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  Subjects -> PHYSICS (Total: 734 journals)
    - ELECTRICITY AND MAGNETISM (7 journals)
    - MECHANICS (18 journals)
    - NUCLEAR PHYSICS (44 journals)
    - OPTICS (84 journals)
    - PHYSICS (536 journals)
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PHYSICS (536 journals)            First | 1 2 3 4 5 6 | Last

International Journal of Quantum Information     Hybrid Journal  
International Journal of Reacting Systems     Open Access  
International Journal of Self-Propagating High-Temperature Synthesis     Hybrid Journal   (Followers: 2)
International Journal of Solids and Structures     Hybrid Journal   (Followers: 9)
International Journal of Surface Science and Engineering     Hybrid Journal   (Followers: 7)
International Journal of Theoretical and Applied Multiscale Mechanics     Hybrid Journal   (Followers: 2)
International Journal of Theoretical Physics     Hybrid Journal   (Followers: 2)
International Journal of Thermal Sciences     Hybrid Journal   (Followers: 4)
International Materials Reviews     Hybrid Journal   (Followers: 11)
Inverse Problems     Hybrid Journal   (Followers: 4)
IOP Conference Series: Materials Science and Engineering     Open Access   (Followers: 3)
Ironmaking & Steelmaking     Hybrid Journal   (Followers: 2)
ISRN Astronomy and Astrophysics     Open Access   (Followers: 11)
Izvestiya Atmospheric and Oceanic Physics     Hybrid Journal   (Followers: 3)
Izvestiya, Physics of the Solid Earth     Hybrid Journal   (Followers: 4)
Japanese Journal of Applied Physics     Full-text available via subscription   (Followers: 3)
JCP : BioChemical Physics     Hybrid Journal  
JETP Letters     Hybrid Journal   (Followers: 3)
Journal of Adhesion Science and Technology     Hybrid Journal   (Followers: 6)
Journal of Advances in Physics     Open Access  
Journal of Applied Mathematics and Mechanics     Full-text available via subscription   (Followers: 5)
Journal of Applied Mechanics and Technical Physics     Hybrid Journal   (Followers: 3)
Journal of Applied Physics     Hybrid Journal   (Followers: 138)
Journal of Applied Remote Sensing     Full-text available via subscription   (Followers: 9)
Journal of Applied Spectroscopy     Hybrid Journal   (Followers: 7)
Journal of Astrophysics     Open Access  
Journal of Astrophysics and Astronomy     Open Access   (Followers: 10)
Journal of Basic and Applied Physics     Open Access   (Followers: 1)
Journal of Building Physics     Hybrid Journal   (Followers: 1)
Journal of Chromatographic Science     Hybrid Journal   (Followers: 20)
Journal of Complex Networks     Hybrid Journal  
Journal of Composite Materials     Hybrid Journal   (Followers: 33)
Journal of Computational Methods in Physics     Open Access  
Journal of Computational Physics     Hybrid Journal   (Followers: 133)
Journal of Contemporary Physics (Armenian Academy of Sciences)     Hybrid Journal   (Followers: 1)
Journal of Dynamic Systems, Measurement, and Control     Full-text available via subscription   (Followers: 7)
Journal of Elasticity     Hybrid Journal   (Followers: 2)
Journal of Electrical Bioimpedance     Full-text available via subscription   (Followers: 2)
Journal of Electron Spectroscopy and Related Phenomena     Hybrid Journal  
Journal of Electronic Materials     Hybrid Journal   (Followers: 5)
Journal of Electronics Cooling and Thermal Control     Open Access   (Followers: 1)
Journal of Engineering Materials and Technology     Full-text available via subscription   (Followers: 13)
Journal of Engineering Physics and Thermophysics     Hybrid Journal  
Journal of Experimental and Theoretical Physics     Hybrid Journal   (Followers: 3)
Journal of Fire Sciences     Hybrid Journal   (Followers: 1)
Journal of Geometry and Physics     Full-text available via subscription  
