these two versions of quantum Fisher information for wavefunctions.It is shown that the two versions of quantum Fisher information differ by a factor 2 and that they dominate the classical Fisher information. The non-coincidence of these two versions of quantum Fisher information may be interpreted as a manifestation of quantum discord. We further calculate the difference between the Helstrom quantum Fisher information and the classical Fisher information, and show that it is precisely the instantaneous phase fluctuation of the wavefunctions.

  16. Some Issues in Quantum Information Theory

    Run-Yao Duan; Zheng-Feng Ji; Yuan Feng; Ming-Sheng Ying

    2006-01-01

    Quantum information theory is a new interdisciplinary research field related to quantum mechanics, computer science, information theory, and applied mathematics. It provides completely new paradigms to do information processing tasks by employing the principles of quantum mechanics. In this review, we first survey some of the significant advances in quantum information theory in the last twenty years. We then focus mainly on two special subjects: discrimination of quantum objects and transformations between entanglements. More specifically, we first discuss discrimination of quantum states and quantum apparatus in both global and local settings. Secondly, we present systematical characterizations and equivalence relations of several interesting entanglement transformation phenomena, namely entanglement catalysis,multiple-copy entanglement transformation, and partial entanglement recovery.

  17. Amplification, Redundancy, and Quantum Chernoff Information

    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.

  18. Holography, Quantum Geometry, and Quantum Information Theory

    P. A. Zizzi

    2000-03-01

    Full Text Available Abstract: We interpret the Holographic Conjecture in terms of quantum bits (qubits. N-qubit states are associated with surfaces that are punctured in N points by spin networks' edges labelled by the spin-½ representation of SU(2, which are in a superposed quantum state of spin "up" and spin "down". The formalism is applied in particular to de Sitter horizons, and leads to a picture of the early inflationary universe in terms of quantum computation. A discrete micro-causality emerges, where the time parameter is being defined by the discrete increase of entropy. Then, the model is analysed in the framework of the theory of presheaves (varying sets on a causal set and we get a quantum history. A (bosonic Fock space of the whole history is considered. The Fock space wavefunction, which resembles a Bose-Einstein condensate, undergoes decoherence at the end of inflation. This fact seems to be responsible for the rather low entropy of our universe.

  19. Quantum Darwinism Requires an Extra-Theoretical Assumption of Encoding Redundancy

    Fields, Chris

    2010-10-01

    Observers restricted to the observation of pointer states of apparatus cannot conclusively demonstrate that the pointer of an apparatus mathcal{A} registers the state of a system of interest S without perturbing S. Observers cannot, therefore, conclusively demonstrate that the states of a system S are redundantly encoded by pointer states of multiple independent apparatus without destroying the redundancy of encoding. The redundancy of encoding required by quantum Darwinism must, therefore, be assumed from outside the quantum-mechanical formalism and without the possibility of experimental demonstration.

  20. Encoding color information for visual tracking: Algorithms and benchmark.

    Liang, Pengpeng; Blasch, Erik; Ling, Haibin

    2015-12-01

    While color information is known to provide rich discriminative clues for visual inference, most modern visual trackers limit themselves to the grayscale realm. Despite recent efforts to integrate color in tracking, there is a lack of comprehensive understanding of the role color information can play. In this paper, we attack this problem by conducting a systematic study from both the algorithm and benchmark perspectives. On the algorithm side, we comprehensively encode 10 chromatic models into 16 carefully selected state-of-the-art visual trackers. On the benchmark side, we compile a large set of 128 color sequences with ground truth and challenge factor annotations (e.g., occlusion). A thorough evaluation is conducted by running all the color-encoded trackers, together with two recently proposed color trackers. A further validation is conducted on an RGBD tracking benchmark. The results clearly show the benefit of encoding color information for tracking. We also perform detailed analysis on several issues, including the behavior of various combinations between color model and visual tracker, the degree of difficulty of each sequence for tracking, and how different challenge factors affect the tracking performance. We expect the study to provide the guidance, motivation, and benchmark for future work on encoding color in visual tracking.

  1. Modern Quantum Technologies of Information Security

    Korchenko, Oleksandr; Gnatyuk, Sergiy

    2010-01-01

    In the paper systematization and classification of modern quantum technologies of the information security against cyber-terrorist attack are carried out. The characteristic of the basic directions of quantum cryptography from the viewpoint of used quantum technologies is given. The qualitative analysis of advantages and disadvantages of concrete quantum protocols is made. The current status of a problem of practical quantum cryptography using in telecommunication networks is considered. In particular, the short review of existing commercial systems of quantum key distribution is given.

  2. Matrix Techniques in Quantum Information Science

    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.

  3. Information, disturbance and Hamiltonian quantum feedback control

    Doherty, A C; Jungman, G; Doherty, Andrew C.; Jacobs, Kurt; Jungman, Gerard

    2001-01-01

    We consider separating the problem of designing Hamiltonian quantum feedback control algorithms into a measurement (estimation) strategy and a feedback (control) strategy, and consider optimizing desirable properties of each under the minimal constraint that the available strength of both is limited. This motivates concepts of information extraction and disturbance which are distinct from those usually considered in quantum information theory. Using these concepts we identify an information trade-off in quantum feedback control.

  4. From information geometry to quantum theory

    Goyal, Philip [Perimeter Institute, Waterloo (Canada)], E-mail: pgoyal@perimeterinstitute.ca

    2010-02-15

    In this paper, we show how information geometry, the natural geometry of discrete probability distributions, can be used to derive the quantum formalism. The derivation rests upon three elementary features of quantum phenomena, namely complementarity, measurement simulability, and global gauge invariance. When these features are appropriately formalized within an information geometric framework, and combined with a novel information-theoretic principle, the central features of the finite-dimensional quantum formalism can be reconstructed.

  5. Quantum Encoder and Decoder for Secret Key Distribution with Check Bits

    T. Godhavari

    2013-12-01

    Full Text Available The focus of this study is to develop a novel method of encoding the qubits and use as secret key in public key cryptography. In BB 84 protocol, 50% of the random number (generated at source is used as secret key and the remaining bits are used as “check bits”. The check bits are used to detect the presence of eve as well as the nature of quantum channels. In this protocol, random qubits are encoded using different type of polarizations like horizontal, veritical and diagonal. In the proposed quantum encoder, basic quantum gates are used to encode the random secret key along with the check bits. Quantum key distribution, (a cryptographic mechanism relies on the inherent randomness of quantum mechanics and serves as an option to replace techniques made vulnerable by quantum computing. However, it is still subject to clever forms of eavesdropping and poses a significant challenge to implementation. To study the challenges, quantum circuits are first simulated using QCAD.

  6. Continuous Variables Quantum Information in Noisy Environments

    Berni, Adriano

    The technological progress of the last few decades has brought us the ability of exploiting quantum effects to accomplish a variety of relevant tasks. Yet, quantum phenomena are fragile, and with the ability to engineer quantum information protocols comes the problem of keeping such information...... safe from the detrimental effects of noise and losses. In the present work we investigate continuous variables Gaussian quantum information in noisy environments, studying the effects of various noise sources in the cases of a quantum metrological task, an error correction scheme and discord...... estimation protocol in a realistic thermalized scenario, we investigate the performance of an error correction scheme for elimination of correlated noise in a quantum channel, and we study the robustness of discord-type quantum correlations when subject to additive noise and attenuation....

  7. Quantum theory informational foundations and foils

    Spekkens, Robert

    2016-01-01

    This book provides the first unified overview of the burgeoning research area at the interface between Quantum Foundations and Quantum Information.  Topics include: operational alternatives to quantum theory, information-theoretic reconstructions of the quantum formalism, mathematical frameworks for operational theories, and device-independent features of the set of quantum correlations. Powered by the injection of fresh ideas from the field of Quantum Information and Computation, the foundations of Quantum Mechanics are in the midst of a renaissance. The last two decades have seen an explosion of new results and research directions, attracting broad interest in the scientific community. The variety and number of different approaches, however, makes it challenging for a newcomer to obtain a big picture of the field and of its high-level goals. Here, fourteen original contributions from leading experts in the field cover some of the most promising research directions that have emerged in the new wave of quant...

  8. Quantum information processing and relativistic quantum fields

    Benincasa, Dionigi M. T.; Borsten, Leron; Buck, Michel; Dowker, Fay

    2014-04-01

    It is shown that an ideal measurement of a one-particle wave packet state of a relativistic quantum field in Minkowski spacetime enables superluminal signalling. The result holds for a measurement that takes place over an intervention region in spacetime whose extent in time in some frame is longer than the light-crossing time of the packet in that frame. Moreover, these results are shown to apply not only to ideal measurements but also to unitary transformations that rotate two orthogonal one-particle states into each other. In light of these observations, possible restrictions on the allowed types of intervention are considered. A more physical approach to such questions is to construct explicit models of the interventions as interactions between the field and other quantum systems such as detectors. The prototypical Unruh-DeWitt detector couples to the field operator itself and so most likely respects relativistic causality. On the other hand, detector models which couple to a finite set of frequencies of field modes are shown to lead to superluminal signalling. Such detectors do, however, provide successful phenomenological models of atom-qubits interacting with quantum fields in a cavity but are valid only on time scales many orders of magnitude larger than the light-crossing time of the cavity.

  9. Memory-based quantum repeater in quantum information communication

    Wu Xiang-Sheng

    2004-01-01

    This paper studies the quantum repeater in quantum information communication. We propose to introduce the photon buffer mechanism for storing photons, which uses fibre delay loops as photon memories and a programmable 1 × N switcher for distributing photon delay time. Meanwhile, we also consider entanglement purification and entanglement swapping restoration at an entanglement purification or entanglement swapping failure and introduce a protection link mechanism that allows the photonic quantum repeater of a broken connection to initiate a connection restoration process.

  10. Quantum information, cognition, and music

    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. Decoherence-Free Quantum Information Processing with Four-Photon Entangled States

    Bourennane, M; Gaertner, S; Kurtsiefer, C; Cabello, A; Weinfurter, H; Bourennane, Mohamed; Eibl, Manfred; Gaertner, Sascha; Kurtsiefer, Christian; Cabello, Adan; Weinfurter, Harald

    2004-01-01

    Decoherence-free states protect quantum information from collective noise, the predominant cause of decoherence in current implementations of quantum communication and computation. Here we demonstrate that spontaneous parametric down-conversion can be used to generate four-photon states which enable the encoding of one qubit in a decoherence-free subspace. The immunity against noise is verified by quantum state tomography of the encoded qubit. We show that particular states of the encoded qubit can be distinguished by local measurements on the four photons only.

  12. Distinguishability and accessible information in quantum theory

    Fuchs, C

    1996-01-01

    This document focuses on translating various information-theoretic measures of distinguishability for probability distributions into measures of distin- guishability for quantum states. These measures should have important appli- cations in quantum cryptography and quantum computation theory. The results reported include the following. An exact expression for the quantum fidelity between two mixed states is derived. The optimal measurement that gives rise to it is studied in detail. Several upper and lower bounds on the quantum mutual information are derived via similar techniques and compared to each other. Of note is a simple derivation of the important upper bound first proved by Holevo and an explicit expression for another (tighter) upper bound that appears implicitly in the same derivation. Several upper and lower bounds to the quan- tum Kullback relative information are derived. The measures developed are also applied to ferreting out the extent to which quantum systems must be disturbed by information...

  13. The Quantum Information of Cosmological Correlations

    Lim, Eugene A

    2014-01-01

    It has been shown that the primordial perturbations sourced by inflation are driven to classicality by unitary evolution alone. However, their coupling with the environment such as photons and subsequent decoherence renders the cosmological correlations quantum, losing primordial information in the process. We argue that the quantumness of the resulting cosmological correlations is given by quantum discord, which captures non-classical behavior beyond quantum entanglement. By considering the environment as a quantum channel in which primordial information contained in the perturbations is transmitted to us, we can then ask how much of this information is inaccessible. We show that this amount of information is given by the discord of the joint primordial perturbations-environment system. To illustrate these points, we model the joint system as a mixed bi-modal Gaussian state, and show that quantum discord is dependent on the basis which decoherence occurs.

  14. Manipulating quantum information on the controllable systems or subspaces

    Zhang, Ming

    2010-01-01

    In this paper, we explore how to constructively manipulate quantum information on the controllable systems or subspaces. It is revealed that one can make full use of distinguished properties of Pauli operators to design control Hamiltonian based on the geometric parametrization of quantum states. It is demonstrated in this research that Bang-Bang controls, triangle-function controls and square-function control can be utilized to manipulate controllable qubits or encoded qubits on controllable subspace for both open quantum dynamical systems and uncontrollable closed quantum dynamical systems. Furthermore, we propose a new kind of time-energy performance index to trade-off time and energy resource cost, and comprehensively discuss how to design control magnitude to minimize a kind of time-energy performance. A comparison has been made among these three kind of optimal control. It is underlined in this research that the optimal time performance can be always expressed as J^{*} =\\lamda{\\cdot}t^{*}_{f} +E^{*} for...

  15. Silicon Quantum Dots for Quantum Information Processing

    2013-11-01

    A. J. Ferguson , A. S. Dzurak, and R. G. Clark. Gate-defined quantum dots in intrinsic silicon. Nano Letters, 7(7), 2051 (2007). 4, 21, 44, 68, 99 132...B, 80(7), 075310 (2009). 66 [105] M. Field, C. Smith, M. Pepper , D. Ritchie, J. Frost, G. Jones, and D. Hasko. Measurements of Coulomb blockade with a...transistor as an integrated charge sensor. Applied Physics Letters, 97(26), 262113 (2010). 68, 74 [111] G. Podd, S. Angus, D. Williams, and A. Ferguson

  16. Data detection algorithms for multiplexed quantum dot encoding.

    Goss, Kelly C; Messier, Geoff G; Potter, Mike E

    2012-02-27

    A group of quantum dots can be designed to have a unique spectral emission by varying the size of the quantum dots (wavelength) and number of quantum dots (intensity). This technique has been previously proposed for biological tags and object identification. The potential of this system lies in the ability to have a large number of distinguishable wavelengths and intensity levels. This paper presents a communications system model for MxQDs including the interference between neighbouring QD colours and detector noise. An analytical model of the signal-to-noise ratio of a Charge-Coupled Device (CCD) spectrometer is presented and confirmed with experimental results. We then apply a communications system perspective and propose data detection algorithms that increase the readability of the quantum dots tags. It is demonstrated that multiplexed quantum dot barcodes can be read with 99.7% accuracy using the proposed data detection algorithms in a system with 6 colours and 6 intensity values resulting in 46,655 unique spectral codes.

  17. Photonic quantum information: science and technology.

    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.

  18. Quantum Causality, Stochastics, Trajectories and Information

    Belavkin, V P

    2002-01-01

    A history of the discovery of quantum mechanics and paradoxes of its interpretation is reconsidered from the modern point of view of quantum stochastics and information. It is argued that in the orthodox quantum mechanics there is no place for quantum phenomenology such as events. The development of quantum measurement theory, initiated by von Neumann, and Bell's conceptual critics of hidden variable theories indicated a possibility for resolution of this crisis. This can be done by divorcing the algebra of the dynamical generators and an extended algebra of the potential (quantum) and the actual (classical) observables. The latter, called beables, form the center of the algebra of all observables, as the only visible (macroscopic) observables must be compatible with any hidden (microscopic) observable. It is shown that within this approach quantum causality can be rehabilitated within an extended quantum mechanics (eventum mechanics) in the form of a superselection rule for compatibility of the consistent hi...

  19. Quantum Information Processing and Relativistic Quantum Fields

    Benincasa, Dionigi M T; Buck, Michel; Dowker, Fay

    2014-01-01

    It is shown that an ideal measurement of a one-particle wave packet state of a relativistic quantum field in Minkowski spacetime enables superluminal signalling. The result holds for a measurement that takes place over an intervention region in spacetime whose extent in time in some frame is longer than the light-crossing time of the packet in that frame. Moreover, these results are shown to apply not only to ideal measurements but also to unitary transformations that rotate two orthogonal one-particle states into each other. In light of these observations, possible restrictions on the allowed types of intervention are considered. A more physical approach to such questions is to construct explicit models of the interventions as interactions between the field and other quantum systems such as detectors. The prototypical Unruh-DeWitt detector couples to the field operator itself and so most likely respects relativistic causality. On the other hand, detector models which couple to a finite set of frequencies of ...

  20. Design of quantum VQ iteration and quantum VQ encoding algorithm taking O(√N) steps for data compression

    Pang Chao-Yang; Zhou Zheng-Wei; Chen Ping-Xing; Guo Guang-Can

    2006-01-01

    Vector quantization (VQ) is an important data compression method. The key of the encoding of VQ is to find the closest vector among N vectors for a feature vector. Many classical linear search algorithms take O(N) steps of distance computing between two vectors. The quantum VQ iteration and corresponding quantum VQ encoding algorithm that takes O(√V) steps are presented in this paper. The unitary operation of distance computing can be performed on a number of vectors simultaneously because the quantum state exists in a superposition of states. The quantum VQ iteration comprises three oracles, by contrast many quantum algorithms have only one oracle, such as Shor's factorization algorithm and Grover's algorithm. Entanglement state is generated and used, by contrast the state in Grover's algorithm is not an entanglement state. The quantum VQ iteration is a rotation over subspace, by contrast the Grover iteration is a rotation over global space. The quantum VQ iteration extends the Grover iteration to the more complex search that requires more oracles. The method of the quantum VQ iteration is universal.

  1. Quantum information theory of the Bell-state quantum eraser

    Glick, Jennifer R.; Adami, Christoph

    2017-01-01

    Quantum systems can display particle- or wavelike properties, depending on the type of measurement that is performed on them. The Bell-state quantum eraser is an experiment that brings the duality to the forefront, as a single measurement can retroactively be made to measure particlelike or wavelike properties (or anything in between). Here we develop a unitary information-theoretic description of this and several related quantum measurement situations that sheds light on the trade-off between the quantum and classical features of the measurement. In particular, we show that both the coherence of the quantum state and the classical information obtained from it can be described using only quantum-information-theoretic tools and that those two measures satisfy an equality on account of the chain rule for entropies. The coherence information and the which-path information have simple interpretations in terms of state preparation and state determination and suggest ways to account for the relationship between the classical and the quantum world.

  2. Step-by-step magic state encoding for efficient fault-tolerant quantum computation.

    Goto, Hayato

    2014-12-16

    Quantum error correction allows one to make quantum computers fault-tolerant against unavoidable errors due to decoherence and imperfect physical gate operations. However, the fault-tolerant quantum computation requires impractically large computational resources for useful applications. This is a current major obstacle to the realization of a quantum computer. In particular, magic state distillation, which is a standard approach to universality, consumes the most resources in fault-tolerant quantum computation. For the resource problem, here we propose step-by-step magic state encoding for concatenated quantum codes, where magic states are encoded step by step from the physical level to the logical one. To manage errors during the encoding, we carefully use error detection. Since the sizes of intermediate codes are small, it is expected that the resource overheads will become lower than previous approaches based on the distillation at the logical level. Our simulation results suggest that the resource requirements for a logical magic state will become comparable to those for a single logical controlled-NOT gate. Thus, the present method opens a new possibility for efficient fault-tolerant quantum computation.

  3. Tradeoffs for reliable quantum information storage in 2D systems

    Bravyi, Sergey; Terhal, Barbara

    2009-01-01

    We ask whether there are fundamental limits on storing quantum information reliably in a bounded volume of space. To investigate this question, we study quantum error correcting codes specified by geometrically local commuting constraints on a 2D lattice of finite-dimensional quantum particles. For these 2D systems, we derive a tradeoff between the number of encoded qubits k, the distance of the code d, and the number of particles n. It is shown that kd^2=O(n) where the coefficient in O(n) depends only on the locality of the constraints and dimension of the Hilbert spaces describing individual particles. We show that the analogous tradeoff for the classical information storage is k\\sqrt{d} =O(n).

  4. Transduction and encoding sensory information by skin mechanoreceptors.

    Hao, Jizhe; Bonnet, Caroline; Amsalem, Muriel; Ruel, Jérôme; Delmas, Patrick

    2015-01-01

    Physical contact with the external world occurs through specialized neural structures called mechanoreceptors. Cutaneous mechanoreceptors provide information to the central nervous system (CNS) about touch, pressure, vibration, and skin stretch. The physiological function of these mechanoreceptors is to convert physical forces into neuronal signals. Key questions concern the molecular identity of the mechanoelectric transducer channels and the mechanisms by which the physical parameters of the mechanical stimulus are encoded into patterns of action potentials (APs). Compelling data indicate that the biophysical traits of mechanosensitive channels combined with the collection of voltage-gated channels are essential to describe the nature of the stimulus. Recent research also points to a critical role of the auxiliary cell-nerve ending communication in encoding stimulus properties. This review describes the characteristics of ion channels responsible for translating mechanical stimuli into the neural codes that underlie touch perception and pain.

  5. Quantum metrology from a quantum information science perspective

    Toth, Geza

    2015-01-01

    We summarise 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 Cramer-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 the speed of a quantum evolution, and how it appears in the theory of the quantum Zeno effect. Finally, we explain how uncorrela...

  6. Quantum metrology from a quantum information science perspective

    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’.

  7. Complementarity and Entanglement in Quantum Information Theory

    Tessier, T E

    2004-01-01

    The restrictions that nature places on the distribution of correlations in a multipartite quantum system play fundamental roles in the evolution of such systems, and yield vital insights into the design of protocols for the quantum control of ensembles with potential applications in the field of quantum computing. We show how this entanglement sharing behavior may be studied in increasingly complex systems of both theoretical and experimental significance and demonstrate that entanglement sharing, as well as other unique features of entanglement, e.g. the fact that maximal information about a multipartite quantum system does not necessarily entail maximal information about its component subsystems, may be understood as specific consequences of the phenomenon of complementarity extended to composite quantum systems. We also present a local hidden-variable model supplemented by an efficient amount of classical communication that reproduces the quantum-mechanical predictions for the entire class of Gottesman-Kni...

  8. Random subspaces in quantum information theory

    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.

  9. Generation of a superposition of odd photon number states for quantum information networks

    Neergaard-Nielsen, Jonas Schou; Nielsen, B.; Hettich, C.

    2006-01-01

    Quantum information networks, quantum memories, quantum repeaters, linear optics quantum computers Udgivelsesdato: 25 August......Quantum information networks, quantum memories, quantum repeaters, linear optics quantum computers Udgivelsesdato: 25 August...

  10. Bibliographic guide to the foundations of quantum mechanics and quantum information

    Cabello, A

    2000-01-01

    This is a collection of references (papers, books, preprints, book reviews, Ph. D. thesis, patents, etc.), sorted alphabetically and (some of them) classified by subject, on foundations of quantum mechanics and quantum information. Specifically, it covers hidden variables (``no-go'' theorems, experiments), interpretations of quantum mechanics, entanglement, quantum effects (quantum Zeno effect, quantum erasure, ``interaction-free'' measurements, quantum ``non-demolition'' measurements), quantum information (cryptography, cloning, dense coding, teleportation), and quantum computation.

  11. Information and Entropy in Quantum Theory

    Maroney, O J E

    2004-01-01

    We look at certain thought experiments based upon the 'delayed choice' and 'quantum eraser' interference experiments, which present a complementarity between information gathered from a quantum measurement and interference effects. It has been argued that these experiments show the Bohm interpretation of quantum theory is untenable. We demonstrate that these experiments depend critically upon the assumption that a quantum optics device can operate as a measuring device, and show that, in the context of these experiments, it cannot be consistently understood in this way. By contrast, we then show how the notion of 'active information' in the Bohm interpretation provides a coherent explanation of the phenomena shown in these experiments. We then examine the relationship between information and entropy. The thought experiment connecting these two quantities is the Szilard Engine version of Maxwell's Demon, and it has been suggested that quantum measurement plays a key role in this. We provide the first complete ...

  12. Information Erasure and Recovery in Quantum Memory

    CAI Qing-Yu

    2004-01-01

    We show that information in quantum memory can be erased and recovered perfectly if it is necessary. The fact that the final states of environment are completely determined by the initial states of the system allows an erasure operation to be realized by a swap operation between the system and an ancilla. Therefore, the erased information can be recovered. When there is an irreversible process, e.g. an irreversible operation or a decoherence process, in the erasure process, the information would be erased perpetually. We present that quantum erasure will also give heat dissipation in the environment. A classical limit of quantum erasure is given to coincide with Landauer's erasure principle.

  13. Quantum Games of Continuous Distributed Incomplete Information

    CHEN Xi; QIN Gan; ZHOU Xian-Yi; DU Jiang-Feng

    2005-01-01

    @@ We study two-player quantum games of incomplete information in which both the sides have partial information.The previous results of Du et al. [Phys. Rev. E 68 (2003) 016124] are incorporated in our more general formalism.Because of different roles played by the total information uncertainty and the information asymmetry, the game exhibits many interesting features.

  14. Quantum Measurements, Information and Entropy Production

    Srivastava, Y N; Widom, A

    1999-01-01

    In order to understand the Landau-Lifshitz conjecture on the relationship between quantum measurements and the thermodynamic second law, we discuss the notion of ``diabatic'' and ``adiabatic'' forces exerted by the quantum object on the classical measurement apparatus. The notion of heat and work in measurements is made manifest in this approach, and the relationship between information entropy and thermodynamic entropy is explored.

  15. Microstrip Superconducting Quantum Interference Devices for Quantum Information Science

    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

  16. Quantum information theory with Gaussian systems

    Krueger, O.

    2006-04-06

    This thesis applies ideas and concepts from quantum information theory to systems of continuous-variables such as the quantum harmonic oscillator. The focus is on three topics: the cloning of coherent states, Gaussian quantum cellular automata and Gaussian private channels. Cloning was investigated both for finite-dimensional and for continuous-variable systems. We construct a private quantum channel for the sequential encryption of coherent states with a classical key, where the key elements have finite precision. For the case of independent one-mode input states, we explicitly estimate this precision, i.e. the number of key bits needed per input state, in terms of these parameters. (orig.)

  17. Random matrix techniques in quantum information theory

    Collins, Benoît, E-mail: collins@math.kyoto-u.ac.jp [Department of Mathematics, Kyoto University, Kyoto 606-8502 (Japan); Département de Mathématique et Statistique, Université d’Ottawa, 585 King Edward, Ottawa, Ontario K1N6N5 (Canada); CNRS, Lyon (France); Nechita, Ion, E-mail: nechita@irsamc.ups-tlse.fr [Zentrum Mathematik, M5, Technische Universität München, Boltzmannstrasse 3, 85748 Garching (Germany); Laboratoire de Physique Théorique, CNRS, IRSAMC, Université de Toulouse, UPS, F-31062 Toulouse (France)

    2016-01-15

    The purpose of this review is to present some of the latest developments using random techniques, and in particular, random matrix techniques in quantum information theory. Our review is a blend of a rather exhaustive review and of more detailed examples—coming mainly from research projects in which the authors were involved. We focus on two main topics, random quantum states and random quantum channels. We present results related to entropic quantities, entanglement of typical states, entanglement thresholds, the output set of quantum channels, and violations of the minimum output entropy of random channels.

  18. Optical technologies for quantum information science

    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.

  19. Quantum Information Processing in Disordered and Complex Quantum Systems

    De, A S; Ahufinger, V; Briegel, H J; Sanpera, A; Lewenstein, M; De, Aditi Sen; Sen, Ujjwal; Ahufinger, Veronica; Briegel, Hans J.; Sanpera, Anna; Lewenstein, Maciej

    2005-01-01

    We investigate quantum information processing and manipulations in disordered systems of ultracold atoms and trapped ions. First, we demonstrate generation of entanglement and local realization of quantum gates in a quantum spin glass system. Entanglement in such systems attains significantly high values, after quenched averaging, and has a stable positive value for arbitrary times. Complex systems with long range interactions, such as ion chains or dipolar atomic gases, can be modeled by neural network Hamiltonians. In such systems, we find the characteristic time of persistence of quenched averaged entanglement, and also find the time of its revival.

  20. Quantum Encoding and Entanglement in Terms of Phase Operators Associated with Harmonic Oscillator

    Singh, Manu Pratap; Rajput, B. S.

    2016-10-01

    Realization of qudit quantum computation has been presented in terms of number operator and phase operators associated with one-dimensional harmonic oscillator and it has been demonstrated that the representations of generalized Pauli group, viewed in harmonic oscillator operators, allow the qudits to be explicitly encoded in such systems. The non-Hermitian quantum phase operators contained in decomposition of the annihilation and creation operators associated with harmonic oscillator have been analysed in terms of semi unitary transformations (SUT) and it has been shown that the non-vanishing analytic index for harmonic oscillator leads to an alternative class of quantum anomalies. Choosing unitary transformation and the Hermitian phase operator free from quantum anomalies, the truncated annihilation and creation operators have been obtained for harmonic oscillator and it has been demonstrated that any attempt of removal of quantum anomalies leads to absence of minimum uncertainty.

  1. The g-theorem and quantum information theory

    Casini, Horacio; Torroba, Gonzalo

    2016-01-01

    We study boundary renormalization group flows between boundary conformal field theories in $1+1$ dimensions using methods of quantum information theory. We define an entropic $g$-function for theories with impurities in terms of the relative entanglement entropy, and we prove that this $g$-function decreases along boundary renormalization group flows. This entropic $g$-theorem is valid at zero temperature, and is independent from the $g$-theorem based on the thermal partition function. We also discuss the mutual information in boundary RG flows, and how it encodes the correlations between the impurity and bulk degrees of freedom. Our results provide a quantum-information understanding of (boundary) RG flow as increase of distinguishability between vacuum states.

  2. The g-theorem and quantum information theory

    Casini, Horacio; Landea, Ignacio Salazar; Torroba, Gonzalo

    2016-10-01

    We study boundary renormalization group flows between boundary conformal field theories in 1 + 1 dimensions using methods of quantum information theory. We define an entropic g-function for theories with impurities in terms of the relative entanglement entropy, and we prove that this g-function decreases along boundary renormalization group flows. This entropic g-theorem is valid at zero temperature, and is independent from the g-theorem based on the thermal partition function. We also discuss the mutual information in boundary RG flows, and how it encodes the correlations between the impurity and bulk degrees of freedom. Our results provide a quantum-information understanding of (boundary) RG flow as increase of distinguishability between the UV fixed point and the theory along the RG flow.

  3. Quantum information processing and nuclear magnetic resonance

    Cummins, H K

    2001-01-01

    as spectrometer pulse sequence programs. Quantum computers are information processing devices which operate by and exploit the laws of quantum mechanics, potentially allowing them to solve problems which are intractable using classical computers. This dissertation considers the practical issues involved in one of the more successful implementations to date, nuclear magnetic resonance (NMR). Techniques for dealing with systematic errors are presented, and a quantum protocol is implemented. Chapter 1 is a brief introduction to quantum computation. The physical basis of its efficiency and issues involved in its implementation are discussed. NMR quantum information processing is reviewed in more detail in Chapter 2. Chapter 3 considers some of the errors that may be introduced in the process of implementing an algorithm, and high-level ways of reducing the impact of these errors by using composite rotations. Novel general expressions for stabilising composite rotations are presented in Chapter 4 and a new class o...

  4. Black holes, quantum information, and unitary evolution

    Giddings, Steven B

    2012-01-01

    The unitary crisis for black holes indicates an apparent need to modify local quantum field theory. This paper explores the idea that quantum mechanics and in particular unitarity are fundamental principles, but at the price of familiar locality. Thus, one should seek to parameterize unitary evolution, extending the field theory description of black holes, such that their quantum information is transferred to the external state. This discussion is set in a broader framework of unitary evolution acting on Hilbert spaces comprising subsystems. Here, various constraints can be placed on the dynamics, based on quantum information-theoretic and other general physical considerations, and one can seek to describe dynamics with "minimal" departure from field theory. While usual spacetime locality may not be a precise concept in quantum gravity, approximate locality seems an important ingredient in physics. In such a Hilbert space approach an apparently "coarser" form of localization can be described in terms of tenso...

  5. Extraction of information from a single quantum

    Paraoanu, G. S.

    2011-01-01

    We investigate the possibility of performing quantum tomography on a single qubit with generalized partial measurements and the technique of measurement reversal. Using concepts from statistical decision theory, we prove that, somewhat surprisingly, no information can be obtained using this scheme. It is shown that, irrespective of the measurement technique used, extraction of information from single quanta is at odds with other general principles of quantum physics.

  6. Quantum complexity: Quantum mutual information, complex networks, and emergent phenomena in quantum cellular automata

    Vargas, David L.

    Emerging quantum simulator technologies provide a new challenge to quantum many body theory. Quantifying the emergent order in and predicting the dynamics of such complex quantum systems requires a new approach. We develop such an approach based on complex network analysis of quantum mutual information. First, we establish the usefulness of quantum mutual information complex networks by reproducing the phase diagrams of transverse Ising and Bose-Hubbard models. By quantifying the complexity of quantum cellular automata we then demonstrate the applicability of complex network theory to non-equilibrium quantum dynamics. We conclude with a study of student collaboration networks, correlating a student's role in a collaboration network with their grades. This work thus initiates a quantitative theory of quantum complexity and provides a new tool for physics education research. (Abstract shortened by ProQuest.).

  7. Mind, Matter, Information and Quantum Interpretations

    Reza Maleeh

    2015-07-01

    Full Text Available In this paper I give a new information-theoretic analysis of the formalisms and interpretations of quantum mechanics (QM in general, and of two mainstream interpretations of quantum mechanics in particular: The Copenhagen interpretation and David Bohm’s interpretation of quantum mechanics. Adopting Juan G. Roederer’s reading of the notion of pragmatic information, I argue that pragmatic information is not applicable to the Copenhagen interpretation since the interpretation is primarily concerned with epistemology rather than ontology. However it perfectly fits Bohm’s ontological interpretation of quantum mechanics in the realms of biotic and artificial systems. Viewing Bohm’s interpretation of QM in the context of pragmatic information imposes serious limitations to the qualitative aspect of such an interpretation, making his extension of the notion active information to every level of reality illegitimate. Such limitations lead to the idea that, contrary to Bohm’s claim, mind is not a more subtle aspect of reality via the quantum potential as active information, but the quantum potential as it affects particles in the double-slit experiment represents the non-algorithmic aspect of the mind as a genuine information processing system. This will provide an information-based ground, firstly, for refreshing our views on quantum interpretations and secondly, for a novel qualitative theory of the relationship of mind and matter in which mind-like properties are exclusive attributes of living systems. To this end, I will also take an information-theoretic approach to the notion of intentionality as interpreted by John Searle.

  8. Quantum probabilities: an information-theoretic interpretation

    Bub, Jeffrey

    2010-01-01

    This Chapter develops a realist information-theoretic interpretation of the nonclassical features of quantum probabilities. On this view, what is fundamental in the transition from classical to quantum physics is the recognition that \\emph{information in the physical sense has new structural features}, just as the transition from classical to relativistic physics rests on the recognition that space-time is structurally different than we thought. Hilbert space, the event space of quantum systems, is interpreted as a kinematic (i.e., pre-dynamic) framework for an indeterministic physics, in the sense that the geometric structure of Hilbert space imposes objective probabilistic or information-theoretic constraints on correlations between events, just as the geometric structure of Minkowski space in special relativity imposes spatio-temporal kinematic constraints on events. The interpretation of quantum probabilities is more subjectivist in spirit than other discussions in this book (e.g., the chapter by Timpson)...

