Subdecoherent Information Encoding in a Quantum-Dot Array
Zanardi, P; Zanardi, Paolo; Rossi, Fausto
1999-01-01
A potential implementation of quantum-information schemes in semiconductor nanostructures is studied. To this end, the formal theory of quantum encoding for avoiding errors is recalled and the existence of noiseless states for model systems is discussed. Based on this theoretical framework, we analize the possibility of designing noiseless quantum codes in realistic semiconductor structures. In the specific implementation considered, information is encoded in the lowest energy sector of charge excitations of a linear array of quantum dots. The decoherence channel considered is electron-phonon coupling We show that besides the well-known phonon bottleneck, reducing single-qubit decoherence, suitable many-qubit initial preparation as well as register design may enhance the decoherence time by several orders of magnitude. This behaviour stems from the effective one-dimensional character of the phononic environment in the relevant region of physical parameters.
Optimal Encoding of Classical Information in a Quantum Medium
Elron, Noam; Yonina C. Eldar
2006-01-01
We investigate optimal encoding and retrieval of digital data, when the storage/communication medium is described by quantum mechanics. We assume an m-ary alphabet with arbitrary prior distribution, and an n-dimensional quantum system. Under these constraints, we seek an encoding-retrieval setup, comprised of code-states and a quantum measurement, which maximizes the probability of correct detection. In our development, we consider two cases. In the first, the measurement is predefined and we...
Secure quantum private information retrieval using phase-encoded queries
International Nuclear Information System (INIS)
We propose a quantum solution to the classical private information retrieval (PIR) problem, which allows one to query a database in a private manner. The protocol offers privacy thresholds and allows the user to obtain information from a database in a way that offers the potential adversary, in this model the database owner, no possibility of deterministically establishing the query contents. This protocol may also be viewed as a solution to the symmetrically private information retrieval problem in that it can offer database security (inability for a querying user to steal its contents). Compared to classical solutions, the protocol offers substantial improvement in terms of communication complexity. In comparison with the recent quantum private queries [Phys. Rev. Lett. 100, 230502 (2008)] protocol, it is more efficient in terms of communication complexity and the number of rounds, while offering a clear privacy parameter. We discuss the security of the protocol and analyze its strengths and conclude that using this technique makes it challenging to obtain the unconditional (in the information-theoretic sense) privacy degree; nevertheless, in addition to being simple, the protocol still offers a privacy level. The oracle used in the protocol is inspired both by the classical computational PIR solutions as well as the Deutsch-Jozsa oracle.
Secure quantum private information retrieval using phase-encoded queries
Energy Technology Data Exchange (ETDEWEB)
Olejnik, Lukasz [CERN, 1211 Geneva 23, Switzerland and Poznan Supercomputing and Networking Center, Noskowskiego 12/14, PL-61-704 Poznan (Poland)
2011-08-15
We propose a quantum solution to the classical private information retrieval (PIR) problem, which allows one to query a database in a private manner. The protocol offers privacy thresholds and allows the user to obtain information from a database in a way that offers the potential adversary, in this model the database owner, no possibility of deterministically establishing the query contents. This protocol may also be viewed as a solution to the symmetrically private information retrieval problem in that it can offer database security (inability for a querying user to steal its contents). Compared to classical solutions, the protocol offers substantial improvement in terms of communication complexity. In comparison with the recent quantum private queries [Phys. Rev. Lett. 100, 230502 (2008)] protocol, it is more efficient in terms of communication complexity and the number of rounds, while offering a clear privacy parameter. We discuss the security of the protocol and analyze its strengths and conclude that using this technique makes it challenging to obtain the unconditional (in the information-theoretic sense) privacy degree; nevertheless, in addition to being simple, the protocol still offers a privacy level. The oracle used in the protocol is inspired both by the classical computational PIR solutions as well as the Deutsch-Jozsa oracle.
Optimal quantum source coding with quantum information at the encoder and decoder
Yard, Jon
2007-01-01
Consider many instances of an arbitrary quadripartite pure state of four quantum systems ACBR. Alice holds the AC part of each state, Bob holds B, while R represents all other parties correlated with ACB. Alice is required to redistribute the C systems to Bob while asymptotically retaining the purity of the global states. We prove that this is possible using Q qubits of communication and E ebits of shared entanglement between Alice and Bob provided that Q < I(R;C|B)/2 and Q + E < H(C|B). This matches the outer bound for this problem given in quant-ph/0611008. The optimal qubit rate provides the first known operational interpretation of quantum conditional mutual information. We also show how our protocol leads to a fully operational proof of strong subaddivity and uncover a general organizing principle, in analogy to thermodynamics, which underlies the optimal rates.
Ca+ quantum bits for quantum information processing
International Nuclear Information System (INIS)
With trapped ions quantum information can be encoded in various two-level systems or quantum bits (qubits). Here, we present an overview on qubit encoding with Ca+ and several state-of-the-art operations involving two and three qubits. The use of decoherence-free subspaces and encoding logical qubits using two physical qubits may offer an advantageous route towards implementing scalable quantum information processing.
Barnett, Stephen M
2009-01-01
Quantum information- the subject- is a new and exciting area of science, which brings together physics, information theory, computer science and mathematics. "Quantum Information"- the book- is based on two successful lecture courses given to advanced undergraduate and beginning postgraduate students in physics. The intention is to introduce readers at this level to the fundamental, but offer rather simple, ideas behind ground-breaking developments including quantum cryptography,teleportation and quantum computing. The text is necessarily rather mathematical in style, but the mathema
International Nuclear Information System (INIS)
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)
Quantum logical operations on encoded qubits
Zurek, W H; Zurek, Wojciech Hubert; Laflamme, Raymond
1996-01-01
We show how to carry out quantum logical operations (controlled-not and Toffoli gates) on encoded qubits for several encodings which protect against various 1-bit errors. This improves the reliability of these operations by allowing one to correct for one bit errors which either preexisted or occurred in course of operation. The logical operations we consider allow one to cary out the vast majority of the steps in the quantum factoring algorithm. Thus, our results help bring quantum factoring and other quantum computations closer to reality
Nonlocal quantum information in bipartite quantum error correction
Wilde, Mark M
2009-01-01
We show how to convert an arbitrary stabilizer code into a bipartite quantum code. A bipartite quantum code is one that involves two senders and one receiver. The two senders exploit both nonlocal and local quantum resources to encode quantum information with local encoding circuits. They transmit their encoded quantum data to a single receiver who then decodes the transmitted quantum information. The nonlocal resources in a bipartite code are ebits and nonlocal information qubits and the local resources are ancillas and local information qubits. The technique of bipartite quantum error correction is useful in both the quantum communication scenario described above and in fault-tolerant quantum computation. It has application in fault-tolerant quantum computation because we can prepare nonlocal resources offline and exploit local encoding circuits. In particular, we derive an encoding circuit for a bipartite version of the Steane code that is local and additionally requires only nearest-neighbor interactions....
Encoding entanglement-assisted quantum stabilizer codes
International Nuclear Information System (INIS)
We address the problem of encoding entanglement-assisted (EA) quantum error-correcting codes (QECCs) and of the corresponding complexity. We present an iterative algorithm from which a quantum circuit composed of CNOT, H, and S gates can be derived directly with complexity O(n2) to encode the qubits being sent. Moreover, we derive the number of each gate consumed in our algorithm according to which we can design EA QECCs with low encoding complexity. Another advantage brought by our algorithm is the easiness and efficiency of programming on classical computers. (general)
Classical and quantum information
Marinescu, Dan C
2011-01-01
A new discipline, Quantum Information Science, has emerged in the last two decades of the twentieth century at the intersection of Physics, Mathematics, and Computer Science. Quantum Information Processing is an application of Quantum Information Science which covers the transformation, storage, and transmission of quantum information; it represents a revolutionary approach to information processing. This book covers topics in quantum computing, quantum information theory, and quantum error correction, three important areas of quantum information processing. Quantum information theory an
Decoherence-Insensitive Quantum Communication by Optimal C^*-Encoding
Bodmann, B G; Paulsen, V I; Bodmann, Bernhard G.; Kribs, David W.; Paulsen, Vern I.
2006-01-01
The central issue in this article is to transmit a quantum state in such a way that after some decoherence occurs, most of the information can be restored by a suitable decoding operation. For this purpose, we incorporate redundancy by mapping a given initial quantum state to a messenger state on a larger-dimensional Hilbert space via a $C^*$-algebra embedding. Our noise model for the transmission is a phase damping channel which admits a noiseless or decoherence-free subspace or subsystem. More precisely, the transmission channel is obtained from convex combinations of a set of lowest rank yes/no measurements that leave a component of the messenger state unchanged. The objective of our encoding is to distribute quantum information optimally across the noise-susceptible component of the transmission when the noiseless component is not large enough to contain all the quantum information to be transmitted. We derive simple geometric conditions for optimal encoding and construct examples.
Quantum information and computation
Bub, Jeffrey
2005-01-01
This article deals with theoretical developments in the subject of quantum information and quantum computation, and includes an overview of classical information and some relevant quantum mechanics. The discussion covers topics in quantum communication, quantum cryptography, and quantum computation, and concludes by considering whether a perspective in terms of quantum information sheds new light on the conceptual problems of quantum mechanics.
A photonic quantum information interface
Tanzilli, S; Halder, M; Alibart, O; Baldi, P; Gisin, Nicolas; Zbinden, H; Tanzilli, Sebastien; Tittel, Wolfgang; Halder, Matthaeus; Alibart, Olivier; Baldi, Pascal; Gisin, Nicolas; Zbinden, Hugo
2005-01-01
Quantum communication is the art of transferring quantum states, or quantum bits of information (qubits), from one place to another. On the fundamental side, this allows one to distribute entanglement and demonstrate quantum nonlocality over significant distances. On the more applied side, quantum cryptography offers, for the first time in human history, a provably secure way to establish a confidential key between distant partners. Photons represent the natural flying qubit carriers for quantum communication, and the presence of telecom optical fibres makes the wavelengths of 1310 and 1550 nm particulary suitable for distribution over long distances. However, to store and process quantum information, qubits could be encoded into alkaline atoms that absorb and emit at around 800 nm wavelength. Hence, future quantum information networks made of telecom channels and alkaline memories will demand interfaces able to achieve qubit transfers between these useful wavelengths while preserving quantum coherence and en...
Quantum Key Distribution using Multilevel Encoding Security Analysis
Bourennane, M; Björk, G; Gisin, Nicolas; Cerf, N J; Bourennane, Mohamed; Karlsson, Anders; Bjork, Gunnar; Gisin, Nicolas; Cerf, Nicolas
2002-01-01
We present security proofs for a protocol for Quantum Key Distribution (QKD) based on encoding in finite high-dimensional Hilbert spaces. This protocol is an extension of Bennett's and Brassard's basic protocol from two bases, two state encoding to a multi bases, multi state encoding. We analyze the mutual information between the legitimate parties and the eavesdropper, and the error rate, as function of the dimension of the Hilbert space, while considering optimal incoherent and coherent eavesdropping attacks. We obtain the upper limit for the legitimate party error rate to ensure unconditional security when the eavesdropper uses incoherent and coherent eavesdropping strategies. We have also consider realistic noise caused by detector's noise.
Quantum teleportation and quantum information
International Nuclear Information System (INIS)
The scheme of quantum teleportation is described in a mathematically rigorous way, including analysis of the role and importance of quantum entanglement. The experiments with quantum teleportation performed in Innsbruck and in Rome are described in detail, and some differences between the two approaches are discussed. The elements of quantum information theory are introduced and compared with Shannon's classical information theory. The phenomenon of quantum teleportation is placed into a wider context of the developing quantum information theory, which enables quantum teleportation to be described by using the particle physics language. (Z.J.)
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 i...
Quantum algorithmic information theory
Svozil, K
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 capable of arbitrary U(2) transformations. Basic to all these considerations is quantum theory, in particular Hilbert space quantum mechanics.
Quantum information to the home
Energy Technology Data Exchange (ETDEWEB)
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.
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...
Encoding qubits into quantum noise resistant states
Energy Technology Data Exchange (ETDEWEB)
Heim, Dennis; Gleisberg, Ferdinand; Freyberger, Matthias [Institut fuer Quantenphysik, Universitaet Ulm, D-89069 Ulm (Germany)
2009-07-01
The intention of the proposed scheme is to protect information of an unknown pure qubit against effects of quantum noise represented by a quantum channel. By applying the proposed scheme before and after the qubit passes the channel the resulting fidelity will be higher than the fidelity without protection. The effect of a phase damping channel, for example, can be reduced by coupling and decoupling an additional qubit to the unknown initial state.
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 lim...
Quantum gloves: Quantum states that encode as much as possible chirality and nothing else
International Nuclear Information System (INIS)
Communicating a physical quantity cannot be done using information only - i.e., using abstract cbits and/or qubits. Rather one needs appropriate physical realizations of cbits and/or qubits. We illustrate this by considering the problem of communicating chirality. We discuss in detail the physical resources this necessitates and introduce the natural concept of quantum gloves - i.e., rotationally invariant quantum states that encode as much as possible the concept of chirality and nothing more
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...
Quantum Information Processing
Leuchs, Gerd
2005-01-01
Quantum processing and communication is emerging as a challenging technique at the beginning of the new millennium. This is an up-to-date insight into the current research of quantum superposition, entanglement, and the quantum measurement process - the key ingredients of quantum information processing. The authors further address quantum protocols and algorithms. Complementary to similar programmes in other countries and at the European level, the German Research Foundation (DFG) started a focused research program on quantum information in 1999. The contributions - written by leading experts - bring together the latest results in quantum information as well as addressing all the relevant questions
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. PMID:23745844
Quantum Particles From Quantum Information
Görnitz, T.; Schomäcker, U.
2012-08-01
Many problems in modern physics demonstrate that for a fundamental entity a more general conception than quantum particles or quantum fields are necessary. These concepts cannot explain the phenomena of dark energy or the mind-body-interaction. Instead of any kind of "small elementary building bricks", the Protyposis, an abstract and absolute quantum information, free of special denotation and open for some purport, gives the solution in the search for a fundamental substance. However, as long as at least relativistic particles are not constructed from the Protyposis, such an idea would remain in the range of natural philosophy. Therefore, the construction of relativistic particles without and with rest mass from quantum information is shown.
Quantum Particles From Quantum Information
International Nuclear Information System (INIS)
Many problems in modern physics demonstrate that for a fundamental entity a more general conception than quantum particles or quantum fields are necessary. These concepts cannot explain the phenomena of dark energy or the mind-body-interaction. Instead of any kind of 'small elementary building bricks', the Protyposis, an abstract and absolute quantum information, free of special denotation and open for some purport, gives the solution in the search for a fundamental substance. However, as long as at least relativistic particles are not constructed from the Protyposis, such an idea would remain in the range of natural philosophy. Therefore, the construction of relativistic particles without and with rest mass from quantum information is shown.
Photonic Quantum Information Processing
International Nuclear Information System (INIS)
The advantage of the photon's mobility makes optical quantum system ideally suited for delegated quantum computation. I will present results for the realization for a measurement-based quantum network in a client-server environment, where quantum information is securely communicated and computed. Related to measurement-based quantum computing I will discuss a recent experiment showing that quantum discord can be used as resource for the remote state preparation, which might shine new light on the requirements for quantum-enhanced information processing. Finally, I will briefly review recent photonic quantum simulation experiments of four frustrated Heisenberg-interactions spins and present an outlook of feasible simulation experiments with more complex interactions or random walk structures. As outlook I will discuss the current status of new quantum technology for improving the scalability of photonic quantum systems by using superconducting single-photon detectors and tailored light-matter interactions. (author)
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...
Elements of quantum information
International Nuclear Information System (INIS)
Elements of Quantum Information introduces the reader to the fascinating field of quantum information processing, which lives on the interface between computer science, physics, mathematics, and engineering. This interdisciplinary branch of science thrives on the use of quantum mechanics as a resource for high potential modern applications. With its wide coverage of experiments, applications, and specialized topics - all written by renowned experts - Elements of Quantum Information provides and indispensable, up-to-date account of the state of the art of this rapidly advancing field and takes the reader straight up to the frontiers of current research. The articles have first appeared as a special issue of the journal 'Fortschritte der Physik / Progress of Physics'. Since then, they have been carefully updated. The book will be an inspiring source of information and insight for anyone researching and specializing in experiments and theory of quantum information. Topics addressed in Elements of Quantum Information include - Cavity Quantum Electrodynamics - Segmented Paul Traps - Cold Atoms and Bose-Einstein Condensates in Microtraps, Optical Lattices, and on Atom Chips - Rydberg Gases - Factorization of Numbers with Physical Systems - Entanglement of Continuous Variables - NMR and Solid State Quantum Computation - Quantum Algorithms and Quantum Machines - Complexity Theory - Quantum Crytography. (orig.)
Quantum catalysis of information
Azuma, Koji; KOASHI, Masato; Imoto, Nobuyuki
2008-01-01
Heisenberg's uncertainty principle and recently derived many no-go theorems including the no-cloning theorem and the no-deleting theorem have corroborated the idea that we can never access quantum information without causing disturbance. Here we disprove this presumption by predicting a novel phenomenon, `quantum catalysis of information,' where a system enables an otherwise impossible task by exchanging information through a quantum communication channel. This fact implies that making use of...
Quantum holographic encoding in a two-dimensional electron gas
Energy Technology Data Exchange (ETDEWEB)
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.
Schumann, R H
2000-01-01
In this thesis I present a short review of ideas in quantum information theory. The first chapter contains introductory material, sketching the central ideas of probability and information theory. Quantum mechanics is presented at the level of advanced undergraduate knowledge, together with some useful tools for quantum mechanics of open systems. In the second chapter I outline how classical information is represented in quantum systems and what this means for agents trying to extract information from these systems. The final chapter presents a new resource: quantum information. This resource has some bewildering applications which have been discovered in the last ten years, and continually presents us with unexpected insights into quantum theory and the universe. The treatment is pedagogical and suitable for beginning graduates in the field.
Quantum information processing with trapped Ca(+) ions.
Gulde, S; Häffner, H; Riebe, M; Lancaster, G; Becher, C; Eschner, J; Schmidt-Kaler, F; Chuang, I L; Blatt, R
2003-07-15
Quantum information processing is performed with single trapped Ca(+) ions, stored in a linear Paul trap and laser-cooled to the ground state of their harmonic quantum motion. Composite laser-pulse sequences were used to implement SWAP gate, phase gate and controlled-NOT gate operations. Stark shifts on the quantum-bit transitions were precisely measured and compensated. For a demonstration of quantum information processing, a Deutsch-Jozsa algorithm has been implemented using two quantum bits encoded on a single ion. PMID:12869313
Quantum information processing with trapped Ca+ ions
Gulde, S.; Häffner, H.; Riebe, M.; et al.
2003-07-01
Quantum information processing is performed with single trapped Ca+ ions, stored in a linear Paul trap and laser-cooled to the ground state of their harmonic quantum motion. Composite laser-pulse sequences were used to implement SWAP gate, phase gate and controlled-NOT gate operations. Stark shifts on the quantum-bit transitions were precisely measured and compensated. For a demonstration of quantum information processing, a Deutsch-Jozsa algorithm has been implemented using two quantum bits encoded on a single ion.
Quantum Information is Physical
DiVincenzo, David P.; Loss, Daniel
1997-01-01
We discuss a few current developments in the use of quantum mechanically coherent systems for information processing. In each of these developments, Rolf Landauer has played a crucial role in nudging us and other workers in the field into asking the right questions, some of which we have been lucky enough to answer. A general overview of the key ideas of quantum error correction is given. We discuss how quantum entanglement is the key to protecting quantum states from decohe...
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...
Lectures on quantum information
International Nuclear Information System (INIS)
Quantum Information Processing is a young and rapidly growing field of research at the intersection of physics, mathematics, and computer science. Its ultimate goal is to harness quantum physics to conceive - and ultimately build - 'quantum' computers that would dramatically overtake the capabilities of today's 'classical' computers. One example of the power of a quantum computer is its ability to efficiently find the prime factors of a large integer, thus shaking the supposedly secure foundations of standard encryption schemes. This comprehensive textbook on the rapidly advancing field introduces readers to the fundamental concepts of information theory and quantum entanglement, taking into account the current state of research and development. It thus covers all current concepts in quantum computing, both theoretical and experimental, before moving on to the latest implementations of quantum computing and communication protocols. With its series of exercises, this is ideal reading for students and lecturers in physics and informatics, as well as experimental and theoretical physicists, and physicists in industry. (orig.)
Isotope - based Quantum Information
Plekhanov, Vladimir G.
2009-01-01
This paper is brief review of three aspects of the isotope - based quantum information: computation, teleportation and cryptography. Our results demonstrate not only that entanglement exists in elementary excitation of isotope - mixed solids but also it can be used for quantum information processing.
Hybrid quantum information processing
Energy Technology Data Exchange (ETDEWEB)
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.
Continuous-variable quantum information processing
DEFF Research Database (Denmark)
Andersen, Ulrik Lund; Leuchs, G.; Silberhorn, C.
2010-01-01
Observables of quantum systems can possess either a discrete or a continuous spectrum. For example, upon measurements of the photon number of a light state, discrete outcomes will result whereas measurements of the light's quadrature amplitudes result in continuous outcomes. If one uses 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...
Fidelity and the communication of quantum information
International Nuclear Information System (INIS)
We compare and contrast the error probability and fidelity as measures of the quality of the receiver's measurement strategy for a quantum communications system. The error probability is a measure of the ability to retrieve classical information and the fidelity measures the retrieval of quantum information. We present the optimal measurement strategies for maximizing the fidelity given a source that encodes information on the symmetric qubit-states. (author)
Quantum Information is Physical
Di Vincenzo, D P; Vincenzo, David P. Di; Loss, Daniel
1998-01-01
We discuss a few current developments in the use of quantum mechanically coherent systems for information processing. In each of these developments, Rolf Landauer has played a crucial role in nudging us and other workers in the field into asking the right questions, some of which we have been lucky enough to answer. A general overview of the key ideas of quantum error correction is given. We discuss how quantum entanglement is the key to protecting quantum states from decoherence in a manner which, in a theoretical sense, is as effective as the protection of digital data from bit noise. We also discuss five general criteria which must be satisfied to implement a quantum computer in the laboratory, and we illustrate the application of these criteria by discussing our ideas for creating a quantum computer out of the spin states of coupled quantum dots.
Entanglement, Quantum Entropy and Mutual Information
Belavkin, V P
2002-01-01
The operational structure of quantum couplings and entanglements is studied and classified for semifinite von Neumann algebras. We show that the classical-quantum correspondences such as quantum encodings can be treated as diagonal semi-classical (d-) couplings, and the entanglements characterized by truly quantum (q-) couplings, can be regarded as truly quantum encodings. The relative entropy of the d-compound and entangled states leads to two different types of entropy for a given quantum state: the von Neumann entropy, which is achieved as the maximum of mutual information over all d-entanglements, and the dimensional entropy, which is achieved at the standard entanglement -- true quantum entanglement, coinciding with a d-entanglement only in the case of pure marginal states. The d- and q- information of a quantum noisy channel are respectively defined via the input d- and q- encodings, and the q-capacity of a quantum noiseless channel is found as the logarithm of the dimensionality of the input algebra. T...
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 special relativity, quantum optics, general relativity, quantum communication and quantum computation. The high level of current interest in these subjects is exemplified by the recent award of the 2012 Nobel Prize in Physics to Serge Haroche and David J Wineland for ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems. It is our hope that this issue will encourage new researchers to enter this rapidly developing and exciting new field. R B Mann and T C RalphGuest Editors
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 ...
Introduction to quantum information science
Energy Technology Data Exchange (ETDEWEB)
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 correction are discussed too. Based on this topic, the secure quantum communication is explained. In particular, the quantification of quantum security which has not been treated in existing book is explained. This book treats quantum cryptography from a more practical viewpoint.
Introduction to quantum information science
International Nuclear Information System (INIS)
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 correction are discussed too. Based on this topic, the secure quantum communication is explained. In particular, the quantification of quantum security which has not been treated in existing book is explained. This book treats quantum cryptography from a more practical viewpoint.
Entanglement and non local correlations: quantum resources for information processing
Prettico, Giuseppe
2013-01-01
Quantum Information Theory (QIT) studies how information can be processed and transmitted when encoded on quantum states. Practically, it can be understood as the effort to generalize Classical Information Theory to the quantum world. Interestingly, the fact that very-small scale Physics differs considerably from that of macroscopic objects offers a richer structure to the new theory. Among other phenomena, entanglement is at the heart of many quantum information protocols. It is the most spe...
Accessible Information and Quantum operations
Cai, Qing-yu
2003-01-01
The accessible information decreases under quantum operations. We analyzed the connection between quantum operations and accessible information. We show that a general quantum process cannot be operated accurately. Futhermore, an unknown state of a closed quantum system can not be operated arbitrarily by a unitary quantum operation.
Quantum-dots-encoded-microbeads based molecularly imprinted polymer.
Liu, Yixi; Liu, Le; He, Yonghong; He, Qinghua; Ma, Hui
2016-03-15
Quantum dots encoded microbeads have various advantages such as large surface area, superb optical properties and the ability of multiplexing. Molecularly imprinted polymer that can mimic the natural recognition entities has high affinity and selectivity for the specific analyte. Here, the concept of utilizing the quantum dots encoded microbeads as the supporting material and the polydopamine as the functional monomer to form the core-shell molecular imprinted polymer was proposed for the first time. The resulted imprinted polymer can provide various merits: polymerization can complete in aqueous environment; fabrication procedure is facile and universal; the obvious economic advantage; the thickness of the imprinting layer is highly controllable; polydopamine coating can improve the biocompatibility of the quantum dot encoded microbeads. The rabbit IgG binding and flow cytometer experiment result showed the distinct advantages of this strategy: cost-saving, facile and fast preparation procedure. Most importantly, the ability for the multichannel detection, which makes the imprinted polydopamine modified encoded-beads very attractive in protein pre-concentration, recognition, separation and biosensing. PMID:26520251
Task unrelated thought whilst encoding information.
Smallwood, Jonathan M; Baracaia, Simona F; Lowe, Michelle; Obonsawin, Marc
2003-09-01
Task unrelated thought (TUT) refers to thought directed away from the current situation, for example a daydream. Three experiments were conducted on healthy participants, with two broad aims. First, to contrast distributed and encapsulated views of cognition by comparing the encoding of categorical and random lists of words (Experiments One and Two). Second, to examine the consequences of experiencing TUT during study on the subsequent retrieval of information (Experiments One, Two, and Three). Experiments One and Two demonstrated lower levels of TUT and higher levels of word-fragment completion whilst encoding categorical relative to random stimuli, supporting the role of a distributed resource in the maintenance of TUT. In addition the results of all three experiments suggested that experiencing TUT during study had a measurable effect on subsequent retrieval. TUT was associated with increased frequency of false alarms at retrieval (Experiment One). In the subsequent experiments TUT was associated with no advantage to retrieval based on recollection, by manipulating instructions at encoding (Experiment Two), and/or at retrieval (Experiment Three). The implications of the results of all three experiments are discussed in terms of recent accounts of memory retrieval and conscious awareness. PMID:12941287
Introduction to Quantum Information Processing
Knill, E.; Laflamme, R; BARNUM, H; Dalvit, D.; Dziarmaga, J.; Gubernatis, J.; Gurvits, L.; Ortiz, G.; VIOLA, L.; Zurek, W. H.
2002-01-01
As a result of the capabilities of quantum information, the science of quantum information processing is now a prospering, interdisciplinary field focused on better understanding the possibilities and limitations of the underlying theory, on developing new applications of quantum information and on physically realizing controllable quantum devices. The purpose of this primer is to provide an elementary introduction to quantum information processing, and then to briefly expla...
Concentrating Tripartite Quantum Information.
Streltsov, Alexander; Lee, Soojoon; Adesso, Gerardo
2015-07-17
We introduce the concentrated information of tripartite quantum states. For three parties Alice, Bob, and Charlie, it is defined as the maximal mutual information achievable between Alice and Charlie via local operations and classical communication performed by Charlie and Bob. We derive upper and lower bounds to the concentrated information, and obtain a closed expression for it on several classes of states including arbitrary pure tripartite states in the asymptotic setting. We show that distillable entanglement, entanglement of assistance, and quantum discord can all be expressed in terms of the concentrated information, thus revealing its role as a unifying informational primitive. We finally investigate quantum state merging of mixed states with and without additional entanglement. The gap between classical and quantum concentrated information is proven to be an operational figure of merit for mixed state merging in the absence of additional entanglement. Contrary to the pure state merging, our analysis shows that classical communication in both directions can provide an advantage for merging of mixed states. PMID:26230778
Quantum information processing with trapped ions
International Nuclear Information System (INIS)
Single Ca+ ions and crystals of Ca+ ions are confined in a linear Paul trap and are investigated for quantum information processing. Here we report on recent experimental advancements towards a quantum computer with such a system. Laser-cooled trapped ions are ideally suited systems for the investigation and implementation of quantum information processing as one can gain almost complete control over their internal and external degrees of freedom. The combination of a Paul type ion trap with laser cooling leads to unique properties of trapped cold ions, such as control of the motional state down to the zero-point of the trapping potential, a high degree of isolation from the environment and thus a very long time available for manipulations and interactions at the quantum level. The very same properties make single trapped atoms and ions well suited for storing quantum information in long lived internal states, e.g. by encoding a quantum bit (qubit) of information within the coherent superposition of the S1/2 ground state and the metastable D5/2 excited state of Ca+. Recently we have achieved the implementation of simple algorithms with up to 3 qubits on an ion-trap quantum computer. We will report on methods to implement single qubit rotations, the realization of a two-qubit universal quantum gate (Cirac-Zoller CNOT-gate), the deterministic generation of multi-particle entangled states (GHZ- and W-states), their full tomographic reconstruction, the realization of deterministic quantum teleportation, its quantum process tomography and the encoding of quantum information in decoherence-free subspaces with coherence times exceeding 20 seconds. (author)
Quantum information and computation
International Nuclear Information System (INIS)
During the past two decades, there has emerged the new subject of quantum information and computation which both offers the possibility of powerful new modes of computing and communication and also suggests deep links between the well established disciplines of quantum theory and information theory and computer science. In recent years, the growth of the subject has been explosive, with significant progress in theory and experiment. The area has a highly interdisciplinary character with contributions from physicists, mathematicians and computer scientists in particular. Developments have occurred in diverse areas including quantum algorithms, quantum communication, quantum cryptography, entanglement and nonlocality. This progress has been reflected in contributions to Journal of Physics A: Mathematical and General which traditionally provides a natural home for this area of research. Furthermore, the journal's commitment to this field has recently been strengthened by the appointments of Sandu Popescu and Nicolas Gisin to the Editorial Board, and in this special issue we take the opportunity to present a snapshot of the present state of the art. (author)
Quantum teleportation for continuous variables and related quantum information processing
International Nuclear Information System (INIS)
Quantum teleportation is one of the most important subjects in quantum information science. This is because quantum teleportation can be regarded as not only quantum information transfer but also a building block for universal quantum information processing. Furthermore, deterministic quantum information processing is very important for efficient processing and it can be realized with continuous-variable quantum information processing. In this review, quantum teleportation for continuous variables and related quantum information processing are reviewed from these points of view
Quantum information. Unconditional quantum teleportation between distant solid-state quantum bits.
Pfaff, W; Hensen, B J; Bernien, H; van Dam, S B; Blok, M S; Taminiau, T H; Tiggelman, M J; Schouten, R N; Markham, M; Twitchen, D J; Hanson, R
2014-08-01
Realizing robust quantum information transfer between long-lived qubit registers is a key challenge for quantum information science and technology. Here we demonstrate unconditional teleportation of arbitrary quantum states between diamond spin qubits separated by 3 meters. We prepare the teleporter through photon-mediated heralded entanglement between two distant electron spins and subsequently encode the source qubit in a single nuclear spin. By realizing a fully deterministic Bell-state measurement combined with real-time feed-forward, quantum teleportation is achieved upon each attempt with an average state fidelity exceeding the classical limit. These results establish diamond spin qubits as a prime candidate for the realization of quantum networks for quantum communication and network-based quantum computing. PMID:25082696
The decoupling approach to quantum information theory
Dupuis, FrÃ©dÃ©ric
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.
Quantum Information and Relativity Theory
Peres, Asher; Terno, Daniel R.
2002-01-01
Quantum mechanics, information theory, and relativity theory are the basic foundations of theoretical physics. The acquisition of information from a quantum system is the interface of classical and quantum physics. Essential tools for its description are Kraus matrices and positive operator valued measures (POVMs). Special relativity imposes severe restrictions on the transfer of information between distant systems. Quantum entropy is not a Lorentz covariant concept. Lorentz transformations o...
Decoherence-Insensitive Quantum Communication by Optimal C^*-Encoding
Bodmann, Bernhard G.; Kribs, David W; Paulsen, Vern I.
2006-01-01
The central issue in this article is to transmit a quantum state in such a way that after some decoherence occurs, most of the information can be restored by a suitable decoding operation. For this purpose, we incorporate redundancy by mapping a given initial quantum state to a messenger state on a larger-dimensional Hilbert space via a $C^*$-algebra embedding. Our noise model for the transmission is a phase damping channel which admits a noiseless or decoherence-free subspa...