Journal of Geophysical Research : Space Physics     Full-text available via subscription   (Followers: 13)
Journal of Gravity     Open Access  
Journal of High Energy Physics     Hybrid Journal   (Followers: 2)
Journal of Hyperspectral Remote Sensing     Open Access  
Journal of Information Display     Hybrid Journal  
Journal of Intelligent Material Systems and Structures     Hybrid Journal   (Followers: 3)
Journal of Lightwave Technology     Hybrid Journal   (Followers: 6)
Journal of Low Frequency Noise, Vibration and Active Control     Full-text available via subscription   (Followers: 6)
Journal of Luminescence     Hybrid Journal   (Followers: 2)
Journal of Magnetic Resonance     Hybrid Journal   (Followers: 4)
Journal of Materials Engineering and Performance     Hybrid Journal   (Followers: 6)
Journal of Materials Science     Hybrid Journal   (Followers: 16)
Journal of Materials Science : Materials in Electronics     Hybrid Journal   (Followers: 4)
Journal of Materials Science : Materials in Medicine     Hybrid Journal   (Followers: 6)
Journal of Mathematical Fluid Mechanics     Hybrid Journal   (Followers: 4)
Journal of Mathematical Physics     Hybrid Journal   (Followers: 3)
Journal of Medical Ultrasonics     Hybrid Journal   (Followers: 2)
Journal of Micro/Nanolithography MEMS and MOEMS     Hybrid Journal   (Followers: 1)
Journal of Modern Physics     Open Access   (Followers: 2)
Journal of Molecular Spectroscopy     Hybrid Journal   (Followers: 6)
Journal of Motor Behavior     Hybrid Journal   (Followers: 5)
Journal of Multiscale Modeling     Hybrid Journal  
Journal of Nanophotonics     Full-text available via subscription   (Followers: 4)
Journal of Neutron Research     Hybrid Journal  
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 2)
Journal of Nonlinear Dynamics     Open Access  
Journal of Nonlinear Mathematical Physics     Hybrid Journal   (Followers: 1)
Journal of Optics     Hybrid Journal   (Followers: 2)
Journal of Physical and Chemical Reference Data     Hybrid Journal   (Followers: 2)
Journal of Physical Chemistry B     Full-text available via subscription   (Followers: 25)
Journal of Physical Chemistry C     Full-text available via subscription   (Followers: 20)
Journal of Physical Oceanography     Full-text available via subscription   (Followers: 8)
Journal of Physical Organic Chemistry     Hybrid Journal   (Followers: 7)
Journal of Physics A : Mathematical and Theoretical     Hybrid Journal   (Followers: 3)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 4)
Journal of Physics D : Applied Physics     Hybrid Journal   (Followers: 11)
Journal of Physics: Condensed Matter     Hybrid Journal   (Followers: 7)
Journal of Physics: Conference Series     Open Access   (Followers: 3)
Journal of Plasma Physics     Hybrid Journal   (Followers: 4)
Journal of Polymer Science Part B: Polymer Physics     Hybrid Journal   (Followers: 22)
Journal of Porous Materials     Hybrid Journal   (Followers: 3)
Journal of Porphyrins and Phthalocyanines     Hybrid Journal   (Followers: 2)
Journal of Quantitative Spectroscopy and Radiative Transfer     Hybrid Journal  
Journal of Reinforced Plastics and Composites     Hybrid Journal   (Followers: 4)
Journal of Research in Physics     Open Access  
Journal of Rheology     Full-text available via subscription   (Followers: 3)
Journal of Romance Studies     Full-text available via subscription   (Followers: 2)
Journal of Sandwich Structures and Materials     Hybrid Journal   (Followers: 1)
Journal of Scientific Research     Open Access  
Journal of Semiconductors     Full-text available via subscription   (Followers: 2)
Journal of Sensors     Open Access   (Followers: 7)
Journal of Sol-Gel Science and Technology     Hybrid Journal   (Followers: 2)
Journal of Solid State Physics     Open Access  
Journal of Spectroscopy     Full-text available via subscription  