  9. Information capacity of quantum observable

    Holevo, A S

    2011-01-01

    In this paper we consider the classical capacities of quantum-classical channels corresponding to measurement of observables. Special attention is paid to the case of continuous observables. We give the formulas for unassisted and entanglement-assisted classical capacities $C,C_{ea}$ and consider some explicitly solvable cases which give new examples of entanglement-breaking channels with $C_{ea}>C.$

  10. Information sharing in Quantum Complex Networks

    Cardillo, Alessio; Zueco, David; Gómez-Gardeñes, Jesús

    2013-01-01

    We introduce the use of entanglement entropy as a tool for studying the amount of information shared between the nodes of quantum complex networks. By considering the ground state of a network of coupled quantum harmonic oscillators, we compute the information that each node has on the rest of the system. We show that the nodes storing the largest amount of information are not the ones with the highest connectivity, but those with intermediate connectivity thus breaking down the usual hierarchical picture of classical networks. We show both numerically and analytically that the mutual information characterizes the network topology. As a byproduct, our results point out that the amount of information available for an external node connecting to a quantum network allows to determine the network topology.

  11. Quantum Computation and Information From Theory to Experiment

    Imai, Hiroshi

    2006-01-01

    Recently, the field of quantum computation and information has been developing through a fusion of results from various research fields in theoretical and practical areas. This book consists of the reviews of selected topics charterized by great progress and cover the field from theoretical areas to experimental ones. It contains fundamental areas, quantum query complexity, quantum statistical inference, quantum cloning, quantum entanglement, additivity. It treats three types of quantum security system, quantum public key cryptography, quantum key distribution, and quantum steganography. A photonic system is highlighted for the realization of quantum information processing.

  12. Measuring the scrambling of quantum information

    Swingle, Brian; Schleier-Smith, Monika; Hayden, Patrick

    2016-01-01

    We provide a protocol to measure out-of-time-order correlation functions. These correlation functions are of theoretical interest for diagnosing the scrambling of quantum information in black holes and strongly interacting quantum systems generally. Measuring them requires an echo-type sequence in which the sign of a many-body Hamiltonian is reversed. We detail an implementation employing cold atoms and cavity quantum electrodynamics to realize the chaotic kicked top model, and we analyze effects of dissipation to verify its feasibility with current technology. Finally, we propose in broad strokes a number of other experimental platforms where similar out-of-time-order correlation functions can be measured.

  13. Quantum Mechanics as Quantum Information (and only a little more)

    Fuchs, C

    2002-01-01

    In this paper, I try once again to cause some good-natured trouble. The issue remains, when will we ever stop burdening the taxpayer with conferences devoted to the quantum foundations? The suspicion is expressed that no end will be in sight until a means is found to reduce quantum theory to two or three statements of crisp physical (rather than abstract, axiomatic) significance. In this regard, no tool appears better calibrated for a direct assault than quantum information theory. Far from a strained application of the latest fad to a time-honored problem, this method holds promise precisely because a large part--but not all--of the structure of quantum theory has always concerned information. It is just that the physics community needs reminding. This paper, though taking quant-ph/0106166 as its core, corrects one mistake and offers several observations beyond the previous version. In particular, I identify one element of quantum mechanics that I would not label a subjective term in the theory--it is the in...

  14. On the realization of quantum Fisher information

    Saha, Aparna; Talukdar, B.; Chatterjee, Supriya

    2017-03-01

    With special attention to the role of information theory in physical sciences we present analytical results for the coordinate- and momentum-space Fisher information of some important one-dimensional quantum systems which differ in spacing of their energy levels. The studies envisaged allow us to relate the coordinate-space information ({I}ρ ) with the familiar energy levels of the quantum system. The corresponding momentum-space information ({I}γ ) does not obey such a simple relationship with the energy spectrum. Our results for the product ({I}ρ {I}γ ) depend quadratically on the principal quantum number n and satisfy an appropriate uncertainty relation derived by Dehesa et al (2007 J. Phys. A: Math. Theor. 40 1845)

  15. Fisher information, nonclassicality and quantum revivals

    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.

  16. Fisher information, nonclassicality and quantum revivals

    Romera, Elvira [Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Santos, Francisco de los, E-mail: dlsantos@onsager.ugr.es [Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Departamento de Electromagnetismo y Física de la Materia, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

    2013-11-08

    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.

  17. Mutual Entropy in Quantum Information and Information Genetics

    Ohya, M

    2004-01-01

    After Shannon, entropy becomes a fundamental quantity to describe not only uncertainity or chaos of a system but also information carried by the system. Shannon's important discovery is to give a mathematical expression of the mutual entropy (information), information transmitted from an input system to an output system, by which communication processes could be analyzed on the stage of mathematical science. In this paper, first we review the quantum mutual entropy and discuss its uses in quantum information theory, and secondly we show how the classical mutual entropy can be used to analyze genomes, in particular, those of HIV.

  18. Encoding and storage of spatial information in the retrosplenial cortex.

    Czajkowski, Rafał; Jayaprakash, Balaji; Wiltgen, Brian; Rogerson, Thomas; Guzman-Karlsson, Mikael C; Barth, Alison L; Trachtenberg, Joshua T; Silva, Alcino J

    2014-06-10

    The retrosplenial cortex (RSC) is part of a network of interconnected cortical, hippocampal, and thalamic structures harboring spatially modulated neurons. The RSC contains head direction cells and connects to the parahippocampal region and anterior thalamus. Manipulations of the RSC can affect spatial and contextual tasks. A considerable amount of evidence implicates the role of the RSC in spatial navigation, but it is unclear whether this structure actually encodes or stores spatial information. We used a transgenic mouse in which the expression of green fluorescent protein was under the control of the immediate early gene c-fos promoter as well as time-lapse two-photon in vivo imaging to monitor neuronal activation triggered by spatial learning in the Morris water maze. We uncovered a repetitive pattern of cell activation in the RSC consistent with the hypothesis that during spatial learning an experience-dependent memory trace is formed in this structure. In support of this hypothesis, we also report three other observations. First, temporary RSC inactivation disrupts performance in a spatial learning task. Second, we show that overexpressing the transcription factor CREB in the RSC with a viral vector, a manipulation known to enhance memory consolidation in other circuits, results in spatial memory enhancements. Third, silencing the viral CREB-expressing neurons with the allatostatin system occludes the spatial memory enhancement. Taken together, these results indicate that the retrosplenial cortex engages in the formation and storage of memory traces for spatial information.

  19. Research on Quantum Algorithms at the Institute for Quantum Information and Matter

    2016-05-29

    Research on Quantum Algorithms at the Institute for Quantum Information and Matter The central goals of our project are (1) to bring large-scale... quantum algorithms , quantum complexity, fault-tolerant quantum computing REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 10. SPONSOR...Research on Quantum Algorithms at the Institute for Quantum Information and Matter Report Title The central goals of our project are (1) to bring large

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

    Xihua Yang; Bolin Xue; Junxiang Zhang; Shiyao Zhu

    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 a...

  1. A Simple Example of ``Quantum Darwinism'': Redundant Information Storage in Many-Spin Environments

    Blume-Kohout, Robin; Zurek, Wojciech H.

    2005-11-01

    As quantum information science approaches the goal of constructing quantum computers, understanding loss of information through decoherence becomes increasingly important. The information about a system that can be obtained from its environment can facilitate quantum control and error correction. Moreover, observers gain most of their information indirectly, by monitoring (primarily photon) environments of the "objects of interest." Exactly how this information is inscribed in the environment is essential for the emergence of "the classical" from the quantum substrate. In this paper, we examine how many-qubit (or many-spin) environments can store information about a single system. The information lost to the environment can be stored redundantly, or it can be encoded in entangled modes of the environment. We go on to show that randomly chosen states of the environment almost always encode the information so that an observer must capture a majority of the environment to deduce the system's state. Conversely, in the states produced by a typical decoherence process, information about a particular observable of the system is stored redundantly. This selective proliferation of "the fittest information" (known as Quantum Darwinism) plays a key role in choosing the preferred, effectively classical observables of macroscopic systems. The developing appreciation that the environment functions not just as a garbage dump, but as a communication channel, is extending our understanding of the environment's role in the quantum-classical transition beyond the traditional paradigm of decoherence.

  2. Irreversibility, Information and Randomness in Quantum Measurements

    Mayburov, S N

    2012-01-01

    Irreversibility in quantum measurements is considered from the point of quantum information theory. For that purpose the information transfer between the measured object S and measuring system O is analyzed. It's found that due to the principal constraints of quantum-mechanical origin, the information about the purity of S state isn't transferred to O during the measurement of arbitraryS observable V. Consequently O can't discriminate the pure and mixed S ensembles with the same . As the result, the random outcomes should be detected by O in V measurement for S pure ensemble of V eigenstate superposition. It's shown that the outcome probabilties obey to Born rule. The influence of O decoherence by its environment is studied, however the account of its effects doesn't change these results principally.

  3. Quantum Fisher information as signature of superradiant quantum phase transition

    Wang, T L; Yang, W; Jin, G R; Lambert, N; Nori, F

    2013-01-01

    The single-mode Dicke model is well-known to undergo a quantum phase transition from the so-called normal phase to the supperradiant phase (hereinafter called the "superradiant quantum phase transition"). Normally, quantum phase transitions are closely related to the critical behavior of quantities such as entanglement, quantum fluctuations, and fidelity. In this paper, we study quantum Fisher information (QFI) of the field mode and that of the atoms in the ground state of the Dicke Hamiltonian. For finite and large enough number of atoms N, our numerical results show that near the critical atom-field coupling, the QFIs of the atomic and the field subsystems can surpass the classical limits, due to the appearance of nonclassical squeezed states. As the coupling increases far beyond the critical point, the two subsystems are in highly mixed states, which degrade the QFI and hence the ultimate phase sensitivity. In the thermodynamic limit, we present analytical results of the QFIs and their relationships with t...

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

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

    2012-04-06

    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.

  5. Nonlocal Quantum Information Transfer Without Superluminal Signalling and Communication

    Walleczek, Jan; Grössing, Gerhard

    2016-09-01

    It is a frequent assumption that—via superluminal information transfers—superluminal signals capable of enabling communication are necessarily exchanged in any quantum theory that posits hidden superluminal influences. However, does the presence of hidden superluminal influences automatically imply superluminal signalling and communication? The non-signalling theorem mediates the apparent conflict between quantum mechanics and the theory of special relativity. However, as a `no-go' theorem there exist two opposing interpretations of the non-signalling constraint: foundational and operational. Concerning Bell's theorem, we argue that Bell employed both interpretations, and that he finally adopted the operational position which is associated often with ontological quantum theory, e.g., de Broglie-Bohm theory. This position we refer to as "effective non-signalling". By contrast, associated with orthodox quantum mechanics is the foundational position referred to here as "axiomatic non-signalling". In search of a decisive communication-theoretic criterion for differentiating between "axiomatic" and "effective" non-signalling, we employ the operational framework offered by Shannon's mathematical theory of communication, whereby we distinguish between Shannon signals and non-Shannon signals. We find that an effective non-signalling theorem represents two sub-theorems: (1) Non-transfer-control (NTC) theorem, and (2) Non-signification-control (NSC) theorem. Employing NTC and NSC theorems, we report that effective, instead of axiomatic, non-signalling is entirely sufficient for prohibiting nonlocal communication. Effective non-signalling prevents the instantaneous, i.e., superluminal, transfer of message-encoded information through the controlled use—by a sender-receiver pair —of informationally-correlated detection events, e.g., in EPR-type experiments. An effective non-signalling theorem allows for nonlocal quantum information transfer yet—at the same time

  6. Quantum information and computation for chemistry

    Kais, Sabre; Rice, Stuart A

    2014-01-01

    Examines the intersection of quantum information and chemical physics The Advances in Chemical Physics series is dedicated to reviewing new and emerging topics as well as the latest developments in traditional areas of study in the field of chemical physics. Each volume features detailed comprehensive analyses coupled with individual points of view that integrate the many disciplines of science that are needed for a full understanding of chemical physics. This volume of the series explores the latest research findings, applications, and new research paths from the quantum information science

  7. Holographic computations of the Quantum Information Metric

    Trivella, Andrea

    2016-01-01

    In this note we show how the Quantum Information Metric can be computed holographically using a perturbative approach. In particular when the deformation of the conformal field theory state is induced by a scalar operator the corresponding bulk configuration reduces to a scalar field perturbatively probing the unperturbed background. We study two concrete examples: a CFT ground state deformed by a primary operator and thermofield double state in $d=2$ deformed by a marginal operator. Finally, we generalize the bulk construction to the case of a multi dimensional parameter space and show that the Quantum Information Metric coincides with the metric of the non-linear sigma model for the corresponding scalar fields.

  8. Quantum control, quantum information processing, and quantum-limited metrology with trapped ions

    Wineland, D J; Barrett, M D; Ben-Kish, A; Bergquist, J C; Blakestad, R B; Bollinger, J J; Britton, J L; Chiaverini, J; De Marco, B L; Hume, D; Itano, W M; Jensen, M; Jost, J D; Knill, E; Koelemeij, J C J; Langer, C; Oskay, W; Ozeri, R; Reichle, R; Rosenband, T; Schätz, T; Schmidt, P O; Seidelin, S

    2005-01-01

    We briefly discuss recent experiments on quantum information processing using trapped ions at NIST. A central theme of this work has been to increase our capabilities in terms of quantum computing protocols, but we have also applied the same concepts to improved metrology, particularly in the area of frequency standards and atomic clocks. Such work may eventually shed light on more fundamental issues, such as the quantum measurement problem.

  9. Noise, errors and information in quantum amplification

    D'Ariano, G M; Maccone, L

    1997-01-01

    We analyze and compare the characterization of a quantum device in terms of noise, transmitted bit-error-rate (BER) and mutual information, showing how the noise description is meaningful only for Gaussian channels. After reviewing the description of a quantum communication channel, we study the insertion of an amplifier. We focus attention on the case of direct detection, where the linear amplifier has a 3 decibels noise figure, which is usually considered an unsurpassable limit, referred to as the standard quantum limit (SQL). Both noise and BER could be reduced using an ideal amplifier, which is feasible in principle. However, just a reduction of noise beyond the SQL does not generally correspond to an improvement of the BER or of the mutual information. This is the case of a laser amplifier, where saturation can greatly reduce the noise figure, although there is no corresponding improvement of the BER. Such mechanism is illustrated on the basis of Monte Carlo simulations.

  10. Photonic Crystal Microcavities for Quantum Information Science

    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

  11. Introduction to the theory of quantum information processing

    Bergou, János A

    2013-01-01

    Introduction to the Theory of Quantum Information Processing provides the material for a one-semester graduate level course on quantum information theory and quantum computing for students who have had a one-year graduate course in quantum mechanics. Many standard subjects are treated, such as density matrices, entanglement, quantum maps, quantum cryptography, and quantum codes. Also included are discussions of quantum machines and quantum walks. In addition, the book provides detailed treatments of several underlying fundamental principles of quantum theory, such as quantum measurements, the no-cloning and no-signaling theorems, and their consequences. Problems of various levels of difficulty supplement the text, with the most challenging problems bringing the reader to the forefront of active research. This book provides a compact introduction to the fascinating and rapidly evolving interdisciplinary field of quantum information theory, and it prepares the reader for doing active research in this area.

  12. Quantum information. Teleportation - cryptography - quantum computer; Quanteninformation. Teleportation - Kryptografie - Quantencomputer

    Koenneker, Carsten (comp.)

    2012-11-01

    The following topics are dealt with: Reality in the test facility, quantum teleportation, the reality of quanta, interaction-free quantum measurement, rules for quantum computers, quantum computers with ions, spintronics with diamond, the limits of the quantum computers, a view in the future of quantum optics. (HSI)

  13. Gravity Dual of Quantum Information Metric

    Miyaji, Masamichi; Shiba, Noburo; Takayanagi, Tadashi; Watanabe, Kento

    2015-01-01

    We study a quantum information metric (or fidelity susceptibility) in conformal field theories with respect to a small perturbation by a primary operator. We argue that its gravity dual is approximately given by a volume of maximal time slice in an AdS spacetime when the perturbation is exactly marginal. We confirm our claim in several examples.

  14. Quantum information processing with optical vortices

    Khoury, Antonio Z. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil)

    2012-07-01

    Full text: In this work we discuss several proposals for quantum information processing using the transverse structure of paraxial beams. Different techniques for production and manipulation of optical vortices have been employed and combined with polarization transformations in order to investigate fundamental properties of quantum entanglement as well as to propose new tools for quantum information processing. As an example, we have recently proposed and demonstrated a controlled NOT (CNOT) gate based on a Michelson interferometer in which the photon polarization is the control bit and the first order transverse mode is the target. The device is based on a single lens design for an astigmatic mode converter that transforms the transverse mode of paraxial optical beams. In analogy with Bell's inequality for two-qubit quantum states, we propose an inequality criterion for the non-separability of the spin-orbit degrees of freedom of a laser beam. A definition of separable and non-separable spin-orbit modes is used in consonance with the one presented in Phys. Rev. Lett. 99, 2007. As the usual Bell's inequality can be violated for entangled two-qubit quantum states, we show both theoretically and experimentally that the proposed spin-orbit inequality criterion can be violated for non-separable modes. The inequality is discussed both in the classical and quantum domains. We propose a polarization to orbital angular momentum teleportation scheme using entangled photon pairs generated by spontaneous parametric down conversion. By making a joint detection of the polarization and angular momentum parity of a single photon, we are able to detect all the Bell-states and perform, in principle, perfect teleportation from a discrete to a continuous system using minimal resources. The proposed protocol implementation demands experimental resources that are currently available in quantum optics laboratories. (author)

  15. Quantum information, oscillations and the psyche

    Martin, F; Carminati, G Galli

    2010-01-01

    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 o...

  16. Information flow in quantum teleportation

    Andrew Whitaker

    2002-08-01

    The flow of information is discussed in the context of quantum teleportation. Situations are described which use a sequence of systems of particles in which, though there is no claim of faster-than-light signaling, it is plausible to suggest that information about measurement procedures in one wing of the apparatus does reach the other end in a non-local manner. The definition of the term ’parameter dependence’ is discussed.

  17. An Improved Quantum Information Hiding Protocol Based on Entanglement Swapping of χ-type Quantum States

    Xu, Shu-Jiang; Chen, Xiu-Bo; Wang, Lian-Hai; Ding, Qing-Yan; Zhang, Shu-Hui

    2016-06-01

    In 2011, Qu et al. proposed a quantum information hiding protocol based on the entanglement swapping of χ-type quantum states. Because a χ-type state can be described by the 4-particle cat states which have good symmetry, the possible output results of the entanglement swapping between a given χ-type state and all of the 16 χ-type states are divided into 8 groups instead of 16 groups of different results when the global phase is not considered. So it is difficult to read out the secret messages since each result occurs twice in each line (column) of the secret messages encoding rule for the original protocol. In fact, a 3-bit instead of a 4-bit secret message can be encoded by performing two unitary transformations on 2 particles of a χ-type quantum state in the original protocol. To overcome this defect, we propose an improved quantum information hiding protocol based on the general term formulas of the entanglement swapping among χ-type states. Supported by the National Natural Science Foundation of China under Grant Nos. 61572297, 61303199, 61272514, and 61373131, the Shandong Provincial Natural Science Foundation of China under Grant Nos. ZR2013FM025, ZR2013FQ001, ZR2014FM003, and ZY2015YL018, the Shandong Provincial Outstanding Research Award Fund for Young Scientists of China under Grant Nos. BS2015DX006 and BS2014DX007, the National Development Foundation for Cryptological Research, China under Grant No. MMJJ201401012, the Priority Academic Program Development of Jiangsu Higher Education Institutions and Jiangsu Collaborative Innovation Center on Atmospheric Environment and Equipment Technology Funds, and the Shandong Academy of Sciences Youth Fund Project, China under Grant Nos. 2015QN003 and 2013QN007

  18. Quantum mechanics and quantum information a guide through the quantum world

    Fayngold, Moses

    2013-01-01

    Alongside a thorough definition of the basic concepts and their interrelations, backed by numerous examples, this textbook features a rare discussion of the quantum information theory. It also deals with other important topics hardly found in the literature, including the Robertson-Schrodinger-relation, angle and angular momentum uncertainties, interaction-free measurements, and the limitations of the no-cloning theorem With its interpretations of quantum mechanics and its discussions of quantum computing, this book is poised to become the standard textbook for advanced undergraduate and beginning graduate quantum mechanics courses and as an essential reference for physics students and physics professionals.

  19. Maximum density of quantum information in a scalable CMOS implementation of the hybrid qubit architecture

    Rotta, Davide; De Michielis, Marco; Ferraro, Elena; Fanciulli, Marco; Prati, Enrico

    2016-06-01

    Scalability from single-qubit operations to multi-qubit circuits for quantum information processing requires architecture-specific implementations. Semiconductor hybrid qubit architecture is a suitable candidate to realize large-scale quantum information processing, as it combines a universal set of logic gates with fast and all-electrical manipulation of qubits. We propose an implementation of hybrid qubits, based on Si metal-oxide-semiconductor (MOS) quantum dots, compatible with the CMOS industrial technological standards. We discuss the realization of multi-qubit circuits capable of fault-tolerant computation and quantum error correction, by evaluating the time and space resources needed for their implementation. As a result, the maximum density of quantum information is extracted from a circuit including eight logical qubits encoded by the [[7, 1, 3

  20. Quantum preparation uncertainty and lack of information

    Rozpędek, Filip; Kaniewski, Jędrzej; Coles, Patrick J.; Wehner, Stephanie

    2017-02-01

    The quantum uncertainty principle famously predicts that there exist measurements that are inherently incompatible, in the sense that their outcomes cannot be predicted simultaneously. In contrast, no such uncertainty exists in the classical domain, where all uncertainty results from ignorance about the exact state of the physical system. Here, we critically examine the concept of preparation uncertainty and ask whether similarly in the quantum regime, some of the uncertainty that we observe can actually also be understood as a lack of information (LOI), albeit a lack of quantum information. We answer this question affirmatively by showing that for the well known measurements employed in BB84 quantum key distribution (Bennett and Brassard 1984 Int. Conf. on Computer System and Signal Processing), the amount of uncertainty can indeed be related to the amount of available information about additional registers determining the choice of the measurement. We proceed to show that also for other measurements the amount of uncertainty is in part connected to a LOI. Finally, we discuss the conceptual implications of our observation to the security of cryptographic protocols that make use of BB84 states.

  1. Quantum information processing with noisy cluster states

    Tame, M S; Kim, M S; Vedral, V

    2005-01-01

    We provide an analysis of basic quantum information processing protocols under the effect of intrinsic non-idealities in cluster states. These non-idealities are based on the introduction of randomness in the entangling steps that create the cluster state and are motivated by the unavoidable imperfections faced in creating entanglement using condensed-matter systems. Aided by the use of an alternative and very efficient method to construct cluster state configurations, which relies on the concatenation of fundamental cluster structures, we address quantum state transfer and various fundamental gate simulations through noisy cluster states. We find that a winning strategy to limit the effects of noise, is the management of small clusters processed via just a few measurements. Our study also reinforces recent ideas related to the optical implementation of a one-way quantum computer.

  2. Revealed Quantum Information in Weak Interaction Processes

    Hiesmayr, B C

    2014-01-01

    We analyze the achievable limits of the quantum information processing of the weak interaction revealed by hyperons with spin. We find that the weak decay process corresponds to an interferometric device with a fixed visibility and fixed phase difference for each hyperon. Nature chooses rather low visibilities expressing a preference to parity conserving or violating processes (except for the decay $\\Sigma^+\\longrightarrow p \\pi^0$). The decay process can be considered as an open quantum channel that carries the information of the hyperon spin to the angular distribution of the momentum of the daughter particles. We find a simple geometrical information theoretic interpretation of this process: two quantization axes are chosen spontaneously with probabilities $\\frac{1\\pm\\alpha}{2}$ where $\\alpha$ is proportional to the visibility times the real part of the phase shift. Differently stated the weak interaction process corresponds to spin measurements with an imperfect Stern-Gerlach apparatus. Equipped with this...

  3. Synchronicity, Quantum Information and the Psyche

    Martin, Francois; Galli Carminati, Giuliana

    2009-01-01

    In this paper we describe synchronicity phenomena. As an explanation of these phenomena we propose quantum entanglement between the psychic realm known as the "unconscious" and also the classical illusion of the collapse of the wave-function. Then, taking the theory of quantum information as a model we consider the human unconscious, pre-consciousness and consciousness as sets of quantum bits (qu-bits). We analyze how there can be communication between these various qu-bit sets. In doing this we are inspired by the theory of nuclear magnetic resonance. In this manner we build quantum processes that permit consciousness to "read" the unconscious and vice-versa. The most elementary interaction, e.g. between a pre-consciousness qu-bit 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 evolu...

  4. Nano and Biological Technology Panel: Quantum Information Science

    2008-12-03

    Electrical Engineering & Telecommunications The University of New South Wales Nano and Biological Technology Panel: Quantum Information Science 26th US Army...Technology Panel: Quantum Information Science 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK...Business School Summary – Quantum Information Science • Quantum information technologies now a reality • First impacts will be secure communications

  5. Integrated Silicon Photonic Transmitter for Polarization-Encoded Quantum Key Distribution

    Ma, Chaoxuan; Tang, Zhiyuan; Mikkelsen, Jared C; Yang, Yisu; Xu, Feihu; Lo, Hoi-Kwong; Poon, Joyce K S

    2016-01-01

    We present a silicon optical transmitter for polarization-encoded quantum key distribution (QKD). The chip was fabricated in a standard silicon photonic foundry process and integrated a pulse generator, intensity modulator, variable optical attenuator, and polarization modulator in a 1.3 mm $\\times$ 3 mm die area. The devices in the photonic circuit meet the requirements for QKD. The transmitter was used in a proof-of-concept demonstration of the BB84 QKD protocol over a 5 km long fiber link.

  6. Observers as Internal Models for Remote Tracking via Encoded Information

    Isidori, Alberto; Marconi, Lorenzo; De Persis, Claudio; Gilles, Ernst Dieter; Graichen, Knut; Meurer, Thomas

    2005-01-01

    In this paper, we consider a servomechanism problem in which the command and control functions are distributed in space, and hence the system consists of different components linked by a communication channel of finite capacity. The desired control goal is achieved by designing appropriate encoders,

  7. Information transfer via implicit encoding with delay time modulation in a time-delay system

    Kye, Won-Ho, E-mail: whkye@kipo.go.kr [Korean Intellectual Property Office, Government Complex Daejeon Building 4, 189, Cheongsa-ro, Seo-gu, Daejeon 302-701 (Korea, Republic of)

    2012-08-20

    A new encoding scheme for information transfer with modulated delay time in a time-delay system is proposed. In the scheme, the message is implicitly encoded into the modulated delay time. The information transfer rate as a function of encoding redundancy in various noise scales is presented and it is analyzed that the implicit encoding scheme (IES) has stronger resistance against channel noise than the explicit encoding scheme (EES). In addition, its advantages in terms of secure communication and feasible applications are discussed. -- Highlights: ► We propose new encoding scheme with delay time modulation. ► The message is implicitly encoded with modulated delay time. ► The proposed scheme shows stronger resistance against channel noise.

  8. Maximum Information and Quantum Prediction Algorithms

    McElwaine, J N

    1997-01-01

    This paper describes an algorithm for selecting a consistent set within the consistent histories approach to quantum mechanics and investigates its properties. The algorithm uses a maximum information principle to select from among the consistent sets formed by projections defined by the Schmidt decomposition. The algorithm unconditionally predicts the possible events in closed quantum systems and ascribes probabilities to these events. A simple spin model is described and a complete classification of all exactly consistent sets of histories formed from Schmidt projections in the model is proved. This result is used to show that for this example the algorithm selects a physically realistic set. Other tentative suggestions in the literature for set selection algorithms using ideas from information theory are discussed.

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

    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

  10. Quantum Information from Graviton-Matter Gas

    Lukasz-Andrzej Glinka

    2007-09-01

    Full Text Available We present basics of conceptually new-type way for explaining of the origin, evolution and current physical properties of our Universe from the graviton-matter gas viewpoint. Quantization method for the Friedmann-Lemaitre Universe based on the canonical Hamilton equations of motion is proposed and quantum information theory way to physics of the Universe is showed. The current contribution from the graviton-matter gas temperature in quintessence approximation is discussed.

  11. Quantum Theory is an Information Theory

    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.

  12. Quantum process discrimination with information from environment

    Wang, Yuan-Mei; Li, Jun-Gang; Zou, Jian; Xu, Bao-Ming

    2016-12-01

    In quantum metrology we usually extract information from the reduced probe system but ignore the information lost inevitably into the environment. However, K. Mølmer [Phys. Rev. Lett. 114, 040401 (2015)] showed that the information lost into the environment has an important effect on improving the successful probability of quantum process discrimination. Here we reconsider the model of a driven atom coupled to an environment and distinguish which of two candidate Hamiltonians governs the dynamics of the whole system. We mainly discuss two measurement methods, one of which obtains only the information from the reduced atom state and the other obtains the information from both the atom and its environment. Interestingly, for the two methods the optimal initial states of the atom, used to improve the successful probability of the process discrimination, are different. By comparing the two methods we find that the partial information from the environment is very useful for the discriminations. Project supported by the National Natural Science Foundation of China (Grant Nos. 11274043, 11375025, and 11005008).

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

    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. Storing Quantum Information via Atomic Dark Resonances

    Caruso, Filippo

    2010-01-01

    In this thesis, after a brief review of some concepts of Quantum Optics, we analyze a three-level atomic system in the conditions of electromagnetically induced transparency (EIT), and we investigate the propagation of a gaussian pulse along a cigar-shaped cloud of both cold and hot atoms in EIT regime. In particular, we show that it is possible to amplify a slow propagating pulse without population inversion. We also analyze the regime of anomalous light propagation showing that it is possible to observe superluminal energy propagation. In these conditions, it is possible to imprint reversibly ('write') the information carried by the photons onto the atoms, specifically as a coherent pattern of atomic spins, and later the information stored in the atomic spins can be transferred back ('read') to the light field, implementing in this way a quantum memory. Besides, we analyze the propagation of a quantum field in an EIT medium sustaining dark state polaritons (DSP) in a quasi-particle picture. Here, the decohe...

  15. Quantum Information Processing using Nonlinear Optical Effects

    Andersen, Lasse Mejling

    of the converted idler depends on the other pump. This allows for temporal-mode-multiplexing. When the effects of nonlinear phase modulation (NPM) are included, the phases of the natural input and output modes are changed, reducing the separability. These effects are to some degree mediated by pre......This PhD thesis treats applications of nonlinear optical effects for quantum information processing. The two main applications are four-wave mixing in the form of Bragg scattering (BS) for quantum-state-preserving frequency conversion, and sum-frequency generation (SFG) in second-order nonlinear...... to obtain a 100 % conversion efficiency is to use multiple stages of frequency conversion, but this setup suffers from the combined effects of NPM. This problem is circumvented by using asymmetrically pumped BS, where one pump is continuous wave. For this setup, NPM is found to only lead to linear phase...

  16. Quantum Mutual Information Along Unitary Orbits

    Jevtic, Sania; Rudolph, Terry

    2011-01-01

    Motivated by thermodynamic considerations, we analyse the variation of the quantum mutual information on a unitary orbit of a bipartite system state, with and without global constraints such as energy conservation. We solve the full optimisation problem for the smallest system of two qubits, and explore thoroughly the effect of unitary operations on the space of reduced-state spectra. We then provide applications of these ideas to physical processes within closed quantum systems, such as a generalized collision model approach to thermal equilibrium and a global Maxwell demon playing tricks on local observers. For higher dimensions, the maximization of correlations is relatively straightforward, however the minimisation of correlations displays non-trivial structures. We characterise a set of separable states in which the minimally correlated state resides, and find a collection of classically correlated states admitting a particular "Young tableau" form. Furthermore, a partial order exists on this set with re...

  17. Informationally complete quantum measurements & entanglement bounds

    Flammia, Steven Thomas

    2007-12-01

    We define a class of measurements which we call pure-state informationally complete (PSI-complete) POVMs. These are measurements which can be used to reconstruct the pure state of a d-dimensional quantum system, but not necessarily a mixed state. We show that 2d measurement outcomes is necessary and sufficient for PSI-completeness. This demonstrates that the measurement complexity (as measured by the number of measurement outcomes) can achieve quadratic improvements when the system is confidently believed to be in a pure state. Next, we consider symmetric informationally complete POVMs (SIC-POVMs). SIC-POVMs are relevant for mixed state quantum tomography, but are not well understood. We prove a theorem related to the conjectured existence of SIC-POVMs showing the uniqueness (up to certain symmetries) of SIC-POVMs of a particular group-covariant type when the dimension of the Hilbert space is a prime number. In the second part of the dissertation, we consider a computational model that has access to only one pure qubit, along with n qubits in the totally mixed state. This model is thought to be capable of performing sonic computational tasks exponentially faster than any known classical algorithm. We show that circuits of this type generally lead to entangled states, but where the entanglement (as measured by the negativity) is bounded by a constant, independent of n, for all bipartite divisions. This suggests that the global nature of entanglement is a more important resource than the magnitude of the entanglement. We then consider multiply constrained bounds on entanglement measures based on convex constraint functions. We outline the general procedure, and then explicitly implement the program for the case of 4 x N quantum systems by bounding the entanglement of formation, the concurrence, and the tangle. Finally, we develop generalized bounds for quantum single-parameter estimation problems for which the coupling to the parameter is described by intrinsic multi

  18. Quantum information paradox: Real or fictitious?

    Abhas Mitra

    2009-09-01

    One of the outstanding puzzles of theoretical physics is whether quantum information indeed gets lost in the case of black hole (BH) evaporation or accretion. Let us recall that quantum mechanics (QM) demands an upper limit on the acceleration of a test particle. On the other hand, it is pointed out here that, if a Schwarzschild BH exists, the acceleration of the test particle would blow up at the event horizon in violation of QM. Thus the concept of an exact BH is in contradiction with QM and quantum gravity (QG). It is also reminded that the mass of a BH actually appears as an integration constant of Einstein equations. And it has been shown that the value of this integration constant is actually zero! Thus even classically, there cannot be finite mass BHs though zero mass BH is allowed. It has been further shown that during continued gravitational collapse, radiation emanating from the contracting object gets trapped within it by the runaway gravitational field. As a consequence, the contracting body attains a quasi-static state where outward trapped radiation pressure gets balanced by inward gravitational pull and the ideal classical BH state is never formed in a finite proper time. In other words, continued gravitational collapse results in an `eternally collapsing object' which is a ball of hot plasma and which is asymptotically approaching the true BH state with = 0 after radiating away its entire mass energy. And if we include QM, this contraction must halt at a radius suggested by the highest QM acceleration. In any case no event horizon (EH) is ever formed and in reality, there is no quantum information paradox.