Quantum: information theory: technological challenge
International Nuclear Information System (INIS)
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
Quantum Information and Spacetime Structure
Volovich, I V
2002-01-01
In modern quantum information theory one deals with 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 qubit, channel, composite systems and entangled states should be formulated in space and time. In this paper some basic notions of quantum information theory are considered from the point of view of quantum field theory and general relativity. It is pointed out an important fact that in quantum field theory there is a statistical dependence between two regions in spacetime even if they are spacelike separated. A classical probabilistic representation for a family of correlation functions in quantum field theory is obtained. A noncommutative generalization of von Neumann`s spectral theorem is discussed. We suggest a new physical principle describing a relation between the mathematical formalism of Hilbert space a...
Spin-based quantum-information processing with semiconductor quantum dots and cavity QED
Rossi, Fausto
2003-01-01
A quantum-information-processing scheme is proposed with semiconductor quantum dots located in a high-Q single-mode QED cavity. The spin degrees of freedom of one excess conduction electron of the quantum dots are employed as qubits. Excitonic states, which can be produced ultrafast with optical operation, are used as auxiliary states in the realization of quantum gates. We show how properly tailored ultrafast laser pulses and Pauli-blocking effects can be used to achieve a universal encoded ...
Bohmian Mechanics and Quantum Information
Goldstein, Sheldon
2009-01-01
Many recent results suggest that quantum theory is about information, and that quantum theory is best understood as arising from principles concerning information and information processing. At the same time, by far the simplest version of quantum mechanics, Bohmian mechanics, is concerned, not with information but with the behavior of an objective microscopic reality given by particles and their positions. What I would like to do here is to examine whether, and to what exte...
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...
A quantum computer in the scheme of an atomic quantum transistor with logical encoding of qubits
Moiseev, S. A.; Andrianov, S. N.; Moiseev, E. S.
2013-09-01
A scheme of a multiqubit quantum computer on atomic ensembles using a quantum transistor implementing two qubit gates is proposed. We demonstrate how multiatomic ensembles permit one to work with a large number of qubits that are represented in a logical encoding in which each qubit is recorded on a superposition of single-particle states of two atomic ensembles. The access to qubits is implemented by appropriate phasing of quantum states of each of atomic ensembles. An atomic quantum transistor is proposed for use when executing two qubit operations. The quantum transistor effect appears when an excitation quantum is exchanged between two multiatomic ensembles located in two closely positioned QED cavities connected with each other by a gate atom. The dynamics of quantum transfer between atomic ensembles can be different depending on one of two states of the gate atom. Using the possibilities of control for of state of the gate atom, we show the possibility of quantum control for the state of atomic ensembles and, based on this, implementation of basic single and two qubit gates. Possible implementation schemes for a quantum computer on an atomic quantum transistor and their advantages in practical implementation are discussed.
Inequalities for quantum skew information
DEFF Research Database (Denmark)
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 sk...
Quantum information theory and quantum statistics
International Nuclear Information System (INIS)
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.)
Quantum information theory and quantum statistics
Petz, Dénes
2008-01-01
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.
Quantum Information Science and Nanotechnology
Vlasov, Alexander Yu.
2009-01-01
In this note is touched upon an application of quantum information science (QIS) in nanotechnology area. The laws of quantum mechanics may be very important for nano-scale objects. A problem with simulating of quantum systems is well known and quantum computer was initially suggested by R. Feynman just as the way to overcome such difficulties. Mathematical methods developed in QIS also may be applied for description of nano-devices. Few illustrative examples are mentioned an...
Quantum information theory of entanglement
Cerf, N J; Cerf, Nicolas J; Adami, Christoph
1996-01-01
We present a quantum information theory that allows for the consistent description of quantum entanglement. It parallels classical (Shannon) information theory but is based entirely on matrices, rather than probability distributions, for the description of quantum ensembles. We find that conditional quantum entropies can be negative for quantum entangled systems, which leads to a violation of well-known bounds in classical information theory. Such a treatment clarifies the link between classical correlation and quantum entanglement: the latter can be understood as ``super-correlation'' which can induce classical correlation, while the reverse is impossible. Furthermore negative entropy and the associated clarification of entanglement paves the way to a natural, unitary, and causal model of the measurement process, while implying all the well-known results of conventional probabilistic quantum mechanics.
Quantum information: primitive notions and quantum correlations
Scarani, Valerio
2009-01-01
This series of introductory lectures consists of two parts. In the first part, I rapidly review the basic notions of quantum physics and many primitives of quantum information (i.e. notions that one must be somehow familiar with in the field, like cloning, teleportation, state estimation...). The second part is devoted to a detailed introduction to the topic of quantum correlations, covering the evidence for failure of alternative theories, some aspects of the formalism of no-signaling probability distributions and some hints towards some current research topics in the field.
Quantum information in loop quantum gravity
Terno, D R
2006-01-01
A coarse-graining of spin networks is expressed in terms of partial tracing, thus allowing to use tools of quantum information theory. This is illustrated by the analysis of a simple black hole model, where the logarithmic correction of the Hawking-Bekenstein entropy is shown to be equal to the total amount of correlations on the horizon. Finally other applications of entanglement to quantum gravity are briefly discussed.
Inequalities for quantum skew information
DEFF Research Database (Denmark)
Audenaert, Koenraad; Cai, Liang; Hansen, Frank
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...
Paszkiewicz, Adam
2012-01-01
We investigate the following generalisation of the entropy of quantum measurement. Let H be an infinite-dimensional separable Hilbert space with a 'density' operator {\\rho}, tr {\\rho}=1. Let I(P)\\in R be defined for any partition P = (P_1,...,P_m), P_1+ ... +P_m=1_H, P_i \\in proj H$ and let I(P_i Qj, i \\leq m, j \\leq n) = I(P) + I(Q) for Q =(Q_1,..., Q_n), \\sum Q_j = 1_H and P_iQ_j = Q_j P_i, tr {\\rho} P_iQ_j = tr {\\rho} P_i tr {\\rho} Q_j (P, Q are physically independent). Assuming some continuity properties we give a general form of generalised information I.
Physics as quantum information processing
D'Ariano, Giacomo Mauro
2010-01-01
The experience from Quantum Information has lead us to look at Quantum Theory (QT) and the whole Physics from a different angle. The information-theoretical paradigm---"It from Bit'---prophesied by John Archibald Wheeler is relentlessly advancing. Recently it has been shown that QT is derivable from pure informational principles. The possibility that there is only QT at the foundations of Physics has been then considered, with space-time, Relativity, quantization rules and Quantum Field Theory (QFT) emerging from a quantum-information processing. The resulting theory is a discrete version of QFT with automatic relativistic invariance, and without fields, Hamiltonian, and quantization rules. In this paper I review some recent advances on these lines. In particular: i) How space-time and relativistic covariance emerge from the quantum computation; ii) The derivation of the Dirac equation as free information flow, without imposing Lorentz covariance; iii) the information-theoretical meaning of inertial mass and ...
Informational derivation of Quantum Theory
Chiribella, G.; D'Ariano, G. M.; Perinotti, P.
2010-01-01
Quantum theory can be derived from purely informational principles. Five elementary axioms-causality, perfect distinguishability, ideal compression, local distinguishability, and pure conditioning-define a broad class of theories of information-processing that can be regarded as a standard. One postulate-purification-singles out quantum theory within this class. The main structures of quantum theory, such as the representation of mixed states as convex combinations of perfec...
Quantum Information: Opportunities and Challenges
Energy Technology Data Exchange (ETDEWEB)
Bennink, Ryan S [ORNL
2008-01-01
Modern society is shaped by the ability to transmit, manipulate, and store large amounts of information. Although we tend to think of information as abstract, information is physical, and computing is a physical process. How then should we understand information in a quantum world, in which physical systems may exist in multiple states at once and are altered by the very act of observation? This question has evolved into an exciting new field of research called Quantum Information (QI). QI challenges many accepted rules and practices in computer science. For example, a quantum computer would turn certain hard problems into soft problems, and would render common computationally-secure encryption methods (such as RSA) insecure. At the same time, quantum communication would provide an unprecedented kind of intrinsic information security at the level of the smallest physical objects used to store or transmit the information. This talk provides a general introduction to the subject of quantum information and its relevance to cyber security. In the first part, two of the stranger aspects of quantum physics namely, superposition and uncertainty are explained, along with their relation to the concept of information. These ideas are illustrated with a few examples: quantum ID cards, quantum key distribution, and Grover s quantum search algorithm. The state-of-the-art in quantum computing and communication hardware is then discussed, along with the daunting technological challenges that must be overcome. Relevant experimental and theoretical efforts at ORNL are highlighted. The talk concludes with speculations on the short- and long-term impact of quantum information on cyber security.
Energy Technology Data Exchange (ETDEWEB)
Xavier, G B; Vilela de Faria, G; Temporao, G P; Von der Weid, J P [Centre for Telecommunication Studies, Pontifical Catholic University of Rio de Janeiro-R Marques de Sao Vicente 225 Gavea, Rio de Janeiro (Brazil); Walenta, N; Gisin, N; Zbinden, H [GAP-Optique, University of Geneva, rue de l' Ecole-de-Medecine 20, CH-1211 Geneva 4 (Switzerland)], E-mail: guix@opto.cetuc.puc-rio.br
2009-04-15
In this paper we demonstrate an active polarization drift compensation scheme for optical fibres employed in a quantum key distribution experiment with polarization encoded qubits. The quantum signals are wavelength multiplexed in one fibre along with two classical optical side channels that provide the control information for the polarization compensation scheme. This set-up allows us to continuously track any polarization change without the need to interrupt the key exchange. The results obtained show that fast polarization rotations of the order of 40{pi} rad s{sup -1} are effectively compensated for. We demonstrate that our set-up allows continuous quantum key distribution even in a fibre stressed by random polarization fluctuations. Our results pave the way for Bell-state measurements using only linear optics with parties separated by long-distance optical fibres.
International Nuclear Information System (INIS)
In this paper we demonstrate an active polarization drift compensation scheme for optical fibres employed in a quantum key distribution experiment with polarization encoded qubits. The quantum signals are wavelength multiplexed in one fibre along with two classical optical side channels that provide the control information for the polarization compensation scheme. This set-up allows us to continuously track any polarization change without the need to interrupt the key exchange. The results obtained show that fast polarization rotations of the order of 40? rad s-1 are effectively compensated for. We demonstrate that our set-up allows continuous quantum key distribution even in a fibre stressed by random polarization fluctuations. Our results pave the way for Bell-state measurements using only linear optics with parties separated by long-distance optical fibres.
International Nuclear Information System (INIS)
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 finally turning his attention to philosophy in 1957, Weizsaecker became interested in nuclear fusion research and educated a generation of postwar German physicists in both plasma physics and astrophysics. Michael Frayn's play 'Copenhagen' has ignited worldwide interest in the mysterious meeting of Niels Bohr with Werner Heisenberg in September 1941. However, an article by R Luest indicates that in 1951 Bohr enjoyed a friendly visit with Heisenberg in Goettingen. This 1941 meeting of Heisenberg and Bohr is discussed further in an article by Goetz Neuneck, who also details the World War II and post-war research and interests of the Uranium Club, a group of 70--100 German physicists and chemists. Neuneck also discusses the resistance of individual scientists, such as Hahn, Heisenberg, and Bothe, to the Nazi regime. We learn that, unlike Wernher von Braun, no member of the Uranium Club was ever granted an audience with Hitler. After the war, German scientists renounced any role for German development of nuclear weapons in various manifestos, such as the Mainau and Goettingen Declarations that were both influenced by Weizsaecker. Time, Quantum and Information contains much anecdotal material. Examples include a touching quotation in a letter from Edward Teller to Weizsaecker: 'If I could share your religious belief, I would wish that you will one day come from a higher heaven and visit me in purgatory.' Another example, less complimentary, is a comment from Pauli after hearing from Weisskopf that Weizsaecker had made numerous errors in his habilitation thesis and realizing that Weizsaecker had accepted an offer from Peter Debye at Berlin: 'The measure of sloppiness in Weizsaecker's work exceeds altogether and by far the tolerable measure, and my pain of not having had him as an assistant has been alleviated by this.' Two-thirds of this compendium also explores the philosophical interests of Weizsaecker. This portion discusses his attempt to reconstruct quantum mechanics and build up a 'theory of everything' based on his 'ur' hypothesis. As stated by the mathematician G G Emch in
Informational derivation of quantum theory
Energy Technology Data Exchange (ETDEWEB)
Chiribella, Giulio; D' Ariano, Giacomo Mauro; Perinotti, Paolo [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Ontario, N2L 2Y5 (Canada); QUIT Group, Dipartimento di Fisica ' ' A. Volta' ' and INFN Sezione di Pavia, via Bassi 6, I-27100 Pavia (Italy)
2011-07-15
We derive quantum theory from purely informational principles. Five elementary axioms - causality, perfect distinguishability, ideal compression, local distinguishability, and pure conditioning - define a broad class of theories of information processing that can be regarded as standard. One postulate - purification - singles out quantum theory within this class.
BRICS and Quantum Information Processing
DEFF Research Database (Denmark)
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....
BRICS and Quantum Information Processing
DEFF Research Database (Denmark)
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.
Hadamard-encoded high-resolution NMR spectroscopy via intermolecular single-quantum coherences
Energy Technology Data Exchange (ETDEWEB)
Ke, Hanping; Cai, Honghao; Cai, Shuhui, E-mail: shcai@xmu.edu.cn; Chen, Hao; Lin, Yanqin, E-mail: linyq@xmu.edu.cn; Chen, Zhong
2014-11-24
Graphical abstract: - Highlights: â€¢ A NMR pulse sequence is proposed based on intermolecular single-quantum coherence. â€¢ Hadamard encoding is utilized to shorten the acquisition time. â€¢ High-resolution NMR spectra can be retrieved under inhomogeneous magnetic fields. â€¢ Good solvent suppression efficiency can be achieved. â€¢ The proposed method facilitates analyses of heterogeneous biological tissues. - Abstract: NMR spectroscopy plays an important role in metabolite studies because it can provide atomic level information critical for understanding biological systems. Nevertheless, NMR investigations on biological tissues are hampered by the magnetic field inhomogeneities originating from variations in macroscopic magnetic susceptibility, which lead to broad spectral lines and subsequently obscure metabolite signals. A new pulse sequence based on intermolecular single-quantum coherences was proposed to obtain one-dimensional high-resolution NMR spectra in inhomogeneous magnetic fields via Hadamard encoding. The new method can provide resolution-improved spectra directly through one-dimensional acquisition within a relatively short acquisition time. Theoretical derivation was performed and the conclusion was tested by solution samples in purposely de-shimmed magnetic fields and pig brain tissue sample. The experimental results show that this sequence can yield useful structural information, even when the field inhomogeneity is sufficiently severe to erase almost all spectral information with conventional one-dimensional single-quantum coherence techniques. Moreover, good solvent suppression efficiency can be achieved by this sequence. This sequence may provide a promising way for high-resolution NMR spectroscopy of biological tissue.
Hadamard-encoded high-resolution NMR spectroscopy via intermolecular single-quantum coherences
International Nuclear Information System (INIS)
Graphical abstract: - Highlights: â€¢ A NMR pulse sequence is proposed based on intermolecular single-quantum coherence. â€¢ Hadamard encoding is utilized to shorten the acquisition time. â€¢ High-resolution NMR spectra can be retrieved under inhomogeneous magnetic fields. â€¢ Good solvent suppression efficiency can be achieved. â€¢ The proposed method facilitates analyses of heterogeneous biological tissues. - Abstract: NMR spectroscopy plays an important role in metabolite studies because it can provide atomic level information critical for understanding biological systems. Nevertheless, NMR investigations on biological tissues are hampered by the magnetic field inhomogeneities originating from variations in macroscopic magnetic susceptibility, which lead to broad spectral lines and subsequently obscure metabolite signals. A new pulse sequence based on intermolecular single-quantum coherences was proposed to obtain one-dimensional high-resolution NMR spectra in inhomogeneous magnetic fields via Hadamard encoding. The new method can provide resolution-improved spectra directly through one-dimensional acquisition within a relatively short acquisition time. Theoretical derivation was performed and the conclusion was tested by solution samples in purposely de-shimmed magnetic fields and pig brain tissue sample. The experimental results show that this sequence can yield useful structural information, even when the field inhomogeneity is sufficiently severe to erase almost all spectral information with conventional one-dimensional single-quantum coherence techniques. Moreover, good solvent suppression efficiency can be achieved by this sequence. This sequence may provide a promising way for high-resolution NMR spectroscopy of biological tissue
Isotope-based quantum information
International Nuclear Information System (INIS)
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 distribution of isotopes with nuclear spins is a prerequisite to implement the quantum bits (or qbits). Therefore, stable semiconductor isotopes are important elements in the development of solid-state quantum information. There are not only different algorithms of quantum computation discussed but also the different models of quantum computers are presented. With numerous illustrations this small book is of great interest for undergraduate students taking courses in mesoscopic physics or nanoelectronics as well as quantum information, and academic and industrial researches working in this field.
Quantum information with Rydberg atoms
DEFF Research Database (Denmark)
Saffman, Mark; Walker, T.G.; Mølmer, Klaus
2010-01-01
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...... 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....
Environment-assisted quantum-information correction for continuous variables
DEFF Research Database (Denmark)
Sabuncu, Metin; Filip, R.
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 as a means to combat excess noise is also investigated.
Quantum-enhanced information processing
M. Mosca; Jozsa, R.; Steane, A.; Ekert, A.
2000-01-01
Information is stored, transmitted and processed always by physical means. Thus the concept of information and computation can be properly formulated only in the context of a physical theory and the study of information processing requires experimentation. It is clear that if computers are to become much smaller in the future, their description must be given by quantum mechanics. Somewhat more surprising is the fact that quantum information processing can be qualitatively different and much m...
On the Automation of Encoding Processes in the Quantum IO Monad
Directory of Open Access Journals (Sweden)
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.
Quantum information as complementary classical information
International Nuclear Information System (INIS)
Since the breakthrough by Calderbank, Shor, and Steane on the existence of quantum error-correcting codes, an oft-used notion in quantum information theory is that we can treat quantum information essentially as a strange combination of two types of classical information, pertaining to two complementary observables ''amplitude'' and ''phase''. Correcting errors afflicting either of these observables is sufficient to restore the quantum information to its original state. However, the central results of quantum information theory established recently, such as the achievable rate of quantum communication over a noisy channel, follow a different approach termed decoupling which has a natural origin in the study of quantum cryptography. We show that the decoupling-based results can be concretely established in the complementary classical information picture. By adopting an information-theoretic approach to complementarity, we are able to construct entanglement distillation protocols which straightforwardly seek to distill amplitude and phase correlations without venturing into decoupling. This gives new and intuitive proofs of both the noisy channel coding theorem and the asymptotic rates of both secret-key distillation and state merging
Identifying mechanisms in the control of quantum dynamics through Hamiltonian encoding
International Nuclear Information System (INIS)
A variety of means are now available to design control fields for manipulating the evolution of quantum systems. However, the underlying physical mechanisms often remain obscure, especially in the cases of strong fields and high quantum state congestion. This paper proposes a method to quantitatively determine the various pathways taken by a quantum system in going from the initial state to the final target. The mechanism is revealed by encoding a signal in the system Hamiltonian and decoding the resultant nonlinear distortion of the signal in the system time-evolution operator. The relevant interfering pathways determined by this analysis give insight into the physical mechanisms operative during the evolution of the quantum system. A hierarchy of mechanism identification algorithms with increasing ability to extract more detailed pathway information is presented. The mechanism identification concept is presented in the context of analyzing computer simulations of controlled dynamics. As illustrations of the concept, mechanisms are identified in the control of several simple, discrete-state quantum systems. The mechanism analysis tools reveal the roles of multiple interacting quantum pathways to maximally take advantage of constructive and destructive interference. Similar procedures may be applied directly in the laboratory to identify control mechanisms without resort to computer modeling, although this extension is not addressed in this paper
Tools for Multimode Quantum Information: Modulation, Detection, and Spatial Quantum Correlations
Lassen, M.; Delaubert, V.; Janousek, J.; Wagner, K.; Bachor, H.-A.; Lam, P. K.; Treps, N.; Buchhave, P.; Fabre, C.; Harb, C. C.
2007-02-01
We present the key elements required for continuous variable parallel quantum information protocols based on spatial multimode quantum correlations. We describe techniques for encoding, combining and detecting spatial quantum information with high efficiency in the individual transverse modes. Until now, the missing feature for the implementation of such protocols was the generation of squeezing in higher order transverse Hermite-Gauss modes. We experimentally demonstrate squeezing in selective modes by fine-tuning the phase matching condition of the nonlinear ?(2) material and the cavity resonance condition of an optical parametric amplifier. Combined, these results open the way to practical multimode optical quantum information systems.
Quantum Correlations, Chaos and Information
Madhok, Vaibhav
Quantum chaos is the study of quantum systems whose classical description is chaotic. How does chaos manifest itself in the quantum world? In this spirit, we study the dynamical generation of entanglement as a signature of chaos in a system of periodically kicked coupled-tops, where chaos and entanglement arise from the same physical mechanism. The long-time entanglement as a function of the position of an initially localized wave packet very closely correlates with the classical phase space surface of section - it is nearly uniform in the chaotic sea, and reproduces the detailed structure of the regular islands. The uniform value in the chaotic sea is explained by the random state conjecture. As classically chaotic dynamics take localized distributions in phase space to random distributions, quantized versions take localized coherent states to pseudo-random states in Hilbert space. Such random states are highly entangled, with an average value near that of the maximally entangled state. For a map with global chaos, we derive that value based on new analytic results for the entropy of random states. For a mixed phase space, we use the Percival conjecture to identify a "chaotic subspace" of the Hilbert space. The typical entanglement, averaged over the unitarily invariant Haar measure in this subspace, agrees with the long-time averaged entanglement for initial states in the chaotic sea. In all cases the dynamically generated entanglement is that of a random complex vector, even though the system is time-reversal invariant, and the Floquet operator is a member of the circular orthogonal ensemble. Continuing on our journey to find the footprints of chaos in the quantum world, we explore quantum signatures of classical chaos by studying the rate of information gain in quantum tomography. The measurement record is obtained as a sequence of expectation values of a Hermitian operator evolving under repeated application of the Floquet operator of the quantum kicked top on a large ensemble of identical systems. We find an increase in the rate of information gain and hence higher fidelities in the process when the Floquet maps employed increase in chaoticity. We make predictions for the information gain using random matrix theory in the fully chaotic regime and show a remarkable agreement between the two. Finally we discuss how this approach can be used in general as a benchmark for information gain in an experimental implementation based on nonlinear dynamics of atomic spins measured weakly by the Faraday rotation of a laser probe. The last part of this thesis is devoted to the study of the nature of quantum correlations themselves. Quantum correlations are at the heart of the weirdness of quantum mechanics and at the same time serve as a resource for the potential benefits quantum information processing might provide. For example, Einstein described quantum entanglement as "spooky action at a distance". However, even entanglement does not fully capture the complete quantum character of a system. Quantum discord aims to fill this gap and captures essentially all the quantum correlations in a quantum state. There is a considerable interest in the research community about quantum discord, since there is evidence showing this very quantity as responsible for the exponential speed up of a certain class of quantum algorithms over classical ones. Now, an important question arises: Is discord just a mathematical construct or does it have a definable physical role in information processing? This thesis provides a link between quantum discord and an actual physical task involving communication between two parties. We present an operational interpretation of quantum discord based on the quantum state merging protocol. Quantum discord is the markup in the cost of quantum communication in the process of quantum state merging, if one discards relevant prior information. We further derive a quantitative relation between the yield of the fully quantum Slepian-Wolf protocol in the presence of noise and the quantum discord of
Djordjevic, Ivan B
2010-04-12
The Bell states preparation circuit is a basic circuit required in quantum teleportation. We describe how to implement it in all-fiber technology. The basic building blocks for its implementation are directional couplers and highly nonlinear optical fiber (HNLF). Because the quantum information processing is based on delicate superposition states, it is sensitive to quantum errors. In order to enable fault-tolerant quantum computing the use of quantum error correction is unavoidable. We show how to implement in all-fiber technology encoders and decoders for sparse-graph quantum codes, and provide an illustrative example to demonstrate this implementation. We also show that arbitrary set of universal quantum gates can be implemented based on directional couplers and HNLFs. PMID:20588656
Quantum information and computing
Ohya, M; Watanabe, N
2006-01-01
The main purpose of this volume is to emphasize the multidisciplinary aspects of this very active new line of research in which concrete technological and industrial realizations require the combined efforts of experimental and theoretical physicists, mathematicians and engineers. Contents: Coherent Quantum Control of ?-Atoms through the Stochastic Limit (L Accardi et al.); Recent Advances in Quantum White Noise Calculus (L Accardi & A Boukas); Joint Extension of States of Fermion Subsystems (H Araki); Fidelity of Quantum Teleportation Model Using Beam Splittings (K-H Fichtner et al.); Quantum
Physics as quantum information processing
D'Ariano, Giacomo Mauro
2010-01-01
The experience from Quantum Information has lead us to look at Quantum Theory (QT) and the whole Physics from a different angle. The information-theoretical paradigm---"It from Bit'---prophesied by John Archibald Wheeler is relentlessly advancing. Recently it has been shown that QT is derivable from pure informational principles. The possibility that there is only QT at the foundations of Physics has been then considered, with space-time, Relativity, quantization rules and Q...
Minimal-memory realization of pearl-necklace encoders of general quantum convolutional codes
International Nuclear Information System (INIS)
Quantum convolutional codes, like their classical counterparts, promise to offer higher error correction performance than block codes of equivalent encoding complexity, and are expected to find important applications in reliable quantum communication where a continuous stream of qubits is transmitted. Grassl and Roetteler devised an algorithm to encode a quantum convolutional code with a ''pearl-necklace'' encoder. Despite their algorithm's theoretical significance as a neat way of representing quantum convolutional codes, it is not well suited to practical realization. In fact, there is no straightforward way to implement any given pearl-necklace structure. This paper closes the gap between theoretical representation and practical implementation. In our previous work, we presented an efficient algorithm to find a minimal-memory realization of a pearl-necklace encoder for Calderbank-Shor-Steane (CSS) convolutional codes. This work is an extension of our previous work and presents an algorithm for turning a pearl-necklace encoder for a general (non-CSS) quantum convolutional code into a realizable quantum convolutional encoder. We show that a minimal-memory realization depends on the commutativity relations between the gate strings in the pearl-necklace encoder. We find a realization by means of a weighted graph which details the noncommutative paths through the pearl necklace. The weight of the longest path in this graph is equal to the minimal amount of memory needed to implement the encoder. The algorithm has a polynomial-time complexity in the number of gate strings in the pearl-necklace encoder.
Energy Technology Data Exchange (ETDEWEB)
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 finally turning his attention to philosophy in 1957, Weizsaecker became interested in nuclear fusion research and educated a generation of postwar German physicists in both plasma physics and astrophysics. Michael Frayn's play 'Copenhagen' has ignited worldwide interest in the mysterious meeting of Niels Bohr with Werner Heisenberg in September 1941. However, an article by R Luest indicates that in 1951 Bohr enjoyed a friendly visit with Heisenberg in Goettingen. This 1941 meeting of Heisenberg and Bohr is discussed further in an article by Goetz Neuneck, who also details the World War II and post-war research and interests of the Uranium Club, a group of 70--100 German physicists and chemists. Neuneck also discusses the resistance of individual scientists, such as Hahn, Heisenberg, and Bothe, to the Nazi regime. We learn that, unlike Wernher von Braun, no member of the Uranium Club was ever granted an audience with Hitler. After the war, German scientists renounced any role for German development of nuclear weapons in various manifestos, such as the Mainau and Goettingen Declarations that were both influenced by Weizsaecker. Time, Quantum and Information contains much anecdotal material. Examples include a touching quotation in a letter from Edward Teller to Weizsaecker: 'If I could share your religious belief, I would wish that you will one day come from a higher heaven and visit me in purgatory.' Another example, less complimentary, is a comment from Pauli after hearing from Weisskopf that Weizsaecker had made numerous errors in his habilitation thesis and realizing that Weizsaecker had accepted an offer from Peter Debye at Berlin: 'The measure of sloppiness in Weizsaecker's work exceeds altogether and by far the tolerable measure, and my pain of not having had him as an assistant has been alleviated by this.' Two-thirds of this compendium also explores the philosophical interests of Weizsaecker. This portion discusses his attempt to reconstruct quantum mechanics and build up a 'theory of everything' based on his
Certainty and Uncertainty in Quantum Information Processing
Rieffel, Eleanor G.
2007-01-01
This survey, aimed at information processing researchers, highlights intriguing but lesser known results, corrects misconceptions, and suggests research areas. Themes include: certainty in quantum algorithms; the "fewer worlds" theory of quantum mechanics; quantum learning; probability theory versus quantum mechanics.
Quantum information and convex optimization
Energy Technology Data Exchange (ETDEWEB)
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.)
Quantum information and convex optimization
International Nuclear Information System (INIS)
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.)
Introduction to relativistic quantum information
Terno, D R
2005-01-01
I discuss the role that relativistic considerations play in quantum information processing. First I describe how the causality requirements limit possible multi-partite measurements. Then the Lorentz transformations of quantum states are introduced, and their implications on physical qubits are described. This is used to describe relativistic effects in communication and entanglement.
A simple encoding of a quantum circuit amplitude as a matrix permanent
Rudolph, Terry
2009-01-01
A simple construction is presented which allows computing the transition amplitude of a quantum circuit to be encoded as computing the permanent of a matrix which is of size proportional to the number of quantum gates in the circuit. This opens up some interesting classical monte-carlo algorithms for approximating quantum circuits.
Languages of Quantum Information Theory
Winter, A
1998-01-01
This note will introduce some notation and definitions for information theoretic quantities in the context of quantum systems, such as (conditional) entropy and (conditional) mutual information. We will employ the natural C*-algebra formalism, and it turns out that one has an allover dualism of language: we can define every- thing for (compatible) observables, but also for (compatible) C*-subalgebras. The two approaches are unified in the formalism of quantum operations, and they are connected by a very satisfying inequality, generalizing the well known Holevo bound. Then we turn to communication via (discrete memoryless) quantum channels: we formulate the Fano inequality, bound the capacity region of quantum multiway channels, and comment on the quantum broadcast channel.
Quantum States as Ordinary Information
Directory of Open Access Journals (Sweden)
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.
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...
Quantum Information Theory and Applications to Quantum Cryptography
Papadakos, Nikolaos P.
2002-01-01
Classical and quantum information theory are simply explained. To be more specific it is clarified why Shannon entropy is used as measure of classical information and after a brief review of quantum mechanics it is possible to demonstrate why the density matrix is the main tool of quantum information theory. Then von Neumann entropy is introduced and with its help a great difference between classical and quantum information theory is presented: quantum entanglement. Moreover...
Persistence of Quantum Information
Schulz, M; Schulz, Michael; Trimper, Steffen
2006-01-01
There is an increasing interest in the role of macroscopic environments to our understanding of the basics of quantum theory. The knowledge of the implications of the quantum theory to other theories, especially to the statistical mechanics and the domain of validity has captivated scientists from the beginning of quantum description. In such a context, the presence of an environment is commonly thought as entanglement, decohering and mixing properties of quantum system. Generically, an environment is assumed to be a noisy reservoir or a heat bath. Whereas in common interpretation of statistical mechanics the heat bath is unspecified, in quantum systems a heat bath can also provide an indirect interaction between otherwise totally decoupled subsystems and consequently a means to entangle them \\cite{cdkl,dvclp,bfp}. In simple example for the entanglement between two qubits due to the interaction with a common heat bath has been explicitly shown in \\cite{b}. Whereas in that paper the bath is described by a coll...
Quantum network teleportation for quantum information distribution and concentration
Zhang, Yong-Liang; Wang, Yi-Nan; Xiao, Xiang-Ru; Jing, Li; Mu, Liang-zhu; Korepin, V. E.; Fan, Heng(Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, PR China)
2012-01-01
We investigate the schemes of quantum network teleportation for quantum information distribution and concentration which are essential in quantum cloud computation and quantum internet. In those schemes, the cloud can send simultaneously identical unknown quantum states to clients located in different places by a network like teleportation with a prior shared multipartite entangled state resource. The cloud first perform the quantum operation, each client can recover their quantum state local...
Quantum information. Teleportation - cryptography - quantum computer
International Nuclear Information System (INIS)
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)
Quantum Entropy and Information
Datta, Nilanjana
As seen in chapter "Classical Information Theory", classical information theory is the mathematical theory of information-processing tasks such as storage and transmission of information. It was born out of a seminal paper by Claude Shannon in 1948.
Unification of quantum information theory
Abeyesinghe, Anura
We present the unification of many previously disparate results in noisy quantum Shannon theory and the unification of all of noiseless quantum Shannon theory. More specifically we deal here with bipartite, unidirectional, and memoryless quantum Shannon theory. We find all the optimal protocols and quantify the relationship between the resources used, both for the one-shot and for the ensemble case, for what is arguably the most fundamental task in quantum information theory: sharing entangled states between a sender and a receiver. We find that all of these protocols are derived from our one-shot superdense coding protocol and relate nicely to each other. We then move on to noisy quantum information theory and give a simple, direct proof of the "mother" protocol, or rather her generalization to the Fully Quantum Slepian-Wolf protocol (FQSW). FQSW simultaneously accomplishes two goals: quantum communication-assisted entanglement distillation, and state transfer from the sender to the receiver. As a result, in addition to her other "children," the mother protocol generates the state merging primitive of Horodecki, Oppenheim, and Winter as well as a new class of distributed compression protocols for correlated quantum sources, which are optimal for sources described by separable density operators. Moreover, the mother protocol described here is easily transformed into the so-called "father" protocol, demonstrating that the division of single-sender/single-receiver protocols into two families was unnecessary: all protocols in the family are children of the mother.