  First | 1 2 3 4 5 6 | Last

Journal Cover International Journal of Quantum Information
   Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0219-7499 - ISSN (Online) 1793-6918
     Published by World Scientific Homepage  [114 journals]   [SJR: 0.588]   [H-I: 18]
  • Self-contained n-qubit quantum refrigerator
    • Authors: sales@wspc.com.sg (Mehdi Ghanavati)
      Abstract: International Journal of Quantum Information, Ahead of Print. Brunner et al. [Phys. Rev. E85 (2012) 05111] have claimed that, "essentially only the smallest machines can approach Carnot efficiency". We have verified this claim by raising self-contained four-qubit quantum refrigerator, and we have shown that according to concepts of virtual qubit, it can reach the maximum efficiency in other words Carnot efficiency. But its efficiency, such as self-contained three-qubit quantum refrigerator is not universal. We also investigated a special case of self-contained four-qubit quantum refrigerator, in other words self-contained four-qubit quantum refrigerator with two hot baths in the same temperature. We demonstrated that its efficiency has the form as efficiency of a self-contained three-qubit quantum refrigerator. In other words, from the perspective of efficiency, this particular model is equivalent to self-contained three-qubit quantum refrigerator. We also demonstrated the efficiency of this particular model in the Carnot limit that is independent from details of system model, but only depends on the environmental temperatures. Also, we raised a system that consists of n-qubit which acts as a refrigerator. According to self-contained four-qubit quantum refrigerator, we also investigated a special case of self-contained n-qubit quantum refrigerator — a self-contained n-qubit quantum refrigerator with (n - 2) baths in the same temperature. We considered the three different special situations of the n-qubit refrigerator and demonstrated their efficiency in three different situations which has the form as efficiency of self-contained three-qubit quantum refrigerator. In this special situations, (n - 2) qubits are in thermal contact with isothermal heat baths.
      PubDate: Fri, 06 Jun 2014 07:22:11 GMT
       
  • Environment-induced mixing processes in quantum walks
    • Authors: sales@wspc.com.sg (Lauri Lehman)
      Abstract: International Journal of Quantum Information, Ahead of Print. The mixing process of discrete-time quantum walks on one-dimensional lattices is revisited in a setting where the walker is coupled to an environment, and the time evolution of the walker and the environment is unitary. The mixing process is found to be incomplete, in the sense that the walker does not approach the maximally mixed state indefinitely, but the distance to the maximally mixed state saturates to some finite value depending on the size of the environment. The quantum speedup of mixing time is investigated numerically as the size of the environment decreases from infinity to a finite value. The mixing process in this unitary setting can be explained by interpreting it as an equilibration process in a closed quantum system, where subsystems can exhibit equilibration even when the entropy of the total system remains zero.
      PubDate: Fri, 06 Jun 2014 07:22:10 GMT
       
  • New quantum MDS codes
    • Authors: sales@wspc.com.sg (Guanghui Zhang)
      Abstract: International Journal of Quantum Information, Ahead of Print. In this paper, we construct two classes of new quantum maximum-distance-separable (MDS) codes with parameters , where q is an odd prime power with q ≡ 3 (mod 4) and ; [[8(q - 1),8(q - 1) - 2d + 2,d]]q, where q is an odd prime power with the form q = 8t - 1 (t is an even positive integer) and . Comparing the parameters with all known quantum MDS codes, the quantum MDS codes exhibited here have minimum distances bigger than the ones available in the literature.
      PubDate: Fri, 06 Jun 2014 07:22:05 GMT
       
  • Entanglement-assisted quantum codes constructed from primitive quaternary
           BCH codes
    • Authors: sales@wspc.com.sg (Liang-Dong Lü)
      Abstract: International Journal of Quantum Information, Ahead of Print. The entanglement-assisted (EA) formalism generalizes the standard stabilizer formalism. All quaternary linear codes can be transformed into entanglement-assisted quantum error correcting codes (EAQECCs) under this formalism. In this work, we discuss construction of EAQECCs from Hermitian non-dual containing primitive Bose–Chaudhuri–Hocquenghem (BCH) codes over the Galois field GF(4). By a careful analysis of the cyclotomic cosets contained in the defining set of a given BCH code, we can determine the optimal number of ebits that needed for constructing EAQECC from this BCH code, rather than calculate the optimal number of ebits from its parity check matrix, and derive a formula for the dimension of this BCH code. These results make it possible to specify parameters of the obtained EAQECCs in terms of the design parameters of BCH codes.
      PubDate: Fri, 06 Jun 2014 07:22:04 GMT
       
  • Limitations on quantum dimensionality reduction
    • Authors: sales@wspc.com.sg (Aram W. Harrow)
      Abstract: International Journal of Quantum Information, Ahead of Print. The Johnson–Lindenstrauss Lemma is a classic result which implies that any set of n real vectors can be compressed to O(logn) dimensions while only distorting pairwise Euclidean distances by a constant factor. Here we consider potential extensions of this result to the compression of quantum states. We show that, by contrast with the classical case, there does not exist any distribution over quantum channels that significantly reduces the dimension of quantum states while preserving the 2-norm distance with high probability. We discuss two tasks for which the 2-norm distance is indeed the correct figure of merit. In the case of the trace norm, we show that the dimension of low-rank mixed states can be reduced by up to a square root, but that essentially no dimensionality reduction is possible for highly mixed states.
      PubDate: Wed, 04 Jun 2014 03:58:56 GMT
       