  19. Topics in quantum information and the theory of open quantum systems

    Oreshkov, Ognyan

    This thesis examines seven topics in quantum information and the theory of open quantum systems. The first one concerns weak measurements and their universality as a means of generating quantum measurements. It is shown that every generalized measurement can be decomposed into a sequence of weak measurements which allows us to think of measurements as resulting form continuous stochastic processes. The second topic concerns an application of the decomposition into weak measurements to the theory of entanglement. Necessary and sufficient differential conditions for entanglement monotones are derived, and are used to find a new entanglement monotone for three-qubit states. The third topic examines the performance of different master equations for the description of non-Markovian dynamics. The system studied is a qubit coupled to a spin bath via the Ising interaction. The fourth topic studies continuous quantum error-correction in the case of non-Markovian decoherence. It is shown that due to the existence of a Zeno regime in non-Markovian dynamics, the performance of continuous quantum error correction may exhibit a quadratic improvement if the time resolution of the error-correcting operations is sufficiently high. The fifth topic concerns conditions for correctability of subsystem codes in the case of continuous decoherence. The obtained conditions on the Lindbladian and the system-environment Hamiltonian can be thought of as generalizations of the previously known conditions for noiseless subsystems to the case where the subsystem is time-dependent. The sixth topic examines the robustness of quantum error-correcting codes against initialization errors. It is shown that operator codes are robust against imperfect initialization without the need for restriction of the standard error-correction conditions. For this purpose, a new measure of fidelity for encoded information is introduced and its properties are discussed. The last topic concerns holonomic quantum

  20. Fluctuation of Quantum Information Density in Curved Time-Space

    BI Qiao

    2007-01-01

    A dynamical equation for quantum information density (QID)in curved spacetime is presented.The related fluctuation of QID with quantum Einstein equation is also discussed,which reveals the measuring of the dynamical mutual information condition using a Gaussian quantum channel.

  1. Magnetic atom lattices for quantum information

    Naber, J.B.

    2016-01-01

    Simply put, a quantum computer aims at solving computational problems using genuine quantum mechanical effects. An important feature is that a quantum computer can simulate the behavior of any other quantum mechanical system. Furthermore, quantum devices are predicted to enable secure communication

  2. Pseudo-random unitary operators for quantum information processing.

    Emerson, Joseph; Weinstein, Yaakov S; Saraceno, Marcos; Lloyd, Seth; Cory, David G

    2003-12-19

    In close analogy to the fundamental role of random numbers in classical information theory, random operators are a basic component of quantum information theory. Unfortunately, the implementation of random unitary operators on a quantum processor is exponentially hard. Here we introduce a method for generating pseudo-random unitary operators that can reproduce those statistical properties of random unitary operators most relevant to quantum information tasks. This method requires exponentially fewer resources, and hence enables the practical application of random unitary operators in quantum communication and information processing protocols. Using a nuclear magnetic resonance quantum processor, we were able to realize pseudorandom unitary operators that reproduce the expected random distribution of matrix elements.

  3. Quantum thermodynamic processes energy and information flow at the nanoscale

    Mahler, Guenter

    2015-01-01

    The point of departure of this book is a triad of themes: information theory, thermodynamics, and quantum mechanics. These are related: thermodynamics and quantum mechanics form the basis of quantum thermodynamics; information and quantum mechanics underly, inter alia, the notorious quantum measurement problem; and information and thermodynamics have much to say about control limits in the tension between micro- and macro-descriptions.Why does the world around us typically look thermal-from cosmology down to individual embedded spins? Do informational measures constitute additional (independen

  4. Quantum: information theory: technological challenge; Computacion Cuantica: un reto tecnologico

    Calixto, M.

    2001-07-01

    The new Quantum Information Theory augurs powerful machines that obey the entangled logic of the subatomic world. Parallelism, entanglement, teleportation, no-cloning and quantum cryptography are typical peculiarities of this novel way of understanding computation. (Author) 24 refs.

  5. A dynamical point of view of Quantum Information: Wigner measures

    Baraviera, A; Lopes, A O; Cunha, M Terra

    2011-01-01

    We analyze a known version of the discrete Wigner function and some connections with Quantum Iterated Funcion Systems. This paper is a follow up of "A dynamical point of view of Quantum Information: entropy and pressure" by the same authors.

  6. Existence of an information unit as a postulate of quantum theory.

    Masanes, Lluís; Müller, Markus P; Augusiak, Remigiusz; Pérez-García, David

    2013-10-08

    Does information play a significant role in the foundations of physics? Information is the abstraction that allows us to refer to the states of systems when we choose to ignore the systems themselves. This is only possible in very particular frameworks, like in classical or quantum theory, or more generally, whenever there exists an information unit such that the state of any system can be reversibly encoded in a sufficient number of such units. In this work, we show how the abstract formalism of quantum theory can be deduced solely from the existence of an information unit with suitable properties, together with two further natural assumptions: the continuity and reversibility of dynamics, and the possibility of characterizing the state of a composite system by local measurements. This constitutes a set of postulates for quantum theory with a simple and direct physical meaning, like the ones of special relativity or thermodynamics, and it articulates a strong connection between physics and information.

  7. Existence of an information unit as a postulate of quantum theory

    Masanes, Lluís; Müller, Markus P.; Augusiak, Remigiusz; Pérez-García, David

    2013-01-01

    Does information play a significant role in the foundations of physics? Information is the abstraction that allows us to refer to the states of systems when we choose to ignore the systems themselves. This is only possible in very particular frameworks, like in classical or quantum theory, or more generally, whenever there exists an information unit such that the state of any system can be reversibly encoded in a sufficient number of such units. In this work, we show how the abstract formalism of quantum theory can be deduced solely from the existence of an information unit with suitable properties, together with two further natural assumptions: the continuity and reversibility of dynamics, and the possibility of characterizing the state of a composite system by local measurements. This constitutes a set of postulates for quantum theory with a simple and direct physical meaning, like the ones of special relativity or thermodynamics, and it articulates a strong connection between physics and information. PMID:24062431

  8. Adaptively measuring the temporal shape of ultrashort single photons for higher-dimensional quantum information processing

    Polycarpou, Constantina; Venturi, Giovanni; Zavatta, Alessandro; Bellini, Marco

    2011-01-01

    A photon is the single excitation of a particular spatiotemporal mode of the electromagnetic field. A precise knowledge of the mode structure is therefore essential for its processing and detection, as well as for applying generic quantum light states to novel technologies. Here we demonstrate an adaptive scheme for reconstructing the arbitrary amplitude and phase spectro-temporal profile of an ultrashort single-photon pulse. The method combines techniques from the fields of ultrafast coherent control and quantum optics to map the mode of a fragile quantum state onto that of an intense coherent field. In addition, we show that the possibility of generating and detecting quantum states in multiple spectro-temporal modes may serve as a basis for encoding qubits (and qudits) into single, broadband, ultrashort, photons. Providing access to a much larger Hilbert space, this scheme may boost the capacity of current quantum information protocols.

  9. Decoding reality the universe as quantum information

    Vedral, Vlatko

    2010-01-01

    In Decoding Reality, Vlatko Vedral offers a mind-stretching look at the deepest questions about the universe--where everything comes from, why things are as they are, what everything is. The most fundamental definition of reality is not matter or energy, he writes, but information--and it is the processing of information that lies at the root of all physical, biological, economic, and social phenomena. This view allows Vedral to address a host of seemingly unrelated questions: Why does DNA bind like it does? What is the ideal diet for longevity? How do you make your first million dollars? We can unify all through the understanding that everything consists of bits of information, he writes, though that raises the question of where these bits come from. To find the answer, he takes us on a guided tour through the bizarre realm of quantum physics. At this sub-sub-subatomic level, we find such things as the interaction of separated quantum particles--what Einstein called "spooky action at a distance." In fact, V...

  10. Measuring orbital interaction using quantum information theory

    Rissler, Joerg [Fachbereich Physik, Philipps-Universitaet Marburg, AG Vielteilchentheorie, Renthof 6, D-35032 Marburg (Germany)], E-mail: rissler@staff.uni-marburg.de; Noack, Reinhard M. [Fachbereich Physik, Philipps-Universitaet Marburg, AG Vielteilchentheorie, Renthof 6, D-35032 Marburg (Germany); White, Steven R. [Department of Physics and Astronomy, University of California, Irvine, CA 92697-4575 (United States)

    2006-04-21

    Quantum information theory gives rise to a straightforward definition of the interaction of electrons I {sub p,q} in two orbitals p,q for a given many-body wave function. A convenient way to calculate the von Neumann entropies needed is presented in this work, and the orbital interaction I {sub p,q} is successfully tested for different types of chemical bonds. As an example of an application of I {sub p,q} beyond the interpretation of wave functions, I {sub p,q} is then used to investigate the ordering problem in the density-matrix renormalization group.

  11. Superconducting circuits for quantum information: an outlook.

    Devoret, M H; Schoelkopf, R J

    2013-03-08

    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.

  12. How Do Expert Soccer Players Encode Visual Information to Make Decisions in Simulated Game Situations?

    Poplu, Gerald; Ripoll, Hubert; Mavromatis, Sebastien; Baratgin, Jean

    2008-01-01

    The aim of this study was to determine what visual information expert soccer players encode when they are asked to make a decision. We used a repetition-priming paradigm to test the hypothesis that experts encode a soccer pattern's structure independently of the players' physical characteristics (i.e., posture and morphology). The participants…

  13. Cryptography from quantum uncertainty in the presence of quantum side information

    Bouman, Niek Johannes

    2012-01-01

    The thesis starts with a high-level introduction into cryptography and quantum mechanics. Chapter 2 gives a theoretical foundation by introducing probability theory, information theory, functional analysis, quantum mechanics and quantum information theory. Chapter 3, 4 and 5 are editions of work pub

  14. Quantum Gravity Sensor by Curvature Energy: their Encoding and Computational Models*

    Francisco Bulnes

    2014-11-01

    Full Text Available Through of the concept of curvature energy encoded in non-harmonic signals due to the effect that characterizes the curvature as a deformation of field in the corresponding resonance space ( and an obstruction to the displacement to the corresponding shape operator is developed and designed a sensor of quantum gravity considering the quantized version of curvature as observable of gravitational field where the space is distorted by the strong interactions between particles, interpreting their observable in this case, as light fields deformations obtained on space-time background. To the application of this measurement we use a hypothetical particle graviton modeled as a magnetic dilaton which must be gauge graviton (gauge boson. Also are obtained several computational models of these photonic measurements, likewise their prototype photonic devices

  15. Landau-Zener transitions in spin qubit encoded in three quantum dots

    Łuczak, Jakub; Bułka, Bogdan R.

    2017-01-01

    We study generation and dynamics of an exchange spin qubit encoded in three coherently coupled quantum dots with three electrons. For two geometries of the system, a linear and a triangular one, the creation and coherent control of the qubit states are performed by the Landau-Zener transitions. In the triangular case, both the qubit states are equivalent and can be easily generated for particular symmetries of the system. If one of the dots is smaller than the others, one can observe Rabi oscillations that can be used for coherent manipulation of the qubit states. The linear system is easier to fabricate; however, then the qubit states are not equivalent, making qubit operations more difficult to control.

  16. Quantum information storage and state transfer based on spin systems

    Song, Z

    2004-01-01

    The idea of quantum state storage is generalized to describe the coherent transfer of quantum information through a coherent data bus. In this universal framework, we comprehensively review our recent systematical investigations to explore the possibility of implementing the physical processes of quantum information storage and state transfer by using quantum spin systems, which may be an isotropic antiferromagnetic spin ladder system or a ferromagnetic Heisenberg spin chain. Our studies emphasize the physical mechanisms and the fundamental problems behind the various protocols for the storage and transfer of quantum information in solid state systems.

  17. Enabling task-based information prioritization via semantic web encodings

    Michaelis, James R.

    2016-05-01

    Modern Soldiers rely upon accurate and actionable information technology to achieve mission objectives. While increasingly rich sensor networks for Areas of Operation (AO) can offer many directions for aiding Soldiers, limitations are imposed by current tactical edge systems on the rate that content can be transmitted. Furthermore, mission tasks will often require very specific sets of information which may easily be drowned out by other content sources. Prior research on Quality and Value of Information (QoI/VoI) has aimed to define ways to prioritize information objects based on their intrinsic attributes (QoI) and perceived value to a consumer (VoI). As part of this effort, established ranking approaches for obtaining Subject Matter Expert (SME) recommendations, such as the Analytic Hierarchy Process (AHP) have been considered. However, limited work has been done to tie Soldier context - such as descriptions of their mission and tasks - back to intrinsic attributes of information objects. As a first step toward addressing the above challenges, this work introduces an ontology-backed approach - rooted in Semantic Web publication practices - for expressing both AHP decision hierarchies and corresponding SME feedback. Following a short discussion on related QoI/VoI research, an ontology-based data structure is introduced for supporting evaluation of Information Objects, using AHP rankings designed to facilitate information object prioritization. Consistent with alternate AHP approaches, prioritization in this approach is based on pairwise comparisons between Information Objects with respect to established criteria, as well as on pairwise comparison of the criteria to assess their relative importance. The paper concludes with a discussion of both ongoing and future work.

  18. Quantum correlations beyond entanglement and their role in quantum information theory

    Streltsov, Alexander

    2015-01-01

    Quantum correlations are not restricted to the well known entanglement investigated in Bell-type experiments. Other forms of correlations, for example quantum discord, have recently been shown to play an important role in several aspects of quantum information theory. First experiments also support these findings. This book is an introduction into this up-and-coming research field and its likely impact on quantum technology. After giving a general introduction to the concept of quantum correlations and their role in quantum information theory, the author describes a number of pertinent results and their implications.

  19. Confabulation in Alzheimer's disease: poor encoding and retrieval of over-learned information.

    Attali, Eve; De Anna, Francesca; Dubois, Bruno; Dalla Barba, Gianfranco

    2009-01-01

    Patients who confabulate retrieve personal habits, repeated events or over-learned information and mistake them for actually experienced, specific unique events. Although some hypotheses favour a disruption of frontal/executive functions operating at retrieval, the respective involvement of encoding and retrieval processes in confabulation is still controversial. The present study sought to investigate experimentally the involvement of encoding and retrieval processes and the interference of over-learned information in the confabulation of Alzheimer's disease patients. Twenty Alzheimer's disease patients and 20 normal controls encoded and retrieved unknown stories, well-known fairy tales (e.g. Snow White) and modified well-known fairy tales (e.g. Little Red Riding Hood is not eaten by the wolf) under three experimental conditions: (i) full attention at encoding and at retrieval; (ii) divided attention at encoding (i.e. performing an attention demanding secondary task) and full attention at retrieval; (iii) full attention at encoding and divided attention at retrieval. We found that confabulations in Alzheimer's disease patients were more frequent for the modified well-known fairy tales and when encoding was weakened by a concurrent secondary task (61%), compared with the other types of stories and experimental conditions. Confabulations in the modified fairy tales always consisted of elements of the original version of the fairy tale (e.g. Little Red Riding Hood is eaten by the wolf). This is the first experimental evidence showing that poor encoding and over-learned information are involved in confabulation in Alzheimer's disease.

  20. Waveform information from quantum mechanical entropy

    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.

  1. Quantum Computers: A New Paradigm in Information Technology

    Mahesh S. Raisinghani

    2001-01-01

    Full Text Available The word 'quantum' comes from the Latin word quantus meaning 'how much'. Quantum computing is a fundamentally new mode of information processing that can be performed only by harnessing physical phenomena unique to quantum mechanics (especially quantum interference. Paul Benioff of the Argonne National Laboratory first applied quantum theory to computers in 1981 and David Deutsch of Oxford proposed quantum parallel computers in 1985, years before the realization of qubits in 1995. However, it may be well into the 21st century before we see quantum computing used at a commercial level for a variety of reasons discussed in this paper. The subject of quantum computing brings together ideas from classical information theory, computer science, and quantum physics. This paper discusses some of the current advances, applications, and chal-lenges of quantum computing as well as its impact on corporate computing and implications for management. It shows how quantum computing can be utilized to process and store information, as well as impact cryptography for perfectly secure communication, algorithmic searching, factorizing large numbers very rapidly, and simulating quantum-mechanical systems efficiently. A broad interdisciplinary effort will be needed if quantum com-puters are to fulfill their destiny as the world's fastest computing devices.

  2. Encoding and reusing linguistic information expressed by Linguistic Properties

    Hagège, Caroline; Bès, Gabriel G.

    2002-01-01

    International audience; This paper presents a way to express linguistic knowledge independently of any algorithmic machinery and of any particular grammatical formalism. This is performed through Linguistic Properties, that will be presented. First, the status of linguistic knowledge in grammars is discussed, then the Linguistic Properties are presented and two experiments are mentioned. They illustrate the reusability of the linguistic information enclosed in these Properties.

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

    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.

  4. Quantum Limitations on the Storage and Transmission of Information

    Bekenstein, J D; Bekenstein, Jacob D.; Schiffer, Marcelo

    1990-01-01

    Information must take up space, must weigh, and its flux must be limited. Quantum limits on communication and information storage leading to these conclusions are here described. Quantum channel capacity theory is reviewed for both steady state and burst communication. An analytic approximation is given for the maximum signal information possible with occupation number signal states as a function of mean signal energy. A theorem guaranteeing that these states are optimal for communication is proved. A heuristic "proof" of the linear bound on communication is given, followed by rigorous proofs for signals with specified mean energy, and for signals with given energy budget. And systems of many parallel quantum channels are shown to obey the linear bound for a natural channel architecture. The time--energy uncertainty principle is reformulated in information language by means of the linear bound. The quantum bound on information storage capacity of quantum mechanical and quantum field devices is reviewed. A sim...

  5. Quantum-Classical Hybrid for Information Processing

    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

  6. Molecular model with quantum mechanical bonding information.

    Bohórquez, Hugo J; Boyd, Russell J; Matta, Chérif F

    2011-11-17

    The molecular structure can be defined quantum mechanically thanks to the theory of atoms in molecules. Here, we report a new molecular model that reflects quantum mechanical properties of the chemical bonds. This graphical representation of molecules is based on the topology of the electron density at the critical points. The eigenvalues of the Hessian are used for depicting the critical points three-dimensionally. The bond path linking two atoms has a thickness that is proportional to the electron density at the bond critical point. The nuclei are represented according to the experimentally determined atomic radii. The resulting molecular structures are similar to the traditional ball and stick ones, with the difference that in this model each object included in the plot provides topological information about the atoms and bonding interactions. As a result, the character and intensity of any given interatomic interaction can be identified by visual inspection, including the noncovalent ones. Because similar bonding interactions have similar plots, this tool permits the visualization of chemical bond transferability, revealing the presence of functional groups in large molecules.

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

    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

  8. Quantum Information Processing in the Radical-Pair Mechanism

    Mouloudakis, K

    2016-01-01

    Radical-ion-pair reactions, central for understanding the avian magnetic compass and spin transport in photosynthetic reaction centers, were recently shown to be a fruitful paradigm of the new synthesis of quantum information science with biological processes. We here show that the master equation so far constituting the theoretical foundation of spin chemistry violates fundamental bounds for the entropy of quantum systems, in particular the Ozawa bound. In contrast, a recently developed theory based on quantum measurements, quantum coherence measures and quantum retrodiction, thus exemplifying the paradigm of quantum biology, satisfies the Ozawa bound as well as the Lanford-Robinson bound on information extraction. By considering the quantum information extracted during the reaction we unravel new magnetic-field effects not conveyed by reaction yields.

  9. What information theory can tell us about quantum reality

    Adami, C

    1998-01-01

    An investigation of Einstein's ``physical'' reality and the concept of quantum reality in terms of information theory suggests a solution to quantum paradoxes such as the Einstein-Podolsky-Rosen (EPR) and the Schroedinger-cat paradoxes. Quantum reality, the picture based on unitarily evolving wavefunctions, is complete, but appears incomplete from the observer's point of view for fundamental reasons arising from the quantum information theory of measurement. Physical reality, the picture based on classically accessible observables is, in the worst case of EPR experiments, unrelated to the quantum reality it purports to reflect. Thus, quantum information theory implies that only correlations, not the correlata, are physically accessible: the mantra of the Ithaca interpretation of quantum mechanics.

  10. Enhanced atom interferometry through quantum information science

    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.

  11. Quantum Stackelberg Duopoly of Continuous Distributed Asymmetric Information

    WANG Xia; YANG Xiao-Hua; MIAO Lin; ZHOU Xiang; HU Cheng-Zheng

    2007-01-01

    The minimal quantization structure is employed to investigate the quantum version of the Stackelberg duopoly with continuous distributed asymmetric information, I.e. The first mover has incomplete information that obeys a continuous distribution while the second mover has complete information. It is found that the effects of the positive quantum entanglement on the outcomes exhibit many interesting features due to the information asymmetry. Moreover, although the first-mover advantage is counteracted by the information asymmetry, the positive quantum entanglement still enhances the first-mover advantage and improves the first-mover tolerance of the information asymmetry beyond the classical limit.

  12. Direct approach to quantum extensions of Fisher information

    CHEN Ping; LUO Shunlong

    2007-01-01

    By manipulating classical Fisher information and employing various derivatives of density operators, and using entirely intuitive and direct methods, we introduce two families of quantum extensions of Fisher information that include those defined via the symmetric logarithmic derivative, via the right logarithmic derivative, via the Bogoliubov-Kubo-Mori derivative, as well as via the derivative in terms of commutators, as special cases. Some fundamental properties of these quantum extensions of Fisher information are investigated, a multi-parameter quantum Cramér-Rao inequality is established, and applications to characterizing quantum uncertainty are illustrated.

  13. Hadamard NMR spectroscopy for two-dimensional quantum information processing and parallel search algorithms.

    Gopinath, T; Kumar, Anil

    2006-12-01

    Hadamard spectroscopy has earlier been used to speed-up multi-dimensional NMR experiments. In this work, we speed-up the two-dimensional quantum computing scheme, by using Hadamard spectroscopy in the indirect dimension, resulting in a scheme which is faster and requires the Fourier transformation only in the direct dimension. Two and three qubit quantum gates are implemented with an extra observer qubit. We also use one-dimensional Hadamard spectroscopy for binary information storage by spatial encoding and implementation of a parallel search algorithm.

  14. The black hole information problem beyond quantum theory

    Mueller, Markus P; Dahlsten, Oscar C O

    2012-01-01

    The origin of black hole entropy and the black hole information problem provide important clues for trying to piece together a quantum theory of gravity. Thus far, discussions on this topic have mostly assumed that in a consistent theory of gravity and quantum mechanics, quantum theory will be unmodified. Here, we examine the black hole information problem in the context of generalisations of quantum theory. In particular, we examine black holes in the setting of generalised probabilistic theories, in which quantum theory and classical probability theory are special cases. We compute the time it takes information to escape a black hole, assuming that information is preserved. We find that under some very general assumptions, the arguments of Page (that information should escape the black hole after half the Hawking photons have been emitted), and the black-hole mirror result of Hayden and Preskill (that information can escape quickly) need to be modified. The modification is determined entirely by what we cal...

  15. Logarithm Versus Square Root:Comparing Quantum Fisher Information

    LUO Shun-Long

    2007-01-01

    In classical statistics,the Fisher information is unique in the sense that it is essentially the only monotone Riemannian metric on the space of probability densities.In quantum theory,this uniqueness breaks down,and there are many natural quantum analogues of the Fisher information,among which two particular versions distinguish themselves by their intuitive and informational significance:The first has its origin in the skew information introduced by Wigner and Yanase in 1963 in the context of quantum measurement,and is defined via the square root of the density operator.The second arises from Helstrom's study of quantum detection in 1967,and is defined via the symmetric logarithmic derivative.The aim of this paper is to compare these two versions of quantum Fisher information,and to establish two informational inequalities relating them.

  16. Confabulation in healthy aging is related to poor encoding and retrieval of over-learned information.

    Attali, Eve; Dalla Barba, Gianfranco

    2013-01-01

    Normal aging is characterized by deficits that cross multiple cognitive domains including episodic memory and attention. Compared to young adults (YA), older adults (OA) not only show reduction in true memories, but also an increase in false memories. In this study we aim to elucidate how the production of confabulation is influenced by encoding and retrieval processes. We hypothesized that in OA, compared to YA, over-learned information interferes with the recall of specific, unique past episodes and this interference should be more prominent when a concurrent task perturbs the encoding of the episodes to be recalled. We tested this hypothesis using an experimental paradigm in which a group of OA and a group of YA had to recall three different types of story: a previously unknown story, a well-known fairy tale (Snow White), and a modified well-known fairy tale (Little Red Riding Hood is not eaten by the wolf), in three different experimental conditions: (1) free encoding and free retrieval; (2) Divided attention (DA) at encoding and free retrieval; and (3) free encoding and DA at retrieval. Results showed that OA produced significantly more confabulations than YA, particularly, in the recall of the modified fairy tale. Moreover, DA at encoding markedly increased the number of confabulations, whereas DA at retrieval had no effect on confabulation. Our findings reveal the implications of two phenomena in the production of confabulation in normal aging: the effect of poor encoding and the interference of strongly represented, over-learned information in episodic memory recall.

  17. Melody recognition revisited: influence of melodic Gestalt on the encoding of relational pitch information.

    Lee, Yune-Sang; Janata, Petr; Frost, Carlton; Martinez, Zachary; Granger, Richard

    2015-02-01

    Melody recognition entails the encoding of pitch intervals between successive notes. While it has been shown that a whole melodic sequence is better encoded than the sum of its constituent intervals, the underlying reasons have remained opaque. Here, we compared listeners' accuracy in encoding the relative pitch distance between two notes (for example, C, E) of an interval to listeners accuracy under the following three modifications: (1) doubling the duration of each note (C - E -), (2) repetition of each note (C, C, E, E), and (3) adding a preceding note (G, C, E). Repeating (2) or adding an extra note (3) improved encoding of relative pitch distance when the melodic sequences were transposed to other keys, but lengthening the duration (1) did not improve encoding relative to the standard two-note interval sequences. Crucially, encoding accuracy was higher with the four-note sequences than with long two-note sequences despite the fact that sensory (pitch) information was held constant. We interpret the results to show that re-forming the Gestalts of two-note intervals into two-note "melodies" results in more accurate encoding of relational pitch information due to a richer structural context in which to embed the interval.

  18. Cavity quantum networks for quantum information processing in decoherence-free subspace

    Hua WEI; Zhi-jiao DENG; Wan-li YANG; Fei ZHOU

    2009-01-01

    We give a brief review on the quantum infor- mation processing in decoherence-free subspace (DFS). We show how to realize the initialization of the entangled quantum states, information transfer and teleportation of quantum states, two-qubit Grover search and how to construct the quantum network in DFS, within the cav- ity QED regime based on a cavity-assisted interaction by single-photon pulses.

  19. Classical and quantum Fisher information in the geometrical formulation of quantum mechanics

    Facchi, Paolo [Dipartimento di Matematica, Universita di Bari, I-70125 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); MECENAS, Universita Federico II di Napoli and Universita di Bari (Italy); Kulkarni, Ravi [Vivekananda Yoga Research Foundation, Bangalore 560 080 (India); Man' ko, V.I., E-mail: manko@na.infn.i [P.N. Lebedev Physical Institute, Leninskii Prospect 53, Moscow 119991 (Russian Federation); Marmo, Giuseppe [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , I-80126 Napoli (Italy); INFN, Sezione di Napoli, I-80126 Napoli (Italy); MECENAS, Universita Federico II di Napoli and Universita di Bari (Italy); Sudarshan, E.C.G. [Department of Physics, University of Texas, Austin, TX 78712 (United States); Ventriglia, Franco [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , I-80126 Napoli (Italy); INFN, Sezione di Napoli, I-80126 Napoli (Italy); MECENAS, Universita Federico II di Napoli and Universita di Bari (Italy)

    2010-11-01

    The tomographic picture of quantum mechanics has brought the description of quantum states closer to that of classical probability and statistics. On the other hand, the geometrical formulation of quantum mechanics introduces a metric tensor and a symplectic tensor (Hermitian tensor) on the space of pure states. By putting these two aspects together, we show that the Fisher information metric, both classical and quantum, can be described by means of the Hermitian tensor on the manifold of pure states.

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

    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.

  1. SAPIENS: Spreading Activation Processor for Information Encoded in Network Structures. Technical Report No. 296.

    Ortony, Andrew; Radin, Dean I.

    The product of researchers' efforts to develop a computer processor which distinguishes between relevant and irrelevant information in the database, Spreading Activation Processor for Information Encoded in Network Structures (SAPIENS) exhibits (1) context sensitivity, (2) efficiency, (3) decreasing activation over time, (4) summation of…

  2. Concepts of a quantum information theory of many letters

    Boström, K J

    2000-01-01

    A theoretical framework is presented allowing the treatment of quantum messages with components of variable length. To this aim a many-letter space is constructed which turns out to be a natural space for quantum messages of this type, generalizing the usual fixed-length quantum information theory which is fully contained within this framework. An observable is defined measuring the amount of quantum information carried by a particular message, with the "qbit" obtaining a second meaning as its unit. A general characterization of quantum codes is given where compression codes are defined by their property of decreasing the average information content of a given a priori message ensemble. A lossless quantum coding scheme - analog to the classical Huffman scheme but different from the Braunstein scheme - is implemented, which not only ensures perfect fidelity in retrieving the original messages but also provides optimal compression.

  3. Quantum theory from first principles an informational approach

    D'Ariano, Giacomo Mauro; Perinotti, Paolo

    2017-01-01

    Quantum theory is the soul of theoretical physics. It is not just a theory of specific physical systems, but rather a new framework with universal applicability. This book shows how we can reconstruct the theory from six information-theoretical principles, by rebuilding the quantum rules from the bottom up. Step by step, the reader will learn how to master the counterintuitive aspects of the quantum world, and how to efficiently reconstruct quantum information protocols from first principles. Using intuitive graphical notation to represent equations, and with shorter and more efficient derivations, the theory can be understood and assimilated with exceptional ease. Offering a radically new perspective on the field, the book contains an efficient course of quantum theory and quantum information for undergraduates. The book is aimed at researchers, professionals, and students in physics, computer science and philosophy, as well as the curious outsider seeking a deeper understanding of the theory.

  4. On the Possibility of Quantum Informational Structural Realism

    Bynum, Terrell Ward

    2013-01-01

    In The Philosophy of Information (2011 book), Luciano Floridi presents an ontological theory of Being qua Being, which he calls "Informational Structural Realism", a theory which applies, he says, to every possible world. He identifies primordial information ("dedomena") as the foundation of any structure in any possible world. The present essay examines Floridi's defense of that theory, as well as his refutation of "Digital Ontology" (which some people might confuse with his own). Then, using Floridi's ontology as a starting point, the present essay adds quantum features to dedomena, yielding an ontological theory for our own universe, Quantum Informational Structural Realism, which provides a metaphysical interpretation of key quantum phenomena, and diminishes the "weirdness" or "spookiness" of quantum mechanics. Key Words: digital ontology, dedomena, structural realism, quantum information, primordial qubit

  5. Quantum information processing with finite resources mathematical foundations

    Tomamichel, Marco

    2016-01-01

    This book provides the reader with the mathematical framework required to fully explore the potential of small quantum information processing devices. As decoherence will continue to limit their size, it is essential to master the conceptual tools which make such investigation possible. A strong emphasis is given to information measures that are essential for the study of devices of finite size, including Rényi entropies and smooth entropies. The presentation is self-contained and includes rigorous and concise proofs of the most important properties of these measures. The first chapters will introduce the formalism of quantum mechanics, with particular emphasis on norms and metrics for quantum states. This is necessary to explore quantum generalizations of Rényi divergence and conditional entropy, information measures that lie at the core of information theory. The smooth entropy framework is discussed next and provides a natural means to lift many arguments from information theory to the quantum setting. F...

  6. Quantum Information Biology: From Theory of Open Quantum Systems to Adaptive Dynamics

    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.

  7. Quantum information science with neutral atoms

    Rakreungdet, Worawarong

    We study a system of neutral atoms trapped in a three-dimensional optical lattice suitable for the encoding, initialization and manipulation of atomic qubits. The qubits are manipulated by applied electromagnetic fields interacting with dipole moments of the atoms via light shifts, Raman transitions, Zeeman shifts, and microwave transitions. Our lattice is formed by three orthogonal one-dimensional lattices, which have different frequencies so that interference terms average to zero. This geometry allows considerable freedom in designing the component one-dimensional lattices, so that they provide not only confinement but also independent control in each dimension. Our atomic qubits are initialized from a laser-cooled atomic sample by Raman sideband cooling in individual lattice potential wells. We have demonstrated accurate and robust one-qubit manipulation using resonant microwave fields. In practice such control operations are always subject to errors, in our case spatial inhomogeneities in the microwave Rabi frequency and the light shifted qubit transition frequency. Observation of qubit dynamics in near real time allows us to minimize these inhomogeneities, and therefore optimize qubit logic gates. For qubits in the lattice, we infer a fidelity of 0.990(3) for a single pi-pulse. We have also explored the use of NMR-type pulse techniques in order to further reduce the effect of errors and thus improve gate robustness in the atom/lattice system. Our schemes for two-qubit quantum logic operations are based on controlled collisional interactions. We have experimented with two schemes in order to probe these collisions. The first involves manipulation of the center-of-mass wavepackets of two qubits in a geometry corresponding to two partially overlapping Mach-Zender interferometers. Unfortunately, this scheme has proven extremely sensitive to phase errors, as the wavepackets are moved by the optical lattice. The other scheme starts with two qubits in spatially

  8. A Matter of Principle: The Principles of Quantum Theory, Dirac's Equation, and Quantum Information

    Plotnitsky, Arkady

    2015-01-01

    This article is concerned with the role of fundamental principles in theoretical physics, especially quantum theory. The fundamental principles of relativity will be 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 for the electron from the principles of relativity and quantum theory, is the main focus of this article. I shall, however, also consider Heisenberg's derivation of quantum mechanics, which inspired Dirac. I argue that Heisenberg's and Dirac's work alike was guided by their adherence to and confidence in the fundamental principles of quantum theory. The final section of the article discusses the recent work by G. M. D' Ariano and his coworkers on the principles of quantum information theory, which extends quantum theory and its principles in a new direction. This extension enabled them to offer a new derivation of Dirac's equation from these principles alone...

  9. Transition from Quantum to Classical Information in a Superfluid

    Granik, A

    2003-01-01

    Whereas the entropy of any deterministic classical system described by a principle of least action is zero, one can assign a "carry quantum information" to quantum mechanical degree of freedom equal to Hausdorff area of the deviation from a classical path. This raises the question whether superfluids have a quantum information. We show that in general the transition from the classical to quantum behavior depends on the probing length scale, and occurs for microscopic length scales, except when the interactions between the particles are very weak. This transition explains why, on macroscopic length scales, physics is described by classical equations.

  10. Can visual information encoded in cortical columns be decoded from magnetoencephalography data in humans?

    Cichy, Radoslaw Martin; Ramirez, Fernando Mario; Pantazis, Dimitrios

    2015-11-01

    It is a principal open question whether noninvasive imaging methods in humans can decode information encoded at a spatial scale as fine as the basic functional unit of cortex: cortical columns. We addressed this question in five magnetoencephalography (MEG) experiments by investigating a columnar-level encoded visual feature: contrast edge orientation. We found that MEG signals contained orientation-specific information as early as approximately 50 ms after stimulus onset even when controlling for confounds, such as overrepresentation of particular orientations, stimulus edge interactions, and global form-related signals. Theoretical modeling confirmed the plausibility of this empirical result. An essential consequence of our results is that information encoded in the human brain at the level of cortical columns should in general be accessible by multivariate analysis of electrophysiological signals.