Quantum information processing and measurement in circuit quantum electrodynamics
Helmer, Ferdinand
2009-01-01
In this thesis, experimentally relevant aspects and open questions of quantum information processing and measurement in circuit quantum electrodynamics have been investigated theoretically. Circuit quantum electrodynamics is a relatively young field combining superconducting transmission line resonators on-chip with superconducting quantum bits which serve as artificial atoms. Remarkable experiments have underlined the prospects of circuit QED as a possible architecture for quantum informatio...
Information transfer through quantum channels
International Nuclear Information System (INIS)
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 channel. We then explain how all known coding theorems can be generalized from memoryless channels to forgetful memory channels. We also present examples for non-forgetful channels, and derive generic entropic upper bounds on their capacities for (private) classical and quantum information transfer. Ch. 7 provides a brief introduction to quantum information spectrum methods as a promising approach to coding theorems for completely general quantum sources and channels. We present a data compression theorem for general quantum sources and apply these results to ergodic as well as mixed sources. Finally we investigate the continuity of distillable entanglement - another key notion of the field, which characterizes the optimal asymptotic rate at which maximally entangled states can be generated from many copies of a less entangled state. We derive uniform norm bounds for all states with full support, and we extend some of these results to quantum channel capacities. (orig.)
Information transfer through quantum channels
Energy Technology Data Exchange (ETDEWEB)
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 channel. We then explain how all known coding theorems can be generalized from memoryless channels to forgetful memory channels. We also present examples for non-forgetful channels, and derive generic entropic upper bounds on their capacities for (private) classical and quantum information transfer. Ch. 7 provides a brief introduction to quantum information spectrum methods as a promising approach to coding theorems for completely general quantum sources and channels. We present a data compression theorem for general quantum sources and apply these results to ergodic as well as mixed sources. Finally we investigate the continuity of distillable entanglement - another key notion of the field, which characterizes the optimal asymptotic rate at which maximally entangled states can be generated from many copies of a less entangled state. We derive uniform norm bounds for all states with full support, and we extend some of these results to quantum channel capacities. (orig.)
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.
Thiollet, Sarah; Higson, Séamus; White, Nicola; Morgan, Sarah L
2012-03-01
The development of screening assays continues to be an active area of research in molecular diagnostics. Fluorescent microspheres conjugated to biomarkers (nucleic acids, proteins, lipids, carbohydrates) and analyzed on flow cytometer instruments offered a new approach for multiplexed detection platform in a suspension format. Quantum dots encoded into synthetic microspheres have the potentials to improve current screening bioassays and specifically suspension array technology. In this paper, commercialized quantum dot-encoded microsphere were evaluated and optimized as fluorescent probes to address some of the limitations of suspension array technologies. A comprehensive study was undertaken to adapt the bioconjugation procedure to the quantum dot-encoded microsphere structural and optical properties. Both the leaching-out of quantum dots and microspheres degradation under bioconjugation experimental conditions were minimized. A rapid, efficient and reproducible conjugation method was developed for the detection of single-stranded DNA with the commercialized quantum dot-encoded microsphere. Approximately ten thousand microspheres were conjugated to short amino-modified DNA sequences in one hour with high efficiency. The bioconjugated microspheres acting as fluorescent probes successfully detected a DNA target in suspension with high specificity. Quantum dot-encoded microsphere commercial products are limited which strongly prevents reproducible and comparative studies between laboratories. The method developed here contributes to the understanding of quantum dot-encoded microsphere reactivity, and to the optimization of adapted experimental procedure. This step is essential in the development of this new fluorescent probe technology for multiplex genotyping assay and molecular diagnostic applications. PMID:22057294
Quantum information and relativity theory
International Nuclear Information System (INIS)
This article discusses the intimate relationship between quantum mechanics, information theory, and relativity theory. Taken together these are the foundations of present-day theoretical physics, and their interrelationship is an essential part of the theory. The acquisition of information from a quantum system by an observer occurs at the interface of classical and quantum physics. The authors review the essential tools needed to describe this interface, i.e., Kraus matrices and positive-operator-valued measures. They then discuss how special relativity imposes severe restrictions on the transfer of information between distant systems and the implications of the fact that quantum entropy is not a Lorentz-covariant concept. This leads to a discussion of how it comes about that Lorentz transformations of reduced density matrices for entangled systems may not be completely positive maps. Quantum field theory is, of course, necessary for a consistent description of interactions. Its structure implies a fundamental tradeoff between detector reliability and localizability. Moreover, general relativity produces new and counterintuitive effects, particularly when black holes (or, more generally, event horizons) are involved. In this more general context the authors discuss how most of the current concepts in quantum information theory may require a reassessment
Information Leakage of Heterogeneous Encoded Correlated Sequences over Eavesdropped Channel
Balmahoon, R; Cheng, L.
2015-01-01
Correlated sources are present in communication systems where protocols ensure that there is some predetermined information for sources. Here correlated sources across an eavesdropped channel that incorporate a heterogeneous encoding scheme and their effect on the information leakage when some channel information and a source have been wiretapped is investigated. The information leakage bounds for the Slepian-Wolf scenario are provided. Thereafter, the Shannon cipher system approach is presen...
Quantum information with Rydberg atoms
DEFF Research Database (Denmark)
Saffman, Mark; Walker, T.G.; Mølmer, Klaus
2010-01-01
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 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 ...
Byrd, M S; Byrd, Mark S.; Lidar, Daniel A.
2002-01-01
Proposals for physical systems to act as quantum computers are inevitably plagued by the unavoidable coupling with the environment (bath) that causes decoherence, and by technological difficulties connected with the controllability of quantum states. Several techniques exist for achieving reliable quantum computation by countering the effects of decoherence. At this time, however, not one, by itself, will serve as a panacea for error correction. In this paper, we introduce a method that combines system-bath decoupling operations with error avoidance or active error correction to address these major concerns. By using an empirical approach to error correction based on experimental data, and an efficient set of decoupling operations that will serve to protect encoded quantum information, we are able to propose a comprehensive method for reducing the adverse effects of decoherence, in particular in scalable solid state quantum computing devices. Our method has the added benefit of significantly reducing design c...
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.
Color schemes for encoding information in digital maps
Zeng, Ruzhu; Zeng, Huanzhao
2010-01-01
Color schemes have been used in maps to visually distinguish different regions or to approximately represent the magnitude of a property. Since human eyes are not able to translate a color to a numerical scale, colors on a traditional map can only be used to visually estimate magnitudes. As maps are represented more and more digitally, a properly designed color scheme may be able to use color to encode numbers and to accurately translate colors into numerical scales of a property. As a mouse (or other pointers) points to a location, the color of the location can be translated into the original encoded number and therefore the numerical property of the location may be displayed. In this paper, method to encode information in digital maps using color schemes is investigated. A hue-based color scheme was developed to encode and decode numerical scales for digital maps. Color gamut issues between display and print are investigated as well.
Scalable quantum information processing with atomic ensembles and flying photons
Mei, Feng; Feng, Mang; Yu, Ya-Fei; ZHANG, ZHI-MING
2009-01-01
We present a scheme for scalable quantum information processing (QIP) with atomic ensembles and flying photons. Using the Rydberg blockade, we encode the qubits in the collective atomic states, which could be manipulated fast and easily due to the enhanced interaction, in comparison to the single-atom case. We demonstrate that our proposed gating could be applied to generation of two-dimensional cluster states for measurement-based quantum computation. Moreover, the atomic e...
Negative entropy and information in quantum mechanics
Cerf, N J
1997-01-01
We describe a consistent framework for information theory in quantum mechanics. Unlike in classical (Shannon) information theory, conditional entropies can be negative when considering quantum entangled systems. This has the remarkable consequence that negative virtual information can be carried by particles. Accordingly, quantum informational processes can be described by diagrams, much like particle physics reactions, involving quantum bits and antibits. This allows us to reinterpret quantum teleportation and superdense coding in a fully consistent way.
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 ...
Endophysical information transfer in quantum processes
Eakins, J; Eakins, Jon; Jaroszkiewicz, George
2004-01-01
We give a mathematical criterion for the concept of information flow within closed quantum systems described by quantum registers. We define the concepts of separations and entanglements over quantum registers and use them with the quantum zip properties of inner products over quantum registers to establish the concept of partition change, which is fundamental to our criterion of endophysical information exchange within such quantum systems.
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...
Fractal states in quantum information processing
Jaeger, Gregg
2007-01-01
The fractal character of some quantum properties has been shown for systems described by continuous variables. Here, a definition of quantum fractal states is given that suits the discrete systems used in quantum information processing, including quantum coding and quantum computing. Several important examples are provided.
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
Quantum Parallelism in Quantum Information Processing
Dugic, Miroljub; Cirkovic, Milan M.
2002-01-01
We investigate distinguishability (measured by fidelity) of the initial and the final state of a qubit, which is an object of the so-called nonideal quantum measurement of the first kind. We show that the fidelity of a nonideal measurement can be greater than the fidelity of the corresponding ideal measurement. This result is somewhat counterintuitive, and can be traced back to the quantum parallelism in quantum operations, in analogy with the quantum parallelism manifested in the quantum com...
Probabilistic quantum encoder for single-photon qubits
International Nuclear Information System (INIS)
We describe an experiment in which a physical qubit represented by the polarization state of a single photon was probabilistically encoded in the logical state of two photons. The experiment relied on linear optics, postselection, and three-photon interference effects produced by a parametric down-conversion photon pair and a weak coherent state. An interesting consequence of the encoding operation was the ability to observe entangled three-photon Greenberger-Horne-Zeilinger states
Efficient Quantum Information Processing via Quantum Compressions
Deng, Y.; Luo, M. X.; Ma, S. Y.
2015-04-01
Our purpose is to improve the quantum transmission efficiency and reduce the resource cost by quantum compressions. The lossless quantum compression is accomplished using invertible quantum transformations and applied to the quantum teleportation and the simultaneous transmission over quantum butterfly networks. New schemes can greatly reduce the entanglement cost, and partially solve transmission conflictions over common links. Moreover, the local compression scheme is useful for approximate entanglement creations from pre-shared entanglements. This special task has not been addressed because of the quantum no-cloning theorem. Our scheme depends on the local quantum compression and the bipartite entanglement transfer. Simulations show the success probability is greatly dependent of the minimal entanglement coefficient. These results may be useful in general quantum network communication.
Negative entropy and information in quantum mechanics
Cerf, N. J.; C. Adami
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 entan...
Scalable quantum information processing with atomic ensembles and flying photons
Mei, Feng; Yu, Ya-Fei; Zhang, Zhi-Ming
2009-01-01
We present a scheme for scalable quantum information processing (QIP) with atomic ensembles and flying photons. Using the Rydberg blockade, we encode the qubits in the collective atomic states, which could be manipulated fast and easily due to the enhanced interaction, in comparison to the single-atom case. We demonstrate that our proposed gating could be applied to generation of two-dimensional cluster states for measurement-based quantum computation. Moreover, the atomic ensembles also function as quantum repeaters useful for long distance quantum state transfer. We show the possibility of our scheme to work in bad cavity or in weak coupling regime, which could much relax the experimental requirement. The efficient coherent operations on the ensemble qubits enable our scheme to be switchable between quantum computation and quantum communication using atomic ensembles.
Information in Quantum Description and Gate Implementation
Krishnan, Gayathre
2006-01-01
This note considers Kak's observer-reference model of quantum information, where it is shown that qubits carry information that is sqrt n / ln n times classical information, where n is the number of components in the measurement system, to analyze information processing in quantum gates. The obverse side of this exponential nature of quantum information is that the computational complexity of implementing unconditionally reliable quantum gates is also exponential.
Information ?ow in quantum teleportation
Indian Academy of Sciences (India)
Andrew Whitaker
2002-08-01
The ?ow 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 de?nition of the term ’parameter dependence’ is discussed.
Quantum Encoder and Decoder for Secret Key Distribution with Check Bits
Directory of Open Access Journals (Sweden)
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.
The role of quantum memory in quantum information processing
Nemoto, Kae; Stephens, Ashley M.; Devitt, Simon J.; Harrison, Keith A.; Munro, William J.
2013-09-01
Until recently, it was believed that long-lived quantum memories were necessary for long-distance quantum communication. However, by using error-correction codes in an efficient wayâ€”specifically, by correcting for photon lossâ€”it is possible to transmit quantum information over long distances without quantum memories. For quantum computation, recent architectures for topological quantum computation indicate that the simplest large-scale structure could be memory-less. While a quantum memory may no longer be an essential resource for quantum networks, it could nonetheless be a key device in the development of quantum information technology. However, it is still not clear what benefits a functioning device could bring to quantum information systems, largely due to a lack of detailed models. Recently we have developed a detailed model for a quantum network based on a simple device designed to act as a building block for a full system architecture. The device is based on an optical cavity containing a negatively charged nitrogen-vacancy center in diamond. This model naturally integrates quantum communication with computation, and using this model we can assess quantitatively the costs and benefits of quantum memories. With or without quantum memories, it is necessary for us to preserve quantum information for a long period of time in either communication or computation.
Channel simulation with quantum side information
Luo, Z; Devetak, Igor; Luo, Zhicheng
2006-01-01
We study and solve the problem of classical channel simulation with quantum side information at the receiver. This is a generalization of both the classical reverse Shannon theorem, and the classical-quantum Slepian-Wolf problem. The optimal noiseless communication rate is found to be reduced from the mutual information between the channel input and output by the Holevo information between the channel output and the quantum side information. Our main theorem has two important corollaries. The first is a quantum generalization of the Wyner-Ziv problem: rate-distortion theory with quantum side information. The second is an alternative proof of the trade-off between classical communication and common randomness distilled from a quantum state. The fully quantum generalization of the problem considered is quantum state redistribution. Here the sender and receiver share a mixed quantum state and the sender wants to transfer part of her state to the receiver using entanglement and quantum communication. We present o...
Information theoretic analysis of rate to phase encoding
Directory of Open Access Journals (Sweden)
Jan-Hendrik Schleimer
2012-05-01
Full Text Available The degree of synchronization between neurons or their relative time delay has long been postulated to carry information [1,2]. When a background oscillation is present, the times at which a neuron fires can be assigned a phase relative to the oscillation. Experimentally, one can observe entrainment to the oscillatory local field potential (LFP in the olfactory bulb, synchrony binding in the visual system, and phase precession in the hippocampus. Once information is encoded into the relative phase of firing, it can be used to facilitate phase based computations [1], influence the dynamics of spike timing based learning rules, or be converted back into a firing rate using bursting neurons [4]. The performance of a rate-to-phase encoder in the hippocampus was assessed by analyzing recorded data and an integrate & fire model [3]. We extend the analysis to a more general class of models, i.e., phase oscillators that are reduced from conductance based models. The frame work also allows one to investigate the hampering effects of various noise sources. Our analysis shows, that the exact shape of the distribution of phase differences between spikes emitted by the encoding neuron and LFP depends on the interplay between the neuron's phase response curve and the frequency content of the LFP. When the background input is a simple oscillation, only the lowest frequency component of the PRC matters. Yet neurons that have simple resonances have a PRC whose first Fourier coefficient is zero--the phase of spiking of such a neuron will not encode information. Only neurons that integrate over their synaptic inputs are good phase encoders. The phase encoding is summarized by the vector strength, which is related to the circular mean and variance of the phase distribution. This is calculated numerically by an efficient continued fraction method. Deterministic coding, in which noise is absent, restricts the phase to one half of the oscillation cycle. In a population of identical neurons, noise extends the dynamic range of encoding, even though the phase of individual neurons ``slips'' outside of the classical entrainment regime. In addition, we make use of the Arimoto-Blahut algorithm to estimate the optimal input statistics for a given rate-to-phase encoder. The boundaries of the entrainment region turn out to be particularly suitable for precise coding.
Quantum Cloning and Deletion in Quantum Information Theory
Adhikari, Satyabrata
2006-01-01
Quantum mechanics put restriction on performing some task which we can do classically. One such restriction is that we cannot copy an arbitrary quantum state. This is known as No-cloning theorem. Although quantum mechanics forbid us to construct a perfect cloner, there is no restriction to construct an imperfect cloner. Therefore, we have constructed and studied a special kind of quantum cloning machine named as Hybrid quantum cloning machine which is nothing but a different combination of pre-existing quantum cloning machines. We showed that this hybrid quantum cloning machine sometime gives better quality copy than the pre-existing quantum cloners. Quantum entanglement is a very astonishing property in a multi-partite system and it is a very useful ingredient of quantum information theory. Therefore broadcasting (cloning) of entanglement is a very important subject to study. In this regard we have studied the broadcasting of entanglement using state dependent quantum cloning machine. Further, we have invest...
Minimum-cost quantum measurements for quantum information
Wallden, Petros; Dunjko, Vedran; Andersson, Erika
2013-01-01
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 mixed states of t...
The decoupling approach to quantum information theory
Dupuis, FrÃ©dÃ©ric
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...
Comparing quantum cloning: A Fisher-information perspective
Song, Hongting; Luo, Shunlong; Li, Nan; Chang, Lina
2013-10-01
Perfect cloning of an unknown quantum state is impossible. Approximate cloning, which is optimal in various senses, has been found in many cases. Paradigmatic examples are Wootters-Zurek cloning and universal cloning. These cloning machines aim at optimal cloning of the full quantum states. However, in practice, what is important and relevant may only involve partial information in quantum states, rather than quantum states themselves. For example, signals are often encoded as parameters in quantum states, whose information content is well synthesized by quantum Fisher information. This raises the basic issue of evaluating the information transferring capability (e.g., distributing quantum Fisher information) of quantum cloning. We assess and compare Wootters-Zurek cloning and universal cloning from this perspective and show that, on average, Wootters-Zurek cloning performs better than universal cloning for the phase (as well as amplitude) parameter, although they are incomparable individually, and universal cloning has many advantages over Wootters-Zurek cloning in other contexts. Physical insights and related issues are further discussed.
The role of quantum discord in quantum information theory
International Nuclear Information System (INIS)
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.
Information and Computation: Classical and Quantum Aspects
Galindo, A; Martin-Delgado, M. A.
2001-01-01
Quantum theory has found a new field of applications in the realm of information and computation during the recent years. This paper reviews how quantum physics allows information coding in classically unexpected and subtle nonlocal ways, as well as information processing with an efficiency largely surpassing that of the present and foreseeable classical computers. Some outstanding aspects of classical and quantum information theory will be addressed here. Quantum teleportat...
Quantum Information Complexity and Amortized Communication
Touchette, Dave
2014-01-01
We define a new notion of information cost for quantum protocols, and a corresponding notion of quantum information complexity for bipartite quantum channels, and then investigate the properties of such quantities. These are the fully quantum generalizations of the analogous quantities for bipartite classical functions that have found many applications recently, in particular for proving communication complexity lower bounds. Our definition is strongly tied to the quantum state redistribution...
Quantum systems, channels, information. A mathematical introduction
International Nuclear Information System (INIS)
The subject of this book is theory of quantum system presented from information science perspective. The central role is played by the concept of quantum channel and its entropic and information characteristics. Quantum information theory gives a key to understanding elusive phenomena of quantum world and provides a background for development of experimental techniques that enable measuring and manipulation of individual quantum systems. This is important for the new efficient applications such as quantum computing, communication and cryptography. Research in the field of quantum informatics, including quantum information theory, is in progress in leading scientific centers throughout the world. This book gives an accessible, albeit mathematically rigorous and self-contained introduction to quantum information theory, starting from primary structures and leading to fundamental results and to exiting open problems.
How much a quantum measurement is informative?
International Nuclear Information System (INIS)
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
How much a quantum measurement is informative?
Energy Technology Data Exchange (ETDEWEB)
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.
Philosophy of Quantum Information and Entanglement
Bokulich, Alisa; Jaeger, Gregg
2010-06-01
Preface; Introduction; Part I. Quantum Entanglement and Nonlocality: 1. Nonlocality beyond quantum mechanics Sandu Popescu; 2. Entanglement and subsystems, entanglement beyond subsystems, and all that Lorenza Viola and Howard Barnum; 3. Formalism locality in quantum theory and quantum gravity Lucien Hardy; Part II. Quantum Probability: 4. Bell's inequality from the contextual probabilistic viewpoint Andrei Khrennikov; 5. Probabilistic theories: what is special about quantum mechanics? Giacomo Mauro D'Ariano; 6. What probabilities tell about quantum systems, with application to entropy and entanglement John Myers and Hadi Madjid; 7. Bayesian updating and information gain in quantum measurements Leah Henderson; Part III. Quantum Information: 8. Schumacher information and the philosophy of physics Arnold Duwell; 9. From physics to information theory and back Wayne Myrvold; 10. Information, immaterialism, and instrumentalism: old and new in quantum information Chris Timpson; Part IV. Quantum Communication and Computing: 11. Quantum computation: where does the speed-up come from? Jeff Bub; 12. Quantum mechanics, quantum computing and quantum cryptography Tai Wu.
Recycling of quantum information Multiple observations of quantum clocks
Buzek, V; Imoto, N; Buzek, Vladimir; Knight, Peter L.; Imoto, Nobuyuki
2000-01-01
How much information about the original state preparation can be extracted from a quantum system which already has been measured? That is, how many independent (non-communicating) observers can measure the quantum system sequentially and give a nontrivial estimation of the original unknown state? We investigate these questions and we show from a simple example that quantum information is not entirely lost as a result of the measurement-induced collapse of the quantum state, and that an infinite number of independent observers who have no prior knowledge about the initial state can gain a partial information about the original preparation of the quantum system.
Quantum States as Objective Informational Bridges
Healey, Richard
2015-09-01
A quantum state represents neither properties of a physical system nor anyone's knowledge of its properties. The important question is not what quantum states represent but how they are used—as informational bridges. Knowing about some physical situations (its backing conditions), an agent may assign a quantum state to form expectations about other possible physical situations (its advice conditions). Quantum states are objective: only expectations based on correct state assignments are generally reliable. If a quantum state represents anything, it is the objective probabilistic relations between its backing conditions and its advice conditions. This paper offers an account of quantum states and their function as informational bridges, in quantum teleportation and elsewhere.
Non-compression of quantum phase information
International Nuclear Information System (INIS)
We raise a general question of quantum information theory: whether quantum phase information can be compressed and retrieved. A general qubit contains both amplitude and phase information, while an equatorial qubit contains only phase information. We study whether it is possible to compress the phase information of n equatorial qubits into m general qubits, with m being less than n, and still perfectly retrieve that information. We prove that this process is not allowed by quantum mechanics. (paper)
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.Â 11304031).
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.
Efficient Computations of Encodings for Quantum Error Correction
Cleve, Richard; Gottesman, Daniel
1996-01-01
We show how, given any set of generators of the stabilizer of a quantum code, an efficient gate array that computes the codewords can be constructed. For an n-qubit code whose stabilizer has d generators, the resulting gate array consists of O(n d) operations, and converts k-qubit data (where k = n - d) into n-qubit codewords.
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 ...
Quantum Information in Space and Time
Volovich, Igor 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 inv...
Quantum entanglement as information theoretic resource
Dugic, M.
2004-01-01
We address the following criterion for quantifying the quantum information resources: classically simulable {\\it vs.} classically non-simulable information processing. This approach gives rise to existence of a deeper level of quantum information processing--which we refer to as "quantum communication channel". We particularly show, that following the recipes of the standard theory of entanglement measures does not necessarily give rise to un-locking the quantum communicatio...
Basic concepts in quantum information theory
International Nuclear Information System (INIS)
Full text: Quantum information theory provides a framework for the description of quantum systems and their applications in the context of quantum computation and quantum communication. Although several of the basic concepts on which such theory is built are reminiscent of those of (classical) Information Theory, the new rules provided by quantum mechanics introduce properties which have no classical counterpart and that are responsible for most of the applications. In particular, entangled states appear as one of the basic resources in this context. In this lecture I will introduce the basic concepts and applications in Quantum Information, particularly stressing the definition of entanglement, its quantification, and its applications. (author)
Physics as Quantum Information Processing: Quantum Fields as Quantum Automata
D'Ariano, Giacomo Mauro
2011-01-01
Can we reduce Quantum Field Theory (QFT) to a quantum computation? Can physics be simulated by a quantum computer? Do we believe that a quantum field is ultimately made of a numerable set of quantum systems that are unitarily interacting? A positive answer to these questions corresponds to substituting QFT with a theory of quantum cellular automata (QCA), and the present work is examining this hypothesis. These investigations are part of a large research program on a "quantu...
Transfer and teleportation of quantum states encoded in decoherence-free subspace
Wei, Hua; Zhang, XiaoLong; Feng, Mang
2007-01-01
Quantum state transfer and teleportation, with qubits encoded in internal states of the atoms in cavities, among spatially separated nodes of a quantum network in decoherence-free subspace are proposed, based on a cavity-assisted interaction by single-photon pulses. We show in details the implementation of a logic-qubit Hadamard gate and a two-logic-qubit conditional gate, and discuss the experimental feasibility of our scheme.
Uniform Additivity in Classical and Quantum Information
Cross, Andrew W.; Li, KE; Smith, Graeme
2016-01-01
Information theory establishes the fundamental limits on data transmission, storage, and processing. Quantum information theory unites information theoretic ideas with an accurate quantum-mechanical description of reality to give a more accurate and complete theory with new and more powerful possibilities for information processing. The goal of both classical and quantum information theory is to quantify the optimal rates of interconversion of different resources. These rates are usually char...
Principles and methods of quantum information technologies
Semba, Kouichi
2016-01-01
This book presents the research and development-related results of the â€œFIRSTâ€ 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. Â 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...
Entropy of quantum channel in the theory of quantum information
Roga, Wojciech
2011-01-01
Quantum channels, also called quantum operations, are linear, trace preserving and completely positive transformations in the space of quantum states. Such operations describe discrete time evolution of an open quantum system interacting with an environment. The thesis contains an analysis of properties of quantum channels and different entropies used to quantify the decoherence introduced into the system by a given operation. Part I of the thesis provides a general introduction to the subject. In Part II, the action of a quantum channel is treated as a process of preparation of a quantum ensemble. The Holevo information associated with this ensemble is shown to be bounded by the entropy exchanged during the preparation process between the initial state and the environment. A relation between the Holevo information and the entropy of an auxiliary matrix consisting of square root fidelities between the elements of the ensemble is proved in some special cases. Weaker bounds on the Holevo information are also es...
Quantum information and physics: some future directions
Preskill, John
1999-01-01
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, an...
Quantum Information in Communication and Imaging
Simon, David S.; Jaeger, Gregg; Sergienko, Alexander V.
2015-10-01
A brief introduction to quantum information theory in the context of quantum optics is presented. After presenting the fundamental theoretical basis of the subject, experimental evaluation of entanglement measures are discussed, followed by applications to communication and imaging.
Holography, Quantum Geometry and Quantum Information Theory
Zizzi, P A
2000-01-01
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 labeled by the spin-1/2 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, which leads to a quantum-computing picture of the early inflationary universe. A discrete micro-causality emerges, where the time parameter is given in terms of 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.
Integrated Information-Induced Quantum Collapse
Kremnizer, Kobi; Ranchin, André
2015-08-01
We present a novel spontaneous collapse model where size is no longer the property of a physical system which determines its rate of collapse. Instead, we argue that the rate of spontaneous localization should depend on a system's quantum Integrated Information (QII), a novel physical property which describes a system's capacity to act like a quantum observer. We introduce quantum Integrated Information, present our QII collapse model and briefly explain how it may be experimentally tested against quantum theory.
The Significance of Information in Quantum Theory
Grinbaum, Alexei
2004-01-01
We propose a system of information-theoretic axioms from which we derive the formalism of quantum theory. Part I is devoted to the conceptual foundations of the information-theoretic approach. We argue that this approach belongs to the epistemological framework depicted as a loop of existences. In Part II we derive the quantum formalism from information-theoretic axioms and we analyze the twofold role of observer as physical system and as informational agent. Quantum logical...
Channel simulation with quantum side information
Luo, Zhicheng; Devetak, Igor
2006-01-01
We study and solve the problem of classical channel simulation with quantum side information at the receiver. This is a generalization of both the classical reverse Shannon theorem, and the classical-quantum Slepian-Wolf problem. The optimal noiseless communication rate is found to be reduced from the mutual information between the channel input and output by the Holevo information between the channel output and the quantum side information. Our main theorem has two import...
Quantum information how much information in a state vector?
Caves, C M; Caves, Carlton M; Fuchs, Christopher A
1996-01-01
Quantum information refers to the distinctive information-processing properties of quantum systems, which arise when information is stored in or retrieved from nonorthogonal quantum states. More information is required to prepare an ensemble of nonorthogonal quantum states than can be recovered from the ensemble by measurements. Nonorthogonal quantum states cannot be distinguished reliably, cannot be copied or cloned, and do not lead to exact predictions for the results of measurements. These properties contrast sharply with those of information stored in the microstates of a classical system.
Polarization states encoded by phase modulation for high bit rate quantum key distribution
International Nuclear Information System (INIS)
We present implementation of quantum cryptography with polarization code by wave-guide type phase modulator. At four different low input voltages of the phase modulator, coder encodes pulses into four different polarization states, 45o, 135o linearly polarized or right, left circle polarized, while the decoder serves as the complementary polarizers
Quantum-information processing in semiconductor quantum dots
Troiani, Filippo; Hohenester, Ulrich; Molinari, Elisa
2001-01-01
We propose an all-optical implementation of quantum-information processing in semiconductor quantum dots, where electron-hole excitations (excitons) serve as the computational degrees of freedom (qubits). The strong dot confinement leads to a strong renormalization of excitonic states, which, in analogy to NMR-based implementations of quantum-information processing, can be exploited for performing conditional and unconditional qubit operations.
Introduction to quantum physics and information processing
Vathsan, Radhika
2015-01-01
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
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...
Philosophy of quantum information and entanglement
Jaeger, Gregg
2010-01-01
Recent work in quantum information science has produced a revolution in our understanding of quantum entanglement. Scientists now view entanglement as a physical resource with many important applications. These range from quantum computers, which would be able to compute exponentially faster than classical computers, to quantum cryptographic techniques, which could provide unbreakable codes for the transfer of secret information over public channels. These important advances in the study of quantum entanglement and information touch on deep foundational issues in both physics and philosophy. This interdisciplinary volume brings together fourteen of the world's leading physicists and philosophers of physics to address the most important developments and debates in this exciting area of research. It offers a broad spectrum of approaches to resolving deep foundational challenges - philosophical, mathematical, and physical - raised by quantum information, quantum processing, and entanglement. This book is ideal f...
Holography, Quantum Geometry, and Quantum Information Theory
Directory of Open Access Journals (Sweden)
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-Ã‚Â½ 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.
Problems and solutions in quantum computing and quantum information
Steeb, Willi-Hans
2004-01-01
Quantum computing and quantum information are two of thefastest-growing and most exciting research areas in physics. Thepossibilities of using non-local behaviour of quantum mechanics tofactorize integers in random polynomial time have added to this newinterest. This invaluable book provides a collection of problems inquantum computing and quantum information together with detailedsolutions. It consists of two parts: in the first partfinite-dimensional systems are considered, while the second part dealswith finite-dimensional systems. All the important concepts and topics are included, such as
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...
Classical data compression with quantum side information
Devetak, I.; Winter, A.
2002-01-01
The problem of classical data compression when the decoder has quantum side information at his disposal is considered. This is a quantum generalization of the classical Slepian-Wolf theorem. The optimal compression rate is found to be reduced from the Shannon entropy of the source by the Holevo information between the source and side information.
Controlled Hawking Process by Quantum Information
Hotta, Masahiro
2009-01-01
Without using any non-established physics of quantum gravity, we show that black holes remember quantum information of swallowed matter even after the shifted horizons are settled. By using saved information, a part of the absorbed energy can be retrieved from the horizon by quantum energy teleportation in quantum information theory. This process can be regarded as a controlled Hawking process by measurement information about field fluctuation, in which negative energy flux is generated outside the horizon, falls into the horizon, and decreases mass of the black hole.
Quantum Information Processing with Semiconductor Macroatoms
Iotti, Rita Claudia; Rossi, Fausto
2000-01-01
An all optical implementation of quantum information processing with semiconductor macroatoms is proposed. Our quantum hardware consists of an array of quantum dots and the computational degrees of freedom are energy-selected interband optical transitions. The quantum-computing strategy exploits exciton-exciton interactions driven by ultrafast multicolor laser pulses. Contrary to existing proposals based on charge excitations, our approach does not require time-dependent electric fields, thus...
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.Â 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...
Quantum nondemolition measurements for quantum information
International Nuclear Information System (INIS)
We discuss the characterization and properties of quantum nondemolition (QND) measurements on qubit systems. We introduce figures of merit which can be applied to systems of any Hilbert space dimension, thus providing universal criteria for characterizing QND measurements. The controlled-NOT gate and an optical implementation are examined as examples of QND devices for qubits. We also consider the QND measurement of weak values
Private Quantum Channels and the Cost of Randomizing Quantum Information
Mosca, Michele; Tapp, Alain; de Wolf, Ronald
2000-01-01
We investigate how a classical private key can be used by two players, connected by an insecure one-way quantum channel, to perform private communication of quantum information. In particular we show that in order to transmit n qubits privately, 2n bits of shared private key are necessary and sufficient. This result may be viewed as the quantum analogue of the classical one-time pad encryption scheme. From the point of view of the eavesdropper, this encryption process can be...