  • Encoding secret information in measurement settings
    • Authors: sales@wspc.com.sg (Syed M. Assad)
      Abstract: International Journal of Quantum Information, Ahead of Print. Secure communication protocols are often formulated in a paradigm where the message is encoded in measurement outcomes. In this work, we propose a rather unexplored framework in which the message is encoded in measurement settings rather than in their outcomes. In particular, we study two different variants of such secure communication protocols in which the message alphabet corresponds to measurement settings of mutually unbiased bases.
      PubDate: Wed, 04 Jun 2014 03:58:49 GMT
       
  • On the construction of optimal asymmetric quantum codes
    • Authors: sales@wspc.com.sg (Liqi Wang)
      Abstract: International Journal of Quantum Information, Ahead of Print. Constacyclic codes are important classes of linear codes that have been applied to the construction of quantum codes. Six new families of asymmetric quantum codes derived from constacyclic codes are constructed in this paper. Moreover, the constructed asymmetric quantum codes are optimal and different from the codes available in the literature.
      PubDate: Wed, 04 Jun 2014 03:58:43 GMT
       
  • Editorial
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print.
      PubDate: Tue, 20 May 2014 08:33:26 GMT
       
  • Quantum state sharing of arbitrary known multi-qubit and multi-qudit
           states
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. In this paper, we propose a new version of quantum state sharing (QSTS) scheme of an arbitrary multi-qubit state. Then we extend the scheme to a general form of sharing an arbitrary multi-qudit state in the high-dimensional system. The schemes consider the most general case where an arbitrary quantum state can be shared among an arbitrary number of agents in a symmetric way that any agent can recover the state with the help of the others. Compared with a traditional QSTS scheme sharing an unknown state, our schemes are more efficient since the dealer only needs to perform a simpler measurement and consume less classical communication costs.
      PubDate: Tue, 20 May 2014 08:33:26 GMT
       
  • Spatio–temporal entanglement of twin photons: An intuitive picture
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. We draw an intuitive picture of the spatio–temporal properties of the entangled state of twin photons, where they are described as classical wave-packets. This picture predicts a precise relation between their temporal and transverse spatial separations at the crystal output. The space-time coupling described by classical arguments turns out to determine in a precise way the spatio–temporal structure of the quantum entanglement, analyzed by means of the biphotonic correlation and of the Schmidt dimensionality of the entanglement.
      PubDate: Wed, 07 May 2014 03:28:14 GMT
       
  • Generation of sub-Poissonian non-Gaussian states from multimode twin beams
           by photon-number-resolving detectors
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. We generate sub-Poissonian non-Gaussian conditional states from pulsed multimode twin beams (TWBs) by measuring with photon-number-resolving detectors. Links among twin-beam non-classicality and the properties of the conditional states are discussed.
      PubDate: Wed, 07 May 2014 03:28:11 GMT
       
  • Deterministic tripartite sharing of eight restricted sets of single-qubit
           operations with two Bell states or a GHZ state
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. Two tripartite schemes with a pair of Bell states and a Green berger–Horne–Zeilinger (GHZ) state respectively have been proposed recently by Zhang and Cheung for remotely sharing two restricted sets of operations in a deterministic manner [J. Phys. B 44 (2011) 165508]. In this paper, we generalize the schemes with the same quantum channels so that another six restricted sets of operations can be shared deterministically, too. Features about scheme security, sharer symmetry, fulfillment determinacy and experimental feasibility are discussed and revealed. Moreover, some comparisons are also made from the aspects of quantum and classical resource consumption, necessary operation complexity and efficiency.
      PubDate: Wed, 07 May 2014 03:28:11 GMT
       
  • Dynamical decoupling of random telegraph noise in a two-qubit gate
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. Controlling the dynamics of entanglement and preventing its disappearance are central requisites for any implementation of quantum information processing. Solid state qubits are frequently affected by random telegraph noise due to bistable impurities of different nature coupled to the device. In this paper, we investigate the possibility to achieve an efficient universal two-qubit gate in the presence of random telegraph noise by periodic dynamical decoupling. We find an analytic form of the gate error as a function of the number of applied pulses valid when the gate time is much shorter then the telegraphic process correlation time. The analysis is further supplemented by exact numerical results demonstrating the feasibility of a highly-efficient universal two-qubit gate.
      PubDate: Wed, 07 May 2014 03:28:07 GMT
       