  11. The future (and past) of quantum theory after the Higgs boson: a quantum-informational viewpoint.

    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.

  12. Realism and Antirealism in Informational Foundations of Quantum Theory

    Tina Bilban

    2014-08-01

    Full Text Available Zeilinger-Brukner's informational foundations of quantum theory, a theory based on Zeilinger's foundational principle for quantum mechanics that an elementary system carried one bit of information, explains seemingly unintuitive quantum behavior with simple theoretical framework. It is based on the notion that distinction between reality and information cannot be made, therefore they are the same. As the critics of informational foundations of quantum theory show, this antirealistic move captures the theory in tautology, where information only refers to itself, while the relationships outside the information with the help of which the nature of information would be defined are lost and the questions "Whose information? Information about what?" cannot be answered. The critic's solution is a return to realism, where the observer's effects on the information are neglected. We show that radical antirealism of informational foundations of quantum theory is not necessary and that the return to realism is not the only way forward. A comprehensive approach that exceeds mere realism and antirealism is also possible: we can consider both sources of the constraints on the information, those coming from the observer and those coming from the observed system/nature/reality. The information is always the observer's information about the observed. Such a comprehensive philosophical approach can still support the theoretical framework of informational foundations of quantum theory: If we take that one bit is the smallest amount of information in the form of which the observed reality can be grasped by the observer, we can say that an elementary system (grasped and defined as such by the observer correlates to one bit of information. Our approach thus explains all the features of the quantum behavior explained by informational foundations of quantum theory: the wave function and its collapse, entanglement, complementarity and quantum randomness. However, it does

  13. Geometric phase, quantum Fisher information, geometric quantum correlation and quantum phase transition in the cavity-Bose-Einstein-condensate system

    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.

  14. Quantum channel for the transmission of information

    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.

  15. Quantum information processing with mesoscopic photonic states

    Madsen, Lars Skovgaard

    2012-01-01

    The thesis is built up around a versatile optical experimental setup based on a laser, two optical parametric ampliers, a few sets of modulators and two sets of homodyne detectors, which together with passive linear optics generate, process and characterize various types of Gaussian quantum states....... Using this setup we have experimentally and theoretically investigated Gaussian quantum discord, continuous variable quantum key distribution and quantum polarization. The Gaussian discord broadens the definition of non-classical correlations from entanglement, to all types of correlations which cannot...... in the mixture of coherent states. Further we investigate the robustness of the discord of a broader range of states and suggest a toolbox of states which can be used to test if a protocol is discord based, before performing a rigid proof. Gaussian quantum key distribution can be implemented with current...

  16. Decoherence, Entanglement and Information Protection in Complex Quantum Systems

    Akulin, V.M; Kurizki, G; Pellegrin, S

    2005-01-01

    This book is a collection of articles on the contemporary status of quantum mechanics, dedicated to the fundamental issues of entanglement, decoherence, irreversibility, information processing, and control of quantum evolution, with a view of possible applications. It has multidisciplinary character and is addressed at a broad readership in physics, computer science, chemistry, and electrical engineering. It is written by the world-leading experts in pertinent fields such as quantum computing, atomic, molecular and optical physics, condensed matter physics, and statistical physics.

  17. Schrodinger cats and their power for quantum information processing

    Gilchrist, A; Munro, W J; Ralph, T C; Glancy, S; Braunstein, S L; Milburn, G J; Nemoto, Kae; Braunstein, Samuel. L.

    2003-01-01

    We outline a toolbox comprised of passive optical elements, single photon detection and superpositions of coherent states (Schrodinger cat states). Such a toolbox is a powerful collection of primitives for quantum information processing tasks. We illustrate its use by outlining a proposal for universal quantum computation. We utilize this toolbox for quantum metrology applications, for instance weak force measurements and precise phase estimation. We show in both these cases that a sensitivity at the Heisenberg limit is achievable.

  18. BOOK REVIEW: Time, Quantum and Information

    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

  19. La Saturated Absorption Spectroscopy for Applications in Quantum Information

    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.

  20. Quantum Teleportation with an Accelerated Observer and Black Hole Information

    Shiokawa, K

    2009-01-01

    Nonperturbative analysis of quantum entanglement and quantum teleportation protocol using oscillator variables carried by observers in relativistic motion under the continuous influence of the environment is given. The full time evolution of quantum entanglement among static and accelerated observers is studied. The environment plays a dual role. While it creates bipartite and tripartite entanglement among observers even when the initial state is separable, it suppresses the entanglement via decoherence. Motivated by the black hole information problem, we consider quantum teleportation between static and accelerated observers. Acceleration of the observer suppresses fidelity of teleportation. Some of the quantum information escapes outside of the horizon in the form of bipartite and tripartite entanglement during the teleportation process. Explicit calculation of information loss is provided. In addition to the loss due to the interaction with the environment, there is an intrinsic loss originated in a measur...

  1. A quantum information theoretic analysis of three flavor neutrino oscillations

    Banerjee, Subhashish; Srikanth, R; Hiesmayr, Beatrix C

    2015-01-01

    Correlations exhibited by neutrino oscillations are studied via quantum information theoretic quantities. We show that the strongest type of entanglement, genuine multipartite entanglement, is persistent in the flavour changing states. We prove the existence of Bell-type nonlocal features, in both its absolute and genuine avatars. Finally, we show that a measure of nonclassicality, dissension, which is a generalization of quantum discord to the tripartite case, is nonzero for almost the entire range of time in the evolution of an initial electron-neutrino. Via these quantum information theoretic quantities capturing different aspects of quantum correlations, we elucidate the differences between the flavour types, shedding light on the quantum-information theoretic aspects of the weak force.

  2. Deterministic multimode photonic device for quantum-information processing

    Nielsen, Anne Ersbak Bang; Mølmer, Klaus

    2010-01-01

    We propose the implementation of a light source that can deterministically generate a rich variety of multimode quantum states. The desired states are encoded in the collective population of different ground hyperfine states of an atomic ensemble and converted to multimode photonic states...... by excitation to optically excited levels followed by cooperative spontaneous emission. Among our examples of applications, we demonstrate how two-photon-entangled states can be prepared and implemented in a protocol for a reference-frame-free quantum key distribution and how one-dimensional as well as higher...

  3. Two-way quantum communication: Generalization of secure quantum information exchange to quantum network

    Maurya Ajay K; Mishra Manoj K; Prakash Hari

    2016-03-01

    The idea of secure quantum information exchange (SQIE) [{\\it J. Phys. B: At. Mol. Opt. Phys.} 44, 115504 (2011)] is introduced for the secure exchange of single qubit information states between two legitimate users, Alice and Bob. In the present paper, we extend this original SQIE protocol by presenting a scheme, which enables the secure exchange of n-single qubit information states among the n nodes of a quantum network, with the aid of a special kind of 4$n$-qubit entangled state and the classical assistance of an extra participant Charlie. For experimental realization of our extended SQIE protocol, we suggest an efficient scheme for the generation of a special kind of 4n-qubit entangled state using the interaction between highly detuned $\\Lambda$-type three-level atoms and optical coherent field. Further, by discussing the various experimental parameters, we show that the special kind 4$n$-qubit entangled state can be generated with the presently available technology.

  4. Physics Colloquium: The optical route to quantum information processing

    Université de Genève

    2011-01-01

    Geneva University Physics Department 24, Quai Ernest Ansermet CH-1211 Geneva 4 Monday 11 April 2011 17h00 - Ecole de Physique, Auditoire Stückelberg The optical route to quantum information processing Prof. Terry Rudolph/Imperial College, London Photons are attractive as carriers of quantum information both because they travel, and can thus transmit information, but also because of their good coherence properties and ease in undergoing single-qubit manipulations. The main obstacle to their use in information processing is inducing an effective interaction between them in order to produce entanglement. The most promising approach in photon-based information processing architectures is so-called measurement-based quantum computing. This relies on creating upfront a multi-qubit highly entangled state (the cluster state) which has the remarkable property that, once prepared, it can be used to perform quantum computation by making only single qubit measurements. In this talk I will discuss generically the...

  5. Uncertainty relations based on skew information with quantum memory

    Ma, ZhiHao; Chen, ZhiHua; Fei, Shao-Ming

    2017-01-01

    We present a new uncertainty relation by defining a measure of uncertainty based on skew information. For bipartite systems, we establish uncertainty relations with the existence of a quantum memory. A general relation between quantum correlations and tight bounds of uncertainty has been presented.

  6. Quantum teleportation and entanglement. A hybrid approach to optical quantum information procesing

    Furusawa, Akira [Tokyo Univ. (Japan). Dept. of Applied Physics; Loock, Peter van [Erlangen-Nuernberg Univ. (Germany). Lehrstuhl fuer Optik

    2011-07-01

    Unique in that it is jointly written by an experimentalist and a theorist, this monograph presents universal quantum computation based on quantum teleportation as an elementary subroutine and multi-party entanglement as a universal resource. Optical approaches to measurement-based quantum computation are also described, including schemes for quantum error correction, with most of the experiments carried out by the authors themselves. Ranging from the theoretical background to the details of the experimental realization, the book describes results and advances in the field, backed by numerous illustrations of the authors' experimental setups. Aimed at researchers, physicists, and graduate and PhD students in physics, theoretical quantum optics, quantum mechanics, and quantum information. (orig.)

  7. Modular quantum-information processing by dissipation

    Marshall, Jeffrey; Campos Venuti, Lorenzo; Zanardi, Paolo

    2016-11-01

    Dissipation can be used as a resource to control and simulate quantum systems. We discuss a modular model based on fast dissipation capable of performing universal quantum computation, and simulating arbitrary Lindbladian dynamics. The model consists of a network of elementary dissipation-generated modules and it is in principle scalable. In particular, we demonstrate the ability to dissipatively prepare all single-qubit gates, and the controlled-not gate; prerequisites for universal quantum computing. We also show a way to implement a type of quantum memory in a dissipative environment, whereby we can arbitrarily control the loss in both coherence, and concurrence, over the evolution. Moreover, our dissipation-assisted modular construction exhibits a degree of inbuilt robustness to Hamiltonian and, indeed, Lindbladian errors, and as such is of potential practical relevance.

  8. Dissociations within human hippocampal subregions during encoding and retrieval of spatial information.

    Suthana, Nanthia; Ekstrom, Arne; Moshirvaziri, Saba; Knowlton, Barbara; Bookheimer, Susan

    2011-07-01

    Although the hippocampus is critical for the formation and retrieval of spatial memories, it is unclear how subregions are differentially involved in these processes. Previous high-resolution functional magnetic resonance imaging (fMRI) studies have shown that CA2, CA3, and dentate gyrus (CA23DG) regions support the encoding of novel associations, whereas the subicular cortices support the retrieval of these learned associations. Whether these subregions are used in humans during encoding and retrieval of spatial information has yet to be explored. Using high-resolution fMRI (1.6 mm × 1.6-mm in-plane), we found that activity within the right CA23DG increased during encoding compared to retrieval. Conversely, right subicular activity increased during retrieval compared to encoding of spatial associations. These results are consistent with the previous studies illustrating dissociations within human hippocampal subregions and further suggest that these regions are similarly involved during the encoding and retrieval of spatial information.

  9. Electric-stimulus rate encoding algorithm of Mandarin tonal information in cochlear implant

    GUAN Tian; GONG Qin; YE Datian

    2006-01-01

    The modem multi-channel cochlear implants usually extract and encode the temporal envelope cues. This kind of algorithms can hardly satisfy the users who speak tonal languages, such as Mandarin. Many studies have tried to enhance the recognition ability of Mandarin through encoding tonal information and made suggestions to frequency-modulate the fixed pulse-rate carrier with the extracted tonal information based on the rate-pitch theory in electric hearing. However, how to encode and deliver the tonal information such as F0 by changing electric-stimulus rate has not got further study in clinical electric-stimulus mode. The present paper focuses on this matter by piecewise calculating the appreciable electric-stimulus rates. Then an electric-stimulus encoding algorithm of Mandarin tone is brought forward and testified through acoustic simulations. Such conclusion can be drawn that this algorithm of electric-stimulus rate could convey tonal information well and help to enhance the Mandarin speech recognition ability.

  10. Information complementarity in multipartite quantum states and security in cryptography

    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.

  11. Quantum-limited biochemical magnetometers designed using the Fisher information and quantum reaction control

    Vitalis, K. M.; Kominis, I. K.

    2016-01-01

    Radical-ion pairs and their reactions have triggered the study of quantum effects in biological systems. This is because they exhibit a number of effects best understood within quantum information science, and at the same time are central in understanding the avian magnetic compass and the spin transport dynamics in photosynthetic reaction centers. Here we address radical-pair reactions from the perspective of quantum metrology. Since the coherent spin motion of radical-pairs is effected by a...

  12. The capacity of black holes to transmit quantum information

    Brádler, Kamil [Department of Astronomy and Physics, Saint Mary’s University,Halifax, Nova Scotia, B3H 3C3 (Canada); Adami, Christoph [Department of Physics and Astronomy, Michigan State University,East Lansing, MI 48824 (United States)

    2014-05-21

    We study the properties of the quantum information transmission channel that emerges from the quantum dynamics of particles interacting with a black hole horizon. We calculate the quantum channel capacity in two limiting cases where a single-letter capacity is known to exist: the limit of perfectly reflecting and perfectly absorbing black holes. We find that the perfectly reflecting black hole channel is closely related to the Unruh channel and that its capacity is non-vanishing, allowing for the perfect reconstruction of quantum information outside of the black hole horizon. We also find that the complementary channel (transmitting entanglement behind the horizon) is entanglement-breaking in this case, with vanishing capacity. We then calculate the quantum capacity of the black hole channel in the limit of a perfectly absorbing black hole and find that this capacity vanishes, while the capacity of the complementary channel is non-vanishing instead. Rather than inviting a new crisis for quantum physics, this finding instead is in accordance with the quantum no-cloning theorem, because it guarantees that there are no space-like surfaces that contain both the sender’s quantum state and the receiver’s reconstructed quantum state.

  13. Quantum Information Protocols with Gaussian States of Light

    Jacobsen, Christian Scheffmann

    and hardware for secure quantum key distribution. These technologies directly exploit quantum effects, and indeed this is where they offer advantages to classical products. This thesis deals with the development and implementation of quantum information protocols that utilize the rather inexpensive resource...... with Gaussian states is a promising avenue for the development of practical quantum key distribution with a relay network structure in environments where the distances are relatively short and there is a high number of users, such as an urban environment. In addition to this we consider various point......-to-point configurations that utilize Gaussian states to achieve security. Notably, we also present a novel experiment demonstrating the feasibility of delegated quantum computing on encrypted data, where we show that we can reliably encrypt and decrypt input and output states when a server with quantum computing...

  14. Objectivity in a Noisy Photonic Environment through Quantum State Information Broadcasting

    Korbicz, J. K.; Horodecki, P.; Horodecki, R.

    2014-03-01

    Recently, the emergence of classical objectivity as a property of a quantum state has been explicitly derived for a small object embedded in a photonic environment in terms of a spectrum broadcast form—a specific classically correlated state, redundantly encoding information about the preferred states of the object in the environment. However, the environment was in a pure state and the fundamental problem was how generic and robust is the conclusion. Here, we prove that despite the initial environmental noise, the emergence of the broadcast structure still holds, leading to the perceived objectivity of the state of the object. We also show how this leads to a quantum Darwinism-type condition, reflecting the classicality of proliferated information in terms of a limit behavior of the mutual information. Quite surprisingly, we find "singular points" of the decoherence, which can be used to faithfully broadcast a specific classical message through the noisy environment.

  15. Objectivity in a noisy photonic environment through quantum state information broadcasting.

    Korbicz, J K; Horodecki, P; Horodecki, R

    2014-03-28

    Recently, the emergence of classical objectivity as a property of a quantum state has been explicitly derived for a small object embedded in a photonic environment in terms of a spectrum broadcast form-a specific classically correlated state, redundantly encoding information about the preferred states of the object in the environment. However, the environment was in a pure state and the fundamental problem was how generic and robust is the conclusion. Here, we prove that despite the initial environmental noise, the emergence of the broadcast structure still holds, leading to the perceived objectivity of the state of the object. We also show how this leads to a quantum Darwinism-type condition, reflecting the classicality of proliferated information in terms of a limit behavior of the mutual information. Quite surprisingly, we find "singular points" of the decoherence, which can be used to faithfully broadcast a specific classical message through the noisy environment.

  16. Quantum field theory, statistical physics, and information theory

    Toyoda, Tadashi [Tokai Univ., Kanagawa (Japan)

    2001-05-01

    It is shown that the one-particle Matsubara temperature Green's function can be regarded as a Fisher information matrix on the basis of the quantum generalization of relative entropy due to Watanabe and Neumann.

  17. Scalable quantum information processing with photons and atoms

    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

  18. Why genetic information processing could have a quantum basis

    Apoorva Patel

    2001-06-01

    Living organisms are not just random collections of organic molecules. There is continuous information processing going on in the apparent bouncing around of molecules of life. Optimization criteria in this information processing can be searched for using the laws of physics. Quantum dynamics can explain why living organisms have 4 nucleotide bases and 20 amino acids, as optimal solutions of the molecular assembly process. Experiments should be able to tell whether evolution indeed took advantage of quantum dynamics or not.

  19. Probabilistic Teleportation via Quantum Channel with Partial Information

    Desheng Liu

    2015-06-01

    Full Text Available Two novel schemes are proposed to teleport an unknown two-level quantum state probabilistically when the sender and the receiver only have partial information about the quantum channel, respectively. This is distinct from the fact that either the sender or the receiver has entire information about the quantum channel in previous schemes for probabilistic teleportation. Theoretical analysis proves that these schemes are straightforward, efficient and cost-saving. The concrete realization procedures of our schemes are presented in detail, and the result shows that our proposals could extend the application range of probabilistic teleportation.

  20. Beating the Classical Limits of Information Transmission using a Quantum Decoder

    Karim, Akib; Huang, Zixin; Chapman, Rob; Tomamichel, Marco; Flammia, Steve; Peruzzo, Alberto

    Reliable transmission of information over a noisy channel is a fundamental challenge in communication theory. The emergence of quantum technologies has created a new class of strategies that allow for message recovery greater than purely classical methods. Despite this, for minimal uses of the channel, finding such schemes remains a challenge. We investigate the amplitude damping channel which describes physical systems that suffer energy loss such as in cavity quantum electrodynamics or spin chain excitations. We derive and experimentally demonstrate the fundamental limit for message recovery possible with only classical methods. We then propose a quantum decoder and experimentally demonstrate message recovery past this classical limit. We use polarisation-encoded photonic qubits. The post-amplitude damping states are generated by an unbalanced Mach-Zehnder interferometer and entanglement is accomplished with a linear optical probabilistic controlled z gate. Our quantum decoder uses a single entangling gate at the receiver where other similar schemes rely on both the sender and the receiver having quantum devices. Our results present an advance in discovering the quantum capabilities of finite resource communications, with specific regard to the amplitude damping channel.

  1. Optomechanical transducers for quantum information processing

    Stannigel, K; Sørensen, A S; Lukin, M D; Zoller, P

    2011-01-01

    We discuss the implementation of optical quantum networks where the interface between stationary and photonic qubits is realized by optomechanical transducers [K. Stannigel et al., PRL 105, 220501 (2010)]. This approach does not rely on the optical properties of the qubit and thereby enables optical quantum communication applications for a wide range of solid-state spin- and charge-based systems. We present an effective description of such networks for many qubits and give a derivation of a state transfer protocol for long-distance quantum communication. We also describe how to mediate local on-chip interactions by means of the optomechanical transducers that can be used for entangling gates. We finally discuss experimental systems for the realization of our proposal.

  2. Information tracking and encoding in early L1: linguistic competence vs. cognitive limitations.

    De Cat, Cécile

    2011-09-01

    This study provides experimental evidence for preschool children's competence in basic information structure, with particular attention to the notions of topic and focus. It investigates their mastery of structural and definiteness distinctions to encode the information status of discourse referents, and seeks to distinguish linguistic competence from cognitive development as the source for children's 'errors'. Evidence comes from a story-telling experiment performed on 45 children acquiring French (between the ages of 2;6·22 and 5;6·15). The article demonstrates continuity between the child and adult systems of basic discourse representation. It further argues that children's definiteness errors are not due to a lack of knowledge of the adult rules of information encoding. Rather, such errors stem from cognitive limitations and from assuming a wider common ground than adults would.

  3. Exponential speed-up with a single bit of quantum information: Testing the quantum butterfly effect

    Poulin, D; Laflamme, R; Ollivier, H; Poulin, David; Blume-Kohout, Robin; Laflamme, Raymond; Ollivier, Harold

    2003-01-01

    We present an efficient quantum algorithm to measure the average fidelity decay of a quantum map under perturbation using a single bit of quantum information. Our algorithm scales only as the complexity of the map under investigation, so for those maps admitting an efficient gate decomposition, it provides an exponential speed up over known classical procedures. Fidelity decay is important in the study of complex dynamical systems, where it is conjectured to be a signature of quantum chaos. Our result also illustrates the role of chaos in the process of decoherence.

  4. Quasi-probability representations of quantum theory with applications to quantum information science

    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.

  5. Quasi-probability representations of quantum theory with applications to quantum information science

    Ferrie, Christoper

    2010-01-01

    This article 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.

  6. Smooth Rényi Entropy of Ergodic Quantum Information Sources

    Schoenmakers, Berry; Tjoelker, Jilles; Tuyls, Pim; Verbitskiy, Evgeny

    2007-01-01

    We investigate the recently introduced notion of smooth Rényi entropy for the case of ergodic information sources, thereby generalizing previous work which concentrated mainly on i.i.d. information sources. We will actually consider ergodic quantum information sources, of which ergodic classical inf

  7. Applied research of quantum information based on linear optics

    Xu, Xiao-Ye

    2016-08-01

    This thesis reports on outstanding work in two main subfields of quantum information science: one involves the quantum measurement problem, and the other concerns quantum simulation. The thesis proposes using a polarization-based displaced Sagnac-type interferometer to achieve partial collapse measurement and its reversal, and presents the first experimental verification of the nonlocality of the partial collapse measurement and its reversal. All of the experiments are carried out in the linear optical system, one of the earliest experimental systems to employ quantum communication and quantum information processing. The thesis argues that quantum measurement can yield quantum entanglement recovery, which is demonstrated by using the frequency freedom to simulate the environment. Based on the weak measurement theory, the author proposes that white light can be used to precisely estimate phase, and effectively demonstrates that the imaginary part of the weak value can be introduced by means of weak measurement evolution. Lastly, a nine-order polarization-based displaced Sagnac-type interferometer employing bulk optics is constructed to perform quantum simulation of the Landau-Zener evolution, and by tuning the system Hamiltonian, the first experiment to research the Kibble-Zurek mechanism in non-equilibrium kinetics processes is carried out in the linear optical system.

  8. Initialization and Readout of Spin Chains for Quantum Information Transport

    Kaur, Gurneet

    2011-01-01

    Linear chains of spins acting as quantum wires are a promising approach to achieve scalable quantum information processors. Nuclear spins in apatite crystals provide an ideal test-bed for the experimental study of quantum information transport, as they closely emulate a one-dimensional spin chain. Nuclear Magnetic Resonance techniques can be used to drive the spin chain dynamics and probe the accompanying transport mechanisms. Here we demonstrate initialization and readout capabilities in these spin chains, even in the absence of single-spin addressability. These control schemes enable preparing desired states for quantum information transport and probing their evolution under the transport Hamiltonian. We further optimize the control schemes by a detailed analysis of $^{19}$F NMR lineshape.

  9. QIS-XML: A metadata specification for Quantum Information Science

    Heus, Pascal

    2007-01-01

    While Quantum Information Science (QIS) is still in its infancy, the ability for quantum based hardware or computers to communicate and integrate with their classical counterparts will be a major requirement towards their success. Little attention however has been paid to this aspect of QIS. To manage and exchange information between systems, today's classic Information Technology (IT) commonly uses the eXtensible Markup Language (XML) and its related tools. XML is composed of numerous specifications related to various fields of expertise. No such global specification however has been defined for quantum computers. QIS-XML is a proposed XML metadata specification for the description of fundamental components of QIS (gates & circuits) and a platform for the development of a hardware independent low level pseudo-code for quantum algorithms. This paper lays out the general characteristics of the QIS-XML specification and outlines practical applications through prototype use cases.

  10. MURI Center for Photonic Quantum Information Systems

    2009-10-16

    Yamamoto, "Quantum Interference Between Single Photons Emitted by Independent Semiconductor Nanodevices ," Submitted to Science (2008). 4. K. Wen, K...transitions, which can be described by a spin-fluctuator model. We showed that due to a process analogous to motional averaging in nuclear magnetic

  11. Scalable Quantum Information Processing and Applications

    2008-01-19

    technique to accelerate the computation of states of the non-separable Schroedinger operator. The development of the iterative method was...from fully 3-dimensional self-consistent Poisson- Schroedinger calculations. The effects of Coulomb interaction on the quantum dot states and hence

  12. Amplification of Information by Photons and the Quantum Chernoff Bound

    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

  13. Toward an Information-based Interpretation of Quantum Mechanics and the Quantum-Classical Transition

    Roederer, Juan G

    2011-01-01

    I will show how an objective definition of the concept of information and the consideration of recent results about information-processing in the human brain help clarify some fundamental and often counter-intuitive aspects of quantum mechanics. In particular, I will discuss entanglement, teleportation, non-interaction measurements and decoherence in the light of the fact that pragmatic information, the one our brain handles, can only be defined in the classical macroscopic domain; it does not operate in the quantum domain. This justifies viewing quantum mechanics as a discipline dealing with mathematical models and procedures aimed exclusively at predicting possible macroscopic changes and their likelihood that a given quantum system may cause when it interacts with its environment, including man-made devices such as measurement instruments. I will discuss the informational and neurobiological reasons of why counter-intuitive aspects arise whenever we attempt to construct mental images of the "inner workings...

  14. A Quantum Rosetta Stone for the Information Paradox

    Zayas, Leopoldo A Pando

    2014-01-01

    The black hole information loss paradox epitomizes the contradictions between general relativity and quantum field theory. The AdS/CFT correspondence provides an implicit answer for the information loss paradox in black hole physics by equating a gravity theory with an explicitly unitary field theory. Gravitational collapse in asymptotically AdS spacetimes is generically turbulent. Given that the mechanism to read out the information about correlations functions in the field theory side is plagued by deterministic classical chaos, we argue that quantum chaos might provide the true Rosetta Stone for answering the information paradox in the context of the AdS/CFT correspondence.

  15. A quantum Rosetta Stone for the information paradox

    Pando Zayas, Leopoldo A.

    2014-11-01

    The black hole information loss paradox epitomizes the contradictions between general relativity and quantum field theory. The AdS/conformal field theory (CFT) correspondence provides an implicit answer for the information loss paradox in black hole physics by equating a gravity theory with an explicitly unitary field theory. Gravitational collapse in asymptotically AdS spacetimes is generically turbulent. Given that the mechanism to read out the information about correlations functions in the field theory side is plagued by deterministic classical chaos, we argue that quantum chaos might provide the true Rosetta Stone for answering the information paradox in the context of the AdS/CFT correspondence.

  16. Quantum-limited biochemical magnetometers designed using the Fisher information and quantum reaction control

    Vitalis, K M

    2016-01-01

    Radical-ion pairs and their reactions have triggered the study of quantum effects in biological systems. This is because they exhibit a number of effects best understood within quantum information science, and at the same time are central in understanding the avian magnetic compass and the spin transport dynamics in photosynthetic reaction centers. Here we address radical-pair reactions from the perspective of quantum metrology. Since the coherent spin motion of radical-pairs is effected by an external magnetic field, these spin-dependent reactions essentially realize a biochemical magnetometer. Using the quantum Fisher information, we find the fundamental quantum limits to the magnetic sensitivity of radical-pair magnetometers. We then explore how well the usual measurement scheme considered in radical-pair reactions, the measurement of reaction yields, approaches the fundamental limits. In doing so, we find the optimal hyperfine interaction Hamiltonian that leads to the best magnetic sensitivity as obtained...

  17. Distribution of quantum information between an atom and two photons

    Weber, Bernhard

    2008-11-03

    The construction of networks consisting of optically interconnected processing units is a promising way to scale up quantum information processing systems. To store quantum information, single trapped atoms are among the most proven candidates. By placing them in high finesse optical resonators, a bidirectional information exchange between the atoms and photons becomes possible with, in principle, unit efficiency. Such an interface between stationary and ying qubits constitutes a possible node of a future quantum network. The results presented in this thesis demonstrate the prospects of a quantum interface consisting of a single atom trapped within the mode of a high-finesse optical cavity. In a two-step process, we distribute entanglement between the stored atom and two subsequently emitted single photons. The long atom trapping times achieved in the system together with the high photon collection efficiency of the cavity make the applied protocol in principle deterministic, allowing for the creation of an entangled state at the push of a button. Running the protocol on this quasi-stationary quantum interface, the internal state of the atom is entangled with the polarization state of a single emitted photon. The entanglement is generated by driving a vacuum-stimulated Raman adiabatic passage between states of the coupled atom-cavity system. In a second process, the atomic part of the entangled state is mapped onto a second emitted photon using a similar technique and resulting in a polarization-entangled two-photon state. To verify and characterize the photon-photon entanglement, we measured a violation of a Bell inequality and performed a full quantum state tomography. The results prove the prior atom-photon entanglement and demonstrate a quantum information transfer between the atom and the two emitted photons. This reflects the advantages of a high-finesse cavity as a quantum interface in future quantum networks. (orig.)

  18. Toolbox for reconstructing quantum theory from rules on information acquisition

    Hoehn, Philipp A

    2015-01-01

    We develop a novel operational approach for reconstructing (qubit) quantum theory from elementary rules on information acquisition. The focus lies on an observer O interrogating a system S with binary questions and S's state is taken as O's `catalogue of knowledge' about S. The mathematical tools of the framework are simple and we attempt to highlight all underlying assumptions to provide a handle for future generalizations. Five principles are imposed, asserting (1) a limit on the amount of information available to O; (2) the mere existence of complementary information; (3) the possibility for O's information to be `in superposition'; (4) O's information to be preserved in between interrogations; and, (5) continuity of time evolution. This approach permits a constructive derivation of quantum theory, elucidating how the ensuing independence, complementarity and compatibility structure of O's questions matches that of projective measurements in quantum theory, how entanglement and monogamy of entanglement and...

  19. Pure sources and efficient detectors for optical quantum information processing

    Zielnicki, Kevin

    Over the last sixty years, classical information theory has revolutionized the understanding of the nature of information, and how it can be quantified and manipulated. Quantum information processing extends these lessons to quantum systems, where the properties of intrinsic uncertainty and entanglement fundamentally defy classical explanation. This growing field has many potential applications, including computing, cryptography, communication, and metrology. As inherently mobile quantum particles, photons are likely to play an important role in any mature large-scale quantum information processing system. However, the available methods for producing and detecting complex multi-photon states place practical limits on the feasibility of sophisticated optical quantum information processing experiments. In a typical quantum information protocol, a source first produces an interesting or useful quantum state (or set of states), perhaps involving superposition or entanglement. Then, some manipulations are performed on this state, perhaps involving quantum logic gates which further manipulate or entangle the intial state. Finally, the state must be detected, obtaining some desired measurement result, e.g., for secure communication or computationally efficient factoring. The work presented here concerns the first and last stages of this process as they relate to photons: sources and detectors. Our work on sources is based on the need for optimized non-classical states of light delivered at high rates, particularly of single photons in a pure quantum state. We seek to better understand the properties of spontaneous parameteric downconversion (SPDC) sources of photon pairs, and in doing so, produce such an optimized source. We report an SPDC source which produces pure heralded single photons with little or no spectral filtering, allowing a significant rate enhancement. Our work on detectors is based on the need to reliably measure single-photon states. We have focused on

  20. Encoding and decoding spatio-temporal information for super-resolution microscopy.

    Lanzanò, Luca; Coto Hernández, Iván; Castello, Marco; Gratton, Enrico; Diaspro, Alberto; Vicidomini, Giuseppe

    2015-04-02

    The challenge of increasing the spatial resolution of an optical microscope beyond the diffraction limit can be reduced to a spectroscopy task by proper manipulation of the molecular states. The nanoscale spatial distribution of the molecules inside the detection volume of a scanning microscope can be encoded within the fluorescence dynamics and decoded by resolving the signal into its dynamics components. Here we present a robust and general method to decode this information using phasor analysis. As an example of the application of this method, we optically generate spatially controlled gradients in the fluorescence lifetime by stimulated emission. Spatial resolution can be increased indefinitely by increasing the number of resolved dynamics components up to a maximum determined by the amount of noise. We demonstrate that the proposed method provides nanoscale imaging of subcellular structures, opening new routes in super-resolution microscopy based on the encoding/decoding of spatial information through manipulation of molecular dynamics.

  1. Impaired encoding of rapid pitch information underlies perception and memory deficits in congenital amusia.

    Albouy, Philippe; Cousineau, Marion; Caclin, Anne; Tillmann, Barbara; Peretz, Isabelle

    2016-01-06

    Recent theories suggest that the basis of neurodevelopmental auditory disorders such as dyslexia or specific language impairment might be a low-level sensory dysfunction. In the present study we test this hypothesis in congenital amusia, a neurodevelopmental disorder characterized by severe deficits in the processing of pitch-based material. We manipulated the temporal characteristics of auditory stimuli and investigated the influence of the time given to encode pitch information on participants' performance in discrimination and short-term memory. Our results show that amusics' performance in such tasks scales with the duration available to encode acoustic information. This suggests that in auditory neuro-developmental disorders, abnormalities in early steps of the auditory processing can underlie the high-level deficits (here musical disabilities). Observing that the slowing down of temporal dynamics improves amusics' pitch abilities allows considering this approach as a potential tool for remediation in developmental auditory disorders.

  2. Cold Trapped Ions as Quantum Information Processors

    Sasura, M; Sasura, Marek; Buzek, Vladimir

    2002-01-01

    In this tutorial we review physical implementation of quantum computing using a system of cold trapped ions. We discuss systematically all the aspects for making the implementation possible. Firstly, we go through the loading and confining of atomic ions in the linear Paul trap, then we describe the collective vibrational motion of trapped ions. Further, we discuss interactions of the ions with a laser beam. We treat the interactions in the travelling-wave and standing-wave configuration for dipole and quadrupole transitions. We review different types of laser cooling techniques associated with trapped ions. We address Doppler cooling, sideband cooling in and beyond the Lamb-Dicke limit, sympathetic cooling and laser cooling using electromagnetically induced transparency. After that we discuss the problem of state detection using the electron shelving method. Then quantum gates are described. We introduce single-qubit rotations, two-qubit controlled-NOT and multi-qubit controlled-NOT gates. We also comment on...