Quantum Bertrand duopoly of incomplete information
International Nuclear Information System (INIS)
We study Bertrand's duopoly of incomplete information. It is found that the effect of quantum entanglement on the outcome of the game is dramatically changed by the uncertainty of information. In contrast with the case of complete information where the outcome increases with entanglement, when information is incomplete the outcome is maximized at some finite entanglement. As a consequence, information and entanglement are both crucial factors that determine the properties of a quantum oligopoly
Kwiatkowska, Monika; Swierczewski, Lukasz
2014-01-01
The work includes implementation and extraction algorithms capabilities test, without any additional data (starting position, the number of bits used, gap between the amount of data encoded) information from encoded files (mostly images). The software is written using OpenMP standard [1], which allowed them to run on parallel computers. Performance tests were carried out on computers, Blue Gene/P [2], Blue Gene/Q [3] and the system consisting of four AMD Opteron 6272 [4]. So...
Towards Nonadditive Quantum Information Theory
Abe, S; Abe, Sumiyoshi
2000-01-01
A definition of the nonadditive (nonextensive) conditional entropy indexed by q is presented. Based on the composition law in terms of it, the Shannon-Khinchin axioms are generalized and the uniqueness theorem is established for the Tsallis entropy. The nonadditive conditional entropy, when considered in the quantum context, is always positive for separable states but takes negative values for entangled states, indicating its utility for characterizing entanglement. A criterion deduced from it for separability of the density matrix is examined in detail by using a bipartite spin-half system. It is found that the strongest criterion for separability obtained by Peres using an algebraic method is recovered in the present information-theoretic approach.
A quantum information approach to statistical mechanics
International Nuclear Information System (INIS)
The field of quantum information and computation harnesses and exploits the properties of quantum mechanics to perform tasks more efficiently than their classical counterparts, or that may uniquely be possible in the quantum world. Its findings and techniques have been applied to a number of fields, such as the study of entanglement in strongly correlated systems, new simulation techniques for many-body physics or, generally, to quantum optics. This thesis aims at broadening the scope of quantum information theory by applying it to problems in statistical mechanics. We focus on classical spin models, which are toy models used in a variety of systems, ranging from magnetism, neural networks, to quantum gravity. We tackle these models using quantum information tools from three different angles. First, we show how the partition function of a class of widely different classical spin models (models in different dimensions, different types of many-body interactions, different symmetries, etc) can be mapped to the partition function of a single model. We prove this by first establishing a relation between partition functions and quantum states, and then transforming the corresponding quantum states to each other. Second, we give efficient quantum algorithms to estimate the partition function of various classical spin models, such as the Ising or the Potts model. The proof is based on a relation between partition functions and quantum circuits, which allows us to determine the quantum computational complexity of the partition function by studying the corresponding quantum circuit. Finally, we outline the possibility of applying quantum information concepts and tools to certain models of dis- crete quantum gravity. The latter provide a natural route to generalize our results, insofar as the central quantity has the form of a partition function, and as classical spin models are used as toy models of matter. (author)
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...
Quantum Stackelberg duopoly with incomplete information
International Nuclear Information System (INIS)
We investigate the quantum version of the Stackelberg duopoly with incomplete information, especially how the quantum entanglement affects the first-mover advantage in the classical form. It is found that while positive entanglement enhances the first-mover advantage beyond the classical limit, the advantage is dramatically suppressed by negative entanglement. Moreover, despite that positive quantum entanglement improves the first-mover's tolerance for the informational incompleteness, the quantum effect does not change the basic fact that Firm A's lack of complete information of Firm B's unit cost is eradicating the first-mover advantage
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
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
Quantum Information and Quantum Black Holes
Bekenstein, Jacob D.
2001-01-01
First, the relation between black holes and limitations on information of other systems is developed. After reviewing the relation of entropy to information, we derive the entropy bound, review its applications to cosmology and its extensions to higher dimensions, and discuss why black holes behave as 1-D objects when emitting entropy. We also discuss fundamental limitations on the information of pulses in curved space, and on the rate of disposal of information into a black...
NMR Quantum Information Processing and Entanglement
Laflamme, R; Negrevergne, C; Viola, L; Laflamme, Raymond; Cory, David G.; Negrevergne, Camille; Viola, Lorenza
2001-01-01
In this essay we discuss the issue of quantum information and recent nuclear magnetic resonance (NMR) experiments. We explain why these experiments should be regarded as quantum information processing (QIP) despite the fact that, in present liquid state NMR experiments, no entanglement is found. We comment on how these experiments contribute to the future of QIP and include a brief discussion on the origin of the power of quantum computers.
Integrated Information-induced quantum collapse
Kremnizer, Kobi; Ranchin, André
2014-01-01
We present a novel spontaneous collapse model where size is no longer the property of a physical system which determines its rate of collapse. Instead, we argue that the rate of spontaneous localization should depend on a system's quantum Integrated Information (QII), a novel physical property which describes a system's capacity to act like a quantum observer. We introduce quantum Integrated Information, present our QII collapse model and briefly explain how it may be experi...
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...
Information free quantum bus for universal quantum computation
Devitt, S J; Hollenberg, L C L; Devitt, Simon J.; Greentree, Andrew D.; Hollenberg, Lloyd C.L.
2005-01-01
Long range transport of quantum information is of huge importance to the physical realisation of large scale quantum computers. This letter introduces a transport bus that deterministically mediates entanglment pairwise between isolated data qubits, while the bus itself never carries information. We demonstrate how this scheme generates standard two qubit operator measurements and its application to the preparation of linear cluster states and teleportation based universal computation.
Stabilization of Quantum Computer Calculation Basis by Qubit Encoding in Virtual Spin Representation
Kessel, A R
2002-01-01
It is proposed to map the quantum information qubit not to individual spin 1/2 states, but to the collective spin states being eigenfunctions of the Hamiltonian including spin-spin interactions, which may be not small. Such an approach allows to introduce more stable calculation basis for quantum computer based on the solid state NMR systems.
Cavity mode entanglement in relativistic quantum information
Friis, Nicolai
2013-01-01
A central aim of relativistic quantum information (RQI) is the investigation of quantum information tasks and resources taking into account the relativistic aspects of nature. More precisely, it is of fundamental interest to understand how the storage, manipulation, and transmission of information utilizing quantum systems are influenced by the fact that these processes take place in a relativistic spacetime. In particular, many studies in RQI have been focused on the effects of non-uniform motion on entanglement, the main resource of quantum information protocols. Early investigations in this direction were performed in highly idealized settings that prompted questions as to the practical accessibility of these results. To overcome these limitations it is necessary to consider quantum systems that are in principle accessible to localized observers. In this thesis we present such a model, the rigid relativistic cavity, and its extensions, focusing on the effects of motion on entanglement and applications such...
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...
Quantum metrology from a quantum information science perspective
International Nuclear Information System (INIS)
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’. (review)
Quantum information processing with circuit quantum electrodynamics
Blais, A; Wallraff, A; Schuster, D I; Girvin, S M; Devoret, M H; Schölkopf, R J; Blais, Alexandre; Gambetta, Jay
2006-01-01
We theoretically study single and two-qubit dynamics in the circuit QED architecture. We focus on the current experimental design [Wallraff et al., Nature 431, 162 (2004); Schuster et al., cond-mat/0608693 (2006)] in which superconducting charge qubits are capacitively coupled to a single high-Q superconducting coplanar resonator. In this system, logical gates are realized by driving the resonator with microwave fields. Advantages of this architecture are that it allows for multi-qubit gates between non-nearest qubits and for the realization of gates in parallel, opening the possibility of fault-tolerant quantum computation with superconduting circuits. In this paper, we focus on one and two-qubit gates that do not require moving away from the charge-degeneracy `sweet spot'. This is advantageous as it helps to increase the qubit dephasing time and does not require modification of the original circuit QED. However these gates can, in some cases, be slower than those that do not use this constraint. Five types ...
Quantum information processing through nuclear magnetic resonance
Scientific Electronic Library Online (English)
J. D., Bulnes; F. A., Bonk; R. S., Sarthour; E. R. de, Azevedo; J. C. C., Freitas; T. J., Bonagamba; I. S., Oliveira.
2005-09-01
Full Text Available We discuss the applications of Nuclear Magnetic Resonance (NMR) to quantum information processing, focusing on the use of quadrupole nuclei for quantum computing. Various examples of experimental implementation of logic gates are given and compared to calculated NMR spectra and their respective dens [...] ity matrices. The technique of Quantum State Tomography for quadrupole nuclei is briefly described, and examples of measured density matrices in a two-qubit I = 3/2 spin system are shown. Experimental results of density matrices representing pseudo-Bell states are given, and an analysis of the entropy of theses states is made. Considering an NMR experiment as a depolarization quantum channel we calculate the entanglement fidelity and discuss the criteria for entanglement in liquid state NMR quantum information. A brief discussion on the perspectives for NMR quantum computing is presented at the end.
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...
Quantum causality, stochastics, trajectories and information
International Nuclear Information System (INIS)
A history of the discovery of 'new' quantum mechanics and the paradoxes of its probabilistic interpretation are briefly reviewed from the modern point of view of quantum probability and information. Modern quantum theory, which has been developed during the last 20 years for the treatment of quantum open systems including quantum noise, decoherence, quantum diffusions and spontaneous jumps occurring under continuous in time observation, is not yet a part of the standard curriculum of quantum physics. It is argued that the conventional formalism of quantum mechanics is insufficient for the description of quantum events, such as spontaneous decays say, and the new experimental phenomena related to individual quantum measurements, but they have all received an adequate mathematical treatment in quantum stochastics of open systems. Moreover, the only reasonable probabilistic interpretation of quantum mechanics put forward by Max Born was, in fact, in irreconcilable contradiction with traditional mechanical reality and causality. This led to numerous quantum paradoxes, some of them due to the great inventors of quantum theory such as Einstein and Schroedinger. They are reconsidered in this paper from the modern point of view of quantum stochastics and information. The development of quantum measurement theory, initiated by von Neumann, indicated a possibility for resolution of this interpretational crisis by divorcing the algebra of the dynamical generators and the algebra of the actual observables, or Bell's beables. It is shown that within this approach quantum causality can be rehabilitated in the form of a superselection rule for compatibility of the actual histories with the potential future. This rule, together with the self-compatibility of the measurements ensuring the consistency of the histories, is called the nondemolition, or causality principle in modern quantum theory. The application of this rule in the form of dynamical commutation relations leads to the derivation of the von Neumann projection postulate, and also to the more general reductions, instantaneous, spontaneous, and even continuous in time. This gives a dynamical solution, in the form of the quantum stochastic filtering equations, of the notorious measurement problem which was tackled unsuccessfully by many famous physicists starting with Schroedinger and Bohr. It has been recently proved that the quantum stochastic model for the continuous in time measurements is equivalent to a Dirac type boundary-value problem for the secondary quantized input 'offer waves from future' in one extra dimension, and to a reduction of the algebra of the consistent histories of past events to an Abelian subalgebra for the 'trajectories of the output particles'. This supports the corpuscular-wave duality in the form of the thesis that everything in the future are quantized waves, while everything in the past are trajectories of the recorded particles. (author)
Random matrix techniques in quantum information theory
Collins, Benoit; Nechita, Ion
2015-01-01
The purpose of this review article 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, combined with more detailed examples -- coming 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 st...
Information sharing in quantum complex networks
Cardillo, Alessio; Galve, Fernando; 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 hierar...
Information sharing in Quantum Complex Networks
2012-01-01
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 hierarc...
Quantum Realism, Information, and Epistemological Modesty
Grinbaum, Alexei
2014-03-01
It is usually asserted that physical theories, in particular quantum mechanics, support a certain view of what the world really is. To such claims I oppose an attitude of epistemological modesty. Ontological statements on the nature of reality, when made on the basis of quantum mechanics, appear unwarranted. I suggest that an epistemic loop connects physical theory grounded in informational notions, and a theory of information developed through a theoretical account of the physical support of information.
Quantum-information processing in disordered and complex quantum systems
International Nuclear Information System (INIS)
We study quantum information processing in complex disordered many body systems that can be implemented by using lattices of ultracold atomic gases and trapped ions. We demonstrate, first in the short range case, the generation of entanglement and the local realization of quantum gates in a disordered magnetic model describing a quantum spin glass. We show that in this case it is possible to achieve fidelities of quantum gates higher than in the classical case. Complex systems with long range interactions, such as ions chains or dipolar atomic gases, can be used to model neural network Hamiltonians. For such systems, where both long range interactions and disorder appear, it is possible to generate long range bipartite entanglement. We provide an efficient analytical method to calculate the time evolution of a given initial state, which in turn allows us to calculate its quantum correlations
Quantum information processing : science & technology.
Energy Technology Data Exchange (ETDEWEB)
Horton, Rebecca; Carroll, Malcolm S.; Tarman, Thomas David
2010-09-01
Qubits demonstrated using GaAs double quantum dots (DQD). The qubit basis states are the (1) singlet and (2) triplet stationary states. Long spin decoherence times in silicon spurs translation of GaAs qubit in to silicon. In the near term the goals are: (1) Develop surface gate enhancement mode double quantum dots (MOS & strained-Si/SiGe) to demonstrate few electrons and spin read-out and to examine impurity doped quantum-dots as an alternative architecture; (2) Use mobility, C-V, ESR, quantum dot performance & modeling to feedback and improve upon processing, this includes development of atomic precision fabrication at SNL; (3) Examine integrated electronics approaches to RF-SET; (4) Use combinations of numerical packages for multi-scale simulation of quantum dot systems (NEMO3D, EMT, TCAD, SPICE); and (5) Continue micro-architecture evaluation for different device and transport architectures.
Critique of Fault-Tolerant Quantum Information Processing
Alicki, Robert
2013-01-01
This is a chapter in a book \\emph{Quantum Error Correction} edited by D. A. Lidar and T. A. Brun, and published by Cambridge University Press (2013)\\\\ (http://www.cambridge.org/us/academic/subjects/physics/quantum-physics-quantum-information-and-quantum-computation/quantum-error-correction)\\\\ presenting the author's view on feasibility of fault-tolerant quantum information processing.
On the quantum information processing in nuclear magnetic resonance quantum computing experiments
International Nuclear Information System (INIS)
Full text: Nuclear Magnetic Resonance appeared in the late nineties to be the most promising candidate to run quantum computing algorithms. An impressive number of experiments demonstrating the implementation of all logic gates and quantum algorithms in systems with a small number of qubits stimulated the general excitement about the technique, and greatly promoted the field. Particularly important were those experiments where entanglement of particles were aimed at. Entanglement is the most fundamental (and weird !) aspect of quantum systems, and is at the basis of quantum teleportation and quantum cryptography, yet impossible to prove in NMR experiments. The hardcore of NMR quantum computing are the so-called pseudo-pure states, upon which radiofrequency (RF) pulses act to implement quantum mechanical unitary transformations, promoting changes in both, Zeeman level populations and coherences in the density matrix. Whereas pseudo-pure states are special non-equilibrium diagonal states, coherences encode information about superposition states. Now, one could safely say that the whole business of quantum computing goes about controlling relative ket phases. In spite of the impossibility to univocally associating a given quantum state to a NMR spectrum, it is possible to demonstrate the phase action of RF pulses over relative ket phases, even if no population changes take place. In this talk these issues will be addressed, and we will show experimental results of our own where this is done in the two-qubit quadrupole nuclei 23Na in C10H21NaO4S liquid crystal. We demonstrate the reversibility of the Hadamard gate, and of a quantum circuit which generates pseudo-Bell states. The success of the operation reaches almost 100% in the case of the state |01+|10, 80% in the cases of |00> + |01> and |10> + |11>, and 65% for the cat-state |00> + |11>. (author)
On the quantum information processing in nuclear magnetic resonance quantum computing experiments
Energy Technology Data Exchange (ETDEWEB)
Azevedo, E.R. de; Bonk, F.A.; Vidoto, E.L.G.; Bonagamba, T.J. [Universidade de Sao Paulo (IFSC/USP), Sao Carlos, SP (Brazil). Inst. de Fisica; Sarthour, R.S.; Guimaraes, A.P.; Oliveira, I.S. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Freitas, J.C.C. [Universidade Federal do Espirito Santo (UFES), Vitoria, ES (Brazil). Dept. de Fisica
2003-07-01
Full text: Nuclear Magnetic Resonance appeared in the late nineties to be the most promising candidate to run quantum computing algorithms. An impressive number of experiments demonstrating the implementation of all logic gates and quantum algorithms in systems with a small number of qubits stimulated the general excitement about the technique, and greatly promoted the field. Particularly important were those experiments where entanglement of particles were aimed at. Entanglement is the most fundamental (and weird !) aspect of quantum systems, and is at the basis of quantum teleportation and quantum cryptography, yet impossible to prove in NMR experiments. The hardcore of NMR quantum computing are the so-called pseudo-pure states, upon which radiofrequency (RF) pulses act to implement quantum mechanical unitary transformations, promoting changes in both, Zeeman level populations and coherences in the density matrix. Whereas pseudo-pure states are special non-equilibrium diagonal states, coherences encode information about superposition states. Now, one could safely say that the whole business of quantum computing goes about controlling relative ket phases. In spite of the impossibility to univocally associating a given quantum state to a NMR spectrum, it is possible to demonstrate the phase action of RF pulses over relative ket phases, even if no population changes take place. In this talk these issues will be addressed, and we will show experimental results of our own where this is done in the two-qubit quadrupole nuclei {sup 23}Na in C{sub 10}H{sub 21}NaO{sub 4}S liquid crystal. We demonstrate the reversibility of the Hadamard gate, and of a quantum circuit which generates pseudo-Bell states. The success of the operation reaches almost 100% in the case of the state |01+|10, 80% in the cases of |00> + |01> and |10> + |11>, and 65% for the cat-state |00> + |11>. (author)
Encoding visual information in retinal ganglion cells with prosthetic stimulation
Freeman, Daniel K.; Rizzo, Joseph F., III; Fried, Shelley I.
2011-06-01
Retinal prostheses aim to restore functional vision to those blinded by outer retinal diseases using electric stimulation of surviving retinal neurons. The ability to replicate the spatiotemporal pattern of ganglion cell spike trains present under normal viewing conditions is presumably an important factor for restoring high-quality vision. In order to replicate such activity with a retinal prosthesis, it is important to consider both how visual information is encoded in ganglion cell spike trains, and how retinal neurons respond to electric stimulation. The goal of the current review is to bring together these two concepts in order to guide the development of more effective stimulation strategies. We review the experiments to date that have studied how retinal neurons respond to electric stimulation and discuss these findings in the context of known retinal signaling strategies. The results from such in vitro studies reveal the advantages and disadvantages of activating the ganglion cell directly with the electric stimulus (direct activation) as compared to activation of neurons that are presynaptic to the ganglion cell (indirect activation). While direct activation allows high temporal but low spatial resolution, indirect activation yields improved spatial resolution but poor temporal resolution. Finally, we use knowledge gained from in vitro experiments to infer the patterns of elicited activity in ongoing human trials, providing insights into some of the factors limiting the quality of prosthetic vision.
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 ...
A Quantum Information Retrieval Approach to Memory
Kitto, Kirsty; Bruza, Peter; Gabora, Liane
2013-01-01
As computers approach the physical limits of information storable in memory, new methods will be needed to further improve information storage and retrieval. We propose a quantum inspired vector based approach, which offers a contextually dependent mapping from the subsymbolic to the symbolic representations of information. If implemented computationally, this approach would provide exceptionally high density of information storage, without the traditionally required physica...
Quantum correlations require multipartite information principles
Gallego, Rodrigo; Acín, Antonio; Navascués, Miguel
2011-01-01
Identifying which correlations among distant observers are possible within our current description of Nature, based on quantum mechanics, is a fundamental problem in Physics. Recently, information concepts have been proposed as the key ingredient to characterize the set of quantum correlations. Novel information principles, such as, information causality or non-trivial communication complexity, have been introduced in this context and successfully applied to some concrete scenarios. We show in this work a fundamental limitation of this approach: no principle based on bipartite information concepts is able to single out the set of quantum correlations for an arbitrary number of parties. Our results reflect the intricate structure of quantum correlations and imply that new and intrinsically multipartite information concepts are needed for their full understanding.
Quantum information theory with Gaussian systems
Energy Technology Data Exchange (ETDEWEB)
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.)
Random matrix techniques in quantum information theory
Collins, Benoît; Nechita, Ion
2016-01-01
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.
Quantum information theory with Gaussian systems
International Nuclear Information System (INIS)
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.)
Superconducting Circuits and Quantum Information
You, J. Q.; Nori, Franco
2006-01-01
Superconducting circuits can behave like atoms making transitions between two levels. Such circuits can test quantum mechanics at macroscopic scales and be used to conduct atomic-physics experiments on a silicon chip.
Quantum Mechanics as Information Fusion
Chapline, George
1999-01-01
We provide evidence that quantum mechanics can be interpreted as a rational algorithm for finding the least complex description for the correlations in the outputs of sensors in a large array. In particular, by comparing the self-organization approach to solving the Traveling Salesman Problem with a solution based on taking the classical limit of a Feynman path integral, we are led to a connection between the quantum mechanics of motion in a magnetic field and self-organized...
A quantum information processor with trapped ions
International Nuclear Information System (INIS)
Quantum computers hold the promise to solve certain problems exponentially faster than their classical counterparts. Trapped atomic ions are among the physical systems in which building such a computing device seems viable. In this work we present a small-scale quantum information processor based on a string of 40Ca+ ions confined in a macroscopic linear Paul trap. We review our set of operations which includes non-coherent operations allowing us to realize arbitrary Markovian processes. In order to build a larger quantum information processor it is mandatory to reduce the error rate of the available operations which is only possible if the physics of the noise processes is well understood. We identify the dominant noise sources in our system and discuss their effects on different algorithms. Finally we demonstrate how our entire set of operations can be used to facilitate the implementation of algorithms by examples of the quantum Fourier transform and the quantum order finding algorithm. (paper)
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...
Information, disturbance and Hamiltonian quantum feedback control
Doherty, Andrew C.; Jacobs, Kurt; Jungman, Gerard
2000-01-01
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 identif...
Thermodynamical cost of accessing quantum information
K. Maruyama; Brukner, C.; V. Vedral
2005-01-01
Thermodynamics is a macroscopic physical theory whose two very general laws are independent of any underlying dynamical laws and structures. Nevertheless, its generality enables us to understand a broad spectrum of phenomena in physics, information science and biology. Recently, it has been realised that information storage and processing based on quantum mechanics can be much more efficient than their classical counterpart. What general bound on storage of quantum informati...
Reconstruction of Quantum Mechanics with Information Operators
Takano, Ken'ichi
2008-01-01
We reconstruct quantum mechanics by introducing "information operators" and excluding the concept of wave functions. Multiple information operators simultaneously describe a single system and continuously develop in time even in the process of a measurement. We also introduce the concept of condensation for a system with many degrees of freedom in a rather general meaning. In terms of the multiplicity of description and the condensation, we explain quantum phenomena including measurements without the collapse of the wave function.
A flow cytometric assay technology based on quantum dots-encoded beads
International Nuclear Information System (INIS)
A flow cytometric detecting technology based on quantum dots (QDs)-encoded beads has been described. Using this technology, several QDs-encoded beads with different code were identified effectively, and the target molecule (DNA sequence) in solution was also detected accurately by coupling to its complementary sequence probed on QDs-encoded beads through DNA hybridization assay. The resolution of this technology for encoded beads is resulted from two longer wavelength fluorescence identification signals (yellow and red fluorescent signals of QDs), and the third shorter wavelength fluorescence signal (green reporting signal of fluorescein isothiocyanate (FITC)) for the determination of reaction between probe and target. In experiment, because of QDs' unique optical character, only one excitation light source was needed to excite the QDs and probe dye FITC synchronously comparing with other flow cytometric assay technology. The results show that this technology has present excellent repeatability and good accuracy. It will become a promising multiple assay platform in various application fields after further improvement
Principles of quantum computation and information
Benenti, Giuliano; Strini, Giuliano
2004-01-01
Quantum computation and information is a new, rapidly developing interdisciplinary field. Therefore, it is not easy to understand its fundamental concepts and central results without facing numerous technical details. This book provides the reader a useful and not-too-heavy guide. It offers a simple and self-contained introduction; no previous knowledge of quantum mechanics or classical computation is required. Volume I may be used as a textbook for a one-semester introductory course in quantum information and computation, both for upper-level undergraduate students and for graduate students.
Quantum contextuality in classical information retrieval
Zapatrin, Roman
2012-01-01
Document ranking based on probabilistic evaluations of relevance is known to exhibit non-classical correlations, which may be explained by admitting a complex structure of the event space, namely, by assuming the events to emerge from multiple sample spaces. The structure of event space formed by overlapping sample spaces is known in quantum mechanics, they may exhibit some counter-intuitive features, called quantum contextuality. In this Note I observe that from the structural point of view quantum contextuality looks similar to personalization of information retrieval scenarios. Along these lines, Knowledge Revision is treated as operationalistic measurement and a way to quantify the rate of personalization of Information Retrieval scenarios is suggested.
Quantum Computation and Quantum Information: Are They Related to Quantum Paradoxology?
Gyftopoulos, Elias P.; von Spakovsky, Michael R.
2004-01-01
We review both the Einstein, Podolsky, Rosen (EPR) paper about the completeness of quantum theory, and Schrodinger's responses to the EPR paper. We find that both the EPR paper and Schrodinger's responses, including the cat paradox, are not consistent with the current understanding of quantum theory and thermodynamics. Because both the EPR paper and Schrodinger's responses play a leading role in discussions of the fascinating and promising fields of quantum computation and quantum information...
Mind, Matter, Information and Quantum Interpretations
Directory of Open Access Journals (Sweden)
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.
Processing Information in Quantum Decision Theory
Directory of Open Access Journals (Sweden)
Vyacheslav I. Yukalov
2009-12-01
Full Text Available A survey is given summarizing the state of the art of describing information processing in Quantum Decision Theory, which has been recently advanced as a novel variant of decision making, based on the mathematical theory of separable Hilbert spaces. This mathematical structure captures the effect of superposition of composite prospects, including many incorporated intended actions. The theory characterizes entangled decision making, non-commutativity of subsequent decisions, and intention interference. The self-consistent procedure of decision making, in the frame of the quantum decision theory, takes into account both the available objective information as well as subjective contextual effects. This quantum approach avoids any paradox typical of classical decision theory. Conditional maximization of entropy, equivalent to the minimization of an information functional, makes it possible to connect the quantum and classical decision theories, showing that the latter is the limit of the former under vanishing interference terms.
Knowledge Activation After Information Encoding: Implications of Trait Priming on Person Judgment
Lerouge, Davy; Smeesters, Dirk
2008-01-01
It is widely assumed that traits primed after the encoding of person information do not lead to assimilation effects on the judgment of that person. The authors challenge this view by providing evidence that post-encoding trait primes can result in assimilative person judgments under certain conditions. In Experiments 1 and 2, we identify the conditions under which these assimilation effects occur. Experiment 1 shows the importance of participants’ goals during person information encoding: as...
Interface between path and OAM entanglement for high-dimensional photonic quantum information
Fickler, Robert; Huber, Marcus; Lavery, Martin P J; Padgett, Miles J; Zeilinger, Anton
2014-01-01
Photonics has become a mature field of quantum information science, where integrated optical circuits offer a way to scale the complexity of the setup as well as the dimensionality of the quantum state. On photonic chips, paths are the natural way to encode information. To distribute those high-dimensional quantum states over large distances, transverse spatial modes, like orbital angular momentum (OAM) possessing Laguerre Gauss modes, are favourable as flying information carriers. Here we demonstrate a quantum interface between these two vibrant photonic fields. We create three-dimensional path entanglement between two photons in a non-linear crystal and use a mode sorter as the quantum interface to transfer the entanglement to the OAM degree of freedom. Thus our results show a novel, flexible way to create high-dimensional spatial mode entanglement. Moreover, they pave the way to implement broad complex quantum networks where high-dimensionally entangled states could be distributed over distant photonic chi...
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.
Information sharing in quantum complex networks
Cardillo, Alessio; Galve, Fernando; Zueco, David; Gómez-Gardeñes, Jesús
2013-05-01
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 by-product, our results point out that the amount of information available for an external node connecting to a quantum network allows one to determine the network topology.
Camera calibration by multiplexed phase encoding of coordinate information.
Juarez-Salazar, Rigoberto; Guerrero-Sanchez, Fermin; Robledo-Sanchez, Carlos; González-García, Jorge
2015-05-20
A simple camera calibration method based on the principle of phase encoding and coordinate transformation is proposed. We use a reference coordinate frame encoded as a phase distribution by multiplexing the x and y directions. From this, we suggest a phase demodulation system. The coordinate transformation induced by the imaging is exploited to estimate the intrinsic and extrinsic camera parameters by using the least-squares method. Thus, a robust and noniterative estimation scheme is obtained. Simulations and experimental results show the feasibility of the proposal. Because of the potential for calibrating projectors, the proposed method could be used to calibrate fringe-projection systems. PMID:26192529
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 $C_{ea}>C.$
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 simple examples of entanglement-breaking channels with $C
Quantum Information in Optical Lattices
Guzmán, Angela M.; Dueñas E., Marco A.
2011-03-01
Experimental realizations of a two-qubit quantum logic gate based on cold atom collisions have been elusive mainly due to the decoherence effects introduced during the quantum gate operation, which cause transitions out of the two-qubit space and lead to a decreased gate operation fidelity. This type of decoherence effects, due to the non closeness of the interacting two-qubit system, are characteristic of the electromagnetic interaction, since the electromagnetic vacuum acts as a reservoir whose eigenmodes might become active during the gate operation. To describe the cold-atom collision we consider the quantum non-Hermitian dipole-dipole interaction instead of the less realistic s-scattering approach widely used in the literature. By adding an ancillary qubit, we take advantage of the spatial modulation of the non-Hermitian part of the interaction potential to obtain a "resonant" condition that should be satisfied to achieve lossless operation of a specific two-qubit quantum phase-gate. We demonstrate that careful engineering of the collision is required to obtain a specific truth table and to suppress the effects inherent in the openness of the system arising from the electromagnetic interaction.
A quantum information approach to statistical mechanics
International Nuclear Information System (INIS)
We review some connections between quantum information and statistical mechanics. We focus on three sets of results for classical spin models. First, we show that the partition function of all classical spin models (including models in different dimensions, different types of many-body interactions, different symmetries, etc) can be mapped to the partition function of a single model. Second, we give efficient quantum algorithms to estimate the partition function of various classical spin models, such as the Ising or the Potts model. The proofs of these two results are based on a mapping from partition functions to quantum states and to quantum circuits, respectively. Finally, we show how classical spin models can be used to describe certain fluctuating lattices appearing in models of discrete quantum gravity. (tutorial)
Quantum information processing with graph states
International Nuclear Information System (INIS)
Graph states are multiparticle states which are associated with graphs. Each vertex of the graph corresponds to a single system or particle. The links describe quantum correlations (entanglement) between pairs of connected particles. Graph states were initiated independently by two research groups: On the one hand, graph states were introduced by Briegel and Raussendorf as a resource for a new model of one-way quantum computing, where algorithms are implemented by a sequence of measurements at single particles. On the other hand, graph states were developed by the author of this thesis and ReinhardWerner in Braunschweig, as a tool to build quantum error correcting codes, called graph codes. The connection between the two approaches was fully realized in close cooperation of both research groups. This habilitation thesis provides a survey of the theory of graph codes, focussing mainly, but not exclusively on the author's own research work. We present the theoretical and mathematical background for the analysis of graph codes. The concept of one-way quantum computing for general graph states is discussed. We explicitly show how to realize the encoding and decoding device of a graph code on a one-way quantum computer. This kind of implementation is to be seen as a mathematical description of a quantum memory device. In addition to that, we investigate interaction processes, which enable the creation of graph states on very large systems. Particular graph states can be created, for instance, by an Ising type interaction between next neighbor particles which sits at the points of an infinitely extended cubic lattice. Based on the theory of quantum cellular automata, we give a constructive characterization of general interactions which create a translationally invariant graph state. (orig.)
Quantum dot - nanocavity QED for quantum information processing
International Nuclear Information System (INIS)
Single quantum dots (QDs) in photonic crystal nanocavities are interesting both as a testbed for fundamental cavity quantum electrodynamics (QED) experiments, as well as a platform for quantum and classical information processing. In addition to providing a scalable, on-chip, platform, these systems also enable large dipole-field interaction strengths, as a result of the localization of the field to very small optical volumes. Such a platform could be employed to demonstrate a number of devices, including nonclassical light sources, electro-optic modulators and switches operating at the single photon level, and quantum gates. QD-cavity QED systems also exhibit interesting phonon-assisted off-resonant interaction between the QD and the cavity which can be employed for spectral filtering, as well as for coherent optical spectroscopy and quantum dot state readout, thereby overcoming issues coming from quantum dot inhomogeneous broadening. In order to make the platform compatible with fiber-optic telecommunication wavelengths, the intrinsic optical nonlinearity of the semiconductor employed to make a nanocavity can be employed for frequency conversion.
The Nature and Location of Quantum Information
Griffiths, R B
2002-01-01
Quantum information is defined by applying the concepts of ordinary (Shannon) information theory to a quantum sample space consisting of a single framework or consistent family. A classical analogy for a spin-half particle and other arguments show that the infinite amount of information needed to specify a precise vector in its Hilbert space is not a measure of the information carried by a quantum entity with a $d$-dimensional Hilbert space; the latter is, instead, bounded by log d bits (1 bit per qubit). The two bits of information transmitted in dense coding are located not in one but in the correlation between two qubits, consistent with this bound. A quantum channel can be thought of as a "structure" or collection of frameworks, and the physical location of the information in the individual frameworks can be used to identify the location of the channel. Analysis of a quantum circuit used as a model of teleportation shows that the location of the channel depends upon which structure is employed; for ordina...