  • About the use of fidelity in continuous variable systems
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. We present examples of continuous variable (CV) states having high fidelity to a given target, say F > 0.9 or F > 0.99, and still showing striking differences in their physical properties, including classical and quantum states within the set, separable and entangled ones, or nearly Gaussian and strongly non-Gaussian ones. We also show that the phenomenon persists also when one imposes additional constraints on the energy or the squeezing fraction of the states, thus generally questioning the use of fidelity to assess properties of CV systems without a tomographic set of additional constraints.
      PubDate: Wed, 07 May 2014 03:28:07 GMT
       
  • Generalized three-party sharing of operations on remote single qutrit
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. Two three-party schemes are put forward for sharing quantum operations on a remote qutrit with local operation and classical communication as well as shared entanglements. The first scheme uses a two-qutrit and three-qutrit non-maximally entangled states as quantum channels, while the second replaces the three-qutrit non-maximally entangled state with a two-qutrit. Both schemes are treated and compared from the four aspects of quantum and classical resource consumption, necessary-operation complexity, success probability and efficiency. It is found that the latter is overall more optimal than the former as far as a restricted set of operations is concerned. In addition, comparisons of both schemes with other four relevant ones are also made to show their two features, including degree generalization and channel-state generalization. Furthermore, some concrete discussions on both schemes are made to expose their important features of security, symmetry and experimental feasibility. Particularly, it is revealed that the success probabilities and intrinsic efficiencies in both schemes are completely determined by the shared entanglement.
      PubDate: Wed, 07 May 2014 03:28:04 GMT
       
  • Inequalities detecting entanglement for arbitrary bipartite systems
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. Based on the generators of SU(n) we present inequalities for detecting quantum entanglement for 2 ⊗ d and M ⊗ N systems. These inequalities provide a sufficient condition of entanglement for bipartite mixed states and give rise to an experimental way of entanglement detection.
      PubDate: Wed, 07 May 2014 03:28:03 GMT
       
  • Bracket states for communication protocols with coherent states
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. We present the generation and characterization of the class of bracket states, namely phase-sensitive mixtures of coherent states exhibiting symmetry properties in the phase-space description. A bracket state can be seen as the statistical ensemble arriving at a receiver in a typical coherent-state-based communication channel. We show that when a bracket state is mixed at a beam splitter with a local oscillator, both the emerging beams exhibit a Fano factor larger than 1 and dependent on the relative phase between the input state and the local oscillator. We discuss the possibility to exploit this dependence to monitor the phase difference for the enhancement of the performances of a simple communication scheme based on direct detection. Our experimental setup involves linear optical elements and a pair of photon-number-resolving detectors operated in the mesoscopic photon-number domain.
      PubDate: Wed, 07 May 2014 03:28:03 GMT
       
  • Measurement facility for the evaluation of the backscattering in fiber:
           Realization of an OTDR operating at single photon level
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. This paper presents the INRIM effort related to the implementation of an optical time domain reflectometer (OTDR) that exploits backscattered light to test an optical fiber operating at single photon level, using two different avalanche photodetectors: a free-running Id220 and a gated Id201. Our tests show that the use of the Id220-based OTDR could be very helpful for QKD application, since it allows testing much longer portions of an optical link. This represents a great advantage for QKD systems, where single components and connections are often embedded in a non-separable optical system.
      PubDate: Fri, 02 May 2014 05:54:27 GMT
       
  • Quantum optical implementation of open quantum walks
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. A quantum optical implementation of the recently proposed open quantum walks (OQWs) is suggested. In the presented quantum optical scheme a two level atom plays the role of the "walker" and the Fock states of the cavity mode correspond to the lattice sites of the OQW. Using the small unitary rotations approach the effective dynamics of the system is shown to be an OQW. The presented scheme allows for a simple physical implementation of the OQW formalism, but it can be extended to create more diverse OQWs.
      PubDate: Fri, 02 May 2014 05:54:23 GMT
       