  3. Geometric algebra and information geometry for quantum computational software

    Cafaro, Carlo

    2017-03-01

    The art of quantum algorithm design is highly nontrivial. Grover's search algorithm constitutes a masterpiece of quantum computational software. In this article, we use methods of geometric algebra (GA) and information geometry (IG) to enhance the algebraic efficiency and the geometrical significance of the digital and analog representations of Grover's algorithm, respectively. Specifically, GA is used to describe the Grover iterate and the discretized iterative procedure that exploits quantum interference to amplify the probability amplitude of the target-state before measuring the query register. The transition from digital to analog descriptions occurs via Stone's theorem which relates the (unitary) Grover iterate to a suitable (Hermitian) Hamiltonian that controls Schrodinger's quantum mechanical evolution of a quantum state towards the target state. Once the discrete-to-continuos transition is completed, IG is used to interpret Grover's iterative procedure as a geodesic path on the manifold of the parametric density operators of pure quantum states constructed from the continuous approximation of the parametric quantum output state in Grover's algorithm. Finally, we discuss the dissipationless nature of quantum computing, recover the quadratic speedup relation, and identify the superfluity of the Walsh-Hadamard operation from an IG perspective with emphasis on statistical mechanical considerations.

  4. Analysis of Information Leakage in Quantum Key Agreement

    LIU Sheng-li; ZHENG Dong; CHENG Ke-fei

    2006-01-01

    Quantum key agreement is one of the approaches to unconditional security. Since 1980's, different protocols for quantum key agreement have been proposed and analyzed. A new quantum key agreement protocol was presented in 2004, and a detailed analysis to the protocol was given. The possible game played between legitimate users and the enemy was described:sitting in the middle, an adversary can play a "man-in-the-middle" attack to cheat the sender and receiver. The information leaked to the adversary is essential to the length of the final quantum secret key. It was shown how to determine the amount of information leaked to the enemy and the amount of uncertainty between the legitimate sender and receiver.

  5. Doubly infinite separation of quantum information and communication

    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.

  6. Quantum mechanics with applications to nanotechnology and information science

    Band, Yehuda B

    2013-01-01

    Quantum mechanics transcends and supplants classical mechanics at the atomic and subatomic levels. It provides the underlying framework for many subfields of physics, chemistry and materials science, including condensed matter physics, atomic physics, molecular physics, quantum chemistry, particle physics, and nuclear physics. It is the only way we can understand the structure of materials, from the semiconductors in our computers to the metal in our automobiles. It is also the scaffolding supporting much of nanoscience and nanotechnology. The purpose of this book is to present the fundamentals of quantum theory within a modern perspective, with emphasis on applications to nanoscience and nanotechnology, and information-technology. As the frontiers of science have advanced, the sort of curriculum adequate for students in the sciences and engineering twenty years ago is no longer satisfactory today. Hence, the emphasis on new topics that are not included in older reference texts, such as quantum information th...

  7. Feasibility of two-way polarization encoded quantum communication in an optical fiber populated with telecom traffic

    Xavier, G B; da Silva, T Ferreira; Temporao, G P; von der Weid, J P

    2009-01-01

    We experimentally show a two-way transmission of polarization encoded pseudo-single photons between two remote parties separated by a single 23 km optical fiber spool. Two optical classical channels are wavelength multiplexed in the same fiber and used as feedback to an active polarization drift compensation scheme. One of the classical channels contains a 10 Gb/s data stream simulating real telecom traffic. The feasibility of quantum communication is demonstrated in the fiber's two opposite directions of propagation over 6 hours of continuous operation, as well as a classical error rate in the data channel better than 1.0 x 10-9. The results are extended to show the estimated maximum transmission distance for the quantum signals based on the noise generated through Raman spontaneous scattering by up to 16 classical channels present in the fiber.

  8. Topological Quantum Information in a 3D Neutral Atom Array

    2015-01-02

    v Prescribed by ANSI Std. Z39.18 12-23-2014 Final 12-01-2008-9-30-2014 ( DARPA ) TOPOLOGICAL QUANTUM INFORMATION IN A 3D NEUTRAL ATOM ARRAY FA9550-09...1-0041 David Weiss Penn State UP76XR0 AFOSR DARPA Approved for public release Work was performed to build core elements of a quantum computer...Hamiltonian within our trapped neutral atoms architecture. quantum computing, ultracold atoms David Weiss 814-861-3578 1 DARPA Final Report Grant

  9. Interactions among emotional attention, encoding, and retrieval of ambiguous information: An eye-tracking study.

    Everaert, Jonas; Koster, Ernst H W

    2015-10-01

    Emotional biases in attention modulate encoding of emotional material into long-term memory, but little is known about the role of such attentional biases during emotional memory retrieval. The present study investigated how emotional biases in memory are related to attentional allocation during retrieval. Forty-nine individuals encoded emotionally positive and negative meanings derived from ambiguous information and then searched their memory for encoded meanings in response to a set of retrieval cues. The remember/know/new procedure was used to classify memories as recollection-based or familiarity-based, and gaze behavior was monitored throughout the task to measure attentional allocation. We found that a bias in sustained attention during recollection-based, but not familiarity-based, retrieval predicted subsequent memory bias toward positive versus negative material following encoding. Thus, during emotional memory retrieval, attention affects controlled forms of retrieval (i.e., recollection) but does not modulate relatively automatic, familiarity-based retrieval. These findings enhance understanding of how distinct components of attention regulate the emotional content of memories. Implications for theoretical models and emotion regulation are discussed.

  10. Encoding of temporal information by timing, rate, and place in cat auditory cortex.

    Kazuo Imaizumi

    Full Text Available A central goal in auditory neuroscience is to understand the neural coding of species-specific communication and human speech sounds. Low-rate repetitive sounds are elemental features of communication sounds, and core auditory cortical regions have been implicated in processing these information-bearing elements. Repetitive sounds could be encoded by at least three neural response properties: 1 the event-locked spike-timing precision, 2 the mean firing rate, and 3 the interspike interval (ISI. To determine how well these response aspects capture information about the repetition rate stimulus, we measured local group responses of cortical neurons in cat anterior auditory field (AAF to click trains and calculated their mutual information based on these different codes. ISIs of the multiunit responses carried substantially higher information about low repetition rates than either spike-timing precision or firing rate. Combining firing rate and ISI codes was synergistic and captured modestly more repetition information. Spatial distribution analyses showed distinct local clustering properties for each encoding scheme for repetition information indicative of a place code. Diversity in local processing emphasis and distribution of different repetition rate codes across AAF may give rise to concurrent feed-forward processing streams that contribute differently to higher-order sound analysis.

  11. Redundant information from thermal illumination: quantum Darwinism in scattered photons

    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.

  12. Quantum mechanics, common sense and the black hole information paradox

    Danielsson, U H; Danielsson, Ulf H.; Schiffer, Marcelo

    1993-01-01

    The purpose of this paper is to analyse, in the light of information theory and with the arsenal of (elementary) quantum mechanics (EPR correlations, copying machines, teleportation, mixing produced in sub-systems owing to a trace operation, etc.) the scenarios available on the market to resolve the so-called black-hole information paradox. We shall conclude that the only plausible ones are those where either the unitary evolution of quantum mechanics is given up, in which information leaks continuously in the course of black-hole evaporation through non-local processes, or those in which the world is polluted by an infinite number of meta-stable remnants.

  13. Redundant information from thermal illumination: quantum Darwinism in scattered photons

    Jess Riedel, C; Zurek, Wojciech H, E-mail: criedel@physics.ucsb.edu [Theory Division, LANL, Los Alamos, NM 87545 (United States)

    2011-07-15

    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.

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

    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.

  15. Quantum information processing using designed defect states in

    Pedersen, Jesper; Flindt, Christian; Mortensen, Niels Asger

    2007-01-01

    We propose a new physical implementation of spin qubits for quantum information processing, namely defect states in antidot lattices de¯ned in the two-dimensional electron gas at a semiconductor heterostructure. Calculations of the band structure of the periodic antidot lattice are presented......-coupled defect states is calculated numerically.We ¯nd results reminiscent of double quantum dot structures, indicating that the suggested structure is a feasible physical implementation of spin qubits....

  16. Experimental continuous-variable cloning of partial quantum information

    Sabuncu, Metin; Leuchs, Gerd; Andersen, Ulrik Lund

    2008-01-01

    The fidelity of a quantum transformation is strongly linked with the prior partial information of the state to be transformed. We illustrate this interesting point by proposing and demonstrating the superior cloning of coherent states with prior partial information. More specifically, we propose...

  17. Coherent control of diamond defects for quantum information science and quantum sensing

    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

  18. Quantum information and information loss in general relativity

    Hooft, G. 't

    1996-01-01

    When it comes to performing thought experiments with black holes, Einstein-Bohr like discussions have to be re-opened. For instance one can ask what happens to the quantum state of a black hole when the wave function of a single ingoing particle is replaced by an other one that is orthogonal to the

  19. Incomplete Erasure of Which-Way Information Encoded in Atomic Hyperfine States

    WEN Ling-Hua; LIU Min; KONG Ling-Bo; ZHAN Ming-Sheng

    2005-01-01

    @@ We propose an experimental scheme to investigate incomplete erasure of which-way information encoded in atomic hyperfine states.Due to the incomplete erasure of the which-way information, it is shown that the interference patterns of the atomic wave packets initially confined in a spin-dependent optical lattice are destroyed to a certain extent, which provides a new straight way to test further the validity of the theoretical model developed in our recent work.The remarkable merit of the proposal is that it is simple and can be implemented easily.

  20. Encoding information using Laguerre Gaussian modes over free space turbulence media.

    Trichili, Abderrahmen; Salem, Amine Ben; Dudley, Angela; Zghal, Mourad; Forbes, Andrew

    2016-07-01

    We experimentally demonstrate an efficient information transmission technique using Laguerre Gaussian (LG) modes. This technique is based on multiplexing and demultiplexing multiple LG modes with different azimuthal and radial components. At the reception, the initially sent modes encoding the information are extracted with high fidelity using a complete decomposition allowing to identify a particular mode from a set of modes within a unique iteration. Importantly, we investigate the effects of the atmospheric turbulence on the proposed communication system. We believe that the proposed technique is promising for high-bit-rate spatial division multiplexing in optical fiber and free space communication systems.

  1. Information hiding based on double random-phase encoding and public-key cryptography.

    Sheng, Yuan; Xin, Zhou; Alam, Mohammed S; Xi, Lu; Xiao-Feng, Li

    2009-03-01

    A novel information hiding method based on double random-phase encoding (DRPE) and Rivest-Shamir-Adleman (RSA) public-key cryptosystem is proposed. In the proposed technique, the inherent diffusion property of DRPE is cleverly utilized to make up the diffusion insufficiency of RSA public-key cryptography, while the RSA cryptosystem is utilized for simultaneous transmission of the cipher text and the two phase-masks, which is not possible under the DRPE technique. This technique combines the complementary advantages of the DPRE and RSA encryption techniques and brings security and convenience for efficient information transmission. Extensive numerical simulation results are presented to verify the performance of the proposed technique.

  2. Using space and time to encode vibrotactile information: toward an estimate of the skin's achievable throughput.

    Novich, Scott D; Eagleman, David M

    2015-10-01

    Touch receptors in the skin can relay various forms of abstract information, such as words (Braille), haptic feedback (cell phones, game controllers, feedback for prosthetic control), and basic visual information such as edges and shape (sensory substitution devices). The skin can support such applications with ease: They are all low bandwidth and do not require a fine temporal acuity. But what of high-throughput applications? We use sound-to-touch conversion as a motivating example, though others abound (e.g., vision, stock market data). In the past, vibrotactile hearing aids have demonstrated improvement in speech perceptions in the deaf. However, a sound-to-touch sensory substitution device that works with high efficacy and without the aid of lipreading has yet to be developed. Is this because skin simply does not have the capacity to effectively relay high-throughput streams such as sound? Or is this because the spatial and temporal properties of skin have not been leveraged to full advantage? Here, we begin to address these questions with two experiments. First, we seek to determine the best method of relaying information through the skin using an identification task on the lower back. We find that vibrotactile patterns encoding information in both space and time yield the best overall information transfer estimate. Patterns encoded in space and time or "intensity" (the coupled coding of vibration frequency and force) both far exceed performance of only spatially encoded patterns. Next, we determine the vibrotactile two-tacton resolution on the lower back-the distance necessary for resolving two vibrotactile patterns. We find that our vibratory motors conservatively require at least 6 cm of separation to resolve two independent tactile patterns (>80 % correct), regardless of stimulus type (e.g., spatiotemporal "sweeps" versus single vibratory pulses). Six centimeter is a greater distance than the inter-motor distances used in Experiment 1 (2.5 cm), which

  3. Topological quantum buses: coherent quantum information transfer between topological and conventional qubits

    Bonderson, Parsa

    2010-01-01

    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.

  4. Topological Quantum Buses: Coherent Quantum Information Transfer between Topological and Conventional Qubits

    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.

  5. Quantum tagging: Authenticating location via quantum information and relativistic signaling constraints

    Kent, Adrian; Munro, William J.; Spiller, Timothy P. [Centre for Quantum Information and Foundations, DAMTP, University of Cambridge, Cambridge, United Kingdom and Perimeter Institute for Theoretical Physics, Waterloo, Ontario (Canada); NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan); Quantum Information Science, School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom)

    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.

  6. Reduced randomness in quantum cryptography with sequences of qubits encoded in the same basis

    Lamoureux, L P; Cerf, N J; Gisin, Nicolas; Macchiavello, C

    2005-01-01

    We consider the cloning of sequences of qubits prepared in the states used in the BB84 or 6-state quantum cryptography protocol, and show that the single-qubit fidelity is unaffected even if entire sequences of qubits are prepared in the same basis. This result is of great importance for practical quantum cryptosystems because it reduces the need for high-speed random number generation without impairing on the security against finite-size attacks.

  7. Versatile Formal Methods Applied to Quantum Information.

    Witzel, Wayne [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Rudinger, Kenneth Michael [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Sarovar, Mohan [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-11-01

    Using a novel formal methods approach, we have generated computer-veri ed proofs of major theorems pertinent to the quantum phase estimation algorithm. This was accomplished using our Prove-It software package in Python. While many formal methods tools are available, their practical utility is limited. Translating a problem of interest into these systems and working through the steps of a proof is an art form that requires much expertise. One must surrender to the preferences and restrictions of the tool regarding how mathematical notions are expressed and what deductions are allowed. Automation is a major driver that forces restrictions. Our focus, on the other hand, is to produce a tool that allows users the ability to con rm proofs that are essentially known already. This goal is valuable in itself. We demonstrate the viability of our approach that allows the user great exibility in expressing state- ments and composing derivations. There were no major obstacles in following a textbook proof of the quantum phase estimation algorithm. There were tedious details of algebraic manipulations that we needed to implement (and a few that we did not have time to enter into our system) and some basic components that we needed to rethink, but there were no serious roadblocks. In the process, we made a number of convenient additions to our Prove-It package that will make certain algebraic manipulations easier to perform in the future. In fact, our intent is for our system to build upon itself in this manner.

  8. Microstrip SQUID amplifiers for quantum information science

    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. Quantum origin of quantum jumps: Breaking of unitary symmetry induced by information transfer in the transition from quantum to classical

    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.

  10. The structure and size of sensory bursts encode stimulus information but only size affects behavior.

    Marsat, Gary; Pollack, Gerald S

    2010-04-01

    Cricket ultrasound avoidance is a classic model system for neuroethology. Avoidance steering is triggered by high-firing-rate bursts of spikes in the auditory command neuron AN2. Although bursting is common among sensory neurons, and although the detailed structure of bursts may encode information about the stimulus, it is as yet unclear whether this information is decoded. We address this question in two ways: from an information coding point of view, by showing the relationship between stimulus and burst structure; and also from a functional point of view by showing the relationship between burst structure and behavior. We conclude that the burst structure carries detailed temporal information about the stimulus but that this has little impact on the behavioral response, which is affected mainly by burst size.

  11. Survey of control performance in quantum information processing

    Hocker, David; Zheng, Yicong; Kosut, Robert; Brun, Todd; Rabitz, Herschel

    2016-11-01

    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.

  12. Survey of control performance in quantum information processing

    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.

  13. Decision theory and information propagation in quantum physics

    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.

  14. Quantum Bio-Informatics:From Quantum Information to Bio-Informatics

    Freudenberg, W; Ohya, M

    2008-01-01

    The purpose of this volume is examine bio-informatics and quantum information, which are growing rapidly at present, and to attempt to connect the two, with a view to enumerating and solving the many fundamental problems they entail. To this end, we look for interdisciplinary bridges in mathematics, physics, and information and life sciences. In particular, research into a new paradigm for information science and life science on the basis of quantum theory is emphasized. Sample Chapter(s). Markov Fields on Graphs (599 KB). Contents: Markov Fields on Graphs (L Accardi & H Ohno); Some Aspects of

  15. Geospatial Information Service System Based on GeoSOT Grid & Encoding

    LI Shizhong

    2016-12-01

    Full Text Available With the rapid development of the space and earth observation technology, it is important to establish a multi-source, multi-scale and unified cross-platform reference for global data. In practice, the production and maintenance of geospatial data are scattered in different units, and the standard of the data grid varies between departments and systems. All these bring out the disunity of standards among different historical periods or orgnizations. Aiming at geospatial information security library for the national high resolution earth observation, there are some demands for global display, associated retrieval and template applications and other integrated services for geospatial data. Based on GeoSOT grid and encoding theory system, "geospatial information security library information of globally unified grid encoding management" data subdivision organization solutions have been proposed; system-level analyses, researches and designs have been carried out. The experimental results show that the data organization and management method based on GeoSOT can significantly improve the overall efficiency of the geospatial information security service system.

  16. A cascade model of information processing and encoding for retinal prosthesis

    Zhi-jun Pei; Guan-xin Gao; Bo Hao; Qing-li Qiao; Hui-jian Ai

    2016-01-01

    Retinal prosthesis offers a potential treatment for individuals suffering from photoreceptor degeneration diseases. Establishing biological retinal models and simulating how the biological retina convert incoming light signal into spike trains that can be properly decoded by the brain is a key issue. Some retinal models have been presented, ranking from structural models inspired by the layered architecture to functional models originated from a set of speciifc physiological phenomena. However, Most of these focus on stimulus image com-pression, edge detection and reconstruction, but do not generate spike trains corresponding to visual image. In this study, based on state-of-the-art retinal physiological mechanism, including effective visual information extraction, static nonlinear rectiifcation of biological systems and neurons Poisson coding, a cascade model of the retina including the out plexiform layer for information processing and the inner plexiform layer for information encoding was brought forward, which integrates both anatomic connections and functional com-putations of retina. Using MATLAB software, spike trains corresponding to stimulus image were numerically computed by four steps:linear spatiotemporal ifltering, static nonlinear rectiifcation, radial sampling and then Poisson spike generation. The simulated results suggested that such a cascade model could recreate visual information processing and encoding functionalities of the retina, which is helpful in developing artiifcial retina for the retinally blind.

  17. A cascade model of information processing and encoding for retinal prosthesis

    Zhi-jun Pei

    2016-01-01

    Full Text Available Retinal prosthesis offers a potential treatment for individuals suffering from photoreceptor degeneration diseases. Establishing biological retinal models and simulating how the biological retina convert incoming light signal into spike trains that can be properly decoded by the brain is a key issue. Some retinal models have been presented, ranking from structural models inspired by the layered architecture to functional models originated from a set of specific physiological phenomena. However, Most of these focus on stimulus image compression, edge detection and reconstruction, but do not generate spike trains corresponding to visual image. In this study, based on state-of-the-art retinal physiological mechanism, including effective visual information extraction, static nonlinear rectification of biological systems and neurons Poisson coding, a cascade model of the retina including the out plexiform layer for information processing and the inner plexiform layer for information encoding was brought forward, which integrates both anatomic connections and functional computations of retina. Using MATLAB software, spike trains corresponding to stimulus image were numerically computed by four steps: linear spatiotemporal filtering, static nonlinear rectification, radial sampling and then Poisson spike generation. The simulated results suggested that such a cascade model could recreate visual information processing and encoding functionalities of the retina, which is helpful in developing artificial retina for the retinally blind.

  18. An optimized encoding method for secure key distribution by swapping quantum entanglement and its extension

    Gao, Gan

    2015-08-01

    Song [Song D 2004 Phys. Rev. A 69 034301] first proposed two key distribution schemes with the symmetry feature. We find that, in the schemes, the private channels which Alice and Bob publicly announce the initial Bell state or the measurement result through are not needed in discovering keys, and Song’s encoding methods do not arrive at the optimization. Here, an optimized encoding method is given so that the efficiencies of Song’s schemes are improved by 7/3 times. Interestingly, this optimized encoding method can be extended to the key distribution scheme composed of generalized Bell states. Project supported by the National Natural Science Foundation of China (Grant No. 11205115), the Program for Academic Leader Reserve Candidates in Tongling University (Grant No. 2014tlxyxs30), and the 2014-year Program for Excellent Youth Talents in University of Anhui Province, China.

  19. Wigner-Yanase skew information as tests for quantum entanglement

    Chen, Z

    2004-01-01

    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 2-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 new light on relationships between quantum entanglement and information theory.

  20. Nanoporous hard data: optical encoding of information within nanoporous anodic alumina photonic crystals

    Santos, Abel; Law, Cheryl Suwen; Pereira, Taj; Losic, Dusan

    2016-04-01

    Herein, we present a method for storing binary data within the spectral signature of nanoporous anodic alumina photonic crystals. A rationally designed multi-sinusoidal anodisation approach makes it possible to engineer the photonic stop band of nanoporous anodic alumina with precision. As a result, the transmission spectrum of these photonic nanostructures can be engineered to feature well-resolved and selectively positioned characteristic peaks across the UV-visible spectrum. Using this property, we implement an 8-bit binary code and assess the versatility and capability of this system by a series of experiments aiming to encode different information within the nanoporous anodic alumina photonic crystals. The obtained results reveal that the proposed nanosized platform is robust, chemically stable, versatile and has a set of unique properties for data storage, opening new opportunities for developing advanced nanophotonic tools for a wide range of applications, including sensing, photonic tagging, self-reporting drug releasing systems and secure encoding of information.Herein, we present a method for storing binary data within the spectral signature of nanoporous anodic alumina photonic crystals. A rationally designed multi-sinusoidal anodisation approach makes it possible to engineer the photonic stop band of nanoporous anodic alumina with precision. As a result, the transmission spectrum of these photonic nanostructures can be engineered to feature well-resolved and selectively positioned characteristic peaks across the UV-visible spectrum. Using this property, we implement an 8-bit binary code and assess the versatility and capability of this system by a series of experiments aiming to encode different information within the nanoporous anodic alumina photonic crystals. The obtained results reveal that the proposed nanosized platform is robust, chemically stable, versatile and has a set of unique properties for data storage, opening new opportunities for

  1. Why Distinctive Information Reduces False Memories: Evidence for Both Impoverished Relational-Encoding and Distinctiveness Heuristic Accounts

    Hege, Amanda C. G.; Dodson, Chad S.

    2004-01-01

    Two accounts explain why studying pictures reduces false memories within the Deese-Roediger-McDermott paradigm (J. Deese, 1959; H. L. Roediger & K. B. McDermott, 1995). The impoverished relational-encoding account suggests that studying pictures interferes with the encoding of relational information, which is the primary basis for false memories…

  2. Reliable Quantum Computers

    Preskill, J

    1997-01-01

    The new field of quantum error correction has developed spectacularly since its origin less than two years ago. Encoded quantum information can be protected from errors that arise due to uncontrolled interactions with the environment. Recovery from errors can work effectively even if occasional mistakes occur during the recovery procedure. Furthermore, encoded quantum information can be processed without serious propagation of errors. Hence, an arbitrarily long quantum computation can be performed reliably, provided that the average probability of error per quantum gate is less than a certain critical value, the accuracy threshold. A quantum computer storing about 10^6 qubits, with a probability of error per quantum gate of order 10^{-6}, would be a formidable factoring engine. Even a smaller, less accurate quantum computer would be able to perform many useful tasks. (This paper is based on a talk presented at the ITP Conference on Quantum Coherence and Decoherence, 15-18 December 1996.)

  3. Encoding of social state information by neuronal activities in the macaque caudate nucleus.

    Santos, Gustavo S; Nagasaka, Yasuo; Fujii, Naotaka; Nakahara, Hiroyuki

    2012-01-01

    Social animals adjust their behavior according to social relationships and momentary circumstances. Dominant-submissive relationships modulate, but do not completely determine, their competitive behaviors. For example, a submissive monkey's decision to retrieve food depends not only on the presence of dominant partners but also on their observed behavior. Thus, behavioral expression requires a dynamic evaluation of reward outcome and momentary social states. The neural mechanisms underlying this evaluation remain elusive. The caudate nucleus (CN) plays a pivotal role in representing reward expectation and translating it into action selection. To investigate whether their activities encode social state information, we recorded from CN neurons in monkeys while they performed a competitive food-grab task against a dominant competitor. We found two groups of CN neurons: one primarily responded to reward outcome, while the other primarily tracked the monkey's social state. These social state-dependent neurons showed greater activity when the monkeys freely retrieved food without active challenges from the competitor and reduced activity when the monkeys were in a submissive state due to the competitor's active behavior. These results indicate that different neuronal activities in the CN encode social state information and reward-related information, which may contribute to adjusting competitive behavior in dynamic social contexts.

  4. Rényi generalizations of the conditional quantum mutual information

    Berta, Mario [Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125 (United States); Seshadreesan, Kaushik P. [Department of Physics and Astronomy, Hearne Institute for Theoretical Physics, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Wilde, Mark M. [Department of Physics and Astronomy, Hearne Institute for Theoretical Physics, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Center for Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

    2015-02-15

    The conditional quantum mutual information I(A; B|C) of a tripartite state ρ{sub ABC} is an information quantity which lies at the center of many problems in quantum information theory. Three of its main properties are that it is non-negative for any tripartite state, that it decreases under local operations applied to systems A and B, and that it obeys the duality relation I(A; B|C) = I(A; B|D) for a four-party pure state on systems ABCD. The conditional mutual information also underlies the squashed entanglement, an entanglement measure that satisfies all of the axioms desired for an entanglement measure. As such, it has been an open question to find Rényi generalizations of the conditional mutual information, that would allow for a deeper understanding of the original quantity and find applications beyond the traditional memoryless setting of quantum information theory. The present paper addresses this question, by defining different α-Rényi generalizations I{sub α}(A; B|C) of the conditional mutual information, some of which we can prove converge to the conditional mutual information in the limit α → 1. Furthermore, we prove that many of these generalizations satisfy non-negativity, duality, and monotonicity with respect to local operations on one of the systems A or B (with it being left as an open question to prove that monotonicity holds with respect to local operations on both systems). The quantities defined here should find applications in quantum information theory and perhaps even in other areas of physics, but we leave this for future work. We also state a conjecture regarding the monotonicity of the Rényi conditional mutual informations defined here with respect to the Rényi parameter α. We prove that this conjecture is true in some special cases and when α is in a neighborhood of one.

  5. Reflections on Zeilinger-Brukner Information Interpretation of Quantum Mechanics

    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.

  6. Reflections on Zeilinger-Brukner information interpretation of quantum mechanics

    Khrennikov, Andrei

    2015-01-01

    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 enlighten 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 as well - in comments of "an external observer" who have been monitoring development of this approach to QM during 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.

  7. Continuous variable quantum information: Gaussian states and beyond

    Adesso, Gerardo; Lee, Antony R

    2014-01-01

    The study of Gaussian states has arisen to a privileged position in continuous variable quantum information in recent years. This is due to vehemently pursued experimental realisations and a magnificently elegant mathematical framework. In this article, we provide a brief, and hopefully didactic, exposition of Gaussian state quantum information and its contemporary uses, including sometimes omitted crucial details. After introducing the subject material and outlining the essential toolbox of continuous variable systems, we define the basic notions needed to understand Gaussian states and Gaussian operations. In particular, emphasis is placed on the mathematical structure combining notions of algebra and symplectic geometry fundamental to a complete understanding of Gaussian informatics. Furthermore, we discuss the quantification of different forms of correlations (including entanglement and quantum discord) for Gaussian states, paying special attention to recently developed measures. The manuscript is conclud...

  8. Renyi generalizations of the conditional quantum mutual information

    Berta, Mario; Wilde, Mark M

    2014-01-01

    The conditional quantum mutual information $I(A;B|C)$ of a tripartite state $\\rho_{ABC}$ is an information quantity which lies at the center of many problems in quantum information theory. Three of its main properties are that it is non-negative for any tripartite state, that it decreases under local operations applied to systems $A$ and $B$, and that it obeys the duality relation $I(A;B|C)=I(A;B|D)$ for a four-party pure state on systems $ABCD$. It has been an open question to find Renyi generalizations of the conditional mutual information, that would allow for a deeper understanding of the original quantity and find applications beyond the traditional memoryless setting of quantum information theory. The present paper addresses this question, by defining different $\\alpha$-Renyi generalizations $I_{\\alpha}(A;B|C)$ of the conditional mutual information that all converge to the conditional mutual information in the limit $\\alpha \\to 1$. Furthermore, we prove that many of these generalizations satisfy the afo...

  9. Generation of optical coherent state superpositions for quantum information processing

    Tipsmark, Anders

    2012-01-01

    I dette projektarbejde med titlen “Generation of optical coherent state superpositions for quantum information processing” har målet været at generere optiske kat-tilstande. Dette er en kvantemekanisk superpositions tilstand af to koherente tilstande med stor amplitude. Sådan en tilstand er...

  10. Hybrid discrete- and continuous-variable quantum information

    Andersen, Ulrik Lund; Neergaard-Nielsen, Jonas Schou; van Loock, Peter

    2015-01-01

    Research in quantum information processing has followed two different directions: the use of discrete variables (qubits) and that of high-dimensional, continuous-variable Gaussian states (coherent and squeezed states). Recently, these two approaches have been converging in potentially more powerful...

  11. Semiclassical gravity from the perspective of quantum information theory

    Landulfo, Andre Gustavo Scagliusi [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil)

    2012-07-01

    Full text: Quantum field theory in curved spacetimes makes remarkable predictions about the behavior of quantum fields in the presence of strong gravitational fields. Nevertheless, these striking discoveries raises several issues. The development of a theory at the interface between relativity, quantum mechanics, and information theory could not only shed new light on such questions as well as allowing to uncover new low-energy quantum gravity effects. In this talk I will review several results in this new field. In particular it will be shown that the Bell inequalities can be satisfied rather than violated by quantum mechanics if the detectors making the measurements are set in relativistic motion. It will also be shown that the entanglement between a pair of quits can suffer a sudden death when one of the quits accelerates uniformly for a finite proper time. This result will be used to analyze the behavior of entanglement in the vicinity of a nonrotating chargeless black hole. I will end with a discussion about the prospects of the field, emphasizing the so called 'black hole information paradox' and the question of what is the microscopic origin of the black hole entropy. (author)

  12. Lattice gauge theory simulations in the quantum information era

    Dalmonte, M.; Montangero, S.

    2016-07-01

    The many-body problem is ubiquitous in the theoretical description of physical phenomena, ranging from the behaviour of elementary particles to the physics of electrons in solids. Most of our understanding of many-body systems comes from analysing the symmetric properties of Hamiltonian and states: the most striking examples are gauge theories such as quantum electrodynamics, where a local symmetry strongly constrains the microscopic dynamics. The physics of such gauge theories is relevant for the understanding of a diverse set of systems, including frustrated quantum magnets and the collective dynamics of elementary particles within the standard model. In the last few years, several approaches have been put forward to tackle the complex dynamics of gauge theories using quantum information concepts. In particular, quantum simulation platforms have been put forward for the realisation of synthetic gauge theories, and novel classical simulation algorithms based on quantum information concepts have been formulated. In this review, we present an introduction to these approaches, illustrating the basics concepts and highlighting the connections between apparently very different fields, and report the recent developments in this new thriving field of research.

  13. Thalamic neuron models encode stimulus information by burst-size modulation.

    Elijah, Daniel H; Samengo, Inés; Montemurro, Marcelo A

    2015-01-01

    Thalamic neurons have been long assumed to fire in tonic mode during perceptive states, and in burst mode during sleep and unconsciousness. However, recent evidence suggests that bursts may also be relevant in the encoding of sensory information. Here, we explore the neural code of such thalamic bursts. In order to assess whether the burst code is generic or whether it depends on the detailed properties of each bursting neuron, we analyzed two neuron models incorporating different levels of biological detail. One of the models contained no information of the biophysical processes entailed in spike generation, and described neuron activity at a phenomenological level. The second model represented the evolution of the individual ionic conductances involved in spiking and bursting, and required a large number of parameters. We analyzed the models' input selectivity using reverse correlation methods and information theory. We found that n-spike bursts from both models transmit information by modulating their spike count in response to changes to instantaneous input features, such as slope, phase, amplitude, etc. The stimulus feature that is most efficiently encoded by bursts, however, need not coincide with one of such classical features. We therefore searched for the optimal feature among all those that could be expressed as a linear transformation of the time-dependent input current. We found that bursting neurons transmitted 6 times more information about such more general features. The relevant events in the stimulus were located in a time window spanning ~100 ms before and ~20 ms after burst onset. Most importantly, the neural code employed by the simple and the biologically realistic models was largely the same, implying that the simple thalamic neuron model contains the essential ingredients that account for the computational properties of the thalamic burst code. Thus, our results suggest the n-spike burst code is a general property of thalamic neurons.

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

    Chapman, Adrian; Miyake, Akimasa

    2015-01-01

    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...

  15. Toward a fully relativistic theory of quantum information

    Adami, Christoph

    2011-01-01

    Information theory is a statistical theory dealing with the relative state of detectors and physical systems. Because of this physicality of information, the classical framework of Shannon needs to be extended to deal with quantum detectors, perhaps moving at relativistic speeds, or even within curved space-time. Considerable progress toward such a theory has been achieved in the last fifteen years, while much is still not understood. This review recapitulates some milestones along this road, and speculates about future ones.

  16. Experimental long-distance decoy-state quantum key distribution based on polarization encoding.

    Peng, Cheng-Zhi; Zhang, Jun; Yang, Dong; Gao, Wei-Bo; Ma, Huai-Xin; Yin, Hao; Zeng, He-Ping; Yang, Tao; Wang, Xiang-Bin; Pan, Jian-Wei

    2007-01-05

    We demonstrate the decoy-state quantum key distribution (QKD) with one-way quantum communication in polarization space over 102 km. Further, we simplify the experimental setup and use only one detector to implement the one-way decoy-state QKD over 75 km, with the advantage to overcome the security loopholes due to the efficiency mismatch of detectors. Our experimental implementation can really offer the unconditionally secure final keys. We use 3 different intensities of 0, 0.2, and 0.6 for the light sources in our experiment. In order to eliminate the influences of polarization mode dispersion in the long-distance single-mode optical fiber, an automatic polarization compensation system is utilized to implement the active compensation.

  17. Experimental Long-Distance Decoy-State Quantum Key Distribution Based On Polarization Encoding

    Peng, C Z; Ma, H X; Pan, J W; Wang, X B; Yang, D; Yang, T; Yin, H; Zeng, H P; Zhang, J; Gao, Wei-Bo; Ma, Huai-Xin; Pan, Jian-Wei; Peng, Cheng-Zhi; Wang, Xiang-Bin; Yang, Dong; Yang, Tao; Yin, Hao; Zeng, He-Ping; Zhang, Jun

    2006-01-01

    We demonstrate the decoy-state quantum key distribution (QKD) with one-way quantum communication in polarization space over 75 km. So far, our experimental implementation is the only one that really offers the unconditionally secure final keys among all the implementations of long-distance QKD with weak coherent states. We use 3 different intensities of 0, 0.2 and 0.6 for the pulses of source in our experiment. In order to eliminate the influences of polarization mode dispersion in the long-distance single-mode optical fiber, an automatic polarization compensation system is utilized to implement the active compensation. Only one detector is used in our experiment. The secure distance can be raised to 120 km given 4 detectors.