Canonical Relational Quantum Mechanics from Information Theory
Munkhammar, Joakim
2011-01-01
In this paper we construct a theory of quantum mechanics based on Shannon information theory. We define a few principles regarding information-based frames of reference, including explicitly the concept of information covariance, and show how an ensemble of all possible physical states can be setup on the basis of the accessible information in the local frame of reference. In the next step the Bayesian principle of maximum entropy is utilized in order to constrain the dynami...
Covariance and Fisher information in quantum mechanics
Petz, Denes
2001-01-01
Variance and Fisher information are ingredients of the Cramer-Rao inequality. We regard Fisher information as a Riemannian metric on a quantum statistical manifold and choose monotonicity under coarse graining as the fundamental property of variance and Fisher information. In this approach we show that there is a kind of dual one-to-one correspondence between the candidates of the two concepts. We emphasis that Fisher informations are obtained from relative entropies as cont...
Unified meta-theory of information, consciousness, time and the classical-quantum universe
Green, Martin A
2013-01-01
As time advances in our perceived real world, existing information is preserved and new information is added to history. All the information that may ever be encoded in history must be about some fundamental, unique, atemporal and pre-physical structure: the bare world. Scientists invent model worlds to efficiently explain aspects of the real world. This paper explores the features of and relationships between the bare, real, and model worlds. Time -- past, present and future -- is naturally explained. Both quantum uncertainty and state reduction are needed for time to progress, since unpredictable new information must be added to history. Deterministic evolution preserves existing information. Finite, but steadily increasing, information about the bare world is jointly encoded in equally uncertain spacetime geometry and quantum matter. Because geometry holds no information independent of matter, there is no need to quantize gravity. At the origin of time, information goes to zero and geometry and matter fade...
Trapped-ion quantum information processing
International Nuclear Information System (INIS)
Full text: Trapped strings of cold ions provide an ideal system for quantum information processing. The quantum information can be stored in individual ions and these qubits can be individually prepared, the corresponding quantum states can be manipulated and measured with nearly 100 % detection efficiency. With a small ion-trap quantum computer based on two and three trapped Ca+ ions as qubits we have generated in a pre-programmed way genuine quantum states. These states are of particular interest for the implementation of an ion quantum register: we have demonstrated selective read-out of single qubits and manipulation of single qubits of the register conditioned on the read-out results. Moreover, entangled states of up to eight particles were generated using an algorithmic procedure and the resulting states were analyzed using state tomography proving genuine multi-partite entanglement. With a new cavity QED setup we create an ion-qubit to photon-qubit interface for interconnecting ion-trap based quantum computers. With this device a source of deterministically generated single photons can be built and atom-photon entanglement can be investigated
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.
Multiparty hierarchical quantum-information splitting
Energy Technology Data Exchange (ETDEWEB)
Wang Xinwen; Zhang Dengyu; Tang Shiqing; Xie Lijun, E-mail: xwwang0826@yahoo.com.cn [Department of Physics and Electronic Information Science, Hengyang Normal University, Hengyang 421008 (China)
2011-02-14
We propose a scheme for multiparty hierarchical quantum-information splitting (QIS) with a multipartite entangled state, where a boss distributes a secret quantum state to two grades of agents asymmetrically. The agents who belong to different grades have different authorities for recovering the boss's secret. Except for the boss's Bell-state measurement, no nonlocal operation is involved. The presented scheme is also shown to be secure against eavesdropping. Such a hierarchical QIS is expected to find useful applications in the field of modern multipartite quantum cryptography.
Information Theoretic Axioms for Quantum Theory
Zaopo, Marco
2012-01-01
In this paper we derive the complex Hilbert space formalism of quantum theory from four simple information theoretic axioms. It is shown that quantum theory is the only non classical probabilistic theory satisfying the following axioms: distinguishability, conservation, reversibility, composition. The new results of this reconstruction compared to other reconstructions by other authors are: (i) we get rid of axiom "subspace" in favor of axiom conservation eliminating mathema...
Fisher information, nonclassicality and quantum revivals
Energy Technology Data Exchange (ETDEWEB)
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.
Information Theoretic Resources in Quantum Theory
Meznaric, Sebastian
2013-01-01
Resource identification and quantification is an essential element of both classical and quantum information theory. Entanglement is one of these resources, arising when quantum communication and nonlocal operations are expensive to perform. In the first part of this thesis we quantify the effective entanglement when operations are additionally restricted. For an important class of errors we find a linear relationship between the usual and effective higher dimensional genera...
A quantum information processor with trapped ions
Schindler, Philipp; Nigg, Daniel; Monz, Thomas; Julio T. Barreiro; Martinez, Esteban; Wang, Shannon X.; Quint, Stephan; Brandl, Matthias F.; Nebendahl, Volckmar; Roos, Christian F; Chwalla, Michael; Hennrich, Markus; Blatt, Rainer
2013-01-01
Quantum computers hold the promise to solve certain problems exponentially faster than their classical counterparts. Trapped atomic ions are among the physical systems in which building such a computing device seems viable. In this work we present a small-scale quantum information processor based on a string of [superscript 40]Ca[superscript +] ions confined in a macroscopic linear Paul trap. We review our set of operations which includes non-coherent operations allowing us to realize arbitra...
Manipulating cold atoms for quantum information processing
International Nuclear Information System (INIS)
Full text: I will describe how cold atoms can be manipulated to realize arrays of addressable qbits as prototype quantum registers, focussing on how atom chips can be used in combination with cavity qed techniques to form such an array. I will discuss how the array can be generated and steered using optical lattices and the Mott transition, and describe the sources of noise and how these place limits on the use of such chips in quantum information processing. (author)
Theory of solid state quantum information processing
Burkard, Guido
2004-01-01
Recent theoretical work on solid-state proposals for the implementation of quantum computation and quantum information processing is reviewed. The differences and similarities between microscopic and macroscopic qubits are highlighted and exemplified by the spin qubit proposal on one side and the superconducting qubits on the other. Before explaining the spin and supercondcuting qubits in detail, some general concepts that are relevant for both types of solid-state qubits ar...
Atomic wave packet basis for quantum information
Muthukrishnan, Ashok; Stroud Jr, C. R.
2001-01-01
We propose a wave packet basis for storing and processing several qubits of quantum information in a single multilevel atom. Using radially localized wave packet states in the Rydberg atom, we construct an orthogonal basis that is related to the usual energy level basis by a quantum Fourier transform. A transform-limited laser pulse that is short compared with the classical Kepler period of the system interacts mainly with the wave packet state localized near the atomic core...
Hause, L.; Rothwell, D; Frey, C.
1983-01-01
The development of a microcomputer-based software package for the entry, encoding, storage and retrieval of medical information in anatomic pathology is described. Computer assisted encoding of diagnostic language was based on SNOMED nomenclature and was found to automatically encode 92% to 98% of the cases in routine surgical pathology. This application package was based on CP/M operating system so it functions on a variety of microcomputers and can integrate with other common microcomputer ...
Minimum-cost quantum measurements for quantum information
Wallden, Petros; Dunjko, Vedran; Andersson, Erika
2014-03-01
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 pure states. For pure symmetric states it turns out that for a certain class of cost matrices, the minimum-cost measurement is the square-root measurement. That is, the optimal minimum-cost measurement is in this case the same as the minimum-error measurement. These results are in agreement with Nakahira and Usuda (2012 Phys. Rev. A 86 062305). Finally, we consider sequences of individual uncorrelated systems, and examine when the global minimum-cost measurement is a sequence of optimal local measurements. We consider an example where the global minimum-cost measurement is, perhaps counter-intuitively, not a sequence of local measurements, and discuss how this is related to the Pusey-Barrett-Rudolph argument for the nature of the wave function.
Countering quantum noise with supplementary classical information
International Nuclear Information System (INIS)
We consider situations in which (i) Alice wishes to send quantum information to Bob via a noisy quantum channel, (ii) Alice has a classical description of the states she wishes to send, and (iii) Alice can make use of a finite amount of noiseless classical information. After setting up the problem in general, we focus attention on one specific scenario in which Alice sends a known qubit down a depolarizing channel along with a noiseless classical bit. We describe a protocol that we conjecture is optimal and calculate the average fidelity obtained. A surprising amount of structure is revealed even for this simple case, which suggests that relationships between quantum and classical information could in general be very intricate
Quantum Information: an invitation for mathematicians
International Nuclear Information System (INIS)
Quantum Information is the science that aims to use the unusual behavior of the microscopic world, governed by the laws of Quantum Mechanics, in order to improve the way in which we compute or communicate information. Though the first ideas in this direction come from the early 80's, it is in the last decade when Quantum Information has suffered an spectacular development. It is impossible to resume in a paper like this one the importance and complexity of the field. Therefore, I will limit to briefly explain some of the initial ideas (considered classical by now), and to briefly suggest some of the modern lines of research. By the nature of this exposition, I have decided to avoid rigor and to concentrate more in ideas and intuitions. Anyhow, I have tried to provide with enough references, in such a way that an interested reader could find there proper theorems and proofs.
Energy Technology Data Exchange (ETDEWEB)
Breuer, Reinhard (comp.)
2010-07-01
The following topics are dealt with: Reality in the test house, quantum teleportation, 100 years of quantum theory, the reality of quanta, interactionless quantum measurement, rules for quantum computers, quantum computers with ions, spintronics with diamond, the limits of the quantum computers, a view into the future of quantum optics. (HSI)
Quantum Information Processing with Modular Networks
Crocker, Clayton; Inlek, Ismail V.; Hucul, David; Sosnova, Ksenia; Vittorini, Grahame; Monroe, Chris
2015-05-01
Trapped atomic ions are qubit standards for the production of entangled states in quantum information science and metrology applications. Trapped ions can exhibit very long coherence times, external fields can drive strong local interactions via phonons, and remote qubits can be entangled via photons. Transferring quantum information across spatially separated ion trap modules for a scalable quantum network architecture relies on the juxtaposition of both phononic and photonic buses. We report the successful combination of these protocols within and between two ion trap modules on a unit structure of this architecture where the remote entanglement generation rate exceeds the experimentally measured decoherence rate. Additionally, we report an experimental implementation of a technique to maintain phase coherence between spatially and temporally distributed quantum gate operations, a crucial prerequisite for scalability. Finally, we discuss our progress towards addressing the issue of uncontrolled cross-talk between photonic qubits and memory qubits by implementing a second ion species, Barium, to generate the photonic link. This work is supported by the ARO with funding from the IARPA MQCO program, the DARPA Quiness Program, the ARO MURI on Hybrid Quantum Circuits, the AFOSR MURI on Quantum Transduction, and the NSF Physics Frontier Center at JQI.
Information Erasure and Recover 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. That the final states of environment are completely determined by the initial states of the system allows that an easure operation can be realized by a swap operation between system and an ancilla. Therefore, the erased information can be recoverd. When there is an irreversible process, e.g. an irreversible operation or a decoherence process, in the erasure process, the information would be er...
The Ion Trap Quantum Information Processor
Steane, Andrew M.
1996-01-01
An introductory review of the linear ion trap is given, with particular regard to its use for quantum information processing. The discussion aims to bring together ideas from information theory and experimental ion trapping, to provide a resource to workers unfamiliar with one or the other of these subjects. It is shown that information theory provides valuable concepts for the experimental use of ion traps, especially error correction, and conversely the ion trap provides a...
Nonlinear coherent states for optimizing quantum information
International Nuclear Information System (INIS)
Part of the difficulties in implementing communication in quantum information stems from the fragility of Schroedinger's cat-like superpositions. A recent experiment in quantum optics by Cook et al (2007 Nature 446 774) has proved the feasibility of a feedback-mediated quantum measurement for discriminating between optical coherent states under photodetection. Minimizing the error in receiver measurement over all possible POVMs leads to the so-called quantum error probability or 'Helstrom bound', and CMG measurements validate the theoretical prediction by Helstrom, Dolinar and Geremia concerning this bound. In this work, we present some preliminary theoretical and numerical explorations concerning the properties of the Helstrom bound in binary (or multibinary) communication involving non-Poissonian or nonlinear coherent states.
Numerical algorithms for use in quantum information
International Nuclear Information System (INIS)
Quantum information theory is the new field of physics and electrical engineering that arose from the application of fundamental physics concepts in communications and computing. In this paper, aiming to calculate some properties of quantum communication systems and the quantum entanglement measure, for C2·C2 systems, based on relative entropy, two numerical algorithms are presented. The first one is based on the codification of the possible solution in a binary string and in the application, in that string, of an assembly algorithm, such as one used in DNA construction. The second one is the construction of a genetic algorithm where a string of density matrices and quantum gates in the reproduction stage are used. Both algorithms are used in situations where the best solution needs to be found. Numerical simulations are presented and the advantages and disadvantages of the algorithms are discussed
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
Protection of information in quantum qatabases
Ozhigov, Yuri
1997-01-01
The conventional protection of information by cryptographical keys makes no sense if a key can be quickly discovered by an unauthorized person. This way of penetration to the protected systems was made possible by a quantum computers in view of results of P.Shor and L.Grover. This work presents the method of protection of an information in a database from a spy even he knows all about its control system and has a quantum computer, whereas a database can not distinguish betwe...
Quantum non-Markovianity based on the Fisher-information matrix
Song, Hongting; Luo, Shunlong; Hong, Yan
2015-04-01
With the development of quantum-information theory, there has been a flurry of investigations of quantum non-Markovian dynamics, and several significant measures for such dynamics have been proposed from various perspectives, such as the breakdown of dynamical divisibility, increase in the distinguishability between quantum states, increase in correlations between the system and an arbitrary ancillary, and so on. Motivated by the idea of exploiting the information content of parameters encoded in initial states, we propose a conceptually simple and physically intuitive characterization for non-Markovianity with the help of a quantum-Fisher-information matrix. The basic features are illustrated through several examples, and relations with other approaches are elucidated. A hierarchial aspect of quantum non-Markovianity is revealed.
Quantum-information-processing architecture with endohedral fullerenes in a carbon nanotube
International Nuclear Information System (INIS)
A potential quantum-information processor is proposed using an array of the endohedral fullerenes 15N-C60 or 31P-C60 contained in a single walled carbon nanotube (SWCNT). The qubits are encoded in the nuclear spins of the doped atoms, while the electronic spins are used for initialization and readout, as well as for two-qubit operations.
Retrieving and routing quantum information in a quantum network
Sazim, S.; Chiranjeevi, V.; Chakrabarty, I.; Srinathan, K.
2015-12-01
In extant quantum secret sharing protocols, once the secret is shared in a quantum network ( qnet) it cannot be retrieved, even if the dealer wishes that his/her secret no longer be available in the network. For instance, if the dealer is part of the two qnets, say {{Q}}_1 and {{Q}}_2 and he/she subsequently finds that {{Q}}_2 is more reliable than {{Q}}_1, he/she may wish to transfer all her secrets from {{Q}}_1 to {{Q}}_2. Known protocols are inadequate to address such a revocation. In this work we address this problem by designing a protocol that enables the source/dealer to bring back the information shared in the network, if desired. Unlike classical revocation, the no-cloning theorem automatically ensures that the secret is no longer shared in the network. The implications of our results are multi-fold. One interesting implication of our technique is the possibility of routing qubits in asynchronous qnets. By asynchrony we mean that the requisite data/resources are intermittently available (but not necessarily simultaneously) in the qnet. For example, we show that a source S can send quantum information to a destination R even though (a) S and R share no quantum resource, (b) R's identity is unknown to S at the time of sending the message, but is subsequently decided, (c) S herself can be R at a later date and/or in a different location to bequeath her information (`backed-up' in the qnet) and (d) importantly, the path chosen for routing the secret may hit a dead end due to resource constraints, congestion, etc., (therefore the information needs to be back-tracked and sent along an alternate path). Another implication of our technique is the possibility of using insecure resources. For instance, if the quantum memory within an organization is insufficient, it may safely store (using our protocol) its private information with a neighboring organization without (a) revealing critical data to the host and (b) losing control over retrieving the data. Putting the two implications together, namely routing and secure storage, it is possible to envision applications like quantum mail (qmail) as an outsourced service.
Retrieving and routing quantum information in a quantum network
Sazim, S.; Chiranjeevi, V.; Chakrabarty, I.; Srinathan, K.
2015-09-01
In extant quantum secret sharing protocols, once the secret is shared in a quantum network (uc(qnet)) it cannot be retrieved, even if the dealer wishes that his/her secret no longer be available in the network. For instance, if the dealer is part of the two uc(qnet)s, say {{Q}}_1 and {{Q}}_2 and he/she subsequently finds that {{Q}}_2 is more reliable than {{Q}}_1 , he/she may wish to transfer all her secrets from {{Q}}_1 to {{Q}}_2 . Known protocols are inadequate to address such a revocation. In this work we address this problem by designing a protocol that enables the source/dealer to bring back the information shared in the network, if desired. Unlike classical revocation, the no-cloning theorem automatically ensures that the secret is no longer shared in the network. The implications of our results are multi-fold. One interesting implication of our technique is the possibility of routing qubits in asynchronous uc(qnets). By asynchrony we mean that the requisite data/resources are intermittently available (but not necessarily simultaneously) in the uc(qnet). For example, we show that a source S can send quantum information to a destination R even though (a) S and R share no quantum resource, (b) R's identity is unknown to S at the time of sending the message, but is subsequently decided, (c) S herself can be R at a later date and/or in a different location to bequeath her information (`backed-up' in the uc(qnet)) and (d) importantly, the path chosen for routing the secret may hit a dead end due to resource constraints, congestion, etc., (therefore the information needs to be back-tracked and sent along an alternate path). Another implication of our technique is the possibility of using insecure resources. For instance, if the quantum memory within an organization is insufficient, it may safely store (using our protocol) its private information with a neighboring organization without (a) revealing critical data to the host and (b) losing control over retrieving the data. Putting the two implications together, namely routing and secure storage, it is possible to envision applications like quantum mail (qmail) as an outsourced service.
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…
Optimal photons for quantum-information processing
International Nuclear Information System (INIS)
Photonic quantum-information processing schemes, such as linear optics quantum computing, and other experiments relying on single-photon interference, inherently require complete photon indistinguishability to enable the desired photonic interactions to take place. Mode-mismatch is the dominant cause of photon distinguishability in optical circuits. Here we study the effects of photon wave-packet shape on tolerance against the effects of mode mismatch in linear optical circuits, and show that Gaussian distributed photons with large bandwidth are optimal. The result is general and holds for arbitrary linear optical circuits, including ones which allow for postselection and classical feed forward. Our findings indicate that some single photon sources, frequently cited for their potential application to quantum-information processing, may in fact be suboptimal for such applications
Quantum Gravity Sensor by Curvature Energy: their Encoding and Computational Models*
Directory of Open Access Journals (Sweden)
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
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.
Bibliographic guide to the foundations of quantum mechanics and quantum information
Cabello, Adan
2000-01-01
This is a collection of references (papers, books, preprints, book reviews, Ph. D. thesis, patents, web sites, 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-demo...
Energy Technology Data Exchange (ETDEWEB)
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)
Quantum Computation and Quantum Information: Are They Related to Quantum Paradoxology?
Gyftopoulos, E P; Gyftopoulos, Elias P.; Spakovsky, Michael R. von
2004-01-01
We review both the Einstein, Podolsky, Rosen (EPR) paper about the completeness of quantum theory, and Schrodinger's responses to the EPR paper. We find that both the EPR paper and Schrodinger's responses, including the cat paradox, are not consistent with the current understanding of quantum theory and thermodynamics. Because both the EPR paper and Schrodinger's responses play a leading role in discussions of the fascinating and promising fields of quantum computation and quantum information, we hope our review will be helpful to researchers in these fields.
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.
Quantum information processing with optical vortices
Energy Technology Data Exchange (ETDEWEB)
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)
Quantum information, oscillations and the psyche
Martin, F.; Carminati, F.; Galli Carminati, G.
2010-05-01
In this paper, taking the theory of quantum information as a model, we consider the human unconscious, pre-consciousness and consciousness as sets of quantum bits (qubits). We view how there can be communication between these various qubit sets. In doing this we are inspired by the theory of nuclear magnetic resonance. In this way we build a model of handling a mental qubit with the help of pulses of a mental field. Starting with an elementary interaction between two qubits we build two-qubit quantum logic gates that allow information to be transferred from one qubit to the other. In this manner we build a quantum process that permits consciousness to “read” the unconscious and vice versa. The elementary interaction, e.g. between a pre-consciousness qubit and a consciousness one, allows us to predict the time evolution of the pre-consciousness + consciousness system in which pre-consciousness and consciousness are quantum entangled. This time evolution exhibits Rabi oscillations that we name mental Rabi oscillations. This time evolution shows how for example the unconscious can influence consciousness. In a process like mourning the influence of the unconscious on consciousness, as the influence of consciousness on the unconscious, are in agreement with what is observed in psychiatry.
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...
Geometrical identification of quantum and information theories
International Nuclear Information System (INIS)
The interrelation of quantum and information theories is investigation on the base of the conception of cross-entropy. It is assumed that ''complex information geometry'' may serve as a tool for ''technological transfer'' from one research field to the other which is not connected directly with the first one. It is pointed out that the ''infinitesimal distance'' ds2 and ''infinitesimal cross-entropy'' dHsub(c) coincide
Quantum Symmetrically-Private Information Retrieval
Kerenidis, I; Kerenidis, Iordanis; Wolf, Ronald de
2003-01-01
Private information retrieval systems (PIRs) allow a user to extract an item from a database that is replicated over k>=1 servers, while satisfying various privacy constraints. We exhibit quantum k-server symmetrically-private information retrieval systems (QSPIRs) that use sublinear communication, do not use shared randomness among the servers, and preserve privacy against honest users and dishonest servers. Classically, SPIRs without shared randomness do not exist at all.
Scavenging quantum information: Multiple observations of quantum systems
Energy Technology Data Exchange (ETDEWEB)
Rapcan, P. [Research Center for Quantum Information, Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava (Slovakia); Calsamiglia, J.; Munoz-Tapia, R. [Fisica Teorica: Informacio i Fenomens Quantics, Edifici Cn, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Barcelona) (Spain); Bagan, E. [Fisica Teorica: Informacio i Fenomens Quantics, Edifici Cn, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Barcelona) (Spain); Department of Physics, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10021 (United States); Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Buzek, V. [Research Center for Quantum Information, Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava (Slovakia); Faculty of Informatics, Masaryk University, Botanicka 68a, CZ-602 00 Brno (Czech Republic)
2011-09-15
Given an unknown state of a qudit that has already been measured optimally, can one still extract any information about the original unknown state? Clearly, after a maximally informative measurement, the state of the system collapses into a postmeasurement state from which the same observer cannot obtain further information about the original state of the system. However, the system still encodes a significant amount of information about the original preparation for a second observer who is unaware of the actions of the first one. We study how a series of independent observers can obtain, or can scavenge, information about the unknown state of a system (quantified by the fidelity) when they sequentially measure it. We give closed-form expressions for the estimation fidelity when one or several qudits are available to carry information about the single-qudit state, and we study the classical limit when an arbitrarily large number of observers can obtain (nearly) complete information on the system. In addition to the case where all observers perform most informative measurements, we study the scenario where a finite number of observers estimates the state with equal fidelity, regardless of their position in the measurement sequence and the scenario where all observers use identical measurement apparatuses (up to a mutually unknown orientation) chosen so that a particular observer's estimation fidelity is maximized.
Covariance and Fisher information in quantum mechanics
Petz, D
2002-01-01
Variance and Fisher information are ingredients of the Cramer-Rao inequality. We regard Fisher information as a Riemannian metric on a quantum statistical manifold and choose monotonicity under coarse graining as the fundamental property of variance and Fisher information. In this approach we show that there is a kind of dual one-to-one correspondence between the candidates of the two concepts. We emphasis that Fisher informations are obtained from relative entropies as contrast functions on the state space and argue that the scalar curvature might be interpreted as an uncertainty density on a statistical manifold.
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.
Quantum information erasure inside black holes
Lowe, David A
2015-01-01
An effective field theory for infalling observers in the vicinity of a quasi-static black hole is given in terms of a freely falling lattice discretization. The lattice model successfully reproduces the thermal spectrum of outgoing Hawking radiation, as was shown by Corley and Jacobson, but can also be used to model observations made by a typical low-energy observer who enters the black hole in free fall at a prescribed time. The explicit short distance cutoff ensures that, from the viewpoint of the infalling observer, any quantum information that entered the black hole more than a scrambling time earlier has been erased by the black hole singularity. This property, combined with the requirement that outside observers need at least of order the scrambling time to extract quantum information from the black hole, ensures that a typical infalling observer does not encounter drama upon crossing the black hole horizon in a theory where black hole information is preserved for asymptotic observers.
Information theoretic approach to tactile encoding and discrimination
Saal, Hannes
2011-01-01
The human sense of touch integrates feedback from a multitude of touch receptors, but how this information is represented in the neural responses such that it can be extracted quickly and reliably is still largely an open question. At the same time, dexterous robots equipped with touch sensors are becoming more common, necessitating better methods for representing sequentially updated information and new control strategies that aid in extracting relevant features for object man...
Quantum Computers: A New Paradigm in Information Technology
Raisinghani, Mahesh S.
2001-01-01
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, i...
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...
Quantum information processing based on cavity QED with mesoscopic systems
Lukin, Mikhail; Fleischhauer, Michael; Imamoglu, Atac
2000-01-01
Introduction: Recent developments in quantum communication and computing [1-3] stimulated an intensive search for physical systems that can be used for coherent processing of quantum information. It is generally believed that quantum entanglement of distinguishable quantum bits (qubits) is at the heart of quantum information processing. Significant efforts have been directed towards the design of elementary logic gates, which perform certain unitary processes on pairs of qubits. These gates m...
Quantum One Go Computation and the Physical Computation Level of Biological Information Processing
Castagnoli, Giuseppe
2010-02-01
By extending the representation of quantum algorithms to problem-solution interdependence, the unitary evolution part of the algorithm entangles the register containing the problem with the register containing the solution. Entanglement becomes correlation, or mutual causality, between the two measurement outcomes: the string of bits encoding the problem and that encoding the solution. In former work, we showed that this is equivalent to the algorithm knowing in advance 50% of the bits of the solution it will find in the future, which explains the quantum speed up. Mutual causality between bits of information is also equivalent to seeing quantum measurement as a many body interaction between the parts of a perfect classical machine whose normalized coordinates represent the qubit populations. This “hidden machine” represents the problem to be solved. The many body interaction (measurement) satisfies all the constraints of a nonlinear Boolean network “together and at the same time”—in one go—thus producing the solution. Quantum one go computation can formalize the physical computation level of the theories that place consciousness in quantum measurement. In fact, in visual perception, we see, thus recognize, thus process, a significant amount of information “together and at the same time”. Identifying the fundamental mechanism of consciousness with that of the quantum speed up gives quantum consciousness, with respect to classical consciousness, a potentially enormous evolutionary advantage.
Black holes, information, and Hilbert space for quantum gravity
Nomura, Yasunori; Varela, Jaime; Weinberg, Sean J.
2013-04-01
A coarse-grained description for the formation and evaporation of a black hole is given within the framework of a unitary theory of quantum gravity preserving locality, without dropping the information that manifests as macroscopic properties of the state at late times. The resulting picture depends strongly on the reference frame one chooses to describe the process. In one description based on a reference frame in which the reference point stays outside the black hole horizon for sufficiently long time, a late black hole state becomes a superposition of black holes in different locations and with different spins, even if the back hole is formed from collapsing matter that had a well-defined classical configuration with no angular momentum. The information about the initial state is partly encoded in relative coefficients—especially phases—of the terms representing macroscopically different geometries. In another description in which the reference point enters into the black hole horizon at late times, an S-matrix description in the asymptotically Minkowski spacetime is not applicable, but it still allows for an “S-matrix” description in the full quantum gravitational Hilbert space including singularity states. Relations between different descriptions are given by unitary transformations acting on the full Hilbert space, and they in general involve superpositions of “distant” and “infalling” descriptions. Despite the intrinsically quantum mechanical nature of the black hole state, measurements performed by a classical physical observer are consistent with those implied by general relativity. In particular, the recently-considered firewall phenomenon can occur only for an exponentially fine-tuned (and intrinsically quantum mechanical) initial state, analogous to an entropy decreasing process in a system with large degrees of freedom.
Precisely timing dissipative quantum information processing
Energy Technology Data Exchange (ETDEWEB)
Kastoryano, Michael; Eisert, Jens [FU Berlin (Germany); Wolf, Michael [TU Muenchen (Germany)
2013-07-01
Dissipative engineering constitutes a framework within which quantum information processing protocols are powered by system-environment interaction rather than by unitary dynamics alone. This framework embraces noise as a resource, and consequently, offers a number of advantages compared to one based on unitary dynamics alone, e.g., that the protocols are typically independent of the initial state of the system. However, the time independent nature of this scheme makes it difficult to imagine precisely timed sequential operations, conditional measurements or error correction. In this work, we provide a path around these challenges, by introducing basic dissipative gadgets which allow us to precisely initiate, trigger and time dissipative operations, while keeping the system Liouvillian time-independent. These gadgets open up novel perspectives for thinking of timed dissipative quantum information processing. As an example, we sketch how measurement based computation can be simulated in the dissipative setting.
Efficient error characterization in quantum information processing
International Nuclear Information System (INIS)
We describe how to use the fidelity decay as a tool to characterize the errors affecting a quantum information processor through a noise generator G?. For weak noise, the initial decay rate of the fidelity proves to be a simple way to measure the magnitude of the different terms in G?. When the generator has only terms associated with few-body couplings, our proposal is scalable. We present the explicit protocol for estimating the magnitude of the noise generators when the noise consists of only one- and two-body terms, and describe a method for measuring the parameters of more general noise models. The protocol focuses on obtaining the magnitude with which these terms affect the system during a time step of length ?; measurement of this information has critical implications for assessing the scalability of fault-tolerant quantum computation in any physical setup
Efficient error characterization in quantum information processing
Lévi, Benjamin; López, Cecilia C.; Emerson, Joseph; Cory, D. G.
2007-02-01
We describe how to use the fidelity decay as a tool to characterize the errors affecting a quantum information processor through a noise generator G? . For weak noise, the initial decay rate of the fidelity proves to be a simple way to measure the magnitude of the different terms in G? . When the generator has only terms associated with few-body couplings, our proposal is scalable. We present the explicit protocol for estimating the magnitude of the noise generators when the noise consists of only one- and two-body terms, and describe a method for measuring the parameters of more general noise models. The protocol focuses on obtaining the magnitude with which these terms affect the system during a time step of length ? ; measurement of this information has critical implications for assessing the scalability of fault-tolerant quantum computation in any physical setup.
A quantum information approach to ultrafast spectroscopy
Yuen-Zhou, Joel
In the first part of the dissertation, we develop a theoretical approach to analyze nonlinear spectroscopy experiments based on the formalism of quantum state (QST) and process tomography (QPT). In it, a quantum system is regarded as a black box which can be systematically tested in its performance, very much like an electric circuit is tested by sending a series of inputs and measuring the corresponding outputs, but in the quantum sense. We show how to collect a series of pump-probe or photon-echo experiments, and by varying polarizations and frequency components of the perturbations, reconstruct the quantum state (density matrix) of the probed system for a set of different initial conditions, hence simultaneously achieving QST and QPT. Furthermore, we establish the conditions under which a set of two-dimensional optical spectra also yield the desired results. Simulations of noisy experiments with inhomogeneous broadening show the feasibility of the protocol. A spin-off of this work is our suggestion of a "witness" that distinguishes between spectroscopic time-oscillations corresponding to vibronic only coherences against their electronic counterparts. We conclude by noting that the QST/QPT approach to nonlinear spectroscopy sheds light on the amount of quantum information contained in the output of an experiment, and hence, is a convenient theoretical and experimental paradigm even when the goal is not to perform a full QPT. In the second part of the thesis, we discuss a methodology to study the electronic dynamics of complex molecular systems, such as photosynthetic units, in the framework of time-dependent density functional theory (TD-DFT). By treating the electronic degrees of freedom as the system and the nuclear ones as the bath, we develop an open quantum systems (OQS) approach to TD-DFT. We formally extend the theoretical backbone of TD-DFT to OQS, and suggest a Markovian bath functional which can be readily included in electronic structure codes.
Quantum Information from Graviton-Matter Gas
Directory of Open Access Journals (Sweden)
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.
Multiparty data hiding of quantum information
Hayden, Patrick; Leung, Debbie; Smith, Graeme
2004-01-01
We present protocols for multiparty data hiding of quantum information that implement all possible threshold access structures. Closely related to secret sharing, data hiding has a more demanding security requirement: that the data remain secure against unrestricted LOCC attacks. In the limit of hiding a large amount of data, our protocols achieve an asymptotic rate of one hidden qubit per local physical qubit. That is, each party holds a share that is the same size as the h...
Processing Information in Quantum Decision Theory
Vyacheslav I. Yukalov; Didier Sornette
2008-01-01
A survey is given summarizing the state of the art of describing information processing in Quantum Decision Theory, which has been recently advanced as a novel variant of decision making, based on the mathematical theory of separable Hilbert spaces. This mathematical structure captures the effect of superposition of composite prospects, including many incorporated intended actions. The theory characterizes entangled decision making, non-commutativity of subsequent decisions, and intention int...
Quantum non-locality Fundamentals and Applications in Quantum Information Science
Brunner, Nicolas
2007-01-01
This thesis is devoted to the study of quantum non-locality, in the framework of quantum information science. The research presented here includes both theoretical works on some fundamental concepts, such as the measurement process and quantum correlations, as well as some applications in modern quantum optics. As it is often the case in quantum information science, the joint study of fundamental notions and applications is very productive. While a better understanding of the fundamental conc...
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.
Beyond bits: The future of quantum information processing
Steane, AM; Rieffel, EG
2000-01-01
Quantum information theory seeks to unite some of the most influential ideas of 20th century science: quantum mechanics, computer science and information theory. The development of quantum information theory has only begun, and only a few applications are known, mostly in quantum system control and data security. The future of the theory is hard to predict, but it seems poised to contribute to some of the most exciting ideas of the 21st century. This theory gives an ideal framework for develo...
Quantum Information Processing with Finite Resources - Mathematical Foundations
Tomamichel, Marco
2015-01-01
One of the predominant challenges when engineering future quantum information processors is that large quantum systems are notoriously hard to maintain and control accurately. It is therefore of immediate practical relevance to investigate quantum information processing with limited physical resources, for example to ask: How well can we perform information processing tasks if we only have access to a small quantum device? Can we beat fundamental limits imposed on informatio...
Geometric information in eight dimensions vs. quantum information
Tarkhanov, Victor I
2008-01-01
Complementary idempotent paravectors and their ordered compositions, are used to represent multivector basis elements of geometric Clifford algebra for 3D Euclidean space as the states of a geometric byte in a given frame of reference. Two layers of information, available in real numbers, are distinguished. The first layer is a continuous one. It is used to identify spatial orientations of similar geometric objects in the same computational basis. The second layer is a binary one. It is used to manipulate with 8D structure elements inside the computational basis itself. An oriented unit cube representation, rather than a matrix one, is used to visualize an inner structure of basis multivectors. Both layers of information are used to describe unitary operations -- reflections and rotations -- in Euclidian and Hilbert spaces. The results are compared with ones for quantum gates. Some consequences for quantum and classical information technologies are discussed.
Quantifying non-Gaussianity for quantum information
Genoni, Marco
2010-01-01
We address the quantification of non-Gaussianity of states and operations in continuous-variable systems and its use in quantum information. We start by illustrating in details the properties and the relationships of two recently proposed measures of non-Gaussianity based on the Hilbert-Schmidt (HS) distance and the quantum relative entropy (QRE) between the state under examination and a reference Gaussian state. We then evaluate the non-Gaussianities of several families of non-Gaussian quantum states and show that the two measures have the same basic properties and also share the same qualitative behaviour on most of the examples taken into account. However, we also show that they introduce a different relation of order, i.e. they are not strictly monotone each other. We exploit the non-Gaussianity measures for states in order to introduce a measure of non-Gaussianity for quantum operations, to assess Gaussification and de-Gaussification protocols, and to investigate in details the role played by non-Gaussia...
Entropy of quantum channel in the theory of quantum information
Roga, Wojciech
2011-01-01
Quantum channels, also called quantum operations, are linear, trace preserving and completely positive transformations in the space of quantum states. Such operations describe discrete time evolution of an open quantum system interacting with an environment. The thesis contains an analysis of properties of quantum channels and different entropies used to quantify the decoherence introduced into the system by a given operation. Part I of the thesis provides a general introduc...
Generalized mutual informations of quantum critical chains
Alcaraz, F C
2015-01-01
We study the R\\'enyi mutual information $\\tilde{I}_n$ of the ground state of different critical quantum chains. The R\\'enyi mutual information definition that we use is based on the well established concept of the R\\'enyi divergence. We calculate this quantity numerically for several distinct quantum chains having either discrete $Z(Q)$ symmetries (Q-state Potts model with $Q=2,3,4$ and $Z(Q)$ parafermionic models with $Q=5,6,7,8$ and also Ashkin-Teller model with different anisotropies) or the $U(1)$ continuous symmetries(Klein-Gordon field theory, XXZ and spin-1 Fateev-Zamolodchikov quantum chains with different anisotropies). For the spin chains these calculations were done by expressing the ground-state wavefunctions in two special basis. Our results indicate some general behavior for particular ranges of values of the parameter $n$ that defines $\\tilde{I}_n$. For a system, with total size $L$ and subsystem sizes $\\ell$ and $L-\\ell$, the$\\tilde{I}_n$ has a logarithmic leading behavior given by $\\frac{\\til...
Generalized mutual information of quantum critical chains
Alcaraz, F. C.; Rajabpour, M. A.
2015-04-01
We study the generalized mutual information I˜n of the ground state of different critical quantum chains. The generalized mutual information definition that we use is based on the well established concept of the Rényi divergence. We calculate this quantity numerically for several distinct quantum chains having either discrete Z (Q ) symmetries (Q -state Potts model with Q =2 ,3 ,4 and Z (Q ) parafermionic models with Q =5 ,6 ,7 ,8 and also Ashkin-Teller model with different anisotropies) or the U (1 ) continuous symmetries (Klein-Gordon field theory, X X Z and spin-1 Fateev-Zamolodchikov quantum chains with different anisotropies). For the spin chains these calculations were done by expressing the ground-state wave functions in two special bases. Our results indicate some general behavior for particular ranges of values of the parameter n that defines I˜n. For a system, with total size L and subsystem sizes ? and L -? , the I˜n has a logarithmic leading behavior given by c/˜n4 log[L/? sin(?/? L ) ] where the coefficient c˜n is linearly dependent on the central charge c of the underlying conformal field theory describing the system's critical properties.
Preskill, John
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 perf...
The Ion Trap Quantum Information Processor
Steane, A M
1996-01-01
An introductory review of the linear ion trap is given, with particular regard to its use for quantum information processing. The discussion aims to bring together ideas from information theory and experimental ion trapping, to provide a resource to workers unfamiliar with one or the other of these subjects. It is shown that information theory provides valuable concepts for the experimental use of ion traps, especially error correction, and conversely the ion trap provides a valuable link between information theory and physics, with attendant physical insights. Example parameters are given for the case of calcium ions. Passive stabilisation will allow about 200 computing operations on 10 ions; with error correction this can be greatly extended.
Asano, Masanari; Basieva, Irina; Khrennikov, Andrei; Ohya, Masanori; Tanaka, Yoshiharu; Yamato, Ichiro
2015-01-01
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...
Information Nano-Technologies: Transition from Classical to Quantum
Vlasov, Alexander Yu
2009-01-01
In this presentation are discussed some problems, relevant with application of information technologies in nano-scale systems and devices. Some methods already developed in quantum information technologies may be very useful here. Here are considered two illustrative models: representation of data by quantum bits and transfer of signals in quantum wires.
Multiparty secret sharing of quantum information based on entanglement swapping
International Nuclear Information System (INIS)
A protocol of multiparty secret sharing of quantum information based on entanglement swapping is analyzed. In this protocol, Bell states are needed in order to realize the quantum information secret sharing and it is convenient to realize the quantum secret sharing among the members of any subset of users
Wang, Xiaogang; Chen, Wen; Chen, Xudong
2015-03-01
In this paper, we develop a new optical information authentication system based on compressed double-random-phase-encoded images and quick-response (QR) codes, where the parameters of optical lightwave are used as keys for optical decryption and the QR code is a key for verification. An input image attached with QR code is first optically encoded in a simplified double random phase encoding (DRPE) scheme without using interferometric setup. From the single encoded intensity pattern recorded by a CCD camera, a compressed double-random-phase-encoded image, i.e., the sparse phase distribution used for optical decryption, is generated by using an iterative phase retrieval technique with QR code. We compare this technique to the other two methods proposed in literature, i.e., Fresnel domain information authentication based on the classical DRPE with holographic technique and information authentication based on DRPE and phase retrieval algorithm. Simulation results show that QR codes are effective on improving the security and data sparsity of optical information encryption and authentication system. PMID:25836845
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...
Quantum Information Processing using Nonlinear Optical Effects
DEFF Research Database (Denmark)
Andersen, Lasse Mejling
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......-chirping the pumps. In the high-conversion regime without the effects of NPM, exact Green functions for BS are derived. In this limit, separability is possible for conversion efficiencies up to 60 %. However, the system still allows for selective frequency conversion as well as re-shaping of the output. One...... phase shifts of the input and output modes, corresponding to shifts of the central frequencies of the fields. The trade-off is that one is only able to select which signals are converted, or change the shape of the output idler. Finally, entanglement swapping using SFG was investigated. Considering two...
Quantum Corrections to Holographic Mutual Information
Agón, Cesar
2015-01-01
We compute the leading contribution to the mutual information (MI) of two disjoint spheres in the large distance regime for arbitrary conformal field theories (CFT) in any dimension. This is achieved by refining the operator product expansion method introduced by Cardy \\cite{Cardy:2013nua}. For CFTs with holographic duals the leading contribution to the MI at long distances comes from bulk quantum corrections to the Ryu-Takayanagi area formula. According to the FLM proposal\\cite{Faulkner:2013ana} this equals the bulk MI between the two disjoint regions spanned by the boundary spheres and their corresponding minimal area surfaces. We compute this quantum correction and provide in this way a non-trivial check of the FLM proposal.
Yu, Leo; Natarajan, Chandra M.; Horikiri, Tomoyuki; Langrock, Carsten; Pelc, Jason S.; Tanner, Michael G.; Abe, Eisuke; Maier, Sebastian; Schneider, Christian; Höfling, Sven; Kamp, Martin; Hadfield, Robert H.; Fejer, Martin M.; Yamamoto, Yoshihisa
2015-11-01
Practical quantum communication between remote quantum memories rely on single photons at telecom wavelengths. Although spin-photon entanglement has been demonstrated in atomic and solid-state qubit systems, the produced single photons at short wavelengths and with polarization encoding are not suitable for long-distance communication, because they suffer from high propagation loss and depolarization in optical fibres. Establishing entanglement between remote quantum nodes would further require the photons generated from separate nodes to be indistinguishable. Here, we report the observation of correlations between a quantum-dot spin and a telecom single photon across a 2-km fibre channel based on time-bin encoding and background-free frequency downconversion. The downconverted photon at telecom wavelengths exhibits two-photon interference with another photon from an independent source, achieving a mean wavepacket overlap of greater than 0.89 despite their original wavelength mismatch (900 and 911 nm). The quantum-networking operations that we demonstrate will enable practical communication between solid-state spin qubits across long distances.
Yu, Leo; Natarajan, Chandra M; Horikiri, Tomoyuki; Langrock, Carsten; Pelc, Jason S; Tanner, Michael G; Abe, Eisuke; Maier, Sebastian; Schneider, Christian; Höfling, Sven; Kamp, Martin; Hadfield, Robert H; Fejer, Martin M; Yamamoto, Yoshihisa
2015-01-01
Practical quantum communication between remote quantum memories rely on single photons at telecom wavelengths. Although spin-photon entanglement has been demonstrated in atomic and solid-state qubit systems, the produced single photons at short wavelengths and with polarization encoding are not suitable for long-distance communication, because they suffer from high propagation loss and depolarization in optical fibres. Establishing entanglement between remote quantum nodes would further require the photons generated from separate nodes to be indistinguishable. Here, we report the observation of correlations between a quantum-dot spin and a telecom single photon across a 2-km fibre channel based on time-bin encoding and background-free frequency downconversion. The downconverted photon at telecom wavelengths exhibits two-photon interference with another photon from an independent source, achieving a mean wavepacket overlap of greater than 0.89 despite their original wavelength mismatch (900 and 911?nm). The quantum-networking operations that we demonstrate will enable practical communication between solid-state spin qubits across long distances. PMID:26597223
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
Quantum information paradox: Real or fictitious?
Indian Academy of Sciences (India)
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 $M = 0$ 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.
Controlling the flow of information in quantum cloners: Asymmetric cloning
Buzek, V.; Hillery, M.; Bednik, R.
1998-01-01
We show that the distribution of information at the output of the quantum cloner can be efficiently controlled via preparation of the quantum cloner. We present a universal cloning network with the help of which asymmetric cloning can be performed.
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.
Quantum: information theory: technological challenge; Computacion Cuantica: un reto tecnologico
Energy Technology Data Exchange (ETDEWEB)
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.
Quantum Side Information: Uncertainty Relations, Extractors, Channel Simulations
Berta, Mario Andrea
2013-01-01
In the first part of this thesis, we discuss the algebraic approach to classical and quantum physics and develop information theoretic concepts within this setup. In the second part, we discuss the uncertainty principle in quantum mechanics. The principle states that even if we have full classical information about the state of a quantum system, it is impossible to deterministically predict the outcomes of all possible measurements. In comparison, the perspective of a quantum observer allows ...
Information-driven current in a quantum Maxwell demon
Deffner, Sebastian
2013-12-01
We describe a minimal model of a quantum Maxwell demon obeying Hamiltonian dynamics. The model is solved exactly, and we analyze its steady-state behavior. We find that writing information to a quantum memory induces a probability current through the demon, which is the quantum analog of the classical Maxwell demon's action. Our model offers a simple and pedagogical paradigm for investigating the thermodynamics of quantum information processing.
Exploring molecular equilibria using quantum information measures
Energy Technology Data Exchange (ETDEWEB)
Nalewajski, Roman F. [Department of Theoretical Chemistry, Jagiellonian University (Poland)
2013-03-15
The quantum information-theoretic description of electron probabilities and currents in molecules is extended. The Harriman-Zumbach-Maschke framework of equidensity orbitals is reexamined and the nonclassical Fisher information contribution it generates is used to determine the system equilibrium states for the fixed (ground-state) electron density/energy. The lowest of such variational ''thermodynamic'' states can in general exhibit the space-dependent phase and hence also nonvanishing probability current. The phase/current feature of electronic states in Harriman's representation is emphasized throughout, the probability interpretation of its key constructs is given, and the phase shifts accompanying interactions between the equidensity orbitals are examined. The phase-''temperature'' concept is introduced as the information-theoretic descriptor of probability currents in molecules and their fragments. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Leftover Hashing Against Quantum Side Information
Tomamichel, Marco; Smith, Adam; Renner, Renato
2010-01-01
The Leftover Hash Lemma states that the output of a two-universal hash function applied to an input with sufficiently high entropy is almost uniformly random. In its standard formulation, the lemma refers to a notion of randomness that is (usually implicitly) defined with respect to classical side information. Here, we prove a (strictly) more general version of the Leftover Hash Lemma that is valid even if side information is represented by the state of a quantum system. Furthermore, our result applies to arbitrary delta-almost two-universal families of hash functions. The generalized Leftover Hash Lemma has applications in cryptography, e.g., for key agreement in the presence of an adversary who is not restricted to classical information processing.
The role of relative entropy in quantum information theory
V. Vedral
2002-01-01
Quantum mechanics and information theory are among the most important scientific discoveries of the last century. Although these two areas initially developed separately, it has emerged that they are in fact intimately related. In this review the author shows how quantum information theory extends traditional information theory by exploring the limits imposed by quantum, rather than classical, mechanics on information storage and transmission. The derivation of many key results differentiates...
The Physics of Quantum Information: Complementarity, Uncertainty, and Entanglement
Joseph M. Renes
2012-01-01
The overarching goal of this thesis is to demonstrate that complementarity is at the heart of quantum information theory, that it allows us to make (some) sense of just what information "quantum information" refers to, and that it is useful in understanding and constructing quantum information processing protocols. The detailed research results which form the basis of these claims are to be found in the included papers, and the aim here is to present an overview comprehensib...
Quantum Information Paradox: Real or Fictitious?
Mitra, Abhas
2009-01-01
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 would exist, 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 of 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 at...
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...
Efficient error characterization in Quantum Information Processing
Lévi, Benjamin; López, Cecilia C.; Emerson, Joseph; Cory, D. G.(Institute for Quantum Computing, University of Waterloo, Waterloo, ON, Canada)
2006-01-01
We describe how to use the fidelity decay as a tool to characterize the errors affecting a quantum information processor through a noise generator $G_{\\tau}$. For weak noise, the initial decay rate of the fidelity proves to be a simple way to measure the magnitude of the different terms in $G_{\\tau}$. When the generator has only terms associated with few-body couplings, our proposal is scalable. We present the explicit protocol for estimating the magnitude of the noise generators when the noi...
Multiparty data hiding of quantum information
International Nuclear Information System (INIS)
We present protocols for multiparty data hiding of quantum information that implement all possible threshold access structures. Closely related to secret sharing, data hiding has a more demanding security requirement: that the data remain secure against unrestricted attacks via local operation and classical communication. In the limit of hiding a large amount of data, our protocols achieve an asymptotic rate of one hidden qubit per local physical qubit. That is, each party holds a share that is the same size as the hidden state to leading order, with accuracy and security parameters incurring an overhead that is asymptotically negligible. The data-hiding states have very unusual entanglement properties, which we briefly discuss
Verma, Vikram; Prakash, Hari
2015-11-01
We explicitly present precise and simple protocols for standard quantum teleportation and controlled quantum teleportation of an arbitrary N-qubit information state and analyse the case of perfect teleportation using general quantum channels and measurement bases. We find condition on resource quantum channel and Bell states for achieving perfect quantum teleportation. We also find the unitary transformation required to be done by Bob for perfect quantum teleportation and discuss the connection with others related works. We also discuss how perfect controlled quantum teleportation demands a correct choice of the measurement basis of additional party.
Measurement and Information Extraction in Complex Dynamics Quantum Computation
Casati, Giulio; Montangero, Simone
Quantum Information processing has several di.erent applications: some of them can be performed controlling only few qubits simultaneously (e.g. quantum teleportation or quantum cryptography) [1]. Usually, the transmission of large amount of information is performed repeating several times the scheme implemented for few qubits. However, to exploit the advantages of quantum computation, the simultaneous control of many qubits is unavoidable [2]. This situation increases the experimental di.culties of quantum computing: maintaining quantum coherence in a large quantum system is a di.cult task. Indeed a quantum computer is a many-body complex system and decoherence, due to the interaction with the external world, will eventually corrupt any quantum computation. Moreover, internal static imperfections can lead to quantum chaos in the quantum register thus destroying computer operability [3]. Indeed, as it has been shown in [4], a critical imperfection strength exists above which the quantum register thermalizes and quantum computation becomes impossible. We showed such e.ects on a quantum computer performing an e.cient algorithm to simulate complex quantum dynamics [5,6].
Encoding efficiency of suprathreshold stochastic resonance on stimulus-specific information
Duan, Fabing; Chapeau-Blondeau, François; Abbott, Derek
2016-01-01
In this paper, we evaluate the encoding efficiency of suprathreshold stochastic resonance (SSR) based on a local information-theoretic measure of stimulus-specific information (SSI), which is the average specific information of responses associated with a particular stimulus. The theoretical and numerical analyses of SSIs reveal that noise can improve neuronal coding efficiency for a large population of neurons, which leads to produce increased information-rich responses. The SSI measure, in contrast to the global measure of average mutual information, can characterize the noise benefits in finer detail for describing the enhancement of neuronal encoding efficiency of a particular stimulus, which may be of general utility in the design and implementation of a SSR coding scheme.
Mascarenhas, E; Cavalcanti, D; Cunha, M Terra; Santos, M França
2010-01-01
We study how to protect quantum information in quantum systems subjected to local dissipation. We show that combining the use of three-level systems, environment monitoring, and local feedback can fully and deterministically protect any available quantum information, including entanglement initially shared by different parties. These results can represent a gain in resources and/or distances in quantum communication protocols such as quantum repeaters and teleportation as well as time for quantum memories. Finally, we show that monitoring local environments physically implements the optimum singlet conversion protocol, essential for classical entanglement percolation.
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.
Demonstrating Quantum Error Correction that Extends the Lifetime of Quantum Information
Ofek, Nissim; Petrenko, Andrei; Heeres, Reinier; Reinhold, Philip; Leghtas, Zaki; Vlastakis, Brian; Liu, Yehan; Frunzio, Luigi; Girvin, S. M.; Jiang, Liang; Mirrahimi, Mazyar; Devoret, M.H.; Schoelkopf, R. J.
2016-01-01
The remarkable discovery of Quantum Error Correction (QEC), which can overcome the errors experienced by a bit of quantum information (qubit), was a critical advance that gives hope for eventually realizing practical quantum computers. In principle, a system that implements QEC can actually pass a "break-even" point and preserve quantum information for longer than the lifetime of its constituent parts. Reaching the break-even point, however, has thus far remained an outstanding and challengin...
Quantum information processing architecture with endohedral fullerenes in a carbon nanotube
Yang, Wan Li; Wei, Hua; Feng, Mang; Suter, Dieter
2010-01-01
A potential quantum information processor is proposed using a fullerene peapod, i.e., an array of the endohedral fullerenes 15N@C60 or 31P@C60 contained in a single walled carbon nanotube (SWCNT). The qubits are encoded in the nuclear spins of the doped atoms, while the electronic spins are used for initialization and readout, as well as for two-qubit operations.
Simple quantum system as a source of coherent information
International Nuclear Information System (INIS)
The set of the simplest quantum systems is analyzed from the viewpoint of the coherent information volume, available by application of the corresponding information channels. It is shown, the coherent information for simple quantum models may be calculated and used for evaluating the potential possibilities of the corresponding quantum channels as a source of physical information in the experiments, related to the effects of the quantum states coherence. The following physical models: the two-level atom in the laser radiation fields; the combination of the two-level subsystems in the multilevel atom (hydrogen); the system of the two-level atoms in the process of combined quantum-determined evolution and under the effect of the quantum measurement and quantum duplication transformants; as well as one or two level atoms in the process of radiation, are considered
Quantum Computers: A New Paradigm in Information Technology
Directory of Open Access Journals (Sweden)
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.
The biophysical basis of the high-bandwidth information encoding in cortical neurons
Directory of Open Access Journals (Sweden)
Andreas Neef
2015-07-01
Full Text Available A cortical neuron receives continuously fluctuating input through thousands of synapses. It encodes and relays this input to thousands of downstream neurons using action potentials. Therefore, the dynamics, with which those discrete action potentials are generated, represents a fundamental bottleneck for the flow of information in neural populations. In the last decade it became clear that the bandwidth of information encoding in neural populations in the cerebral cortex is much higher than it had been previously predicted by simulations with conductance based models (Fourcaud-Trocme et al., 2003; Naundorf et al., 2005, 2006; Kondgen et al., 2008; Higgs and Spain, 2009; Tchumatchenko et al., 2011. The biophysical basis of this experimentally observed large bandwidth is not understood, as even basic parameters such as sodium channel surface density and kinetics are still under debate(Kole et al., 2008; Baranauskas et al., 2013. The work presented here uses high resolution electrophysiology and fluorescence microscopy to quantify sodium channel properties and distributions in neurons. In combination with numerical modelling of active and passive neurons, we identify contributions to the ability to encode information with a high bandwidth. A characterization of sodium channels properties in the cell bodies of cortical pyramidal cells allowed us to conclude that each square micrometer contains 20 to 30 sodium channels. By combining current clamp and immunofluorescence in cultured hippocampal neurons we could achieve semi-quantitative fluorescence labeling and obtained estimates for the axonal density of sodium channels. We found the bandwidth of information encoding to be similar between cultured neurons and neurons in slices. Using cultured neurons as a model system, we studied the maturation of neuronal properties in the first weeks in culture. In parallel to the increased bandwidth, other neuronal properties changed: the axonal sodium channel density, the dendritic morphology and the sub-micrometer organization of axon initial segment structure(Xu et al., 2013; Zhong et al.. The presentation details, how those properties influenced the bandwidth of information encoding.
Pitch and loudness information encoded in auditory imagery as revealed by event-related potentials.
Wu, Jianhui; Yu, Zulin; Mai, Xiaoqin; Wei, Jinghan; Luo, Yuejia
2011-03-01
Two experiments using the ERP method and a task that involved comparing an imagined-S1 (the first stimulus) with a perceived-S2 (the second stimulus) were conducted to investigate whether imagined auditory representations encode pitch and loudness information. It was found that the amplitude of the imagery-related late positive complex (LPC) decreased with pitch but increased with loudness of the imagined sound, which was consistent with amplitude modulations of the auditory perception-related N1 component, thereby providing the first neural evidence that auditory imagery encodes perceptual attributes of auditory experiences. PMID:20636291
Secure sequential transmission of quantum information
Jeong, Kabgyun; Kim, Jaewan
2015-09-01
We propose a quantum communication protocol that can be used to transmit any quantum state, one party to another via several intermediate nodes, securely on quantum communication network. The scheme makes use of the sequentially chained and approximate version of private quantum channels satisfying certain commutation relation of n-qubit Pauli operations. In this paper, we study the sequential structure, security analysis, and efficiency of the quantum sequential transmission protocol in depth.
Quantum metrology from a quantum information science perspective
Toth, Geza; Apellaniz, Iagoba
2014-01-01
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 scali...
Quantum Logic circuits for solid-state quantum information processing
Del Duce, A.
2010-01-01
This thesis describes research on the design of quantum logic circuits suitable for the experimental demonstration of a three-qubit quantum computation prototype. The design is based on a proposal for optically controlled, solid-state quantum logic gates. In this proposal, typically referred to as SFG model, the qubits are stored in the electron spin of donors in a solid-state substrate while the interactions between them are mediated through the optical excitation of control particles placed...
Entanglement, Information, and the Interpretation of Quantum Mechanics
Jaeger, Gregg
2009-01-01
This book explores the nature of quantum entanglement and quantum information and their role in the quantum world. Their relations to a number of key experiments and thought experiments in the history of quantum physics are considered, as is a range of interpretations of quantum mechanics that have been put forward as a means of understanding the fundamental nature of microphysics - the traditionally accepted domain of quantum mechanics - and in some cases, the universe as a whole. In this way, the book reveals the deep significance of entanglement and quantum information for our understanding of the physical world. This book is a major accomplishment and invaluable contribution -- Arkady Plotnitsky An encyclopedic treatment of conceptual quantum mechanics as seen from a very up-to-date point of view --Tom Toffoli A mine of ideas for physicists, philosophers, and all intellectuals interested in this scientific revolution -- Giacomo Mauro D'Ariano
Lipinska, B; Bäckman, L
1997-07-01
Normal old adults and patients in an early phase of Alzheimer's disease (AD) were presented with photographs of common objects under two different encoding conditions: naming and naming along with category decisions. Memory was assessed with free recall, category cued recall, and recognition. For both groups, recognition was superior to cued recall which was higher than that for free recall. Most importantly, cue utilization in AD was optimized in the naming + category decision condition, although the normal old showed equivalent gains from cues following both encoding conditions. These results suggest that AD patients require more cognitive support at encoding than normal old adults to make effective use of retrieval cues. Dementia-related deficits in processing categorical information spontaneously may underlie the observed group differences in patterns of performance. PMID:9220090
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.
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, or a sender of the signal, because each receiver can become a sender as well. An observer receives a signal by performing certain measurements synchronized with the measurements of the others. This means that the signal is uniformly and simultaneously distributed over the observers in a decentralized way. The signals transmit no intentional information that would favor one agent over another. All the sequence of signals received by different observers are not only statistically equivalent, but are also point-by-point identical. It is important to assume that each agent knows that the other agent simultaneously receives the identical signals. The sequences of the signals are true random, so that no agent could predict the next step with the probability different from those described by the density. Under these quite general assumptions, the entangled observers-agents can perform non-trivial tasks that include transmission of conditional information from one agent to another, simple paradigm of cooperation, etc. The problem of behavior of intelligent agents correlated by identical random messages in a decentralized way has its own significance: it simulates evolutionary behavior of biological and social systems correlated only via simultaneous sensoring sequences of unexpected events.
Quantum mutual information along unitary orbits
Jevtic, Sania; Jennings, David; Rudolph, Terry
2012-05-01
Motivated by thermodynamic considerations, we analyze the variation of the quantum mutual information on a unitary orbit of a bipartite system's state with and without global constraints such as energy conservation. We solve the full optimization 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 for equal-sized subsystems, however their minimization displays nontrivial structures. We characterize a set of separable states in which the minimally correlated state resides: a collection of classically correlated states admitting a particular “Young tableau” form. Furthermore, a partial order exists on this set with respect to individual marginal entropies, and the presence of a “see-saw effect” for these entropies forces a finer analysis to determine the optimal tableau.
Classical and quantum Fisher information in the geometrical formulation of quantum mechanics
Energy Technology Data Exchange (ETDEWEB)
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.
Classical and quantum Fisher information in the geometrical formulation of quantum mechanics
International Nuclear Information System (INIS)
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.
Spin-based quantum information processing with semiconductor quantum dots and cavity QED
Feng, Mang; D'Amico, Irene; Zanardi, Paolo; Rossi, Fausto
2002-01-01
A quantum information processing scheme is proposed with semiconductor quantum dots located in a high-Q single mode QED cavity. The spin degrees of freedom of one excess conduction electron of the quantum dots are employed as qubits. Excitonic states, which can be produced ultrafastly with optical operation, are used as auxiliary states in the realization of quantum gates. We show how properly tailored ultrafast laser pulses and Pauli-blocking effects, can be used to achieve...
Routing quantum information in spin chains
Paganelli, Simone; De Lorenzo, Salvatore; Apollaro, Tony J. G.; Plastina, Francesco; Giorgi, Gian Luca
2013-01-01
Two different models for performing efficiently routing of a quantum state are presented. Both cases involve an XX spin chain working as data bus and additional spins that play the role of sender and receivers, one of which is selected to be the target of the quantum state transmission protocol via a coherent quantum coupling mechanism making use of local/global magnetic fields. Quantum routing is achieved, in the first of the models considered, by weakly coupling the sender...
Diagrams of States in Quantum Information: an Illustrative Tutorial
Felloni, Sara; Strini, Giuliano
2009-01-01
We present "Diagrams of States", a way to graphically represent and analyze how quantum information is elaborated during the execution of quantum circuits. This introductory tutorial illustrates the basics, providing useful examples of quantum computations: elementary operations in single-qubit, two-qubit and three-qubit systems, immersions of gates on higher dimensional spaces, generation of single and multi-qubit states, procedures to synthesize unitary, controlled and diagonal matrices. To perform the analysis of quantum processes, we directly derive diagrams of states from physical implementations of quantum circuits associated to the processes. Complete diagrams are then rearranged into simplified diagrams, to visualize the overall effects of computations. Conversely, diagrams of states help to conceive new quantum algorithms, by schematically describing desired manipulations of quantum information with intuitive diagrams and then by guessing the equivalent complete diagrams, from which the corresponding...
Albouy, Philippe; Cousineau, Marion; Caclin, Anne; Tillmann, Barbara; Peretz, Isabelle
2016-01-01
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. PMID:26732511
Gaze patterns in navigation: Encoding information in large-scale environments
Hamid, Sahar N.; Stankiewicz, Brian; Hayhoe, Mary
2010-01-01
We investigated the role of gaze in encoding of object landmarks in navigation. Gaze behavior was measured while participants learnt to navigate in a virtual large-scale environment in order to understand the sampling strategies subjects use to select visual information during navigation. The results showed a consistent sampling pattern. Participants preferentially directed gaze at a subset of the available object landmarks with a preference for object landmarks at the end of hallways and T-j...
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...
Quantum Kolmogorov Complexity and Information-Disturbance Theorem
Miyadera, Takayuki
2011-01-01
In this paper, a representation of the information-disturbance theorem based on the quantum Kolmogorov complexity that was defined by P. Vitanyi has been examined. In the quantum information theory, the information-disturbance relationship, which treats the trade-off relationship between information gain and its caused disturbance, is a fundamental result that is related to Heisenberg's uncertainty principle. The problem was formulated in a cryptographic setting and quantitative relationships between complexities have been derived.
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. PMID:25775233
Towards Quantum Information Theory in Space and Time
Volovich, I V
2002-01-01
Modern quantum information theory deals with 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 qubit, channel, composite systems and entangled states should be formulated in space and time. In particlular we suggest that instead of a two level system (qubit) the basic notion in a relativistic quantum information theory should be a notion of an elementary quantum system, i.e. an infinite dimensional Hilbert space $H$ invariant under an irreducible representation of the Poincare group labeled by $[m,s]$ where $m\\geq 0$ is mass and $s=0,1/2,1,...$ is spin. We emphasize an importance of consideration of quantum information theory from the point of view of quantum field theory. We point out and discuss a fundamental fact that in quantum field theory there is a statistical dependence between two regions in spacetime e...
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...
Information driven current in a quantum Maxwell demon
Deffner, Sebastian
2014-03-01
We describe a minimal model of a quantum Maxwell demon obeying Hamiltonian dynamics. The model is solved exactly, and we analyze its steady-state behavior. We find that writing information to a quantum memory induces a probability current through the demon, which is the quantum analog of the classical Maxwell demon's action. Our model offers a simple and pedagogical paradigm for investigating the thermodynamics of quantum information processing. We acknowledge financial support by a fellowship within the postdoc-program of the German Academic Exchange Service (DAAD, contract No D/11/40955) and from the National Science Foundation (USA) under grant DMR-1206971.
Realism and Antirealism in Informational Foundations of Quantum Theory
Directory of Open Access Journals (Sweden)
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 so in a more comprehensive and intuitive way. The presented approach is close to Husserl's explanation of the relationship between reality and the knowledge we have about it, and to Bohr's personal explanation of quantum mechanics, the complexity of which has often been missed and simplified to mere antirealism. Our approach thus reconnects phenomenology with contemporary philosophy of science and introduces the comprehensive approach that exceeds mere realism and antirealism to the field of quantum theories with informational foundations, where such an approach has not been taken before.Quanta 2014; 3: 32–42.