  18. Algebraic geometry informs perturbative quantum field theory

    Broadhurst, David

    2014-01-01

    Single-scale Feynman diagrams yield integrals that are periods, namely projective integrals of rational functions of Schwinger parameters. Algebraic geometry may therefore inform us of the types of number to which these integrals evaluate. We give examples at 3, 4 and 6 loops of massive Feynman diagrams that evaluate to Dirichlet $L$-series of modular forms and examples at 6, 7 and 8 loops of counterterms that evaluate to multiple zeta values or polylogarithms of the sixth root of unity. At 8 loops and beyond, algebraic geometry informs us that polylogs are insufficient for the evaluation of terms in the beta-function of $\\phi^4$ theory. Here, modular forms appear as obstructions to polylogarithmic evaluation.

  19. EDITORIAL: Focus on Quantum Information and Many-Body Theory

    Eisert, Jens; Plenio, Martin B.

    2010-02-01

    Quantum many-body models describing natural systems or materials and physical systems assembled piece by piece in the laboratory for the purpose of realizing quantum information processing share an important feature: intricate correlations that originate from the coherent interaction between a large number of constituents. In recent years it has become manifest that the cross-fertilization between research devoted to quantum information science and to quantum many-body physics leads to new ideas, methods, tools, and insights in both fields. Issues of criticality, quantum phase transitions, quantum order and magnetism that play a role in one field find relations to the classical simulation of quantum systems, to error correction and fault tolerance thresholds, to channel capacities and to topological quantum computation, to name but a few. The structural similarities of typical problems in both fields and the potential for pooling of ideas then become manifest. Notably, methods and ideas from quantum information have provided fresh approaches to long-standing problems in strongly correlated systems in the condensed matter context, including both numerical methods and conceptual insights. Focus on quantum information and many-body theory Contents TENSOR NETWORKS Homogeneous multiscale entanglement renormalization ansatz tensor networks for quantum critical systems M Rizzi, S Montangero, P Silvi, V Giovannetti and Rosario Fazio Concatenated tensor network states R Hübener, V Nebendahl and W Dür Entanglement renormalization in free bosonic systems: real-space versus momentum-space renormalization group transforms G Evenbly and G Vidal Finite-size geometric entanglement from tensor network algorithms Qian-Qian Shi, Román Orús, John Ove Fjærestad and Huan-Qiang Zhou Characterizing symmetries in a projected entangled pair state D Pérez-García, M Sanz, C E González-Guillén, M M Wolf and J I Cirac Matrix product operator representations B Pirvu, V Murg, J I Cirac

  20. Hybrid ququart-encoded quantum cryptography protected by Kochen-Specker contextuality

    Cabello, Adan; Nagali, Eleonora; Sciarrino, Fabio; 10.1103/PhysRevA.84.030302

    2011-01-01

    Quantum cryptographic protocols based on complementarity are nonsecure against attacks in which complementarity is imitated with classical resources. The Kochen-Specker (KS) theorem provides protection against these attacks, without requiring entanglement or spatially separated composite systems. We analyze the maximum tolerated noise to guarantee the security of a KS-protected cryptographic scheme against these attacks, and describe a photonic realization of this scheme using hybrid ququarts defined by the polarization and orbital angular momentum of single photons.

  1. Quantum secret sharing based on quantum error-correcting codes

    Zhang Zu-Rong; Liu Wei-Tao; Li Cheng-Zu

    2011-01-01

    Quantum secret sharing(QSS) is a procedure of sharing classical information or quantum information by using quantum states. This paper presents how to use a [2k - 1,1, k] quantum error-correcting code (QECC) to implement a quantum (k, 2k - 1) threshold scheme. It also takes advantage of classical enhancement of the [2k - 1, l,k] QECC to establish a QSS scheme which can share classical information and quantum information simultaneously. Because information is encoded into QECC, these schemes can prevent intercept-resend attacks and be implemented on some noisy channels.

  2. Multiplexed CV quantum teleportation for high rates in quantum communication

    Christ, Andreas; Silberhorn, Christine

    2012-01-01

    A major challenge of today's quantum communication systems lies in the transmission of quantum information with high rates over long distances in the presence of unavoidable losses. Thereby the achievable quantum communication rate is fundamentally limited by the amount of energy that can be transmitted per use of the channel. It is hence vital to develop quantum communication protocols which encode quantum information as energy efficiently as possible. To this aim we investigate continuous-variable quantum teleportation as a method of distributing quantum information. We explore the possibility to encode information on multiple optical modes and derive upper and lower bounds on the achievable quantum channel capacities. This analysis enables us to benchmark single-mode vs. multi-mode entanglement resources. Our research reveals that multiplexing does not only feature an enhanced energy efficiency, significantly increasing the achievable quantum communication rates in comparison to single-mode coding, but als...

  3. Photon Temporal Modes: A Complete Framework for Quantum Information Science

    Brecht, B.; Reddy, Dileep V.; Silberhorn, C.; Raymer, M. G.

    2015-10-01

    Field-orthogonal temporal modes of photonic quantum states provide a new framework for quantum information science (QIS). They intrinsically span a high-dimensional Hilbert space and lend themselves to integration into existing single-mode fiber communication networks. We show that the three main requirements to construct a valid framework for QIS—the controlled generation of resource states, the targeted and highly efficient manipulation of temporal modes, and their efficient detection—can be fulfilled with current technology. We suggest implementations of diverse QIS applications based on this complete set of building blocks.

  4. Information Geometry of Entanglement Renormalization for free Quantum Fields

    Molina-Vilaplana, Javier

    2015-01-01

    We provide an explicit connection between the differential generation of entanglement entropy in a tensor network representation of the ground states of two field theories, and a geometric description of these states based on the Fisher information metric. We show how the geometrical description remains invariant despite there is an irreducible gauge freedom in the definition of the tensor network. The results might help to understand how spacetimes may emerge from distributions of quantum states, or more concretely, from the structure of the quantum entanglement concomitant to those distributions.

  5. Collective dynamics of solid-state spin chains and ensembles in quantum information processing

    Ping, Yuting

    This thesis is concerned with the collective dynamics in different spin chains and spin ensembles in solid-state materials. The focus is on the manipulation of electron spins, through spin-spin and spin-photon couplings controlled by voltage potentials or electromagnetic fields. A brief review of various systems is provided to describe the possible physical implementation of the ideas, and also outlines the basis of the adopted effective interaction models. The first two ideas presented explore the collective behaviour of non-interacting spin chains with external couplings. One focuses on mapping the identical state of spin-singlet pairs in two currents onto two distant, static spins downstream, creating distributed entanglement that may be accessed. The other studies a quantum memory consisting of an array of non-interacting, static spins, which may encode and decode multiple flying spins. Both chains could effectively `enhance' weak couplings in a cumulative fashion, and neither scheme requires active quantum control. Moreover, the distributed entanglement generated can offer larger separation between the qubits than more conventional protocols that only exploit the tunnelling effects between quantum dots. The quantum memory can also `smooth' the statistical fluctuations in the effects of local errors when the stored information is spread. Next, an interacting chain of static spins with nearest-neighbour interactions is introduced to connect distant end spins. Previously, it has been shown that this approach provides a cubic speed-up when compared with the direct coupling between the target spins. The practicality of this scheme is investigated by analysing realistic error effects via numerical simulations, and from that perspective relaxation of the nearest-neighbour assumption is proposed. Finally, a non-interacting electron spin ensemble is reviewed as a quantum memory to store single photons from an on-chip stripline cavity. It is then promoted to a full

  6. Mathematical Foundations of Quantum Information and Computation and Its Applications to Nano- and Bio-systems

    Ohya, Masanori

    2011-01-01

    This monograph provides a mathematical foundation  to  the theory of quantum information and computation, with applications to various open systems including nano and bio systems. It includes introductory material on algorithm, functional analysis, probability theory, information theory, quantum mechanics and quantum field theory. Apart from standard material on quantum information like quantum algorithm and teleportation, the authors discuss findings on the theory of entropy in C*-dynamical systems, space-time dependence of quantum entangled states, entangling operators, adaptive dynamics, relativistic quantum information, and a new paradigm for quantum computation beyond the usual quantum Turing machine. Also, some important applications of information theory to genetics and life sciences, as well as recent experimental and theoretical discoveries in quantum photosynthesis are described.

  7. Information capacities of quantum measurement channels

    Holevo, A. S.

    2013-03-01

    We study the relation between the unassisted and entanglement-assisted classical capacities C and Cea of entanglement-breaking channels. We argue that the gain of entanglement assistance Cea/C > 1 generically for measurement channels with unsharp observables; in particular for the measurements with pure posterior states the information loss in the entanglement-assisted protocol is zero, resulting in an arbitrarily large gain for very noisy or weak signal channels. This is illustrated by examples of continuous observables corresponding to state tomography in finite dimensions and heterodyne measurement. In contrast, state preparations are characterized by the property of having no gain of entanglement assistance, Cea/C = 1.

  8. Spying on photons with photons: quantum interference and information

    Ataman, Stefan

    2016-01-01

    The quest to have both which-path knowledge and interference fringes in a double-slit experiment dates back to the inception of quantum mechanics (QM) and to the famous Einstein-Bohr debates. In this paper we propose and discuss an experiment able to spy on one photon's path with another photon. We modify the quantum state inside the interferometer as opposed to the traditional physical modification of the "wave-like" or "particle-like" experimental setup. We are able to show that it is the ability to harvest or not which-path information that finally limits the visibility of the interference pattern and not the "wave-like" or "particle-like" experimental setups. Remarkably, a full "particle-like" experimental setup is able to show interference fringes with 100 % visibility if the quantum state is carefully engineered.

  9. A Framework for Non-Asymptotic Quantum Information Theory

    Tomamichel, Marco

    2012-01-01

    This thesis consolidates, improves and extends the smooth entropy framework for non-asymptotic information theory and cryptography. We investigate the conditional min- and max-entropy for quantum states, generalizations of classical R\\'enyi entropies. We introduce the purified distance, a novel metric for unnormalized quantum states and use it to define smooth entropies as optimizations of the min- and max-entropies over a ball of close states. We explore various properties of these entropies, including data-processing inequalities, chain rules and their classical limits. The most important property is an entropic formulation of the asymptotic equipartition property, which implies that the smooth entropies converge to the von Neumann entropy in the limit of many independent copies. The smooth entropies also satisfy duality and entropic uncertainty relations that provide limits on the power of two different observers to predict the outcome of a measurement on a quantum system. Finally, we discuss three example...

  10. Spying on photons with photons: quantum interference and information

    Ataman, Stefan

    2016-07-01

    The quest to have both which-path knowledge and interference fringes in a double-slit experiment dates back to the inception of quantum mechanics (QM) and to the famous Einstein-Bohr debates. In this paper we propose and discuss an experiment able to spy on one photon's path with another photon. We modify the quantum state inside the interferometer as opposed to the traditional physical modification of the "wave-like" or "particle-like" experimental setup. We are able to show that it is the ability to harvest or not which-path information that finally limits the visibility of the interference pattern and not the "wave-like" or "particle-like" experimental setups. Remarkably, a full "particle-like" experimental setup is able to show interference fringes with 100% visibility if the quantum state is carefully engineered.

  11. Some applications of uncertainty relations in quantum information

    Majumdar, A. S.; Pramanik, T.

    2016-08-01

    We discuss some applications of various versions of uncertainty relations for both discrete and continuous variables in the context of quantum information theory. The Heisenberg uncertainty relation enables demonstration of the Einstein, Podolsky and Rosen (EPR) paradox. Entropic uncertainty relations (EURs) are used to reveal quantum steering for non-Gaussian continuous variable states. EURs for discrete variables are studied in the context of quantum memory where fine-graining yields the optimum lower bound of uncertainty. The fine-grained uncertainty relation is used to obtain connections between uncertainty and the nonlocality of retrieval games for bipartite and tripartite systems. The Robertson-Schrödinger (RS) uncertainty relation is applied for distinguishing pure and mixed states of discrete variables.

  12. Controlled teleportation of multi-qudit quantum information

    2007-01-01

    We propose a scheme for realizing a controlled teleportation of random M-qudit quantum information under the control of N agents. The resource consumption includes a prearranged (2M + N + 1)-qudit entangled quantum channel and (2M + N + 1) log2 d-bit classical communication. And the quantum operations used in the teleportation process are a series of generalized Bell-state measurements, single-qudit measurements, qudit H-gates, qudit-Pauli gates and qudit phase gates. It is shown that the original state can be restored by the receiver only on condition that all the agents work in collaboration with each others. If one agent does not cooperate with the other, the original state cannot be fully recovered.

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

    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.

  14. Nambu-Goldstone Effective Theory of Information at Quantum Criticality

    Dvali, Gia; Gomez, Cesar; Wintergerst, Nico

    2015-01-01

    We establish a fundamental connection between quantum criticality of a many-body system, such as Bose-Einstein condensates, and its capacity of information-storage and processing. For deriving the effective theory of modes in the vicinity of the quantum critical point we develop a new method by mapping a Bose-Einstein condensate of $N$-particles onto a sigma model with a continuous global (pseudo)symmetry that mixes bosons of different momenta. The Bogolyubov modes of the condensate are mapped onto the Goldstone modes of the sigma model, which become gapless at the critical point. These gapless Goldstone modes are the quantum carriers of information and entropy. Analyzing their effective theory, we observe the information-processing properties strikingly similar to the ones predicted by the black hole portrait. The energy cost per qubit of information-storage vanishes in the large-$N$ limit and the total information-storage capacity increases with $N$ either exponentially or as a power law. The longevity of i...

  15. High-resolution 1H NMR spectroscopy of fish muscle, eggs and small whole fish via Hadamard-encoded intermolecular multiple-quantum coherence.

    Honghao Cai

    Full Text Available BACKGROUND AND PURPOSE: Nuclear magnetic resonance (NMR spectroscopy has become an important technique for tissue studies. Since tissues are in semisolid-state, their high-resolution (HR spectra cannot be obtained by conventional NMR spectroscopy. Because of this restriction, extraction and high-resolution magic angle spinning (HR MAS are widely applied for HR NMR spectra of tissues. However, both of the methods are subject to limitations. In this study, the feasibility of HR (1H NMR spectroscopy based on intermolecular multiple-quantum coherence (iMQC technique is explored using fish muscle, fish eggs, and a whole fish as examples. MATERIALS AND METHODS: Intact salmon muscle tissues, intact eggs from shishamo smelt and a whole fish (Siamese algae eater are studied by using conventional 1D one-pulse sequence, Hadamard-encoded iMQC sequence, and HR MAS. RESULTS: When we use the conventional 1D one-pulse sequence, hardly any useful spectral information can be obtained due to the severe field inhomogeneity. By contrast, HR NMR spectra can be obtained in a short period of time by using the Hadamard-encoded iMQC method without shimming. Most signals from fatty acids and small metabolites can be observed. Compared to HR MAS, the iMQC method is non-invasive, but the resolution and the sensitivity of resulting spectra are not as high as those of HR MAS spectra. CONCLUSION: Due to the immunity to field inhomogeneity, the iMQC technique can be a proper supplement to HR MAS, and it provides an alternative for the investigation in cases with field distortions and with samples unsuitable for spinning. The acquisition time of the proposed method is greatly reduced by introduction of the Hadamard-encoded technique, in comparison with that of conventional iMQC method.

  16. Coherent versus Measurement Feedback: Linear Systems Theory for Quantum Information

    Yamamoto, Naoki

    2014-10-01

    To control a quantum system via feedback, we generally have two options in choosing a control scheme. One is the coherent feedback, which feeds the output field of the system, through a fully quantum device, back to manipulate the system without involving any measurement process. The other one is measurement-based feedback, which measures the output field and performs a real-time manipulation on the system based on the measurement results. Both schemes have advantages and disadvantages, depending on the system and the control goal; hence, their comparison in several situations is important. This paper considers a general open linear quantum system with the following specific control goals: backaction evasion, generation of a quantum nondemolished variable, and generation of a decoherence-free subsystem, all of which have important roles in quantum information science. Some no-go theorems are proven, clarifying that those goals cannot be achieved by any measurement-based feedback control. On the other hand, it is shown that, for each control goal there exists a coherent feedback controller accomplishing the task. The key idea to obtain all the results is system theoretic characterizations of the above three notions in terms of controllability and observability properties or transfer functions of linear systems, which are consistent with their standard definitions.

  17. Parallel Information Transfer in a Multi-Node Quantum Information Processor

    Borneman, Troy W; Cory, David G

    2011-01-01

    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.

  18. Quantum engineering of continuous variable quantum states

    Sabuncu, Metin

    2009-10-29

    Quantum information with continuous variables is a field attracting increasing attention recently. In continuous variable quantum information one makes use of the continuous information encoded into the quadrature of a quantized light field instead of binary quantities such as the polarization state of a single photon. This brand new research area is witnessing exciting theoretical and experimental achievements such as teleportation, quantum computation and quantum error correction. The rapid development of the field is mainly due higher optical data rates and the availability of simple and efficient manipulation tools in continuous-variable quantum information processing. We in this thesis extend the work in continuous variable quantum information processing and report on novel experiments on amplification, cloning, minimal disturbance and noise erasure protocols. The promising results we obtain in these pioneering experiments indicate that the future of continuous variable quantum information is bright and many advances can be foreseen. (orig.)

  19. Long-term time series analysis of quantum dot encoded cells by deconvolution of the autofluorescence signal.

    Brown, M Rowan; Summers, Huw D; Rees, Paul; Chappell, Sally C; Silvestre, Oscar F; Khan, Imtiaz A; Smith, Paul J; Errington, Rachel J

    2010-10-01

    The monitoring of cells labeled with quantum dot endosome-targeted markers in a highly proliferative population provides a quantitative approach to determine the redistribution of quantum dot signal as cells divide over generations. We demonstrate that the use of time-series flow cytometry in conjunction with a stochastic numerical simulation to provide a means to describe the proliferative features and quantum dot inheritance over multiple generations of a human tumor population. However, the core challenge for long-term tracking where the original quantum dot fluorescence signal over time becomes redistributed across a greater cell number requires accountability of background fluorescence in the simulation. By including an autofluorescence component, we are able to continue even when this signal predominates (i.e., >80% of the total signal) and obtain valid readouts of the proliferative system. We determine the robustness of the technique by tracking a human osteosarcoma cell population over 8 days and discuss the accuracy and certainty of the model parameters obtained. This systems biology approach provides insight into both cell heterogeneity and division dynamics within the population and furthermore informs on the lineage history of its members.

  20. Event-related potential variations in the encoding and retrieval of different amounts of contextual information.

    Estrada-Manilla, Cinthya; Cansino, Selene

    2012-06-15

    Episodic memory events occur within multidimensional contexts; however, the electrophysiological manifestations associated with processing of more than one context have been rarely investigated. The effect of the amount of context on the ERPs was studied using two single and one double source memory tasks and by comparing full and partial context retrieval within a double source task. The single source tasks elicited waveforms with a larger amplitude during successful encoding and retrieval than the double source task. Compared with the waveforms elicited with a full source response, a partial source response elicited waveforms with a smaller amplitude, probably because the retrieval success for one context was combined with the retrieval attempt processes for the missing source. Comparing the tasks revealed that the larger the amount of contextual information processed, the smaller the amplitude of the ERPs, indicating that greater effort or further control processes were required during double source retrieval.

  1. Quantum information transmission in the quantum wireless multihop network based on Werner state

    Shi, Li-Hui; Yu, Xu-Tao; Cai, Xiao-Fei; Gong, Yan-Xiao; Zhang, Zai-Chen

    2015-05-01

    Many previous studies about teleportation are based on pure state. Study of quantum channel as mixed state is more realistic but complicated as pure states degenerate into mixed states by interaction with environment, and the Werner state plays an important role in the study of the mixed state. In this paper, the quantum wireless multihop network is proposed and the information is transmitted hop by hop through teleportation. We deduce a specific expression of the recovered state not only after one-hop teleportation but also across multiple intermediate nodes based on Werner state in a quantum wireless multihop network. We also obtain the fidelity of multihop teleportation. Project supported by the Prospective Future Network Project of Jiangsu Province, China (Grant No. BY2013095-1-18) and the Independent Project of State Key Laboratory of Millimeter Waves (Grant No. Z201504).

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

    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.

  3. Adaptive Controller Design for Faulty UAVs via Quantum Information Technology

    Fuyang Chen

    2012-12-01

    Full Text Available In this paper, an adaptive controller is designed for a UAV flight control system against faults and parametric uncertainties based on quantum information technology and the Popov hyperstability theory. First, considering the bounded control input, the state feedback controller is designed to make the system stable. The model of adaptive control is introduced to eliminate the impact by the uncertainties of system parameters via quantum information technology. Then, according to the model reference adaptive principle, an adaptive control law based on the Popov hyperstability theory is designed. This law enable better robustness of the flight control system and tracking control performances. The closed‐loop system’s stability is guaranteed by the Popov hyperstability theory. The simulation results demonstrate that a better dynamic performance of the UAV flight control system with faults and parametric uncertainties can be maintained with the proposed method.

  4. Correlations in complex nonlinear systems and quantum information theory

    Guehne, Otfried [Institut fuer Quantenoptik und Quanteninformation, Oesterreichische Akademie der Wissenschaften, Innsbruck (Austria); Galla, Tobias [School of Physics and Astronomy, University of Manchester (United Kingdom)

    2010-07-01

    The dynamical evolution of classical complex systems such as coupled logistic maps or simple models of lattice gases and cellular automata can result in correlations between distant parts of the system. For the understanding of these systems, it is crucial to develop methods to characterize and quantify these multi-party correlations. On the other hand, the study of correlations between distant particles is also a central problem in the field of quantum information theory. There, correlations are often viewed as a resource and many tools have been developed for their characterization. In this talk, we explore the extent to which the tools from quantum information can be applied to study classical complex systems and whether they allow to study complex systems from a different perspective.

  5. Minimising the heat dissipation of quantum information erasure

    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.

  6. Quantum Information in Non-physics Departments at Liberal Arts Colleges

    Westmoreland, Michael

    2012-02-01

    Quantum information and quantum computing have changed our thinking about the basic concepts of quantum physics. These fields have also introduced exciting new applications of quantum mechanics such as quantum cryptography and non-interactive measurement. It is standard to teach such topics only to advanced physics majors who have completed coursework in quantum mechanics. Recent encounters with teaching quantum cryptography to non-majors and a bout of textbook-writing suggest strategies for teaching this interesting material to those without the standard quantum mechanics background. This talk will share some of those strategies.

  7. Quantum Fisher and skew information for Unruh accelerated Dirac qubit

    Banerjee, Subhashish; Alok, Ashutosh Kumar [Indian Institute of Technology Jodhpur, Jodhpur (India); Omkar, S. [Indian Institute of Science Education and Research, Thiruvananthapuram (India)

    2016-08-15

    We develop a Bloch vector representation of the Unruh channel for a Dirac field mode. This is used to provide a unified, analytical treatment of quantum Fisher and skew information for a qubit subjected to the Unruh channel, both in its pure form as well as in the presence of experimentally relevant external noise channels. The time evolution of Fisher and skew information is studied along with the impact of external environment parameters such as temperature and squeezing. The external noises are modelled by both purely dephasing phase damping and the squeezed generalised amplitude damping channels. An interesting interplay between the external reservoir temperature and squeezing on the Fisher and skew information is observed, in particular, for the action of the squeezed generalised amplitude damping channel. It is seen that for some regimes, squeezing can enhance the quantum information against the deteriorating influence of the ambient environment. Similar features are also observed for the analogous study of skew information, highlighting a similar origin of the Fisher and skew information. (orig.)

  8. PREFACE: Nobel Symposium 141: Qubits for Future Quantum Information Nobel Symposium 141: Qubits for Future Quantum Information

    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

  9. Multi-photon entanglement and applications in quantum information

    Schmid, Christian I.T.

    2008-05-30

    In this thesis, two new linear optics networks are introduced and their application for several quantum information tasks is presented. Spontaneous parametric down conversion, is used in different configurations to provide the input states for the networks. The first network is a new design of a controlled phase gate which is particularly interesting for applications in multi-photon experiments as it constitutes an improvement of former realizations with respect to stability and reliability. This is explicitly demonstrated by employing the gate in four-photon experiments. In this context, a teleportation and entanglement swapping protocol is performed in which all four Bell states are distinguished by means of the phase gate. A similar type of measurement applied to the subsystem parts of two copies of a quantum state, allows further the direct estimation of the state's entanglement in terms of its concurrence. Finally, starting from two Bell states, the controlled phase gate is applied for the observation of a four photon cluster state. The analysis of the results focuses on measurement based quantum computation, the main usage of cluster states. The second network, fed with the second order emission of non-collinear type ii spontaneous parametric down conversion, constitutes a tunable source of a whole family of states. Up to now the observation of one particular state required one individually tailored setup. With the network introduced here many different states can be obtained within the same arrangement by tuning a single, easily accessible experimental parameter. These states exhibit many useful properties and play a central role in several applications of quantum information. Here, they are used for the solution of a four-player quantum Minority game. It is shown that, by employing four-qubit entanglement, the quantum version of the game clearly outperforms its classical counterpart. Experimental data obtained with both networks are utilized to

  10. Integrated System Technologies for Modular Trapped Ion Quantum Information Processing

    Crain, Stephen G.

    Although trapped ion technology is well-suited for quantum information science, scalability of the system remains one of the main challenges. One of the challenges associated with scaling the ion trap quantum computer is the ability to individually manipulate the increasing number of qubits. Using micro-mirrors fabricated with micro-electromechanical systems (MEMS) technology, laser beams are focused on individual ions in a linear chain and steer the focal point in two dimensions. Multiple single qubit gates are demonstrated on trapped 171Yb+ qubits and the gate performance is characterized using quantum state tomography. The system features negligible crosstalk to neighboring ions (system photon collection efficiency is increased from 2.2% to 3.4%, which allows for fast state detection of the qubit. For a detection beam intensity of 11 mW/cm 2, the average detection time is 23.7 mus with 99.885(7)% detection fidelity. The technologies demonstrated in this thesis can be integrated to form a single quantum register with all of the necessary resources to perform local gates as well as high fidelity readout and provide a photon link to other systems.

  11. Encoding and Retrieval Processes Involved in the Access of Source Information in the Absence of Item Memory

    Ball, B. Hunter; DeWitt, Michael R.; Knight, Justin B.; Hicks, Jason L.

    2014-01-01

    The current study sought to examine the relative contributions of encoding and retrieval processes in accessing contextual information in the absence of item memory using an extralist cuing procedure in which the retrieval cues used to query memory for contextual information were "related" to the target item but never actually studied.…

  12. Quantum Image Steganography and Steganalysis Based On LSQu-Blocks Image Information Concealing Algorithm

    A. AL-Salhi, Yahya E.; Lu, Songfeng

    2016-08-01

    Quantum steganography can solve some problems that are considered inefficient in image information concealing. It researches on Quantum image information concealing to have been widely exploited in recent years. Quantum image information concealing can be categorized into quantum image digital blocking, quantum image stereography, anonymity and other branches. Least significant bit (LSB) information concealing plays vital roles in the classical world because many image information concealing algorithms are designed based on it. Firstly, based on the novel enhanced quantum representation (NEQR), image uniform blocks clustering around the concrete the least significant Qu-block (LSQB) information concealing algorithm for quantum image steganography is presented. Secondly, a clustering algorithm is proposed to optimize the concealment of important data. Finally, we used Con-Steg algorithm to conceal the clustered image blocks. Information concealing located on the Fourier domain of an image can achieve the security of image information, thus we further discuss the Fourier domain LSQu-block information concealing algorithm for quantum image based on Quantum Fourier Transforms. In our algorithms, the corresponding unitary Transformations are designed to realize the aim of concealing the secret information to the least significant Qu-block representing color of the quantum cover image. Finally, the procedures of extracting the secret information are illustrated. Quantum image LSQu-block image information concealing algorithm can be applied in many fields according to different needs.

  13. Concept of chemical bond and aromaticity based on quantum information theory

    Szilvási, T; Legeza, Ö

    2015-01-01

    Quantum information theory (QIT) emerged in physics as standard technique to extract relevant information from quantum systems. It has already contributed to the development of novel fields like quantum computing, quantum cryptography, and quantum complexity. This arises the question what information is stored according to QIT in molecules which are inherently quantum systems as well. Rigorous analysis of the central quantities of QIT on systematic series of molecules offered the introduction of the concept of chemical bond and aromaticity directly from physical principles and notions. We identify covalent bond, donor-acceptor dative bond, multiple bond, charge-shift bond, and aromaticity indicating unified picture of fundamental chemical models from ab initio.

  14. Experimental implementation of a three qubit quantum game with corrupt source using nuclear magnetic resonance quantum information processor.

    Mitra, Avik; Sivapriya, K; Kumar, Anil

    2007-08-01

    In a three player quantum 'Dilemma' game each player takes independent decisions to maximize his/her individual gain. The optimal strategy in the quantum version of this game has a higher payoff compared to its classical counterpart. However, this advantage is lost if the initial qubits provided to the players are from a noisy source. We have experimentally implemented the three player quantum version of the 'Dilemma' game as described by Johnson, [N.F. Johnson, Phys. Rev. A 63 (2001) 020302(R)] using nuclear magnetic resonance quantum information processor and have experimentally verified that the payoff of the quantum game for various levels of corruption matches the theoretical payoff.

  15. Quantum Interference between Transverse Spatial Waveguide Modes

    Mohanty, Aseema; Dutt, Avik; Ramelow, Sven; Nussenzveig, Paulo; Lipson, Michal

    2016-01-01

    Integrated quantum optics has drastically reduced the size of table-top optical experiments to the chip-scale, allowing for demonstrations of large-scale quantum information processing and quantum simulation. However, despite these advances, practical implementations of quantum photonic circuits remain limited because they consist of large networks of waveguide interferometers that path encode information which do not easily scale. Increasing the dimensionality of current quantum systems using higher degrees of freedom such as transverse spatial field distribution, polarization, time, and frequency to encode more information per carrier will enable scalability by simplifying quantum computational architectures, increasing security and noise tolerance in quantum communication channels, and simulating richer quantum phenomena. Here we demonstrate a scalable platform for photonic quantum information processing using waveguide quantum circuit building blocks based on the transverse spatial mode degree of freedom:...

  16. Decoding quantum information via the Petz recovery map

    Beigi, Salman; Datta, Nilanjana; Leditzky, Felix

    2016-08-01

    We obtain a lower bound on the maximum number of qubits, Q n , ɛ ( N ) , which can be transmitted over n uses of a quantum channel N , for a given non-zero error threshold ɛ. To obtain our result, we first derive a bound on the one-shot entanglement transmission capacity of the channel, and then compute its asymptotic expansion up to the second order. In our method to prove this achievability bound, the decoding map, used by the receiver on the output of the channel, is chosen to be the Petz recovery map (also known as the transpose channel). Our result, in particular, shows that this choice of the decoder can be used to establish the coherent information as an achievable rate for quantum information transmission. Applying our achievability bound to the 50-50 erasure channel (which has zero quantum capacity), we find that there is a sharp error threshold above which Q n , ɛ ( N ) scales as √{ n } .

  17. Decoherence, Control, and Symmetry in Quantum Computers

    Bacon, D J

    2003-01-01

    In this thesis we describe methods for avoiding the detrimental effects of decoherence while at the same time still allowing for computation of the quantum information. The philosophy of the method discussed in the first part of this thesis is to use a symmetry of the decoherence mechanism to find robust encodings of the quantum information. Stability, control, and methods for using decoherence-free information in a quantum computer are presented with a specific emphasis on decoherence due to a collective coupling between the system and its environment. Universal quantum computation on such collective decoherence decoherence-free encodings is demonstrated. Rigorous definitions of control and the use of encoded universality in quantum computers are addressed. Explicit gate constructions for encoded universality on ion trap and exchange based quantum computers are given. In the second part of the thesis we examine physical systems with error correcting properties. We examine systems that can store quantum infor...

  18. Learning weighted sparse representation of encoded facial normal information for expression-robust 3D face recognition

    Li, Huibin

    2011-10-01

    This paper proposes a novel approach for 3D face recognition by learning weighted sparse representation of encoded facial normal information. To comprehensively describe 3D facial surface, three components, in X, Y, and Z-plane respectively, of normal vector are encoded locally to their corresponding normal pattern histograms. They are finally fed to a sparse representation classifier enhanced by learning based spatial weights. Experimental results achieved on the FRGC v2.0 database prove that the proposed encoded normal information is much more discriminative than original normal information. Moreover, the patch based weights learned using the FRGC v1.0 and Bosphorus datasets also demonstrate the importance of each facial physical component for 3D face recognition. © 2011 IEEE.

  19. Probabilistic protocols in quantum information science: Use and abuse

    Caves, Carlton

    2014-03-01

    Protocols in quantum information science often succeed with less than unit probability, but nonetheless perform useful tasks because success occurs often enough to make tolerable the overhead from having to perform the protocol several times. Any probabilistic protocol must be analyzed from the perspective of the resources required to make the protocol succeed. I present results from analyses of two probabilistic protocols: (i) nondeterministic (or immaculate) linear amplification, in which an input coherent state is amplified some of the time to a larger-amplitude coherent state, and (ii) probabilistic quantum metrology, in which one attempts to improve estimation of a parameter (or parameters) by post-selecting on a particular outcome. The analysis indicates that there is little to be gained from probabilistic protocols in these two situations.

  20. Quadrature Uncertainty and Information Entropy of Quantum Elliptical Vortex States

    Banerji, Anindya; Singh, Ravindra Pratap; Chowdhury, Saurav; Bandyopadhyay, Abir

    2013-01-01

    We study the quadrature uncertainty of the quantum elliptical vortex state using the associated Wigner function. Deviations from the minimum uncertainty states were observed due to the absence of the Gaussian nature. In our study of the entropy, we noticed that with increasing vorticity, entropy increases for both the modes. We further observed that, there exists an optimum value of ellipticity which gives rise to maximum entanglement of the two modes of the quantum elliptical vortex states. A further increase in ellipticity reduces the entropy thereby resulting in a loss of information carrying capacity. We check the validity of the entropic inequality relations, namely the subaddivity and the Araki-Lieb inequality. The later was satisfied only for a very small range of the ellipticity of the vortex while the former seemed to be valid at all values.

  1. A quantum informational approach for dissecting chemical reactions

    Duperrouzel, Corinne; Boguslawski, Katharina; Barcza, Gergerly; Legeza, Örs; Ayers, Paul W

    2014-01-01

    We present a conceptionally different approach to dissect bond-formation processes in metal-driven catalysis using concepts from quantum information theory. Our method uses the entanglement and correlation among molecular orbitals to analyze changes in electronic structure that accompany chemical processes. As a proof-of-principle example, the evolution of nickel-ethene bond-formation is dissected which allows us to monitor the interplay of back-bonding and $\\pi$-donation along the reaction coordinate. Furthermore, the reaction pathway of nickel-ethene complexation is analyzed using quantum chemistry methods revealing the presence of a transition state. Our study supports the crucial role of metal-to-ligand back-donation in the bond-forming process of nickel-ethene.