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 explains the poor identification performance of spatially encoded patterns. Hence, when using an array of vibrational motors, spatiotemporal sweeps can overcome the limitations of vibrotactile two-tacton resolution. The results provide the first steps toward obtaining a realistic estimate of the skin's achievable throughput, illustrating the best ways to encode data to the skin (using as many dimensions as possible) and how far such interfaces would need to be separated if using multiple arrays in parallel. PMID:26080756
Generating the Depth Map from the Motion Information of H.264-Encoded 2D Video Sequence
Pourazad MahsaT; Nasiopoulos Panos; Ward RababK
2010-01-01
An efficient method that estimates the depth map of a 3D-scene using the motion information of the H.264-encoded 2D-video is presented. The motion information of the video-frames captured via a single camera is either directly used or modified to approximate the displacement (disparity) that exists between the right and left images when the scene is captured by stereoscopic cameras. Then, depth is estimated based on its inverse relation with disparity. The low-complexity of this met...
Continuous-Variable Quantum Information Distributor: Reversible Telecloning
Zhang, J; Xie, C; Peng, Kunchi; Xie, Changde; Zhang, Jing
2005-01-01
We propose a scheme of continuous-variable reversible telecloning, which broadcast the information of an unknown state without loss from a sender to several spatially separated receivers exploiting multipartite entanglement as quantum channels. In this scheme, quantum information of an unknown state is distributed into $M$ optimal clones and $M-1$ anticlones using $2M$% -partite entanglement. For the perfect quantum information distribution that is optimal cloning, $2M$-partite entanglement is required to be a maximum two-party entanglement. Comparing with the quantum telecloning proposed by Loock and Braunstein [Phys. Rev. Lett. 87, 247901 (2001)], this protocol produces the anticlones (or time-reversed state) of the unknown quantum state, thus, keep all information of an unknown state.
Retrieving and Routing Quantum Information in a Quantum Network
Sazim, Sk; Vanarasa, Chiranjeevi; Chakrabarty, Indranil; Srinathan, Kannan
2013-01-01
In extant quantum secret sharing protocols, once the secret is shared in a quantum network (\\textsc{qnet}) it can not be retrieved back, even if the dealer wishes that her secret no longer be available in the network. For instance, if the dealer is part of two \\textsc{qnet}s, say $\\mathcal{Q}_1$ and $\\mathcal{Q}_2$ and subsequently finds that $\\mathcal{Q}_2$ is more reliable than $\\mathcal{Q}_1$, the dealer may wish to transfer all her secrets from $\\mathcal{Q}_1$ to $\\mathc...
The mother of all protocols: Restructuring quantum information's family tree
Abeyesinghe, A; Hayden, P; Winter, A; Abeyesinghe, Anura; Devetak, Igor; Hayden, Patrick; Winter, Andreas
2006-01-01
We give a simple, direct proof of the "mother" protocol of quantum information theory. In this new formulation, it is easy to see that the mother, or rather her generalization to the fully quantum Slepian-Wolf protocol, simultaneously accomplishes two goals: quantum communication-assisted entanglement distillation, and state transfer from the sender to the receiver. As a result, in addition to her other "children," the mother protocol generates the state merging primitive of Horodecki, Oppenheim and Winter, a fully quantum reverse Shannon theorem, and a new class of distributed compression protocols for correlated quantum sources which are optimal for sources described by separable density operators. Moreover, the mother protocol described here is easily transformed into the so-called "father" protocol whose children provide the quantum capacity and the entanglement-assisted capacity of a quantum channel, demonstrating that the division of single-sender/single-receiver protocols into two families was unnecess...
Self-Assembled Wigner Crystals as Mediators of Spin Currents and Quantum Information
Antonio, Bobby; Bayat, Abolfazl; Kumar, Sanjeev; Pepper, Michael; Bose, Sougato
2015-11-01
Technological applications of many-body structures that emerge in gated devices under minimal control are largely unexplored. Here we show how emergent Wigner crystals in a semiconductor quantum wire can facilitate a pivotal requirement for a scalable quantum computer, namely, transmitting quantum information encoded in spins faithfully over a distance of micrometers. The fidelity of the transmission is remarkably high, faster than the relevant decohering effects, independent of the details of the spatial charge configuration in the wire, and realizable in dilution refrigerator temperatures. The transfer can evidence near unitary many-body nonequilibrium dynamics hitherto unseen in a solid-state device. It could also be useful in spintronics as a method for pure spin current over a distance without charge movement.
Dell'Acqua, Roberto; Dux, Paul E; Wyble, Brad; Doro, Mattia; Sessa, Paola; Meconi, Federica; Jolicœur, Pierre
2015-04-01
This article explores the time course of the functional interplay between detection and encoding stages of information processing in the brain and the role they play in conscious visual perception. We employed a multitarget rapid serial visual presentation (RSVP) approach and examined the electrophysiological P3 component elicited by a target terminating an RSVP sequence. Target-locked P3 activity was detected both at frontal and parietal recording sites and an independent component analysis confirmed the presence of two distinct P3 components. The posterior P3b varied with intertarget lag, with diminished amplitude and postponed latency at short relative to long lags-an electroencephalographic signature of the attentional blink (AB). Under analogous conditions, the anterior P3a was also reduced in amplitude but did not vary in latency. Collectively, the results provide an electrophysiological record of the interaction between frontal and posterior components linked to detection (P3a) and encoding (P3b) of visual information. Our findings suggest that, although the AB delays target encoding into working memory, it does not slow down detection of a target but instead reduces the efficacy of this process. A functional characterization of P3a in attentive tasks is discussed with reference to current models of the AB phenomenon. PMID:25390207
School on Advances in Quantum Information: Theory and Applications
2014-01-01
The Abdus Salam International Centre for Theoretical Physics (ICTP) in collaboration with the University Mohamed V Agdal in Rabat and the COST Action MP1006, is organizing a "School in Advances in Quantum Information: Theory and Applications" from 15 to 19 September 2014, followed by the "3rd Quantum Africa Conference: Advances in Quantum Sciences", from 22 to 26 Sep 2014, both events to be held at University Mohamed V Agdal in Rabat, Morocco. The last years have witnessed fast growing developments in the use of quantum mechanics in technology-oriented and information-related fields, including metrology, nano-devices development, biophysics together with computation, communication and cryptography. Topics as quantum entanglement, quantum coherence and decohering phenomena both in microscopic and mesoscopic systems have been attracting the interest of a growing number of researchers, especially young ones from developing countries. A School on these themes would provide an invaluable focus on the interdiscipl...
Dorsomedial prefrontal cortex encodes value information during a sequential choice task
Directory of Open Access Journals (Sweden)
Chung-Hay Luk
2010-02-01
Full Text Available Many choices require evaluating possible options one after another as exemplified in wine tasting. The underlying neuronal mechanisms in such a sequential choice paradigm are largely unknown though. Hence we have recorded neuronal and local field potential activity from dorsomedial and dorsolateral prefrontal cortex (PFdm and PFdl, respectively as subjects performed a sequential choice task. We expected PFdm to encode the valuation of choice options, owing to its strong anatomical inputs from areas processing reward. In our task, two monkeys (Macaca mulatta chose between two different juices on a trial-by-trial basis. During the sampling phase, the subject made two sample responses separated by delays, each of which resulted in the delivery of a small drop of one of three juices (apple, orange or quinine. During the choice phase, the subject then chose to repeat one of the responses, and received a larger amount of the juice that had been associated with that response earlier in the trial. Thus, in order to receive juices that are more preferable at the choice phase of the task, the subject had to maintain information about the first sampled reward and which response produced it to compare that reward to the subsequent reward. We recorded the activity of 112 PFdm neurons and 172 PFdl neurons from 180 recording sites as the subjects performed the task. Following the sampling of the first juice, a similar proportion of neurons encoded the action producing the reward in PFdm (46% and PFdl (48%, whereas encoding of the juice reward was prominent in PFdm (60% but not PFdl (28%. The neuronal activity correlated with high power around the 40 Hz gamma range. Moreover, reward-selective neurons showed a monotonic relationship between their firing rate and the subject's preference for the juice, suggesting that PFdm neurons encoded the juice as a value signal. PFdm neurons encoded the value of the second juice relative to the first, typically showing a higher firing rate when the second juice was less preferred than the first. These findings suggest that options in a sequential choice are evaluated with respect to previous options. By maintaining the value of the first juice and then encoding the value of the second juice relative to the first, PFdm neurons provide the appropriate information to enable the subjects to make their choice.
Quantum Oblivious Transfer Based on a Quantum Symmetrically Private Information Retrieval Protocol
Yang, Yu-Guang; Sun, Si-Jia; Wang, Yan
2015-03-01
Private information retrieval implies oblivious transfer in classical cryptography. Following this clue, we present a novel quantum one-out-of-two OT protocol based on a practical quantum symmetrically private information retrieval protocol Jakobi et al. (Phys. Rev. A 83, 022301 2011), with changes only in the classical postprocessing of the key. While unconditionally secure oblivious transfer is known to be impossible, we argue that an interesting degree of security can be achieved by means of quantum physical principles instead of unproven security assumptions in order to protect both the sender and the receiver. The proposed OT protocol is loss tolerant, practical and robust against quantum memory attack.
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.
Schroedinger cats and their power for quantum information processing
International Nuclear Information System (INIS)
We outline a toolbox comprised of passive optical elements, single photon detection and superpositions of coherent states (Schroedinger 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
Schroedinger cats and their power for quantum information processing
Energy Technology Data Exchange (ETDEWEB)
Gilchrist, A [Centre for Quantum Computer Technology, University of Queensland, QLD 4072 (Australia); Nemoto, Kae [National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430 (Japan); Munro, W J [Hewlett Packard Laboratories, Filton Road, Stoke Gifford, Bristol BS34 8QZ (United Kingdom); Ralph, T C [Centre for Quantum Computer Technology, University of Queensland, QLD 4072 (Australia); Glancy, S [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Braunstein, Samuel L [Computer Science, York University, York YO10 5DD (United Kingdom); Milburn, G J [Centre for Quantum Computer Technology, University of Queensland, QLD 4072 (Australia)
2004-08-01
We outline a toolbox comprised of passive optical elements, single photon detection and superpositions of coherent states (Schroedinger 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.
Schrodinger cats and their power for quantum information processing
Gilchrist, A; Nemoto, Kae; Munro, W. J.; Ralph, T C; Glancy, S.; Braunstein, Samuel. L.; Milburn, G J
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...
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.
Information Gain vs. State Disturbance in Quantum Theory
Christopher A. Fuchs
1996-01-01
The engine that powers quantum cryptography is the principle that there are no physical means for gathering information about the identity of a quantum system's state (when it is known to be prepared in one of a set of nonorthogonal states) without disturbing the system in a statistically detectable way. This situation is often mistakenly described as a consequence of the ``Heisenberg uncertainty principle.'' A more accurate account is that it is a unique feature of quantum phenomena that res...
Coding for quantum channels with side information at the transmitter
Dupuis, FrÃ©dÃ©ric
2008-01-01
We consider the problem of coding for quantum channels with side information that is available ahead of time at the transmitter but not at the receiver. We find a single-letter expression for the entanglement-assisted quantum capacity of such channels which closely parallels Gel'fand and Pinsker's solution to the classical version of the same problem. This theorem can also be used to find a lower bound on the unassisted quantum capacity of these channels.
Diagrams of States in Quantum Information: an Illustrative Tutorial
Felloni, Sara; LEPORATI, ALBERTO; Strini, Giuliano
2009-01-01
We present "Diagrams of States", a way to graphically represent and analyze how quantum information is elaborated during the execution of quantum circuits. This introductory tutorial illustrates the basics, providing useful examples of quantum computations: elementary operations in single-qubit, two-qubit and three-qubit systems, immersions of gates on higher dimensional spaces, generation of single and multi-qubit states, procedures to synthesize unitary, controlled and dia...
Information-theoretic differential geometry of quantum phase transitions.
Zanardi, Paolo; Giorda, Paolo; Cozzini, Marco
2007-09-01
The manifold of coupling constants parametrizing a quantum Hamiltonian is equipped with a natural Riemannian metric with an operational distinguishability content. We argue that the singularities of this metric are in correspondence with the quantum phase transitions featured by the corresponding system. This approach provides a universal conceptual framework to study quantum critical phenomena which is differential geometric and information theoretic at the same time. PMID:17930382
Quantum Gravity and Recovery of Information in Black Hole Evaporation
Nozari, Kourosh; Mehdipour, S. Hamid
2008-01-01
The Generalized Uncertainty Principle (GUP), motivated by current alternatives of quantum gravity, produces significant modifications to the Hawking radiation and the final stage of black hole evaporation. We show that incorporation of the GUP into the quantum tunneling process (based on the null-geodesic method) causes correlations between the tunneling probability of different modes in the black hole radiation spectrum. In this manner, the quantum information becomes encry...
QIS-XML: A metadata specification for Quantum Information Science
Heus, Pascal; Gomez, Richard
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 ...
Quantum Key Distribution in Large Scale Quantum Network Assisted by Classical Routing Information
Wu, Diance; Yu, Wanrong; Zhao, Baokang; Wu, Chunqing
2014-10-01
Recently, small-scale Quantum Key Distribution (QKD) networks have been demonstrated and continuously operated in field environment. However, nodes of these QKD networks are less than 10 nodes. When the scale and structure of these networks becomes large and complex, such networks will subject to problem of intractable routing selection and limited transmission distance. We present a novel quantum network model and the corresponding protocol to solve these problems. The proposed quantum network model integrates classical communication network with quantum key distribution layer. Nodes in this quantum network model are divided into communication nodes for classical communication and quantum nodes for quantum key distribution. We use atomic ensembles to create entangled photons inside quantum nodes. Quantum repeaters are used to establish entanglement between remote quantum nodes so the maximum distribution distance of entangled photons can be extended. The main idea is to establish an appropriate key distribution path in the quantum key distribution layer based on the routing information obtained by the upper classical communication network. After the entanglement has been established between remote quantum nodes, these nodes will use the Ekert91 or BBM92 protocol to generate secret keys shared between each other. Then, these keys can be used to ensure the security of communication in the classical communication network.
Encoding a qudit in an oscillator
Gottesman, D; Preskill, J; Gottesman, Daniel; Kitaev, Alexei; Preskill, John
2001-01-01
Quantum error-correcting codes are constructed that embed a finite-dimensional code space in the infinite-dimensional Hilbert space of a system described by continuous quantum variables. These codes exploit the noncommutative geometry of phase space to protect against errors that shift the values of the canonical variables q and p. In the setting of quantum optics, fault-tolerant universal quantum computation can be executed on the protected code subspace using linear optical operations, squeezing, homodyne detection, and photon counting; however, nonlinear mode coupling is required for the preparation of the encoded states. Finite-dimensional versions of these codes can be constructed that protect encoded quantum information against shifts in the amplitude or phase of a d-state system. Continuous-variable codes can be invoked to establish lower bounds on the quantum capacity of Gaussian quantum channels.
Quantum Information Processing using Nonlinear Optical Effects
DEFF Research Database (Denmark)
Andersen, Lasse Mejling
2014-01-01
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 materials for heralded entanglement. BS is shown to be separable in the input and output modes in the low-conversion regime, the regime of small pump powers or short interaction times. The selective frequency conversion of a signal is found to only depend on one of the pumps, while the temporal output 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-chirping the pumps. In the high-conversion regime without the effects of NPM, exact Green functions for BS are derived. In this limit, separability is possible for conversion efficiencies up to 60 %. However, the system still allows for selective frequency conversion as well as re-shaping of the output. One way 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 shifts of the input and output modes, corresponding to shifts of the central frequencies of the fields. The trade-off is that one is only able to select which signals are converted, or change the shape of the output idler. Finally, entanglement swapping using SFG was investigated. Considering two pairs of entangled photons, the process of up-converting one photon from each pair leads to heralded entangled pairs by successful detection of the up-converted photon. It was seen that this was indeed possible in the case of anti-correlated phasematching in the up-conversion crystal. Possible ways of increasing the probability of an up-conversion event were investigated briefly.
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 finally turning his attention to philosophy in 1957, Weizsäcker became interested in nuclear fusion research and educated a generation of postwar German physicists in both plasma physics and astrophysics. Michael Frayn’s play `Copenhagen' has ignited worldwide interest in the mysterious meeting of Niels Bohr with Werner Heisenberg in September 1941. However, an article by R Lüst indicates that in 1951 Bohr enjoyed a friendly visit with Heisenberg in Göttingen. This 1941 meeting of Heisenberg and Bohr is discussed further in an article by Götz Neuneck, who also details the World War II and post-war research and interests of the Uranium Club, a group of 70--100 German physicists and chemists. Neuneck also discusses the resistance of individual scientists, such as Hahn, Heisenberg, and Bothe, to the Nazi regime. We learn that, unlike Wernher von Braun, no member of the Uranium Club was ever granted an audience with Hitler. After the war, German scientists renounced any role for German development of nuclear weapons in various manifestos, such as the Mainau and G\\"ottingen Declarations that were both influenced by Weizsäcker. Time, Quantum and Information contains much anecdotal material. Examples include a touching quotation in a letter from Edward Teller to Weizsäcker: `If I could share your religious belief, I would wish that you will one day come from a higher heaven and visit me in purgatory.' Another example, less complimentary, is a comment from Pauli after hearing from Weisskopf that Weizsäcker had made numerous errors in his habilitation thesis and realizing that Weizsäcker had accepted an offer from Peter Debye at Berlin: `The measure of sloppiness in Weizsäcker’s work exceeds altogether and by far the tolerable measure, and my pain of not having had him as an assistant has been alleviated by this.' Two-thirds of this compendium also explores the philosophical interests of Weizsäcker. This portion discusses his attempt to reconstruct quantum mechanics and build up a `theory of everything' based on his `ur' hypothesis. As stated by the mat
Zhuang, Xiahai; Arridge, Simon; Hawkes, David J; Ourselin, Sebastien
2011-10-01
Mutual information (MI) registration including spatial information has been shown to perform better than the traditional MI measures for certain nonrigid registration tasks. In this work, we first provide new insight to problems of the MI-based registration and propose to use the spatially encoded mutual information (SEMI) to tackle these problems. To encode spatial information, we propose a hierarchical weighting scheme to differentiate the contribution of sample points to a set of entropy measures, which are associated to spatial variable values. By using free-form deformations (FFDs) as the transformation model, we can first define the spatial variable using the set of FFD control points, and then propose a local ascent optimization scheme for nonrigid SEMI registration. The proposed SEMI registration can improve the registration accuracy in the nonrigid cases where the traditional MI is challenged due to intensity distortion, contrast enhancement, or different imaging modalities. It also has a similar computation complexity to the registration using traditional MI measures, improving up to two orders of magnitude of computation time compared to the traditional schemes. We validate our algorithms using phantom brain MRI, simulated dynamic contrast enhanced mangetic resonance imaging (MRI) of the liver, and in vivo cardiac MRI. The results show that the SEMI registration significantly outperforms the traditional MI registration. PMID:21550878
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.
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…
Quantum teleportation and entanglement. A hybrid approach to optical quantum information procesing
Energy Technology Data Exchange (ETDEWEB)
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.)
Semiconductor sources of twin photons for quantum information
International Nuclear Information System (INIS)
A large number of scientific proposals made in the last few years are based on transport and manipulation of information using single quantum objects. Some of them make use of entanglement in pairs of particles such as twin photons. Although theoretical proposals have demonstrated highly interesting perspectives in the quantum information domain, experimental realizations and applications still suffer from the complexity of experimental set-ups and technological limitations. This paper presents various approaches aiming at efficient twin photon semiconductor sources. The emergence of these compact and integrated devices would be an important technological breakthrough in quantum information applications
Extremal properties of the variance and the quantum Fisher information
Energy Technology Data Exchange (ETDEWEB)
Toth, Geza [Theoretical Physics, University of the Basque Country UPV/EHU, E-48080 Bilbao (Spain); IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao (Spain); Wigner Research Centre for Physics, H-1525 Budapest (Hungary); Petz, Denes [Alfred Renyi Institute of Mathematics, Realtanoda utca 13-15, H-1051 Budapest (Hungary)
2013-07-01
We show that the variance is its own concave roof. For rank-2 density matrices and operators with zero diagonal elements in the eigenbasis of the density matrix, we show analytically that the quantum Fisher information is 4 times the convex roof of the variance. Strong numerical evidence suggests that the quantum Fisher information is very close to the convex roof even for operators with nonzero diagonal elements or density matrices with a rank larger than 2. Hence, we conjecture that the quantum Fisher information is 4 times the convex roof of the variance even for the general case.
Physics Colloquium: The optical route to quantum information processing
UniversitÃ© de GenÃ¨ve
2011-01-01
Geneva University Physics Department 24, Quai Ernest Ansermet CH-1211 Geneva 4 Monday 11 April 2011 17h00 - Ecole de Physique, Auditoire StÃ¼ckelberg 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...
Fisher information and quantum potential well model for finance
Nastasiuk, V. A.
2015-09-01
The probability distribution function (PDF) for prices on financial markets is derived by extremization of Fisher information. It is shown how on that basis the quantum-like description for financial markets arises and different financial market models are mapped by quantum mechanical ones.
Fisher information and quantum mechanical models for finance
Vadim Nastasiuk
2015-01-01
The probability distribution function (PDF) for prices on financial markets is derived by extremization of Fisher information. It is shown how on that basis the quantum-like description for financial markets arises and different financial market models are mapped by quantum mechanical ones.
Nonlocal quantum information transfer without superluminal signalling and communication
Walleczek, Jan; Groessing, Gerhard
2015-01-01
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, a...
Controlling the flow of information in quantum cloners: asymmetric cloning
International Nuclear Information System (INIS)
We show that the distribution of information at the output of the quantum cloner can be efficiently controlled via preparation of the quantum cloner. We present a universal cloning network with the help of which asymmetric cloning can be performed. (author)
Fractal hard drives for quantum information
Wootton, James R.
2016-02-01
A quantum hard drive, capable of storing qubits for unlimited timescales, would be very useful for quantum computation. Unfortunately, the most ideal solutions currently known can only be built in a universe of four spatial dimensions. In a recent publication (Brell 2016 New J. Phys. 18 013050), Brell introduces a new family of models based on these ideal solutions. These use fractal lattices, and result in models whose Hausdorff dimension is less than 3. This opens a new avenue of research towards a quantum hard drive that can be build in our own 3D universe.
Reduced randomness in quantum cryptography with sequences of qubits encoded in the same basis
International Nuclear Information System (INIS)
We consider the cloning of sequences of qubits prepared in the states used in the BB84 or six-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 only valid provided that the sequences are much shorter than the total key. It 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 cloning attacks
Xavier, G B; Temporao, G P; von der Weid, J P
2007-01-01
A real-time polarization control system employing two nonorthogonal reference signals multiplexed in either time or wavelength with the data signal is presented. It is shown, theoretically and experimentally, that complete control of multiple polarization states can be attained employing polarization controllers in closed-loop configuration. Experimental results show that negligible added penalties, corresponding to an average added optical Quantum Bit Error Rate of 0.044%, can be achieved with response times smaller than 10 ms, without significant introduction of noise counts in the quantum channel.
Routing quantum information in spin chains
Paganelli, Simone; Lorenzo, Salvatore; Apollaro, Tony J. G.; Plastina, Francesco; Giorgi, Gian Luca
2013-06-01
Two different models are presented that allow for efficiently performing routing of a quantum state. Both cases involve an XX spin chain working as a data bus and additional spins that play the role of sender and receivers, one of which is selected to be the target of the quantum state transmission protocol via a coherent quantum coupling mechanism making use of local and/or global magnetic fields. Quantum routing is achieved in the first of the models considered by weakly coupling the sender and the receiver to the data bus. On the other hand, in the second model, local magnetic fields acting on additional spins located between the sender and receiver and the data bus allow us to perform high-fidelity routing.
Quantum uncertainty of mixed states based on skew information
International Nuclear Information System (INIS)
The uncertainty of a mixed state has two quite different origins: classical mixing and quantum randomness. While the classical aspect (mixedness) is significantly quantified by the von Neumann entropy, it seems that we still do not have a well accepted measure of quantum uncertainty. In terms of the skew information introduced by Wigner and Yanase in 1963 in the context of quantum measurements, we will propose an intrinsic measure for synthesizing quantum uncertainty of a mixed state and investigate its fundamental properties. We illustrate how it arises naturally from a naive hidden-variable approach to entanglement and how it exhibits a simple relation to the notion of negativity, which is an entanglement monotone introduced quite recently. We further show that it has a dramatic nonextensive feature resembling the probability law relating operations of two events. This measure of quantum uncertainty provides an alternative quantity complementary to the von Neumann entropy for studying mixedness and quantum correlations
Quantum Stackelberg Duopoly with Continuous Distributed Incomplete Information
Wang, Xia; Hu, Cheng-Zheng
2012-12-01
A general model of the quantum Stackelberg duopoly is constructed by introducing the “minimal" quantum structure into the Stackelberg duopoly with continuous distributed incomplete information, where both players only know the continuous distribution of the competitor's unit cost. In this model, the cases with complete information, discrete distributed incomplete information, and continuous distributed asymmetric information are all involved. Because of different roles played by the total information uncertainty and the information asymmetry, the game exhibits some new interesting features, such as the total information uncertainty can counteract or improve the first-mover advantage according to the value of the quantum entanglement. What's more, this general model will be helpful for the government to reduce the abuses of oligopolistic competition and to improve the economic efficiency.
Quantum Stackelberg Duopoly with Continuous Distributed Incomplete Information
International Nuclear Information System (INIS)
A general model of the quantum Stackelberg duopoly is constructed by introducing the 'minimal' quantum structure into the Stackelberg duopoly with continuous distributed incomplete information, where both players only know the continuous distribution of the competitor's unit cost. In this model, the cases with complete information, discrete distributed incomplete information, and continuous distributed asymmetric information are all involved. Because of different roles played by the total information uncertainty and the information asymmetry, the game exhibits some new interesting features, such as the total information uncertainty can counteract or improve the first-mover advantage according to the value of the quantum entanglement. What's more, this general model will be helpful for the government to reduce the abuses of oligopolistic competition and to improve the economic efficiency
Designing robust gate implementations for quantum-information processing
International Nuclear Information System (INIS)
Quantum-information processing systems are often operated through time-dependent controls; choosing these controls in a way that makes the resulting operation insensitive to variations in unknown or uncontrollable system parameters is an important prerequisite for obtaining high-fidelity gate operations. In this article we present a numerical method for constructing such robust control sequences for a quite general class of quantum-information processing systems. As an application of the method we have designed a robust implementation of a phase-shift operation central to rare-earth-metal quantum computing, an ensemble quantum computing system proposed by Ohlsson et al. [Opt. Commun. 201, 71 (2002)]. In this case the method has been used to obtain a high degree of insensitivity with respect to differences between ensemble members, but it is equally well suited for quantum computing with a single physical system
Lattice gauge theories simulations in the quantum information era
Dalmonte, M
2016-01-01
The many-body problem is ubiquitous in the theoretical description of physical phenomena, ranging from the behavior of elementary particles to the physics of electrons in solids. Most of our understanding of many-body systems comes from analyzing the symmetry properties of Hamiltonian and states: the most striking example 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 realization of synthetic gauge theories, and novel classical simulation algorithms based on quantum information concepts have been formulated....
Quantum Information Processing with Continuous Variables and Atomic Ensembles
Zwierz, Marcin
2011-01-01
This thesis presents three different results in quantum information theory. The first result addresses the theoretical foundations of quantum metrology. The Heisenberg limit considered as the ultimate limit in quantum metrology sets a lower bound on how precisely a physical quantity can be measured given a certain amount of resources in any possible measurement. Recently, however, several measurement procedures have been proposed in which the Heisenberg limit seemed to be surpassed. This led to an extensive debate over the question how the sensitivity scales with the physical resources and the computational resources that are used in estimation procedures. Here, we reconcile the physical definition of the relevant resources with the information-theoretical scaling in terms of the query complexity of a quantum network. This leads to a novel and ultimate Heisenberg limit that applies to all conceivable measurement procedures. The second result reveals a close relationship between quantum metrology and the Deuts...
Adaptive Controller Design for Faulty UAVs via Quantum Information Technology
Fuyang Chen; Rui Hou; Gang Tao
2012-01-01
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 refe...
Why genetic information processing could have a quantum basis
Indian Academy of Sciences (India)
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.
Limitations on information theoretically secure quantum homomorphic encryption
Yu, Li; Perez-Delgado, Carlos A.; Joseph F. Fitzsimons
2014-01-01
Homomorphic encryption is a form of encryption which allows computation to be carried out on the encrypted data without the need for decryption. The success of quantum approaches to related tasks in a delegated computation setting has raised the question of whether quantum mechanics may be used to achieve information theoretically secure fully homomorphic encryption. Here we show, via an information localisation argument, that deterministic fully homomorphic encryption necessarily incurs expo...
Information–theoretic implications of quantum causal structures
DEFF Research Database (Denmark)
Chaves, Rafael; Majenz, Christian; Gross, David
2014-01-01
. However, no systematic method is known for treating such problems in a way that generalizes to quantum systems. Here, we describe a general algorithm for computing information–theoretic constraints on the correlations that can arise from a given causal structure, where we allow for quantum systems as well......It is a relatively new insight of classical statistics that empirical data can contain information about causation rather than mere correlation. First algorithms have been proposed that are capable of testing whether a presumed causal relationship is compatible with an observed distribution...... architecture, where a set of few-body quantum systems is distributed among some parties....
Quantum information transfer between topological and spin qubit systems
International Nuclear Information System (INIS)
In this talk I introduce a method to coherently transfer quantum information, and to create entanglement, between topological qubits and conventional spin qubits. The transfer method uses gated control to transfer an electron (spin qubit) between a quantum dot and edge Majorana modes in adjacent topological superconductors. Because of the spin polarization of the Majorana modes, the electron transfer translates spin superposition states into superposition states of the Majorana system, and vice versa. Furthermore, I discuss how a topological superconductor can be used to facilitate long-distance quantum information transfer and entanglement between spatially separated spin qubits.
Probabilistic Teleportation via Quantum Channel with Partial Information
Directory of Open Access Journals (Sweden)
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.
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.
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...
Gesture is more effective than spatial language in encoding spatial information.
So, Wing-Chee; Shum, Priscilla Lok-Chee; Wong, Miranda Kit-Yi
2015-12-01
The present research investigates whether producing gestures with and without speech facilitates route learning at different levels of route complexity and in learners with different levels of spatial skills. It also examines whether the facilitation effect of gesture is stronger than that of spatial language. Adults studied routes with 10, 13, and 16 steps and reconstructed them with sticks, either without rehearsal or after rehearsal by producing gestures with speech, gestures alone, or speech only. For all levels of route complexity and spatial skills, participants who were encouraged to gesture (with or without speech) during rehearsal had the best recall. Additionally, we found that number of steps rehearsed in gesture, but not that rehearsed in speech, predicted the recall accuracy. Thus, gesture is more effective than spatial language in encoding spatial information, and thereby enhancing spatial recall. These results further corroborate the beneficial nature of gesture in processing spatial information. PMID:25671654
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. PMID:19259163
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.
Quantum Theory, Namely the Pure and Reversible Theory of Information
Directory of Open Access Journals (Sweden)
Paolo Perinotti
2012-10-01
Full Text Available After more than a century since its birth, Quantum Theory still eludes our understanding. If asked to describe it, we have to resort to abstract and ad hoc principles about complex Hilbert spaces. How is it possible that a fundamental physical theory cannot be described using the ordinary language of Physics? Here we offer a contribution to the problem from the angle of Quantum Information, providing a short non-technical presentation of a recent derivation of Quantum Theory from information-theoretic principles. The broad picture emerging from the principles is that Quantum Theory is the only standard theory of information that is compatible with the purity and reversibility of physical processes.
Are problems in Quantum Information Theory (un)decidable?
Wolf, Michael M; Perez-Garcia, David
2011-01-01
This note is intended to foster a discussion about the extent to which typical problems arising in quantum information theory are algorithmically decidable (in principle rather than in practice). Various problems in the context of entanglement theory and quantum channels turn out to be decidable via quantifier elimination as long as they admit a compact formulation without quantification over integers. For many asymptotically defined properties which have to hold for all or for one integer N, however, effective procedures seem to be difficult if not impossible to find. We review some of the main tools for (dis)proving decidability and apply them to problems in quantum information theory. We find that questions like "can we overcome fidelity 1/2 w.r.t. a two-qubit singlet state?" easily become undecidable. A closer look at such questions might rule out some of the "single-letter" formulas sought in quantum information theory.
State reduction, information and entropy in quantum measurement processes
International Nuclear Information System (INIS)
Information obtained by a quantum measurement process performed on a physical system and the entropy change of the measured physical system are considered in detail. It is shown that the condition for the amount of information obtained by the quantum measurement process to be represented by the Shannon mutual entropy is that the intrinsic observable of the measured physical system commutes with the operational observable defined by the quantum measurement process. When some measurement outcome is obtained, the decrease of the Shannon entropy of the measured system is compared with that of the von Neumann entropy. Furthermore, a condition is established under which the amount of information that can be established by the quantum measurement process becomes equal to the decrease of the Shannon entropy of the measured physical system. (author)
Projection methods in quantum information science
Cheung, Yuen-lam; Drusvyatskiy, Dmitriy; Li, Chi-Kwong; Pelejo, Diane; Wolkowicz, Henry
2014-01-01
We consider the problem of constructing quantum operations or channels, if they exist, that transform a given set of quantum states $\\{\\rho_1, \\dots, \\rho_k\\}$ to another such set $\\{\\hat\\rho_1, \\dots, \\hat\\rho_k\\}$. In other words, we must find a {\\em completely positive linear map}, if it exists, that maps a given set of density matrices to another given set of density matrices. This problem, in turn, is an instance of a positive semi-definite feasibility problem, but with...