  2. Information Geometry of Quantum Entangled Gaussian Wave-Packets

    Kim, D -H; Cafaro, C; Mancini, S

    2011-01-01

    Describing and understanding the essence of quantum entanglement and its connection to dynamical chaos is of great scientific interest. In this work, using information geometric (IG) techniques, we investigate the effects of micro-correlations on the evolution of maximal probability paths on statistical manifolds induced by systems whose microscopic degrees of freedom are Gaussian distributed. We use the statistical manifolds associated with correlated and non-correlated Gaussians to model the scattering induced quantum entanglement of two spinless, structureless, non-relativistic particles, the latter represented by minimum uncertainty Gaussian wave-packets. Knowing that the degree of entanglement is quantified by the purity P of the system, we express the purity for s-wave scattering in terms of the micro-correlation coefficient r - a quantity that parameterizes the correlated microscopic degrees of freedom of the system; thus establishing a connection between entanglement and micro-correlations. Moreover, ...

  3. Planar ion chip design for scalable quantum information processing

    Wan Jin-Yin; Wang Yu-Zhu; Liu Liang

    2008-01-01

    We investigate a planar ion chip design with a two-dimensional array of linear ion traps for scalable quantum information processing.Qubits are formed from the internal electronic states of trapped 40Ca+ ions.The segmented electrodes reside in a single plane on a substrate and a grounded metal plate separately,a combination of appropriaterf and DC potentials is applied to them for stable ion confinement.Every two adjacent electrodes can generate a linear ion trap in and between the electrodes above the chip at a distance dependent on the geometrical scale and other considerations.The potential distributions are calculated by using a static electric field qualitatively.This architecture provides a conceptually simple avenue to achieving the microfabrication and large-scale quantum computation based on the axrays of trapped ions.

  4. Quantum Darwinism: Entanglement, branches, and the emergent classicality of redundantly stored quantum information

    Blume-Kohout, Robin; Zurek, Wojciech H.

    2006-06-01

    We lay a comprehensive foundation for the study of redundant information storage in decoherence processes. Redundancy has been proposed as a prerequisite for objectivity, the defining property of classical objects. We consider two ensembles of states for a model universe consisting of one system and many environments: the first consisting of arbitrary states, and the second consisting of “singly branching” states consistent with a simple decoherence model. Typical states from the random ensemble do not store information about the system redundantly, but information stored in branching states has a redundancy proportional to the environment’s size. We compute the specific redundancy for a wide range of model universes, and fit the results to a simple first-principles theory. Our results show that the presence of redundancy divides information about the system into three parts: classical (redundant); purely quantum; and the borderline, undifferentiated or “nonredundant,” information.

  5. Few-Qubit Magnetic Resonance Quantum Information Processors: Simulating Chemistry and Physics

    Criger, Ben; Baugh, Jonathan

    2012-01-01

    We review recent progress made in quantum information processing (QIP) which can be applied in the simulation of quantum systems and chemical phenomena. The review is focused on quantum algorithms which are useful for quantum simulation of chemistry and advances in nuclear magnetic resonance (NMR) and electron spin resonance (ESR) QIP. Discussions also include a number of recent experiments demonstrating the current capabilities of the NMR QIP for quantum simulation and prospects for spin-based implementations of QIP.

  6. The Introduction of Quantum Computation and Quantum Information%量子计算与量子信息简介

    2015-01-01

    介绍量子计算与量子信息的产生背景、发展简史,量子比特与量子门的数学描述以及它们与物理概念之间的关系。介绍量子并行基础的线性叠加、量子力学独特资源的纠缠及其应用。介绍量子密码无条件安全的理论基础、发展历史,量子信息学研究、量子计算机实现的现状,并对未来作展望。%Introduces the background and the brief history of quantum computation and quantum information, describes the mathematical description of qubits and quantum gates and the relation between the mathematical description and their physical concepts. Introduces the linear su-perposition principle, which is the foundation of parallel computation, and quantum entanglement which is the unique property of quantum mechanics, and its application. Introduces the theory foundation of unconditional security of quantum cryptography and its history, intro-duces the current situation of the research on quantum information theory and the implement of quantum computer, and the future per-spective of quantum computation and quantum information.

  7. Decoherence-free quantum-information processing using dipole-coupled qubits

    Brooke, P G

    2007-01-01

    We propose a quantum-information processor that consists of decoherence-free logical qubits encoded into arrays of dipole-coupled qubits. High-fidelity single-qubit operations are performed deterministically within a decoherence-free subsystem without leakage via global addressing of bichromatic laser fields. Two-qubit operations are realized locally with four physical qubits, and between separated logical qubits using linear optics. We show how to prepare cluster states using this method. We include all non-nearest-neighbor effects in our calculations, and we assume the qubits are not located in the Dicke limit. Although our proposal is general to any system of dipole-coupled qubits, throughout the paper we use nitrogen-vacancy (NV) centers in diamond as an experimental context for our theoretical results.

  8. Episodic retrieval involves early and sustained effects of reactivating information from encoding.

    Johnson, Jeffrey D; Price, Mason H; Leiker, Emily K

    2015-02-01

    Several fMRI studies have shown a correspondence between the brain regions activated during encoding and retrieval, consistent with the view that memory retrieval involves hippocampally-mediated reinstatement of cortical activity. With the limited temporal resolution of fMRI, the precise timing of such reactivation is unclear, calling into question the functional significance of these effects. Whereas reactivation influencing retrieval should emerge with neural correlates of retrieval success, that signifying post-retrieval monitoring would trail retrieval. The present study employed EEG to provide a temporal landmark of retrieval success from which we could investigate the sub-trial time course of reactivation. Pattern-classification analyses revealed that early-onsetting reactivation differentiated the outcome of recognition-memory judgments and was associated with individual differences in behavioral accuracy, while reactivation was also evident in a sustained form later in the trial. The EEG findings suggest that, whereas prior fMRI findings could be interpreted as reflecting the contribution of reinstatement to retrieval success, they could also indicate the maintenance of episodic information in service of post-retrieval evaluation.

  9. Information encoded in non-native states drives substrate-chaperone pairing.

    Mapa, Koyeli; Tiwari, Satyam; Kumar, Vignesh; Jayaraj, Gopal Gunanathan; Maiti, Souvik

    2012-09-05

    Many proteins refold in vitro through kinetic folding intermediates that are believed to be by-products of native-state centric evolution. These intermediates are postulated to play only minor roles, if any, in vivo because they lack any information related to translation-associated vectorial folding. We demonstrate that refolding intermediate of a test protein, generated in vitro, is able to find its cognate chaperone, from the whole complement of Escherichia coli soluble chaperones. Cognate chaperone-binding uniquely alters the conformation of non-native substrate. Importantly, precise chaperone targeting of substrates are maintained as long as physiological molar ratios of chaperones remain unaltered. Using a library of different chaperone substrates, we demonstrate that kinetically trapped refolding intermediates contain sufficient structural features for precise targeting to cognate chaperones. We posit that evolution favors sequences that, in addition to coding for a functional native state, encode folding intermediates with higher affinity for cognate chaperones than noncognate ones.

  10. Fault-tolerant quantum computation

    Preskill, J

    1997-01-01

    The discovery of quantum error correction has greatly improved the long-term prospects for quantum computing technology. Encoded quantum information can be protected from errors that arise due to uncontrolled interactions with the environment, or due to imperfect implementations of quantum logical operations. Recovery from errors can work effectively even if occasional mistakes occur during the recovery procedure. Furthermore, encoded quantum information can be processed without serious propagation of errors. In principle, an arbitrarily long quantum computation can be performed reliably, provided that the average probability of error per gate is less than a certain critical value, the accuracy threshold. It may be possible to incorporate intrinsic fault tolerance into the design of quantum computing hardware, perhaps by invoking topological Aharonov-Bohm interactions to process quantum information.

  11. Information-theoretic approach to quantum error correction and reversible measurement

    Nielsen, M A; Schumacher, B; Barnum, H N; Caves, Carlton M.; Schumacher, Benjamin; Barnum, Howard

    1997-01-01

    Quantum operations provide a general description of the state changes allowed by quantum mechanics. The reversal of quantum operations is important for quantum error-correcting codes, teleportation, and reversing quantum measurements. We derive information-theoretic conditions and equivalent algebraic conditions that are necessary and sufficient for a general quantum operation to be reversible. We analyze the thermodynamic cost of error correction and show that error correction can be regarded as a kind of ``Maxwell demon,'' for which there is an entropy cost associated with information obtained from measurements performed during error correction. A prescription for thermodynamically efficient error correction is given.

  12. Role of information theoretic uncertainty relations in quantum theory

    Jizba, Petr, E-mail: p.jizba@fjfi.cvut.cz [FNSPE, Czech Technical University in Prague, Břehová 7, 115 19 Praha 1 (Czech Republic); ITP, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin (Germany); Dunningham, Jacob A., E-mail: J.Dunningham@sussex.ac.uk [Department of Physics and Astronomy, University of Sussex, Falmer, Brighton, BN1 9QH (United Kingdom); Joo, Jaewoo, E-mail: j.joo@surrey.ac.uk [Advanced Technology Institute and Department of Physics, University of Surrey, Guildford, GU2 7XH (United Kingdom)

    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. Information dynamics and open systems classical and quantum approach

    Ingarden, R S; Ohya, M

    1997-01-01

    This book aims to present an information-theoretical approach to thermodynamics and its generalisations On the one hand, it generalises the concept of `information thermodynamics' to that of `information dynamics' in order to stress applications outside thermal phenomena On the other hand, it is a synthesis of the dynamics of state change and the theory of complexity, which provide a common framework to treat both physical and nonphysical systems together Both classical and quantum systems are discussed, and two appendices are included to explain principal definitions and some important aspects of the theory of Hilbert spaces and operator algebras The concept of higher-order temperatures is explained and applied to biological and linguistic systems The theory of open systems is presented in a new, much more general form Audience This volume is intended mainly for theoretical and mathematical physicists, but also for mathematicians, experimental physicists, physical chemists, theoretical biologists, communicat...

  14. Trapped-ion antennae for the transmission of quantum information

    Harlander, Maximilian; Brownnutt, Micheal; Blatt, Rainer; Hänsel, Wolfgang

    2010-01-01

    More than one hundred years ago Heinrich Hertz succeeded in transmitting signals over a few meters to a receiving antenna using an electromagnetic oscillator and thus proving the electromagnetic theory developed by James C. Maxwell[1]. Since then, technology has developed, and today a variety of oscillators is available at the quantum mechanical level. For quantized electromagnetic oscillations atoms in cavities can be used to couple electric fields[2, 3]. For mechanical oscillators realized, for example, with cantilevers[4, 5] or vibrational modes of trapped atoms[6] or ions[7, 8], a quantum mechanical link between two such oscillators has, to date, been demonstrated in very few cases and has only been achieved in indirect ways. Examples of this include the mechanical transport of atoms carrying the quantum information[9] or the use of spontaneously emitted photons[10]. In this work, direct coupling between the motional dipoles of separately trapped ions is achieved over a distance of 54 {\\mu}m, using the di...

  15. Classical Information Storage in an n-Level Quantum System

    Frenkel, Péter E.; Weiner, Mihály

    2015-12-01

    A game is played by a team of two—say Alice and Bob—in which the value of a random variable x is revealed to Alice only, who cannot freely communicate with Bob. Instead, she is given a quantum n-level system, respectively a classical n-state system, which she can put in possession of Bob in any state she wishes. We evaluate how successfully they managed to store and recover the value of x by requiring Bob to specify a value z and giving a reward of value f ( x, z) to the team. We show that whatever the probability distribution of x and the reward function f are, when using a quantum n-level system, the maximum expected reward obtainable with the best possible team strategy is equal to that obtainable with the use of a classical n-state system. The proof relies on mixed discriminants of positive matrices and—perhaps surprisingly—an application of the Supply-Demand Theorem for bipartite graphs. As a corollary, we get an infinite set of new, dimension dependent inequalities regarding positive operator valued measures and density operators on complex n-space. As a further corollary, we see that the greatest value, with respect to a given distribution of x, of the mutual information I ( x; z) that is obtainable using an n-level quantum system equals the analogous maximum for a classical n-state system.

  16. Arbitrary Waveform Generator for Quantum Information Processing with Trapped Ions

    Bowler, R; Britton, J W; Sawyer, B C; Amini, J

    2013-01-01

    Atomic ions confined in multi-electrode traps have been proposed as a basis for scalable quantum information processing. This scheme involves transporting ions between spatially distinct locations by use of time-varying electric potentials combined with laser or microwave pulses for quantum logic in specific locations. We report the development of a fast multi-channel arbitrary waveform generator for applying the time-varying electric potentials used for transport and for shaping quantum logic pulses. The generator is based on a field-programmable gate array controlled ensemble of 16-bit digital-to-analog converters with an update frequency of 50 MHz and an output range of $\\pm$10 V. The update rate of the waveform generator is much faster than relevant motional frequencies of the confined ions in our experiments, allowing diabatic control of the ion motion. Numerous pre-loaded sets of time-varying voltages can be selected with 40 ns latency conditioned on real-time signals. Here we describe the device and de...

  17. The encoding of individual identity in dolphin signature whistles: how much information is needed?

    Arik Kershenbaum

    Full Text Available Bottlenose dolphins (Tursiops truncatus produce many vocalisations, including whistles that are unique to the individual producing them. Such "signature whistles" play a role in individual recognition and maintaining group integrity. Previous work has shown that humans can successfully group the spectrographic representations of signature whistles according to the individual dolphins that produced them. However, attempts at using mathematical algorithms to perform a similar task have been less successful. A greater understanding of the encoding of identity information in signature whistles is important for assessing similarity of whistles and thus social influences on the development of these learned calls. We re-examined 400 signature whistles from 20 individual dolphins used in a previous study, and tested the performance of new mathematical algorithms. We compared the measure used in the original study (correlation matrix of evenly sampled frequency measurements to one used in several previous studies (similarity matrix of time-warped whistles, and to a new algorithm based on the Parsons code, used in music retrieval databases. The Parsons code records the direction of frequency change at each time step, and is effective at capturing human perception of music. We analysed similarity matrices from each of these three techniques, as well as a random control, by unsupervised clustering using three separate techniques: k-means clustering, hierarchical clustering, and an adaptive resonance theory neural network. For each of the three clustering techniques, a seven-level Parsons algorithm provided better clustering than the correlation and dynamic time warping algorithms, and was closer to the near-perfect visual categorisations of human judges. Thus, the Parsons code captures much of the individual identity information present in signature whistles, and may prove useful in studies requiring quantification of whistle similarity.

  18. A quantum information perspective of fermionic quantum many-body systems

    Kraus, Christina V.

    2009-11-02

    In this Thesis fermionic quantum many-body system are theoretically investigated from a quantum information perspective. Quantum correlations in fermionic many-body systems, though central to many of the most fascinating effects of condensed matter physics, are poorly understood from a theoretical perspective. Even the notion of ''paired'' fermions which is widely used in the theory of superconductivity and has a clear physical meaning there, is not a concept of a systematic and mathematical theory so far. Applying concepts and tools from entanglement theory, we close this gap, developing a pairing theory allowing to unambiguously characterize paired states. We develop methods for the detection and quantification of pairing according to our definition which are applicable to current experimental setups. Pairing is shown to be a quantum correlation distinct from any notion of entanglement proposed for fermionic systems, giving further understanding of the structure of highly correlated quantum states. In addition, we show the resource character of paired states for precision metrology, proving that BCS-states allow phase measurements at the Heisenberg limit. Next, the power of fermionic systems is considered in the context of quantum simulations, where we study the possibility to simulate Hamiltonian time evolutions on a cubic lattice under the constraint of translational invariance. Given a set of translationally invariant local Hamiltonians and short range interactions we determine time evolutions which can and those which can not be simulated. Bosonic and finite-dimensional quantum systems (''spins'') are included in our investigations. Furthermore, we develop new techniques for the classical simulation of fermionic many-body systems. First, we introduce a new family of states, the fermionic Projected Entangled Pair States (fPEPS) on lattices in arbitrary spatial dimension. These are the natural generalization of the PEPS

  19. Encoding and retrieval processes involved in the access of source information in the absence of item memory.

    Ball, B Hunter; DeWitt, Michael R; Knight, Justin B; Hicks, Jason L

    2014-09-01

    The current study sought to examine the relative contributions of encoding and retrieval processes in accessing contextual information in the absence of item memory using an extralist cuing procedure in which the retrieval cues used to query memory for contextual information were related to the target item but never actually studied. In Experiments 1 and 2, participants studied 1 category member (e.g., onion) from a variety of different categories and at test were presented with an unstudied category label (e.g., vegetable) to probe memory for item and source information. In Experiments 3 and 4, 1 member of unidirectional (e.g., credit or card) or bidirectional (e.g., salt or pepper) associates was studied, whereas the other unstudied member served as a test probe. When recall failed, source information was accessible only when items were processed deeply during encoding (Experiments 1 and 2) and when there was strong forward associative strength between the retrieval cue and target (Experiments 3 and 4). These findings suggest that a retrieval probe diagnostic of semantically related item information reinstantiates information bound in memory during encoding that results in reactivation of associated contextual information, contingent upon sufficient learning of the item itself and the association between the item and its context information.

  20. State preparation for quantum information science and metrology

    Samblowski, Aiko

    2012-06-08

    The precise preparation of non-classical states of light is a basic requirement for performing quantum information tasks and quantum metrology. Depending on the assignment, the range of required states varies from preparing and modifying squeezed states to generating bipartite entanglement and establishing multimode entanglement networks. Every state needs special preparation techniques and hence it is important to develop the experimental expertise to generate all states with the desired degree of accuracy. In this thesis, the experimental preparation of different kinds of non-classical states of light is demonstrated. Starting with a multimode entangled state, the preparation of an unconditionally generated bound entangled state of light of unprecedented accuracy is shown. Its existence is of fundamental interest, since it certifies an intrinsic irreversibility of entanglement and suggests a connection with thermodynamics. The state is created in a network of linear optics, utilizing optical parametric amplifiers, operated below threshold, beam splitters and phase gates. The experimental platform developed here afforded the precise and stable control of all experimental parameters. Focusing on the aspect of quantum information networks, the generation of suitable bipartite entangled states of light is desirable. The optical connection between atomic transitions and light that can be transmitted via telecommunications fibers opens the possibility to employ quantum memories within fiber networks. For this purpose, a non-degenerate optical parametric oscillator is operated above threshold and the generation of bright bipartite entanglement between its twin beams at the wavelengths of 810 nm and 1550 nm is demonstrated. In the field of metrology, quantum states are used to enhance the measurement precision of interferometric gravitational wave (GW) detectors. Recently, the sensitivity of a GW detector operated at a wavelength of 1064 nm was increased using squeezed

  1. What Density Functional Theory could do for Quantum Information

    Mattsson, Ann

    2015-03-01

    The Hohenberg-Kohn theorem of Density Functional Theory (DFT), and extensions thereof, tells us that all properties of a system of electrons can be determined through their density, which uniquely determines the many-body wave-function. Given access to the appropriate, universal, functionals of the density we would, in theory, be able to determine all observables of any electronic system, without explicit reference to the wave-function. On the other hand, the wave-function is at the core of Quantum Information (QI), with the wave-function of a set of qubits being the central computational resource in a quantum computer. While there is seemingly little overlap between DFT and QI, reliance upon observables form a key connection. Though the time-evolution of the wave-function and associated phase information is fundamental to quantum computation, the initial and final states of a quantum computer are characterized by observables of the system. While observables can be extracted directly from a system's wave-function, DFT tells us that we may be able to intuit a method for extracting them from its density. In this talk, I will review the fundamentals of DFT and how these principles connect to the world of QI. This will range from DFT's utility in the engineering of physical qubits, to the possibility of using it to efficiently (but approximately) simulate Hamiltonians at the logical level. The apparent paradox of describing algorithms based on the quantum mechanical many-body wave-function with a DFT-like theory based on observables will remain a focus throughout. The ultimate goal of this talk is to initiate a dialog about what DFT could do for QI, in theory and in practice. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. A quantum-information theoretic analysis of three-flavor neutrino oscillations. Quantum entanglement, nonlocal and nonclassical features of neutrinos

    Banerjee, Subhashish; Alok, Ashutosh Kumar [Indian Institute of Technology Jodhpur, Jodhpur (India); Srikanth, R. [Poornaprajna Institute of Scientific Research, Banglore (India); Hiesmayr, Beatrix C. [University of Vienna, Vienna (Austria)

    2015-10-15

    Correlations exhibited by neutrino oscillations are studied via quantum-information theoretic quantities. We show that the strongest type of entanglement, genuine multipartite entanglement, is persistent in the flavor changing states. We prove the existence of Bell-type nonlocal features, in both its absolute and genuine avatars. Finally, we show that a measure of nonclassicality, dissension, which is a generalization of quantum discord to the tripartite case, is nonzero for almost the entire range of time in the evolution of an initial electron-neutrino. Via these quantum-information theoretic quantities, capturing different aspects of quantum correlations, we elucidate the differences between the flavor types, shedding light on the quantum-information theoretic aspects of the weak force. (orig.)

  3. A quantum-information theoretic analysis of three-flavor neutrino oscillations. Quantum entanglement, nonlocal and nonclassical features of neutrinos

    Banerjee, Subhashish; Alok, Ashutosh Kumar; Srikanth, R.; Hiesmayr, Beatrix C.

    2015-10-01

    Correlations exhibited by neutrino oscillations are studied via quantum-information theoretic quantities. We show that the strongest type of entanglement, genuine multipartite entanglement, is persistent in the flavor changing states. We prove the existence of Bell-type nonlocal features, in both its absolute and genuine avatars. Finally, we show that a measure of nonclassicality, dissension, which is a generalization of quantum discord to the tripartite case, is nonzero for almost the entire range of time in the evolution of an initial electron-neutrino. Via these quantum-information theoretic quantities, capturing different aspects of quantum correlations, we elucidate the differences between the flavor types, shedding light on the quantum-information theoretic aspects of the weak force.

  4. Unlocking the proteomic information encoded in MALDI-TOF-MS data used for microbial identification and characterization

    Introduction: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS)is increasingly utilized as a rapid technique to identify microorganisms including pathogenic bacteria. However, little attention has been paid to the significant proteomic information encoded in ...

  5. Quantum error correcting codes and one-way quantum computing: Towards a quantum memory

    Schlingemann, D

    2003-01-01

    For realizing a quantum memory we suggest to first encode quantum information via a quantum error correcting code and then concatenate combined decoding and re-encoding operations. This requires that the encoding and the decoding operation can be performed faster than the typical decoherence time of the underlying system. The computational model underlying the one-way quantum computer, which has been introduced by Hans Briegel and Robert Raussendorf, provides a suitable concept for a fast implementation of quantum error correcting codes. It is shown explicitly in this article is how encoding and decoding operations for stabilizer codes can be realized on a one-way quantum computer. This is based on the graph code representation for stabilizer codes, on the one hand, and the relation between cluster states and graph codes, on the other hand.

  6. The energy-level crossing behavior and quantum Fisher information in a quantum well with spin-orbit coupling.

    Wang, Z H; Zheng, Q; Wang, Xiaoguang; Li, Yong

    2016-03-02

    We study the energy-level crossing behavior in a two-dimensional quantum well with the Rashba and Dresselhaus spin-orbit couplings (SOCs). By mapping the SOC Hamiltonian onto an anisotropic Rabi model, we obtain the approximate ground state and its quantum Fisher information (QFI) via performing a unitary transformation. We find that the energy-level crossing can occur in the quantum well system within the available parameters rather than in cavity and circuit quantum eletrodynamics systems. Furthermore, the influence of two kinds of SOCs on the QFI is investigated and an intuitive explanation from the viewpoint of the stationary perturbation theory is given.

  7. Demonstration of sufficient control for two rounds of quantum error correction in a solid state ensemble quantum information processor

    Moussa, Osama; Ryan, Colm A; Laflamme, Raymond

    2011-01-01

    We report the implementation of a 3-qubit quantum error correction code (QECC) on a quantum information processor realized by the magnetic resonance of Carbon nuclei in a single crystal of Malonic Acid. The code corrects for phase errors induced on the qubits due to imperfect decoupling of the magnetic environment represented by nearby spins, as well as unwanted evolution under the internal Hamiltonian. We also experimentally demonstrate sufficiently high fidelity control to implement two rounds of quantum error correction. This is a demonstration of state-of-the-art control in solid state nuclear magnetic resonance, a leading test-bed for the implementation of quantum algorithms.

  8. Demonstration of sufficient control for two rounds of quantum error correction in a solid state ensemble quantum information processor.

    Moussa, Osama; Baugh, Jonathan; Ryan, Colm A; Laflamme, Raymond

    2011-10-14

    We report the implementation of a 3-qubit quantum error-correction code on a quantum information processor realized by the magnetic resonance of carbon nuclei in a single crystal of malonic acid. The code corrects for phase errors induced on the qubits due to imperfect decoupling of the magnetic environment represented by nearby spins, as well as unwanted evolution under the internal Hamiltonian. We also experimentally demonstrate sufficiently high-fidelity control to implement two rounds of quantum error correction. This is a demonstration of state-of-the-art control in solid state nuclear magnetic resonance, a leading test bed for the implementation of quantum algorithms.

  9. Holographic view on quantum correlations and mutual information between disjoint blocks of a quantum critical system

    Molina-Vilaplana, Javier; Sodano, Pasquale

    2011-10-01

    In ( d + 1) dimensional Multiscale Entanglement Renormalization Ansatz (MERA) networks, tensors are connected so as to reproduce the discrete, ( d + 2) holographic geometry of Anti de Sitter space (AdS d+2) with the original system lying at the boundary. We analyze the MERA renormalization flow that arises when computing the quantum correlations between two disjoint blocks of a quantum critical system, to show that the structure of the causal cones characteristic of MERA, requires a transition between two different regimes attainable by changing the ratio between the size and the separation of the two disjoint blocks. We argue that this transition in the MERA causal developments of the blocks may be easily accounted by an AdS d+2 black hole geometry when the mutual information is computed using the Ryu-Takayanagi formula. As an explicit example, we use a BTZ AdS3 black hole to compute the MI and the quantum correlations between two disjoint intervals of a one dimensional boundary critical system. Our results for this low dimensional system not only show the existence of a phase transition emerging when the conformal four point ratio reaches a critical value but also provide an intuitive entropic argument accounting for the source of this instability. We discuss the robustness of this transition when finite temperature and finite size effects are taken into account.

  10. Quantum information processing in the radical-pair mechanism: Haberkorn's theory violates the Ozawa entropy bound.

    Mouloudakis, K; Kominis, I K

    2017-02-01

    Radical-ion-pair reactions, central for understanding the avian magnetic compass and spin transport in photosynthetic reaction centers, were recently shown to be a fruitful paradigm of the new synthesis of quantum information science with biological processes. We show here that the master equation so far constituting the theoretical foundation of spin chemistry violates fundamental bounds for the entropy of quantum systems, in particular the Ozawa bound. In contrast, a recently developed theory based on quantum measurements, quantum coherence measures, and quantum retrodiction, thus exemplifying the paradigm of quantum biology, satisfies the Ozawa bound as well as the Lanford-Robinson bound on information extraction. By considering Groenewold's information, the quantum information extracted during the reaction, we reproduce the known and unravel other magnetic-field effects not conveyed by reaction yields.

  11. Quantum-like model of processing of information in the brain based on classical electromagnetic field

    Khrennikov, Andrei

    2010-01-01

    We propose a model of quantum-like (QL) processing of mental information. This model is based on quantum information theory. However, in contrast to models of ``quantum physical brain'' reducing mental activity (at least at the highest level) to quantum physical phenomena in the brain, our model matches well with the basic neuronal paradigm of the cognitive science. QL information processing is based (surprisingly) on classical electromagnetic signals induced by joint activity of neurons. This novel approach to quantum information is based on representation of quantum mechanics as a version of classical signal theory which was recently elaborated by the author. The brain uses the QL representation (QLR) for working with abstract concepts; concrete images are described by classical information theory. Two processes, classical and QL, are performed parallely. Moreover, information is actively transmitted from one representation to another. A QL concept given in our model by a density operator can generate a var...

  12. Determining the continuous family of quantum Fisher information from linear-response theory

    Shitara, Tomohiro; Ueda, Masahito

    2016-12-01

    The quantum Fisher information represents a continuous family of metrics on the space of quantum states and places the fundamental limit on the accuracy of quantum state estimation. We show that the entire family of quantum Fisher information can be determined from linear-response theory through generalized covariances. We derive the generalized fluctuation-dissipation theorem that relates linear-response functions to generalized covariances and hence allows us to determine the quantum Fisher information from linear-response functions, which are experimentally measurable quantities. As an application, we examine the skew information, which is a quantum Fisher information, of a harmonic oscillator in thermal equilibrium, and show that the equality of the skew-information-based uncertainty relation holds.

  13. Privacy-preserving point-inclusion protocol for an arbitrary area based on phase-encoded quantum private query

    Shi, Run-hua; Mu, Yi; Zhong, Hong; Cui, Jie; Zhang, Shun

    2017-01-01

    The point-inclusion problem is an important secure multi-party computation that it involves two parties, where one has a private point and the other has a private area, and they want to determine whether the point is inside the area without revealing their respective private information. All previously proposed point-inclusion protocols are only suitable for a specific area, such as circle, rectangle and convex polygon. In this paper, we present a novel privacy-preserving point-inclusion quantum protocol for an arbitrary area, which is surrounded by any plane geometric figure. Compared to the classical related protocols, our protocol has the advantages of the higher security and the lower communication complexity.

  14. Limits on the storage of quantum information in a volume of space

    Flammia, Steven T; Kastoryano, Michael J; Kim, Isaac H

    2016-01-01

    We study the fundamental limits on the reliable storage of quantum information in lattices of qubits by deriving tradeoff bounds for approximate quantum error correcting codes. We introduce a notion of local approximate correctability and code distance, and give a number of equivalent formulations thereof, generalizing various exact error-correction criteria. Our tradeoff bounds relate the number of physical qubits $n$, the number of encoded qubits $k$, the code distance $d$, the accuracy parameter $\\delta$ that quantifies how well the erasure channel can be reversed, and the locality parameter $\\ell$ that specifies the length scale at which the recovery operation can be done. In a regime where the recovery is successful to accuracy $\\epsilon$ that is exponentially small in $\\ell$, which is the case for perturbations of local commuting projector codes, our bound reads $kd^{\\frac{2}{D-1}} \\le O\\bigl(n (\\log n)^{\\frac{2D}{D-1}} \\bigr)$ for codes on $D$-dimensional lattices of Euclidean metric. We also find that...

  15. EDITORIAL: Quantum control theory for coherence and information dynamics Quantum control theory for coherence and information dynamics

    Viola, Lorenza; Tannor, David

    2011-08-01

    Precisely characterizing and controlling the dynamics of realistic open quantum systems has emerged in recent years as a key challenge across contemporary quantum sciences and technologies, with implications ranging from physics, chemistry and applied mathematics to quantum information processing (QIP) and quantum engineering. Quantum control theory aims to provide both a general dynamical-system framework and a constructive toolbox to meet this challenge. The purpose of this special issue of Journal of Physics B: Atomic, Molecular and Optical Physics is to present a state-of-the-art account of recent advances and current trends in the field, as reflected in two international meetings that were held on the subject over the last summer and which motivated in part the compilation of this volume—the Topical Group: Frontiers in Open Quantum Systems and Quantum Control Theory, held at the Institute for Theoretical Atomic, Molecular and Optical Physics (ITAMP) in Cambridge, Massachusetts (USA), from 1-14 August 2010, and the Safed Workshop on Quantum Decoherence and Thermodynamics Control, held in Safed (Israel), from 22-27 August 2010. Initial developments in quantum control theory date back to (at least) the early 1980s, and have been largely inspired by the well-established mathematical framework for classical dynamical systems. As the above-mentioned meetings made clear, and as the burgeoning body of literature on the subject testifies, quantum control has grown since then well beyond its original boundaries, and has by now evolved into a highly cross-disciplinary field which, while still fast-moving, is also entering a new phase of maturity, sophistication, and integration. Two trends deserve special attention: on the one hand, a growing emphasis on control tasks and methodologies that are specifically motivated by QIP, in addition and in parallel to applications in more traditional areas where quantum coherence is nevertheless vital (such as, for instance

  16. Quantum entanglement in non-local games, graph parameters and zero-error information theory

    Scarpa, G.

    2013-01-01

    We study quantum entanglement and some of its applications in graph theory and zero-error information theory. In Chapter 1 we introduce entanglement and other fundamental concepts of quantum theory. In Chapter 2 we address the question of how much quantum correlations generated by entanglement can d

  17. Quantum Information and Entropy Spueezing of a Nonlinear Multiquantum JC Model

    Mahmoud Abdel-Aty

    2002-01-01

    We investigate the entropy squeezing of the nonlinear k-quantum JC model. A definition of squeezing is presented for this system based on the quantum information theory. The utility of the definition is illustrated by examining squeezing in the information entropy of a nonlinear k-quantum two-level atom. The influence of the atomic coherence and the detuning parameter on the properties of the information entropy and squeezing of the atomic variables is examined.

  18. Continuous-variable quantum computing in optical time-frequency modes using quantum memories.

    Humphreys, Peter C; Kolthammer, W Steven; Nunn, Joshua; Barbieri, Marco; Datta, Animesh; Walmsley, Ian A

    2014-09-26

    We develop a scheme for time-frequency encoded continuous-variable cluster-state quantum computing using quantum memories. In particular, we propose a method to produce, manipulate, and measure two-dimensional cluster states in a single spatial mode by exploiting the intrinsic time-frequency selectivity of Raman quantum memories. Time-frequency encoding enables the scheme to be extremely compact, requiring a number of memories that are a linear function of only the number of different frequencies in which the computational state is encoded, independent of its temporal duration. We therefore show that quantum memories can be a powerful component for scalable photonic quantum information processing architectures.

  19. QIS-XML: An Extensible Markup Language for Quantum Information Science

    Heus, Pascal

    2011-01-01

    This Master thesis examines issues of interoperability and integration between the Classic Information Science (CIS) and Quantum Information Science (QIS). It provides a short introduction to the Extensible Markup Language (XML) and proceeds to describe the development steps that have lead to a prototype XML specification for quantum computing (QIS-XML). QIS-XML is a proposed framework, based on the widely used standard (XML) to describe, visualize, exchange and process quantum gates and quantum circuits. It also provides a potential approach to a generic programming language for quantum computers through the concept of XML driven compilers. Examples are provided for the description of commonly used quantum gates and circuits, accompanied with tools to visualize them in standard web browsers. An algorithmic example is also presented, performing a simple addition operation with quantum circuits and running the program on a quantum computer simulator. Overall, this initial effort demonstrates how XML technologi...

  20. The geometrical structure of quantum theory as a natural generalization of information geometry

    Reginatto, Marcel [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)

    2015-01-13

    Quantum mechanics has a rich geometrical structure which allows for a geometrical formulation of the theory. This formalism was introduced by Kibble and later developed by a number of other authors. The usual approach has been to start from the standard description of quantum mechanics and identify the relevant geometrical features that can be used for the reformulation of the theory. Here this procedure is inverted: the geometrical structure of quantum theory is derived from information geometry, a geometrical structure that may be considered more fundamental, and the Hilbert space of the standard formulation of quantum mechanics is constructed using geometrical quantities. This suggests that quantum theory has its roots in information geometry.

  1. Construction of a single atom trap for quantum information protocols

    Shea, Margaret E.; Baker, Paul M.; Gauthier, Daniel J.; Duke Physics Department Team

    2016-05-01

    The field of quantum information science addresses outstanding problems such as achieving fundamentally secure communication and solving computationally hard problems. Great progress has been made in the field, particularly using photons coupled to ions and super conducting qubits. Neutral atoms are also interesting for these applications and though the technology for control of neutrals lags behind that of trapped ions, they offer some key advantages: primarily coupling to optical frequencies closer to the telecom band than trapped ions or superconducting qubits. Here we report progress on constructing a single atom trap for 87 Rb. This system is a promising platform for studying the technical problems facing neutral atom quantum computing. For example, most protocols destroy the trap when reading out the neutral atom's state; we will investigate an alternative non-destructive state detection scheme. We detail the experimental systems involved and the challenges addressed in trapping a single atom. All of our hardware components are off the shelf and relatively inexpensive. Unlike many other systems, we place a high numerical aperture lens inside our vacuum system to increase photon collection efficiency. We gratefully acknowledge the financial support of the ARO through Grant # W911NF1520047.

  2. Integrated optics architecture for trapped-ion quantum information processing

    Kielpinski, D.; Volin, C.; Streed, E. W.; Lenzini, F.; Lobino, M.

    2016-12-01

    Standard schemes for trapped-ion quantum information processing (QIP) involve the manipulation of ions in a large array of interconnected trapping potentials. The basic set of QIP operations, including state initialization, universal quantum logic, and state detection, is routinely executed within a single array site by means of optical operations, including various laser excitations as well as the collection of ion fluorescence. Transport of ions between array sites is also routinely carried out in microfabricated trap arrays. However, it is still not possible to perform optical operations in parallel across all array sites. The lack of this capability is one of the major obstacles to scalable trapped-ion QIP and presently limits exploitation of current microfabricated trap technology. Here we present an architecture for scalable integration of optical operations in trapped-ion QIP. We show theoretically that diffractive mirrors, monolithically fabricated on the trap array, can efficiently couple light between trap array sites and optical waveguide arrays. Integrated optical circuits constructed from these waveguides can be used for sequencing of laser excitation and fluorescence collection. Our scalable architecture supports all standard QIP operations, as well as photon-mediated entanglement channels, while offering substantial performance improvements over current techniques.

  3. A Scalable Microfabricated Ion Trap for Quantum Information Processing

    Maunz, Peter; Haltli, Raymond; Hollowell, Andrew; Lobser, Daniel; Mizrahi, Jonathan; Rembetski, John; Resnick, Paul; Sterk, Jonathan D.; Stick, Daniel L.; Blain, Matthew G.

    2016-05-01

    Trapped Ion Quantum Information Processing (QIP) relies on complex microfabricated trap structures to enable scaling of the number of quantum bits. Building on previous demonstrations of surface-electrode ion traps, we have designed and characterized the Sandia high-optical-access (HOA-2) microfabricated ion trap. This trap features high optical access, high trap frequencies, low heating rates, and negligible charging of dielectric trap components. We have observed trap lifetimes of more than 100h, measured trap heating rates for ytterbium of less than 40quanta/s, and demonstrated shuttling of ions from a slotted to an above surface region and through a Y-junction. Furthermore, we summarize demonstrations of high-fidelity single and two-qubit gates realized in this trap. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000. This work was supported by the Intelligence Advanced Research Projects Activity (IARPA).

  4. Myoelectric Control of Artificial Limb by Quantum Information Processing

    Siomau, Michael

    2013-01-01

    Precise and elegant coordination of a prosthesis across many degrees of freedom is highly desired for rehabilitation of people with limb deficiency. Processing the electrical neural signals, collected from the surface of the remnant muscles of the stump, is a common way to activate certain function of the artificial limb. Based on the assumption that there are distinguishable and repeatable signal patterns among different types of muscular activation, the problem of the prosthesis control reduces to the pattern recognition. Widely accepted classical methods for pattern recognition, however, can not provide simultaneous and proportional control of the artificial limb. Here we show that quantum information processing of the neural signals allows us to overcome above difficulties suggesting a very simple scheme for myoelectric control of artificial limb with advanced functionalities.

  5. Dynamical entanglement transfer for quantum-information networks

    Paternostro, Mauro; Son, W.; Kim, M. S.; Falci, Giuseppe; Palma, G. Massimo

    2004-08-01

    A key element in the architecture of a quantum-information processing network is a reliable physical interface between fields and qubits. We study a process of entanglement transfer engineering, where two remote qubits respectively interact with an entangled two-mode continuous-variable (CV) field. We quantify the entanglement induced in the qubit state at the expenses of the loss of entanglement in the CV system. We discuss the range of mixed entangled states which can be obtained with this setup. Furthermore, we suggest a protocol to determine the residual entangling power of the light fields inferring, thus, the entanglement left in the field modes which, after the interaction, are no longer in a Gaussian state. Two different setups are proposed: a cavity-QED system and an interface between superconducting qubits and field modes. We address in detail the practical difficulties inherent in these two proposals, showing that the latter is promising in many aspects.

  6. Quantum information analysis of electronic states at different molecular structures

    Barcza, G; Marti, K H; Reiher, M

    2010-01-01

    We have studied transition metal clusters from a quantum information theory perspective using the density-matrix renormalization group (DMRG) method. We demonstrate the competition between entanglement and interaction localization. We also discuss the application of the configuration interaction based dynamically extended active space procedure which significantly reduces the effective system size and accelerates the speed of convergence for complicated molecular electronic structures to a great extent. Our results indicate the importance of taking entanglement among molecular orbitals into account in order to devise an optimal orbital ordering and carry out efficient calculations on transition metal clusters. We propose a recipe to perform DMRG calculations in a black-box fashion and we point out the connections of our work to other tensor network state approaches.

  7. Myoelectric control of artificial limb inspired by quantum information processing

    Siomau, Michael; Jiang, Ning

    2015-03-01

    Precise and elegant coordination of a prosthesis across many degrees of freedom represents a significant challenge to efficient rehabilitation of people with limb deficiency. Processing the electrical neural signals collected from the surface of the remnant muscles of the stump is a common way to initiate and control the different movements available to the artificial limb. Based on the assumption that there are distinguishable and repeatable signal patterns among different types of muscular activation, the problem of prosthesis control reduces to one of pattern recognition. Widely accepted classical methods for pattern recognition, however, cannot provide simultaneous and proportional control of the artificial limb. Here we show that, in principle, quantum information processing of the neural signals allows us to overcome the above-mentioned difficulties, suggesting a very simple scheme for myoelectric control of artificial limb with advanced functionalities.

  8. Information flow during the quantum-classical transition

    Kowalski, A.M., E-mail: kowalski@fisica.unlp.edu.a [Instituto de Fisica (IFLP-CCT-Conicet), Fac. de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 727, 1900 La Plata (Argentina)] [Comision de Investigaciones Cientificas (CIC) (Argentina); Martin, M.T., E-mail: mtmartin@fisica.unlp.edu.a [Instituto de Fisica (IFLP-CCT-Conicet), Fac. de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 727, 1900 La Plata (Argentina)] [Argentina' s National Research Council (CONICET) (Argentina); Plastino, A., E-mail: plastino@fisica.unlp.edu.a [Instituto de Fisica (IFLP-CCT-Conicet), Fac. de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 727, 1900 La Plata (Argentina)] [Argentina' s National Research Council (CONICET) (Argentina); Zunino, L., E-mail: lucianoz@ciop.unlp.edu.a [Instituto de Fisica Interdisciplinar y Sistemas Complejos (IFISC) CSIC-UIB, Campus Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)] [Centro de Investigaciones Opticas (CONICET La Plata - CIC), C.C. 3, 1897 Gonnet (Argentina)] [Departamento de Ciencias Basicas, Facultad de Ingenieria, Universidad Nacional de La Plata (UNLP), 1900 La Plata (Argentina)

    2010-04-12

    We have exhaustively investigated the classical limit of the semi-classical evolution with reference to a well-known model that represents the interaction between matter and a given field. In this Letter we approach this issue by recourse to a new statistical quantifier called the 'symbolic transfer entropy' [T. Schreiber, Phys. Rev. Lett. 85 (2000) 461; M. Staniek, K. Lehnertz, Phys. Rev. Lett. 100 (2008) 158101]. We encounter that the quantum-classical transition gets thereby described as the sign reversal of the dominating direction of the information flow between classical and quantal variables. This can be considered as an evidence of the physical useful of this new statistical quantifier.

  9. Thermodynamics of information exchange between two coupled quantum dots

    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.

  10. Fundamental properties of devices for quantum information technology

    Nielsen, Per Kær

    This thesis reports a theoretical investigation of the influence of the electronphonon interaction on semiconductor cavity quantum electrodynamical systems, specifically a quantum dot coupled to an optical microcavity. We develop a theoretical description of the decay dynamics of the quantum dot ...

  11. Continuous Variable Quantum State Sharing via Quantum Disentanglement

    Lance, A M; Bowen, W P; Sanders, B C; Tyc, T; Ralph, T C; Lam, P K; Lance, Andrew M.; Symul, Thomas; Bowen, Warwick P.; Sanders, Barry C.; Tyc, Tomas; Ralph, Timothy C.; Lam, Ping Koy

    2004-01-01

    Quantum state sharing is a protocol where perfect reconstruction of quantum states is achieved with incomplete or partial information in a multi-partite quantum networks. Quantum state sharing allows for secure communication in a quantum network where partial information is lost or acquired by malicious parties. This protocol utilizes entanglement for the secret state distribution, and a class of "quantum disentangling" protocols for the state reconstruction. We demonstrate a quantum state sharing protocol in which a tripartite entangled state is used to encode and distribute a secret state to three players. Any two of these players can collaborate to reconstruct the secret state, whilst individual players obtain no information. We investigate a number of quantum disentangling processes and experimentally demonstrate quantum state reconstruction using two of these protocols. We experimentally measure a fidelity, averaged over all reconstruction permutations, of F = 0.73. A result achievable only by using quan...

  12. Neutral Radical Molecules Ordered in Self-Assembled Monolayer Systems for Quantum Information Processing

    Tamulis, A; Tretiak, S; Berman, G P; Allara, D L

    2003-01-01

    Implementation of quantum information processing based on spatially localized electronic spins in stable molecular radicals is discussed. The necessary operating conditions for such molecules are formulated in self-assembled monolayer (SAM) systems. As a model system we start with 1, 3 -diketone types of neutral radicals. Using first principles quantum chemical calculations we prove that these molecules have the stable localized electron spin, which may represent a qubit in quantum information processing.

  13. Quantum String Seal Is Insecure

    Chau, H F

    2006-01-01

    A quantum string seal encodes the value of a (bit) string as a quantum state in such a way that everyone can extract a non-negligible amount of information on the string by a suitable measurement. Moreover, such measurement must disturb the quantum state and is likely to be detected by an authorized verifier. In this way, the intactness of the encoded quantum state plays the role of a wax seal in the digital world. Here I analyze the security of quantum string seal by studying the information disturbance tradeoff of a measurement. This information disturbance tradeoff analysis extends the earlier results of Bechmann-Pasquinucci et al. and Chau by concluding that all quantum string seals are insecure. Specifically, I find a way to obtain non-trivial information on the string that escapes the verifier's detection with probability at least one half.

  14. Holographic View on Quantum Correlations and Mutual Information between Disjoint Blocks of a Quantum Critical System

    Molina-Vilaplana, Javier

    2011-01-01

    We exploit the Multiscale Entanglement Renormalization Ansatz (MERA) to explicitly build the bulk AdSd+2 space associated to a (d+1) dimensional conformal field theory describing a critical system lying at the boundary of the AdS space. We show that, when computing the quantum correlations between two disjoint blocks of the boundary critical system, the structure of the causal cones characteristic of MERA requires a transition between two different regimes attainable by changing the ratio between the size and the separation of the two disjoint blocks. We argue that this transition may be easily accounted for if the metric of the MERA induced holographic dual bulk spacetime is described by an AdSd+2 black hole and the mutual information is computed using the Ryu-Takayanagi formula. As an explicit example, we use a BTZ AdS3 black hole to compute the MI and the quantum correlations between two disjoint intervals of a one dimensional boundary critical system. Our results for this low dimensional system not only s...

  15. Manipulating atom and photon entanglement from 'thought experiments' to quantum information processing

    CERN. Geneva. Audiovisual Unit

    2002-01-01

    Composite quantum systems cannot generally be analysed as a juxtaposition of separate entities, each described by its own wave function. They are described instead by a global entangled state. Entanglement appears thus as an essential concept, lying at the heart of quantum physics. At a fundamental level it is closely related to non-locality, quantum measurement, complementarity and decoherence, concepts that the founding fathers of quantum physics have analysed in various 'thought experiments'. At a more applied level, the engineering of entanglement in systems of increasing complexity could in principle open the way to various kinds of fascinating quantum information processing applications (quantum cryptography, teleportation, quantum computation). The study of entanglement has recently evolved as a very competitive field of research, both theoretical and experimental. In quantum optics, entanglement has been studied with twin-photon beams, trapped ions and with atoms and photons in cavities. After a gener...

  16. QUBIT4MATLAB V3.0: A program package for quantum information science and quantum optics for MATLAB

    Tóth, Géza

    2008-09-01

    A program package for MATLAB is introduced that helps calculations in quantum information science and quantum optics. It has commands for the following operations: (i) Reordering the qudits of a quantum register, computing the reduced state of a quantum register. (ii) Defining important quantum states easily. (iii) Formatted input and output for quantum states and operators. (iv) Constructing operators acting on given qudits of a quantum register and constructing spin chain Hamiltonians. (v) Partial transposition, matrix realignment and other operations related to the detection of quantum entanglement. (vi) Generating random state vectors, random density matrices and random unitaries. Program summaryProgram title:QUBIT4MATLAB V3.0 Catalogue identifier:AEAZ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAZ_v1_0.html Program obtainable from:CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions:Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.:5683 No. of bytes in distributed program, including test data, etc.: 37 061 Distribution format:tar.gz Programming language:MATLAB 6.5; runs also on Octave Computer:Any which supports MATLAB 6.5 Operating system:Any which supports MATLAB 6.5; e.g., Microsoft Windows XP, Linux Classification:4.15 Nature of problem: Subroutines helping calculations in quantum information science and quantum optics. Solution method: A program package, that is, a set of commands is provided for MATLAB. One can use these commands interactively or they can also be used within a program. Running time:10 seconds-1 minute

  17. Controlling Atomic, Solid-State and Hybrid Systems for Quantum Information Processing

    Gullans, Michael John

    Quantum information science involves the use of precise control over quantum systems to explore new technologies. However, as quantum systems are scaled up they require an ever deeper understanding of many-body physics to achieve the required degree of control. Current experiments are entering a regime which requires active control of a mesoscopic number of coupled quantum systems or quantum bits (qubits). This thesis describes several approaches to this goal and shows how mesoscopic quantum systems can be controlled and utilized for quantum information tasks. The first system we consider is the nuclear spin environment of GaAs double quantum dots containing two electrons. We show that the through appropriate control of dynamic nuclear polarization one can prepare the nuclear spin environment in three distinct collective quantum states which are useful for quantum information processing with electron spin qubits. We then investigate a hybrid system in which an optical lattice is formed in the near field scattering off an array of metallic nanoparticles by utilizing the plasmonic resonance of the nanoparticles. We show that such a system would realize new regimes of dense, ultra-cold quantum matter and can be used to create a quantum network of atoms and plasmons. Finally we investigate quantum nonlinear optical systems. We show that the intrinsic nonlinearity for plasmons in graphene can be large enough to make a quantum gate for single photons. We also consider two nonlinear optical systems based on ultracold gases of atoms. In one case, we demonstrate an all-optical single photon switch using cavity quantum electrodynamics (QED) and slow light. In the second case, we study few photon physics in strongly interacting Rydberg polariton systems, where we demonstrate the existence of two and three photon bound states and study their properties.

  18. Efficient On-line Schemes for Encoding Individual Sequences with Side Information at the Decoder

    Reani, Avraham

    2009-01-01

    We present adaptive on-line schemes for lossy encoding of individual sequences under the conditions of the Wyner-Ziv (WZ) problem. In the first part of this article, a set of fixed-rate scalar source codes with zero delay is presented. We propose a randomized on-line coding scheme, which achieves asymptotically (and with high probability), the performance of the best source code in the set, uniformly over all source sequences. The scheme uses the same rate and has zero delay. We then present an efficient algorithm for implementing our on-line coding scheme in the case of a relatively small set of encoders. We also present an efficient algorithm for the case of a larger set of encoders with a structure, using the method of the weighted graph and the Weight Pushing Algorithm (WPA). In the second part of this article, we extend our results to the case of variable-rate coding. A set of variable-rate scalar source codes is presented. We generalize the randomized on-line coding scheme, to our case. This time, the p...

  19. Finite-block-length analysis in classical and quantum information theory.

    Hayashi, Masahito

    2017-01-01

    Coding technology is used in several information processing tasks. In particular, when noise during transmission disturbs communications, coding technology is employed to protect the information. However, there are two types of coding technology: coding in classical information theory and coding in quantum information theory. Although the physical media used to transmit information ultimately obey quantum mechanics, we need to choose the type of coding depending on the kind of information device, classical or quantum, that is being used. In both branches of information theory, there are many elegant theoretical results under the ideal assumption that an infinitely large system is available. In a realistic situation, we need to account for finite size effects. The present paper reviews finite size effects in classical and quantum information theory with respect to various topics, including applied aspects.

  20. Quantum computers.

    Ladd, T D; Jelezko, F; Laflamme, R; Nakamura, Y; Monroe, C; O'Brien, J L

    2010-03-04

    Over the past several decades, quantum information science has emerged to seek answers to the question: can we gain some advantage by storing, transmitting and processing information encoded in systems that exhibit unique quantum properties? Today it is understood that the answer is yes, and many research groups around the world are working towards the highly ambitious technological goal of building a quantum computer, which would dramatically improve computational power for particular tasks. A number of physical systems, spanning much of modern physics, are being developed for quantum computation. However, it remains unclear which technology, if any, will ultimately prove successful. Here we describe the latest developments for each of the leading approaches and explain the major challenges for the future.

  1. Syntax Encodes Information Structure: Evidence from On-Line Reading Comprehension

    Brown, Meredith; Savova, Virginia; Gibson, Edward

    2012-01-01

    Although sentences are thought to be generally easier to process when given information precedes new information, closer examination reveals that these preferences only manifest within some syntactic structures. Here, we examine the consequences of the relative ordering of given and new information ("information structure") for the on-line…

  2. Optimal encoding and decoding of a spin direction

    Bagán, E; Brey, A; Muñoz-Tàpia, R; Tarrach, Rolf

    2001-01-01

    For a system of N spins 1/2 there are quantum states that can encode a direction in an intrinsic way. Information on this direction can later be decoded by means of a quantum measurement. We present here the optimal encoding and decoding procedure using the fidelity as a figure of merit. We compute the maximal fidelity and prove that it is directly related to the largest zeroes of the Legendre and Jacobi polynomials. We show that this maximal fidelity approaches unity quadratically in 1/N. We also discuss this result in terms of the dimension of the encoding Hilbert space.

  3. Can quantum mechanics be almighty even in information science?

    Nagata, Koji

    2008-01-01

    We discuss that there is a crucial contradiction within quantum mechanics. We derive a proposition concerning a quantum expectation value under the assumption of the existence of the directions in a spin-1/2 system. The quantum predictions within the formalism of von Neumann's projective measurement cannot coexist with the proposition concerning the existence of the directions. Therefore, we have to give up either the existence of the directions or the formalism of von Neumann's projective measurement. Hence there is a crucial contradiction within the Hilbert space formalism of the quantum theory. This implies that there is no axiomatic system for the quantum theory. This also reveals that we need new physical theories in order to explain the handing of raw experimental data. We discuss that this crucial contradiction makes the quantum-theoretical formulation of Deutsch's algorithm questionable.

  4. Quantum Darwinism in Quantum Brownian Motion

    Blume-Kohout, Robin; Zurek, Wojciech H.

    2008-12-01

    Quantum Darwinism—the redundant encoding of information about a decohering system in its environment—was proposed to reconcile the quantum nature of our Universe with apparent classicality. We report the first study of the dynamics of quantum Darwinism in a realistic model of decoherence, quantum Brownian motion. Prepared in a highly squeezed state—a macroscopic superposition—the system leaves records whose redundancy increases rapidly with initial delocalization. Redundancy appears rapidly (on the decoherence time scale) and persists for a long time.

  5. Stabilization of Quantum Information A Unified Dynamical-Algebraic Approach

    Zanardi, P

    2002-01-01

    The notion of symmetry is shown to be at the heart of all error correction/avoidance strategies for preserving quantum coherence of an open quantum system S e.g., a quantum computer. The existence of a non-trivial group of symmetries of the dynamical algebra of S provides state-space sectors immune to decoherence. Such noiseless sectors, that can be viewed as a noncommutative version of the pointer basis, are shown to support universal quantum computation and to be robust against perturbations. When the required symmetry is not present one can generate it artificially resorting to active symmetrization procedures.

  6. Actionable Information, Repeatability, Quantum Jumps, and the Wavepacket Collapse

    Zurek, Wojciech H

    2013-01-01

    Unknown quantum state cannot be discovered as the measured system is re-prepared -- it jumps into an eigenstate of the measured observable. This impossibility to find out a quantum state and other symptoms of the wavepacket collapse follow (as was recently demonstrated for pure states of measured systems) from unitarity (that doesn't, however, allow for a literal collapse) and from the repeatability of measurements. Here we extend this result to mixtures and decohering systems. This accounts for quantum jumps in a macroscopic and open (but ultimately quantum) apparatus.

  7. Information processing biases concurrently and prospectively predict depressive symptoms in adolescents: Evidence from a self-referent encoding task.

    Connolly, Samantha L; Abramson, Lyn Y; Alloy, Lauren B

    2016-01-01

    Negative information processing biases have been hypothesised to serve as precursors for the development of depression. The current study examined negative self-referent information processing and depressive symptoms in a community sample of adolescents (N = 291, Mage at baseline = 12.34 ± 0.61, 53% female, 47.4% African-American, 49.5% Caucasian and 3.1% Biracial). Participants completed a computerised self-referent encoding task (SRET) and a measure of depressive symptoms at baseline and completed an additional measure of depressive symptoms nine months later. Several negative information processing biases on the SRET were associated with concurrent depressive symptoms and predicted increases in depressive symptoms at follow-up. Findings partially support the hypothesis that negative information processing biases are associated with depressive symptoms in a nonclinical sample of adolescents, and provide preliminary evidence that these biases prospectively predict increases in depressive symptoms.

  8. Efficient quantum dialogue using entangled states and entanglement swapping without information leakage

    Wang, He; Zhang, Yu Qing; Liu, Xue Feng; Hu, Yu Pu

    2016-06-01

    We propose a novel quantum dialogue protocol by using the generalized Bell states and entanglement swapping. In the protocol, a sequence of ordered two-qutrit entangled states acts as quantum information channel for exchanging secret messages directly and simultaneously. Besides, a secret key string is shared between the communicants to overcome information leakage. Different from those previous information leakage-resistant quantum dialogue protocols, the particles, composed of one of each pair of entangled states, are transmitted only one time in the proposed protocol. Security analysis shows that our protocol can overcome information leakage and resist several well-known attacks. Moreover, the efficiency of our scheme is acceptable.

  9. Quantum trajectories making use of all the information in measurement records

    Mølmer, Klaus

    2014-01-01

    The evolution of a continuously probed quantum system is referred to as a quantum trajectory. We discuss how to infer unknown parameters, and we derive resolution limits by detection of, e.g., light emitted by atomic systems. Probing affects not only the current state but also the quantum state o...... of a system in the past and we discuss how a theory of past quantum states may yield useful information in precision metrology [1-3]. [1] PRA 87, 032115 (2013) [2] arXiv:1310.5802 [3] PRL 111, 160401 (2013)......The evolution of a continuously probed quantum system is referred to as a quantum trajectory. We discuss how to infer unknown parameters, and we derive resolution limits by detection of, e.g., light emitted by atomic systems. Probing affects not only the current state but also the quantum state...

  10. The Generalized Quantization Schemes for Games and its Application to Quantum Information

    Nawaz, Ahmad

    2010-01-01

    Theory of quantum games is relatively new to the literature and its applications to various areas of research are being explored. It is a novel interpretation of strategies and decisions in quantum domain. In the earlier work on quantum games considerable attention was given to the resolution of dilemmas present in corresponding classical games. Two separate quantum schemes were presented by Eisert et al. and Marinatto and Weber to resolve dilemmas in Prisoners' Dilemma and Battle of Sexes games respectively. However for the latter scheme it was argued that dilemma was not resolved. We have modified the quantization scheme of Marinatto and Weber to resolve the dilemma. We have developed a generalized quantization scheme for two person non-zero sum games which reduces to the existing schemes under certain conditions. Applications of this generalized quantization scheme to quantum information theory are studied. Measurement being ubiquitous in quantum mechanics can not be ignored in quantum games. With the help...

  11. Superconducting nanowire single photon detectors for quantum information and communications

    Wang, Zhen; Fujiwara, Mikio

    2010-01-01

    Superconducting nanowire single photon detectors (SNSPD or SSPD) are highly promising devices in the growing field of quantum information and communications technology. We have developed a practical SSPD system with our superconducting thin films and devices fabrication, optical coupling packaging, and cryogenic technology. The SSPD system consists of six-channel SSPD devices and a compact Gifford-McMahon (GM) cryocooler, and can operate continuously on 100 V ac power without the need for any cryogens. The SSPD devices were fabricated from high-quality niobium nitride (NbN) ultra-thin films that were epitaxially grown on single-crystal MgO substrates. The packaged SSPD devices were temperature stabilized to 2.96 K +/- 10 mK. The system detection efficiency for an SSPD device with an area of 20x20 $\\mu m^2$ was found to be 2.6% and 4.5% at wavelengths of 1550 and 1310 nm, respectively, at a dark count rate of 100 c/s, and a jitter of 100 ps full width at half maximum (FWHM). We also performed ultra-fast BB84 q...

  12. Communicating through Probabilities: Does Quantum Theory Optimize the Transfer of Information?

    William K. Wootters

    2013-08-01

    Full Text Available A quantum measurement can be regarded as a communication channel, in which the parameters of the state are expressed only in the probabilities of the outcomes of the measurement. We begin this paper by considering, in a non-quantum-mechanical setting, the problem of communicating through probabilities. For example, a sender, Alice, wants to convey to a receiver, Bob, the value of a continuous variable, θ, but her only means of conveying this value is by sending Bob a coin in which the value of θ is encoded in the probability of heads. We ask what the optimal encoding is when Bob will be allowed to flip the coin only a finite number of times. As the number of tosses goes to infinity, we find that the optimal encoding is the same as what nature would do if we lived in a world governed by real-vector-space quantum theory. We then ask whether the problem might be modified, so that the optimal communication strategy would be consistent with standard, complex-vector-space quantum theory.

  13. Disorder overtakes Order in Information Concentration over Quantum Networks

    Prabhu, R; De, Aditi Sen; Sen, Ujjwal

    2011-01-01

    We consider different classes of quenched disordered quantum XY spin chains, including quantum XY spin glass and quantum XY model with a random transverse field, and investigate the behavior of genuine multiparty entanglement in the ground states of these models. We find that there are distinct ranges of the disorder parameter that gives rise to a higher genuine multiparty entanglement than in the corresponding systems without disorder -- an order-from-disorder in genuine multiparty entanglement. Moreover, we show that such a disorder-induced advantage in the genuine multiparty entanglement is useful -- it is almost certainly accompanied by a order-from-disorder for a multiport quantum dense coding capacity with the same ground state used as a multiport quantum network.

  14. Information carriers and (reading them through) information theory in quantum chemistry.

    Geerlings, Paul; Borgoo, Alex

    2011-01-21

    This Perspective discusses the reduction of the electronic wave function via the second-order reduced density matrix to the electron density ρ(r), which is the key ingredient in density functional theory (DFT) as a basic carrier of information. Simplifying further, the 1-normalized density function turns out to contain essentially the same information as ρ(r) and is even of preferred use as an information carrier when discussing the periodic properties along Mendeleev's table where essentially the valence electrons are at stake. The Kullback-Leibler information deficiency turns out to be the most interesting choice to obtain information on the differences in ρ(r) or σ(r) between two systems. To put it otherwise: when looking for the construction of a functional F(AB) = F[ζ(A)(r),ζ(B)(r)] for extracting differences in information from an information carrier ζ(r) (i.e. ρ(r), σ(r)) for two systems A and B the Kullback-Leibler information measure ΔS is a particularly adequate choice. Examples are given, varying from atoms, to molecules and molecular interactions. Quantum similarity of atoms indicates that the shape function based KL information deficiency is the most appropriate tool to retrieve periodicity in the Periodic Table. The dissimilarity of enantiomers for which different information measures are presented at global and local (i.e. molecular and atomic) level leads to an extension of Mezey's holographic density theorem and shows numerical evidence that in a chiral molecule the whole molecule is pervaded by chirality. Finally Kullback-Leibler information profiles are discussed for intra- and intermolecular proton transfer reactions and a simple S(N)2 reaction indicating that the theoretical information profile can be used as a companion to the energy based Hammond postulate to discuss the early or late transition state character of a reaction. All in all this Perspective's answer is positive to the question of whether an even simpler carrier of

  15. Entropy generation in Gaussian quantum transformations: applying the replica method to continuous-variable quantum information theory

    Gagatsos, Christos N.; Karanikas, Alexandros I.; Kordas, Georgios; Cerf, Nicolas J.

    2016-02-01

    In spite of their simple description in terms of rotations or symplectic transformations in phase space, quadratic Hamiltonians such as those modelling the most common Gaussian operations on bosonic modes remain poorly understood in terms of entropy production. For instance, determining the quantum entropy generated by a Bogoliubov transformation is notably a hard problem, with generally no known analytical solution, while it is vital to the characterisation of quantum communication via bosonic channels. Here we overcome this difficulty by adapting the replica method, a tool borrowed from statistical physics and quantum field theory. We exhibit a first application of this method to continuous-variable quantum information theory, where it enables accessing entropies in an optical parametric amplifier. As an illustration, we determine the entropy generated by amplifying a binary superposition of the vacuum and a Fock state, which yields a surprisingly simple, yet unknown analytical expression.

  16. Scheme for realizing quantum computation and quantum information transfer with superconducting qubits coupling to a 1D transmission line resonator

    Shi Zhen-Gang; Chen Xiong-Wen; Zhu Xi-Xiang; Song Ke-Hui

    2009-01-01

    This paper proposes a simple scheme for realizing one-qubit and two-qubit quantum gates as well as multiqubit entanglement based on dc-SQUID charge qubits through the control of their coupling to a ID transmission line resonator (TLR). The TLR behaves effectively as a quantum data-bus mode of a harmonic oscillator, which has several practical advantages including strong coupling strength, reproducibility, immunity to 1// noise, and suppressed spontaneous emission. In this protocol, the data-bus does not need to stay adiabatically in its ground state, which results in not only fast quantum operation, but also high-fidelity quantum information processing. Also, it elaborates the transfer process with the 1D transmission line.

  17. Experimental realization of information transmission between not-directly-coupled spins on NMR quantum computers

    Wei Da-Xiu; Luo Jun; Yang Xiao-Dong; Sun Xian-Ping; Zeng Xi-Zhi; Liu Mai-Li; Ding Shang-Wu; Zhan Ming-Sheng

    2004-01-01

    This paper presents a simple scheme for information transmission between two non-directly interactive qubits in an n-qubit system. An example has been realized on a three-qubit nuclear magnetic resonance(NMR) spectrometer quantum computer. The experimental result successfully demonstrates that the feasible measure can also be extended to other quantum logical gates, or other quantum algorithms, where some qubits have no direct interactions in a multi-qubit system.

  18. Forecast Modelling via Variations in Binary Image-Encoded Information Exploited by Deep Learning Neural Networks.

    Liu, Da; Xu, Ming; Niu, Dongxiao; Wang, Shoukai; Liang, Sai

    2016-01-01

    Traditional forecasting models fit a function approximation from dependent invariables to independent variables. However, they usually get into trouble when date are presented in various formats, such as text, voice and image. This study proposes a novel image-encoded forecasting method that input and output binary digital two-dimensional (2D) images are transformed from decimal data. Omitting any data analysis or cleansing steps for simplicity, all raw variables were selected and converted to binary digital images as the input of a deep learning model, convolutional neural network (CNN). Using shared weights, pooling and multiple-layer back-propagation techniques, the CNN was adopted to locate the nexus among variations in local binary digital images. Due to the computing capability that was originally developed for binary digital bitmap manipulation, this model has significant potential for forecasting with vast volume of data. The model was validated by a power loads predicting dataset from the Global Energy Forecasting Competition 2012.

  19. Experimental demonstration of graph-state quantum secret sharing

    Bell, B A; Herrera-Martí, D A; Marin, A; Wadsworth, W J; Rarity, J G; Tame, M S

    2014-01-01

    Distributed quantum communication and quantum computing offer many new opportunities for quantum information processing. Here networks based on highly nonlocal quantum resources with complex entanglement structures have been proposed for distributing, sharing and processing quantum information. Graph states in particular have emerged as powerful resources for such tasks using measurement-based techniques. We report an experimental demonstration of graph-state quantum secret sharing, an important primitive for a quantum network. We use an all-optical setup to encode quantum information into photons representing a five-qubit graph state. We are able to reliably encode, distribute and share quantum information between four parties. In our experiment we demonstrate the integration of three distinct secret sharing protocols, which allow for security and protocol parameters not possible with any single protocol alone. Our results show that graph states are a promising approach for sophisticated multi-layered protoc...

  20. Quantum information tapping using a fiber optical parametric amplifier with noise figure improved by correlated inputs.

    Guo, Xueshi; Li, Xiaoying; Liu, Nannan; Ou, Z Y

    2016-07-26

    One of the important functions in a communication network is the distribution of information. It is not a problem to accomplish this in a classical system since classical information can be copied at will. However, challenges arise in quantum system because extra quantum noise is often added when the information content of a quantum state is distributed to various users. Here, we experimentally demonstrate a quantum information tap by using a fiber optical parametric amplifier (FOPA) with correlated inputs, whose noise is reduced by the destructive quantum interference through quantum entanglement between the signal and the idler input fields. By measuring the noise figure of the FOPA and comparing with a regular FOPA, we observe an improvement of 0.7 ± 0.1 dB and 0.84 ± 0.09 dB from the signal and idler outputs, respectively. When the low noise FOPA functions as an information splitter, the device has a total information transfer coefficient of Ts+Ti = 1.5 ± 0.2, which is greater than the classical limit of 1. Moreover, this fiber based device works at the 1550 nm telecom band, so it is compatible with the current fiber-optical network for quantum information distribution.