Virtual photonic couplings of quantum nanostructures for quantum information technology
DEFF Research Database (Denmark)
Matsueda, H.; Hvam, JØrn Märcher
2008-01-01
The effectiveness of virtual photons (VPHs) that need neither to conserve energy nor to follow temporal sequences because of the time-energy uncertainty principle, in the electric interactions between detuned non-identical two level atoms having different size and shape is demonstrated in terms of a model of resonance dynamic multipolemultipole interaction (RDMMI), on the basis of microphotoluminescence (?-PL) experiment of a single asymmetric pair of GaAs/AlGaAs quantum dots (QDs). The ranges of the mediating photons in various RDMMI are estimated, proving the significance of RDMMI in the nanometer regime. Furthermore, prospective device concepts based on the RDMMI assistedby the VPHs, having possibility of autonomic routing of signals like a fallingdominoes effect not only throughout spatial extent but also over temporal differences are deiscussed.
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.
Quantum Kolmogorov Complexity and Information-Disturbance Theorem
Directory of Open Access Journals (Sweden)
Takayuki Miyadera
2011-03-01
Full Text Available In this paper, a representation of the information-disturbance theorem based on the quantum Kolmogorov complexity that was defined by P. Vit´anyi has been examined. In the quantum information theory, the information-disturbance relationship, which treats the trade-off relationship between information gain and its caused disturbance, is a fundamental result that is related to Heisenberg’s uncertainty principle. The problem was formulated in a cryptographic setting and the quantitative relationships between complexities have been derived.
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.
The information-theoretic costs of simulating quantum measurements
International Nuclear Information System (INIS)
Winter’s measurement compression theorem stands as one of the most penetrating insights of quantum information theory. In addition to making an original and profound statement about measurement in quantum theory, it also underlies several other general protocols used for entanglement distillation and local purity distillation. The theorem provides for an asymptotic decomposition of any quantum measurement into noise and information. This decomposition leads to an optimal protocol for having a sender simulate many independent instances of a quantum measurement and send the measurement outcomes to a receiver, using as little communication as possible. The protocol assumes that the parties have access to some amount of common randomness, which is a strictly weaker resource than classical communication. In this review, we provide a second look at Winter’s measurement compression theorem, detailing the information processing task, giving examples for understanding it, reviewing Winter’s achievability proof, and detailing a new approach to its single-letter converse theorem. We prove an extension of the theorem to the case in which the sender is not required to receive the outcomes of the simulated measurement. The total cost of common randomness and classical communication can be lower for such a ‘non-feedback’ simulation, and we prove a single-letter converse theorem demonstrating optimality. We then review the Devetak–Winter theorem on classical data compression with quantum side information, providing new proofs of its achievability and converse parts. From there, we outline a new protocol that we call ‘measurement compression with quantum side information,’ announced previously by two of us in our work on triple trade-offs in quantum Shannon theory. This protocol has several applications, including its part in the ‘classically-assisted state redistribution’ protocol, which is the most general protocol on the static side of the quantum information theory tree, and its role in reducing the classical communication cost in a task known as local purity distillation. We also outline a connection between measurement compression with quantum side information and recent work on entropic uncertainty relations in the presence of quantum memory. Finally, we prove a single-letter theorem characterizing measurement compression with quantum side information when the sender is not required to obtain the measurement outcome. (topical review)
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.)
Quantum Coding with Entanglement
Wilde, Mark M
2008-01-01
Quantum error-correcting codes will be the ultimate enabler of a future quantum computing or quantum communication device. This theory forms the cornerstone of practical quantum information theory. We provide several contributions to the theory of quantum error correction--mainly to the theory of ``entanglement-assisted'' quantum error correction where the sender and receiver share entanglement in the form of entangled bits (ebits) before quantum communication begins. Our first contribution is an algorithm for encoding and decoding an entanglement-assisted quantum block code. We then give several formulas that determine the optimal number of ebits for an entanglement-assisted code. The major contribution of this thesis is the development of the theory of entanglement-assisted quantum convolutional coding. A convolutional code is one that has memory and acts on an incoming stream of qubits. We explicitly show how to encode and decode a stream of information qubits with the help of ancilla qubits and ebits. Our...
Distribution of quantum information between an atom and two photons
International Nuclear Information System (INIS)
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.)
Distribution of quantum information between an atom and two photons
Energy Technology Data Exchange (ETDEWEB)
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.)
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...
International Nuclear Information System (INIS)
In an optical encoder, light from an optical fibre input A is encoded by means of the encoding disc and is subsequently collected for transmission via optical fibre B. At some point in the optical path between the fibres A and B, the light is separated into component form by means of a filtering or dispersive system and each colour component is associated with a respective one of the coding channels of the disc. In this way, the significance of each bit of the coded information is represented by a respective colour thereby enabling the components to be re-combined for transmission by the fibre B without loss of information. (author)
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 optimizing the detection efficiency of visible light photon counters (VLPCs), a single-photon detection technology that is also capable of resolving photon number states. We report a record-breaking quantum efficiency of 91 +/- 3% observed with our detection system. Both sources and detectors are independently interesting physical systems worthy of study, but together they promise to enable entire new classes and applications of information based on quantum mechanics.
An improved derivation of minimum information quantum gravity
Mandrin, Pierre A
2014-01-01
It is shown that, in minimum information quantum gravity (MIQG), the action can be derived using a more elegant and straight-forward method than has been used in the first existence proof. Assumptions regarding the quantum boxes, the exact differential of the entropy variation and the role of the boundary can be omitted, and the model structure requirements can be reduced. Moreover, the open problem of the quantum occupation number per box is solved. Thus, the arguments in favour of MIQG become even more stringent. The remaining assumptions are 1. the principle of optimization of the resulting per imposed degrees of freedom, 2. abstract quantum number conservation, 3. the validity of the laws of thermodynamics, 4. identification of a macroscopic parametrization with space-time and 6. unspecific interactions. Even though the assuptions are considerably reduced, all former results remain valid. In particular, no explicite microscopic quantum structure is required in order to recover all well established physics...
Correlation dynamics of quantum fields and black hole information paradox
Hu, B L
1995-01-01
In recent years a statistical mechanics description of particles, fields and spacetime based on the concept of quantum open systems and the influence functional formalism has been introduced. It reproduces in full the established theory of quantum fields in curved spacetime and contains also a microscopic description of their statistical properties, such as noise, fluctuations, decoherence, and dissipation. This new framework allows one to explore the quantum statistical properties of spacetime at the interface between the semiclassical and quantum gravity regimes, as well as important non-equilibrium processes in the early universe and black holes, such as particle creation, entropy generation, galaxy formation, Hawking radiation, gravitational collapse, backreaction and the black hole end-state and information lost issues. Here we give a summary of the theory of correlation dynamics of quantum fields and describe how this conceptual scheme coupled with scaling behavior near the infrared limit can shed light...
Quantum fluctuations from a local-causal information dynamics
Budiyono, Agung
2014-04-01
We shall show that the abstract and formal rules which govern the quantum kinematic and dynamics can be derived from a law of change of the information content or the degree of uncertainty that the system has a certain configuration in a microscopic time scale, which is singled out uniquely, up to a free parameter, by imposing the condition of Macroscopic Classicality and the principle of Locality. Unlike standard quantum mechanics, however, the system always has a definite configuration all the time as in classical mechanics, following a continuous trajectory fluctuating randomly in time. Moreover, we shall show that the average of the relevant physical quantities over the distribution of the configuration is equal to the quantum mechanical average of the corresponding quantum mechanical Hermitian operators over a quantum state.
Hollén, L I; Manser, M B
2007-01-01
In contrast to historical assumptions about the affective nature of animal vocalizations, it is now clear that many vertebrates are capable of producing specific alarm calls in response to different predators, calls that provide information that goes beyond the motivational state of a caller. However, although these calls function referentially, it does not mean that they are devoid of motivational content. Studies on meerkats (Suricata suricatta) directly support this conclusion. The acousti...
Abuturab, Muhammad Rafiq
2015-12-01
A novel asymmetric multiple information encoding using superposition of two beams and Fresnel transform, is proposed. In this scheme, each channel of individual user image is separately phase encoded and then modulated by random phase mask. The three modulated user channels are independently multiplied to produce three complex user channels. They are individually multiplied with three channels of carrier image and Fresnel transformed, and then phase- and amplitude truncated to produce first set of three encrypted channels and three asymmetric keys. Now each channel of secret image is normalized, phase-only masked, and then independently multiplied by corresponding modulated user channels. The three resultant channels are separately multiplied to construct three complex secret channels. Afterward, the three encrypted channels are multiplied with corresponding three complex secret channels and Fresnel transformed, and then phase- and amplitude truncated to obtain second set of three encrypted channels and three asymmetric keys. The wavelengths and propagation distances of two Fresnel transforms, and two asymmetric keys are common keys to all authorized-users, while two individual keys are provided to each authorized-user. The encryption process is implemented digitally while the decryption process can be performed optoelectronically. The proposed method is asymmetric, noniterative and larger multiplexing capacity without any cross-talk noise effects. Owing to the individual user image based method, high robustness against existing attacks can be achieved. Numerical simulation results demonstrate that the proposed method is feasible and efficient.
Quantum-information processing with circuit quantum electrodynamics
International Nuclear Information System (INIS)
We theoretically study single and two-qubit dynamics in the circuit QED architecture. We focus on the current experimental design [Wallraff et al., Nature (London) 431, 162 (2004); Schuster et al., ibid. 445, 515 (2007)] in which superconducting charge qubits are capacitively coupled to a single high-Q superconducting coplanar resonator. In this system, logical gates are realized by driving the resonator with microwave fields. Advantages of this architecture are that it allows for multiqubit gates between non-nearest qubits and for the realization of gates in parallel, opening the possibility of fault-tolerant quantum computation with superconducting circuits. In this paper, we focus on one- and two-qubit gates that do not require moving away from the charge-degeneracy ''sweet spot'. This is advantageous as it helps to increase the qubit dephasing time and does not require modification of the original circuit QED. However, these gates can, in some cases, be slower than those that do not use this constraint. Five types of two-qubit gates are discussed, these include gates based on virtual photons, real excitation of the resonator, and a gate based on the geometric phase. We also point out the importance of selection rules when working at the charge degeneracy point
Orthogonalization of partly unknown quantum states
Jezek, M.; Micuda, M.; Straka, I.; Mikova, M.; Dusek, M.; Fiurasek, J.
2014-01-01
A quantum analog of the fundamental classical NOT gate is a quantum gate that would transform any input qubit state onto an orthogonal state. Intriguingly, this universal NOT gate is forbidden by the laws of quantum physics. This striking phenomenon has far-reaching implications concerning quantum information processing and encoding information about directions and reference frames into quantum states. It also triggers the question under what conditions the preparation of quantum states ortho...
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 and F Verstraete SIMULATION AND DYNAMICS A quantum differentiation of k-SAT instances B Tamir and G Ortiz Classical Ising model test for quantum circuits Joseph Geraci and Daniel A Lidar Exact matrix product solutions in the Heisenberg picture of an open quantum spin chain S R Clark, J Prior, M J Hartmann, D Jaksch and M B Plenio Exact solution of Markovian master equations for quadratic Fermi systems: thermal baths, open XY spin chains and non-equilibrium phase transition Tomaž Prosen and Bojan Žunkovi? Quantum kinetic Ising models R Augusiak, F M Cucchietti, F Haake and M Lewenstein ENTANGLEMENT AND SPECTRAL PROPERTIES Ground states of unfrustrated spin Hamiltonians satisfy an area law Niel de Beaudrap, Tobias J Osborne and Jens Eisert Correlation density matrices for one-dimensional quantum chains based on the density matrix renormalization group W Münder, A Weichselbaum, A Holzner, Jan von Delft and C L Henley The invariant-comb approach and its relation to the balancedness of multipartite entangled states Andreas Osterloh and Jens Siewert Entanglement scaling of fractional quantum Hall states through geometric deformations Andreas M Läuchli, Emil J Bergholtz and Masudul Haque Entanglement versus gap for one-dimensional spin systems Daniel Gottesman and M B Hastings Entanglement spectra of critical and near-critical systems in one dimension F Pollmann and J E Moore Macroscopic bound entanglement in thermal graph states D Cavalcanti, L Aolita, A Ferraro, A García-Saez and A Acín Entanglement at the quantum phase transition in a harmonic lattice Elisabeth Rieper, Janet Anders and Vlatko Vedral Multipartite entanglement and frustration P Facchi, G Florio, U Marzolino, G Parisi and S Pascazio Entropic uncertainty relations—a survey Stephanie Wehner and Andreas Winter Entanglement in a spin system with inverse square statistical interaction D Giuliano, A Sindona, G Falcone, F Plastina and L Amico APPLICATIONS Time-dependent currents of one-dimensional bosons in an optical lattice J Schachenmayer, G Pupillo and A J Daley Implementing quantum gates using t
Theoretical foundations of quantum information processing and communication. Selected topics
International Nuclear Information System (INIS)
Based on eight extensive lectures selected from those given at the renowned Chris Engelbrecht Summer School in Theoretical Physics in South Africa, this text on the theoretical foundations of quantum information processing and communication covers an array of topics, including quantum probabilities, open systems, and non-Markovian dynamics and decoherence. It also addresses quantum information and relativity as well as testing quantum mechanics in high energy physics. Because these self-contained lectures discuss topics not typically covered in advanced undergraduate courses, they are ideal for post-graduate students entering this field of research. Some of the lectures are written at a more introductory level while others are presented as tutorials that survey recent developments and results in various subfields. (orig.)
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...
Towards the quantification of the semantic information encoded in written language
Montemurro, Marcelo A
2009-01-01
Written language is a complex communication signal capable of conveying information encoded in the form of ordered sequences of words. Beyond the local order ruled by grammar, semantic and thematic structures affect long-range patterns in word usage. Here, we show that a direct application of information theory quantifies the relationship between the statistical distribution of words and the semantic content of the text. We show that there is a characteristic scale, roughly around a few thousand words, which establishes the typical size of the most informative segments in written language. Moreover, we find that the words whose contributions to the overall information is larger, are the ones more closely associated with the main subjects and topics of the text. This scenario can be explained by a model of word usage that assumes that words are distributed along the text in domains of a characteristic size where their frequency is higher than elsewhere. Our conclusions are based on the analysis of a large data...
Quantum correlation: Comparison of measures with geometry and mutual information
Xu, Zhenyu; Xiao, Xin; Feng, Mang
2010-01-01
Two measures for quantum correlations were proposed recently from a geometric perspective [Phys. Rev. Lett. 104, 080501 (2010); e-print arXiv:1004.0190]. We prove the the equivalence of the two geometric measures with respect to Bell-diagonal states, and demonstrate the similarities and differences for quantum correlation using the geometry-based measure and mutual-information-based measure. Our study on critical point of sudden transition might be useful for keeping long time quantum correlation under decoherence.
Efficient Classical Simulation of Continuous Variable Quantum Information Processes
Bartlett, S D; Braunstein, S L; Nemoto, K; Bartlett, Stephen D.; Sanders, Barry C.; Braunstein, Samuel L.; Nemoto, Kae
2002-01-01
We obtain sufficient conditions for the efficient simulation of a continuous variable quantum algorithm or process on a classical computer. The resulting theorem is an extension of the Gottesman-Knill theorem to continuous variable quantum information. For a collection of harmonic oscillators, any quantum process that begins with unentangled Gaussian states, performs only transformations generated by Hamiltonians that are quadratic in the canonical operators, and involves only measurements of canonical operators (including finite losses) and suitable operations conditioned on these measurements can be simulated efficiently on a classical computer.
Controllable quantum information network with a superconducting system
International Nuclear Information System (INIS)
We propose a controllable and scalable architecture for quantum information processing using a superconducting system network, which is composed of current-biased Josephson junctions (CBJJs) as tunable couplers between the two superconducting transmission line resonators (TLRs), each coupling to multiple superconducting qubits (SQs). We explicitly demonstrate that the entangled state, the phase gate, and the information transfer between any two selected SQs can be implemented, respectively. Lastly, numerical simulation shows that our scheme is robust against the decoherence of the system. -- Highlights: •An architecture for quantum information processing is proposed. •The quantum information transfer between any two selected SQs is implemented. •This proposal is robust against the decoherence of the system. •This architecture can be fabricated on a chip down to the micrometer scale
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.
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.
Transfer of Gravitational Information through a Quantum Channel
Zhang, Baocheng; Zhan, Ming-sheng
2013-01-01
Gravitational information is incorporated into an atomic state by correlation of the internal and external degrees of freedom of the atom, in the present study of the atomic interferometer. Thus it is difficult to transfer information by using a standard teleportation scheme. In this paper, we propose a novel scheme for the transfer of gravitational information through a quantum channel provided by the entangled atomic state. Significantly, the existence of a quantum channel suppresses phase noise, improving the sensitivity of the atomic interferometer. Thus our proposal provides novel readout mechanism for the interferometer with an improved signal-to-noise ratio.
Byuons, Quantum Information Channel, Consciousness and Universe
Y. A. Baurov
2011-01-01
The physics of consciousness and universal mind is shown on the base of theory of byuons, the theory of â€œlifeâ€™ of special unobservable discrete objectsâ€”byuons from which the surrounding space and the world of elementary particles are formed. An essential distinction of that theory from the modern models in the classical and quantum field theories is that the potentials of physical fields (gravitational, electromagnetic, asf.) gain exactly fixable, measurable values. Basic axioms and some conc...
A few experiments of quantum information processing.
Czech Academy of Sciences Publication Activity Database
?ernoch, Antonín; Soubusta, Jan; Dušek, M.
Košice : Slovak Physical Society, 2006 - (Ková?, J.; Reiffers, M.), s. 35-36 ISBN 80-969124-2-9. [Conference of Slovak and Czech Physicists /15./. Košice (SK), 05.09.2005-08.09.2005] Grant ostatní: EU(XE) IST-2002-506813 Institutional research plan: CEZ:AV0Z10100522 Keywords : quantum multimeter * interference * down-conversion Subject RIV: BH - Optics, Masers, Lasers
Entangling neutral atoms for quantum information processing
Calarco, T.; Briegel, HJ; Jaksch, D.; Cirac, JI; Zoller, P.
2000-01-01
We review recent proposals for performing entanglement manipulation via cold collisions between neutral atoms. State-dependent, time-varying trapping potentials allow one to control the interaction between atoms, so that conditional phase shifts realizing a universal quantum gate can be obtained with high fidelity. We discuss possible physical implementations with existing experimental techniques, for example optical lattices and magnetic micro-traps. © 2000 Taylor and Francis Ltd.
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. This opens the door for the engineering of nano-scaled chemical reactions to the study of temperature dependent biological processes. Finally, a novel technique is introduced that facilitates optical spin detection with nanoscale resolution based on an optical far-field technique; by combining this with a 'quantum Zeno' like effect coherent manipulation of nominally identical spins at a nanoscale is achieved.
Quantum fluctuations from a local-causal information dynamics
Budiyono, Agung
2013-01-01
We shall show that the abstract and formal rules which govern the quantum kinematic and dynamics can be derived from a law of change of the information content or the degree of uncertainty that the system has a certain configuration in a microscopic time scale, which is singled out uniquely, up to a free parameter, by imposing the condition of Macroscopic Classicality and the principle of Locality. Unlike standard quantum mechanics, however, the system always has a definite configuration all ...
Quantum theory from Hamilton's Principle with imperfect information
Hegseth, John
2007-01-01
Many quantization schemes rely on analogs of classical mechanics where the connections with classical mechanics are indirect. In this work I propose a new and direct connection between classical mechanics and quantum mechanics where the quantum mechanical propagator is derived from a variational principle. This principle allows a physical system to have imperfect information, i.e., there is incomplete knowledge of the physical state, and many paths are allowed.
Quantum information, Bell inequalities and the no-signalling principle
Pitalúa-García, Damián
2014-01-01
This PhD thesis contains a general introduction and three main chapters. Chapter 2 investigates Bell inequalities that generalize the CHSH and Braunstein-Caves inequalities. Chapter 3 shows a derivation of an upper bound on the success probability of a class of quantum teleportation protocols, denoted as port-based teleportation, from the no-cloning theorem and the no-signalling principle. Chapter 4 introduces the principle of quantum information causality. Chapter 2 considers the predict...
Insights into classical irreversible computation using quantum information concepts
Groisman, Berry
2008-01-01
The method of using concepts and insight from quantum information theory in order to solve problems in reversible classical computing (introduced in Ref. [1]) have been generalized to irreversible classical computing. The method have been successfully tested on two computational tasks. Several basic logic gates have been analyzed and the nonlocal content of the associate quantum transformations have been calculated. The results provide us with new interesting insight into th...
Quantum-information processing using strongly dipolar coupled nuclear spins
International Nuclear Information System (INIS)
Dipolar coupled homonuclear spins present challenging, yet useful systems for quantum-information processing. In such systems, the eigenbasis of the system Hamiltonian is the appropriate computational basis and coherent control can be achieved by specially designed strongly modulating pulses. In this paper we describe the first experimental implementation of the quantum algorithm for numerical gradient estimation by nuclear magnetic resonance, using the eigenbasis of a four spin system
Photon temporal modes: a complete framework for quantum information science
Brecht, B; Reddy, Dileep V.; Silberhorn, C.; Raymer, M G
2015-01-01
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 effic...
Information trade-offs for optical quantum communication
Wilde, Mark M.; Hayden, Patrick; Guha, Saikat
2012-01-01
Recent work has precisely characterized the achievable trade-offs between three key information processing tasks---classical communication (generation or consumption), quantum communication (generation or consumption), and shared entanglement (distribution or consumption), measured in bits, qubits, and ebits per channel use, respectively. Slices and corner points of this three-dimensional region reduce to well-known protocols for quantum channels. A trade-off coding techniqu...
Quantum information processing using designed defect states in
DEFF Research Database (Denmark)
Pedersen, Jesper; Flindt, Christian; Mortensen, Niels Asger; Jauho, Antti-Pekka
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. A......-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....
Nambu-Goldstone Effective Theory of Information at Quantum Criticality
Dvali, Gia; Franca, Andre; 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 co...
The 50% advanced information rule of the quantum algorithms
Castagnoli, Giuseppe
2009-01-01
The oracle chooses a function out of a known set of functions and gives to the player a black box that, given an argument, evaluates the function. The player should find out a certain character of the function through function evaluation. This is the typical problem addressed by the quantum algorithms. In former theoretical work, we showed that a quantum algorithm requires the number of function evaluations of a classical algorithm that knows in advance 50% of the information that specifies t...
Information and fundamental elements of the structure of quantum theory
Brukner, Caslav; Zeilinger, Anton
2002-01-01
Niels Bohr wrote: "There is no quantum world. There is only an abstract quantum physical description. It is wrong to think that the task of physics is to find out how Nature is. Physics concerns what we can say about Nature." In an analogous way, von Weizsaecker suggested that the notion of the elementary alternative, the "Ur", should play a pivotal role when constructing physics. Both approaches suggest that the concept of information should play an essential role in the fo...
Teleportation of a two-mode entangled coherent state encoded with two-qubit information
Energy Technology Data Exchange (ETDEWEB)
Mishra, Manoj K; Prakash, Hari, E-mail: manoj.qit@gmail.co, E-mail: prakash_hari123@rediffmail.co [Department of physics, University of Allahabad, Allahabad (India)
2010-09-28
We propose a scheme to teleport a two-mode entangled coherent state encoded with two-qubit information, which is better than the two schemes recently proposed by Liao and Kuang (2007 J. Phys. B: At. Mol. Opt. Phys. 40 1183) and by Phien and Nguyen (2008 Phys. Lett. A 372 2825) in that our scheme gives higher value of minimum assured fidelity and minimum average fidelity without using any nonlinear interactions. For involved coherent states | {+-} {alpha}), minimum average fidelity in our case is {>=}0.99 for |{alpha}| {>=} 1.6 (i.e. |{alpha}|{sup 2} {>=} 2.6), while previously proposed schemes referred above report the same for |{alpha}| {>=} 5 (i.e. |{alpha}|{sup 2} {>=} 25). Since it is very challenging to produce superposed coherent states of high coherent amplitude (|{alpha}|), our teleportation scheme is at the reach of modern technology.
Amselem, Elias
2012-01-01
The rapidly developing interdisciplinary field of quantum information, which merges quantum and information science, studies non-classical aspects of quantum systems. These studies are motivated by the promise that the non-classicality can be used to solve tasks more efficiently than classical methods would allow. In many quantum informational studies, non-classical behaviour is attributed to the notion of entanglement. In this thesis we use photons to experimentally investigate fundamental q...
Nambu-Goldstone effective theory of information at quantum criticality
Dvali, Gia; Franca, Andre; Gomez, Cesar; Wintergerst, Nico
2015-12-01
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 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 information-storage also increases with N , whereas the scrambling time in the over-critical regime is controlled by the Lyapunov exponent and scales logarithmically with N . This connection reveals that the origin of black hole information storage lies in the quantum criticality of the graviton Bose-gas, and that much simpler systems that can be manufactured in table-top experiments can exhibit very similar information-processing dynamics.
Quantum Private Information Retrieval with Sublinear Communication Complexity
Gall, François Le
2011-01-01
This note presents a quantum protocol for private information retrieval, in the single-server case and with information-theoretical privacy, that has O(\\sqrt{n})-qubit communication complexity, where n denotes the size of the database. In comparison, it is known that any classical protocol must use \\Omega(n) bits of communication in this setting.
Energy Technology Data Exchange (ETDEWEB)
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.
Multi-user multiplexed scheme for decoding modulated-encoded sequential information
Mosso, Fabian; Tebaldi, Myrian; Barrera, John Fredy; Bolognini, Néstor; Torroba, Roberto
2011-08-01
Encrypting procedures with multiplexed operations exhibit an inherent noise. We presented options to avoid background noise arising from the non-decoded images. We have a coding mask corresponding to each single input object, thus resulting in a static decrypting mechanism. Besides, if we manage the spatial destination of each decoded output, then we avoid the noise superposition. In those schemes, the displaying output order was irrelevant. However, when we face a sequence of events including multi-users, we need to develop another strategy. We present a multi-user encrypting scheme with a single encoding mask that removes the background noise, also showing the decrypted data in a prescribed sequence. The multiplexing scheme is based on the 4f double random phase encryption architecture and a theta modulation method, which consists in superposing each encrypted information with a determined sinusoidal grating. Afterwards we proceed to the completely encoded data multiplexing. In a multi-user scheme, we employ different encrypting masks in the 4f optical setup for each user, and the same mask is employed for the user sequence. We store the encrypted data in the single medium. After a Fourier transform operation and an appropriate filtering procedure, we reach the sequence of isolated encrypted spots corresponding to the right user. With the aid of the pertaining decoding mask, the user can decrypt the sequence. We avoid the noise by the appropriate choice of the modulating gratings pitch as to elude the overlapping of spots at the Fourier plane, which is the cause of information degradation.
Quantum information processing with mesoscopic photonic states
DEFF Research Database (Denmark)
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 be extracted by local measurements due to the limitations dictated by the Heisenberg's uncertainty principle. We experimentally characterize the evolution of the discord of EPR states and mixtures of coherent states in an attenuating channel. We demonstrate that the discord can grow by local dissipation 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 commercially available equipment. However the performance in terms of achievable distance is highly limited. We first experimentally demonstrate that the boundaries of coherent states can be surpassed using modulated entangled states. A simplied experiment is also presented where the modulation of a single-mode squeezed state gives a very reconciliation efficiency robust protocol. All of this is done to achieve higher key rates at the current limits of the coherent state protocols and to extend the boundaries for tolerable channel noise, loss and reconciliation efficiency. As any degree of squeezing improves the performance the extra effort of implementing squeezing in commercial devices is overshadowed by the extended range and increased security margin achieved. Still using the same experimental setup, but now in the context of polarization we have experimentally bridged the gab between the states with very low photon numbers and the states where one of Stokes parameters is highly excited. To describe the polarization of these state we introduce several new polarization measures which take into account the covariance of the polarization and resolve the polarization manifolds. We experimentally demonstrate states for which the polarization is hidden in the unresolved measures and as well a state which is unpolarized for both first order polarization measures. Finally we illustrate the polarization with SU2 Wigner functions to give a richer picture, not only of the degree of polarization but also its distribution among the manifolds.
PT -symmetric Hamiltonians and their application in quantum information
Croke, Sarah
2015-05-01
We discuss the prospect of PT -symmetric Hamiltonians finding applications in quantum information science, and conclude that such evolution is unlikely to provide any benefit over existing techniques. Although it has been known for some time that PT -symmetric quantum theory, when viewed as a unitary theory, is exactly equivalent to standard quantum mechanics, proposals continue to be put forward for schemes in which PT -symmetric quantum theory can outperform standard quantum theory. The most recent of these is the suggestion to use PT -symmetric Hamiltonians to perform an exponentially fast database search, a task known to be impossible with a quantum computer. Further, such a scheme has been shown to apparently produce effects in conflict with fundamental information-theoretic principles, such as the impossibility of superluminal information transfer, and the invariance of entanglement under local operations. In this paper we propose three inequivalent experimental implementations of PT -symmetric Hamiltonians, with careful attention to the resources required to realize each such evolution. Such an operational approach allows us to resolve these apparent conflicts, and evaluate fully schemes proposed in the literature for faster time evolution and state discrimination.
Statistical properties of quantum entanglement and information entropy
International Nuclear Information System (INIS)
Key words: entropy, entanglement, atom-field interaction, trapped ions, cold atoms, information entropy. Objects of research: Pure state entanglement, entropy squeezing mazer. The aim of the work: Study of the new entanglement features and new measures for both pure-state and mixed state of particle-field interaction. Also, the impact of the information entropy on the quantum information theory. Method of investigation: Methods of theoretical physics and applied mathematics (statistical physics, quantum optics) are used. Results obtained and their novelty are: All the results of the dissertation are new and many new features have been discovered. Particularly: the most general case of the pure state entanglement has been introduced. Although various special aspects of the quantum entropy have been investigated previously, the general features of the dynamics, when a multi-level system and a common environment are considered, have not been treated before and our work therefore, field a gap in the literature. Specifically: 1) A new entanglement measure due to quantum mutual entropy (mixed-state entanglement) we called it DEM, has been introduced, 2) A new treatment of the atomic information entropy in higher level systems has been presented. The problem has been completely solved in the case of three-level system, 3) A new solution of the interaction between the ultra cold atoms and cavity field has been discovered, 4) Some new models of the atom-field interaction have been adopted. Practical value: The subject carries out theoretic character. Application region: Results can be used in quantum computer developments. Also, the presented results can be used for further developments of the quantum information and quantum communications. (author)
The encoding of fine spatial information in salamander retinal ganglion cells
Directory of Open Access Journals (Sweden)
Frederick Soo
2010-03-01
Full Text Available Classical models of retinal ganglion cell signaling assume that ganglion cell receptive fields are smoothly varying, approximately Gaussian in profile and arranged in a regular array. This model predicts that the receptive fields of neighboring ganglion cells will be highly overlapping and that the cells will convey largely redundant visual information. In whole-cell voltage clamp recordings from salamander retina, however, the receptive fields of ganglion cells were irregular on a fine scale and non-Gaussian, and the information conveyed by neighboring ganglion cells about a flashed spot stimulus was nearly independent. Large groups of ganglion cells encoded significantly more information than expected from the classical model even when the approximate sizes and positions of the cells’ receptive fields were taken into account. The discrepancy was only explained by including the receptive field irregularities in the model. This result suggests that irregularities in spatial receptive field profiles are a positive design feature rather than an unavoidable defect and that subsequent brain circuits can benefit from recognizing such irregularities when they interpret retinal spike trains.
Quantum nonlocality and applications in quantum-information processing of hybrid entangled states
Chen, Z B; Zhang, Y D; Chen, Zeng-Bing; Hou, Guang; Zhang, Yong-De
2002-01-01
The hybrid entangled states generated, e.g., in a trapped-ion or atom-cavity system, have exactly one ebit of entanglement, but are not maximally entangled. We demonstrate this by showing that they violate, but in general do not maximally violate, Bell's inequality due to Clauser, Horne, Shimony and Holt. These states are interesting in that they exhibit the entanglement between two distinct degrees of freedom (one is discrete and another is continuous). We then demonstrate these entangled states as a valuable resource in quantum information processing including quantum teleportation, entanglement swapping and quantum computation with "parity qubits". Our work establishes an interesting link between quantum information protocols of discrete and continuous variables.
A Matter of Principle: The Principles of Quantum Theory, Dirac's Equation, and Quantum Information
Plotnitsky, Arkady
2015-10-01
This article is concerned with the role of fundamental principles in theoretical physics, especially quantum theory. The fundamental principles of relativity will be addressed as well, in view of their role in quantum electrodynamics and quantum field theory, specifically Dirac's work, which, in particular Dirac's derivation of his relativistic equation of the electron from the principles of relativity and quantum theory, is the main focus of this article. I shall also consider Heisenberg's earlier work leading him to the discovery of quantum mechanics, which inspired Dirac's work. I argue that Heisenberg's and Dirac's work was guided by their adherence to and their confidence in the fundamental principles of quantum theory. The final section of the article discusses the recent work by D'Ariano and coworkers on the principles of quantum information theory, which extend quantum theory and its principles in a new direction. This extension enabled them to offer a new derivation of Dirac's equations from these principles alone, without using the principles of relativity.
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.…