  • Detecting the work statistics through Ramsey-like interferometry
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. Out-of-equilibrium statistical mechanics is attracting considerable interest due to the recent advances in the control and manipulations of systems at the quantum level. Recently, an interferometric scheme for the detection of the characteristic function of the work distribution following a time-dependent process has been proposed [L. Mazzola et al., Phys. Rev. Lett.110 (2013) 230602]. There, it was demonstrated that the work statistics of a quantum system undergoing a process can be reconstructed by effectively mapping the characteristic function of work on the state of an ancillary qubit. Here, we expand that work in two important directions. We first apply the protocol to an interesting specific physical example consisting of a superconducting qubit dispersively coupled to the field of a microwave resonator, thus enlarging the class of situations for which our scheme would be key in the task highlighted above. We then account for the interaction of the system with an additional one (which might embody an environment), and generalize the protocol accordingly.
      PubDate: Fri, 02 May 2014 05:54:22 GMT
       
  • Using solitons for manipulating qubits
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. Many proposals for quantum devices are based on qubits that are physically realized by the spin magnetic moment of some quantum object. In this case, one of the most often adopted strategies for manipulating qubits is that of using external magnetic fields. However, selectively applying a field just to one qubit may be a practically unattainable goal, as it is, for instance, in most solid-state based setups. In this work, we present a proposal for using nonlinear excitations of solitonic type to accomplish the above task. Our scheme entails the generation of a dynamical soliton in a classical spin-chain which is locally coupled with one qubit: as the soliton runs through, the qubit behaves, due to its interaction with the chain, as if it were subject to a magnetic field with a time dependence that follows from the soliton's features. We here present results for the time evolution of the qubit density-matrix induced by the overall dynamics of the above scheme.
      PubDate: Fri, 02 May 2014 05:54:21 GMT
       
  • Hidden entanglement, system-environment information flow and
           non-Markovianity
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. It is known that entanglement dynamics of two non-interacting qubits, locally subjected to classical environments, may exhibit revivals. A simple explanation of this phenomenon may be provided by using the concept of hidden entanglement (HE), which signals the presence of entanglement that may be recovered without the help of nonlocal operations. Here we discuss the link between HE and the (non-Markovian) flow of classical information between the system and the environment.
      PubDate: Fri, 02 May 2014 05:54:20 GMT
       
  • Entanglement and algebraic independence in fermion systems
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. In the case of systems composed of identical particles, a typical instance in quantum statistical mechanics, the standard approach to separability and entanglement ought to be reformulated and rephrased in terms of correlations between operators from subalgebras localized in spatially disjoint regions. While this algebraic approach is straightforward for bosons, in the case of fermions it is subtler since one has to distinguish between micro-causality, that is the anti-commutativity of the basic creation and annihilation operators, and algebraic independence that is the commutativity of local observables. We argue that a consistent algebraic formulation of separability and entanglement should be compatible with micro-causality rather than with algebraic independence.
      PubDate: Tue, 29 Apr 2014 02:27:15 GMT
       
  • Effective dephasing for a qubit interacting with a transverse classical
           field
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. We address the dynamics of a qubit interacting with a quasi static random classical field having both a longitudinal and a transverse component and described by a Gaussian stochastic process. In particular, we analyze in detail the conditions under which the dynamics may be effectively approximated by a unitary operation or a pure dephasing without relaxation.
      PubDate: Tue, 29 Apr 2014 02:27:11 GMT
       
  • Probing qubit by qubit: Properties of the POVM and the
           information/disturbance tradeoff
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. We address the class of positive operator-valued measures (POVMs) for qubit systems that are obtained by coupling the signal qubit with a probe qubit and then performing a projective measurement on the sole probe system. These POVMs, which represent the simplest class of qubit POVMs, depends on 3 + 3 + 2 = 8 free parameters describing the initial preparation of the probe qubit, the Cartan representative of the unitary coupling, and the projective measurement at the output, respectively. We analyze in some detail the properties of the POVM matrix elements, and investigate their values for given ranges of the free parameters. We also analyze in detail the tradeoff between information and disturbance for different ranges of the free parameters, showing, among other things, that (i) typical values of the tradeoff are close to optimality and (ii) even using a maximally mixed probe one may achieve optimal tradeoff.
      PubDate: Thu, 24 Apr 2014 06:27:33 GMT
       
  • Quantum limits to estimation of photon deformation
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. We address potential deviations of radiation field from the bosonic behavior and employ local quantum estimation theory to evaluate the ultimate bounds to precision in the estimation of these deviations using quantum-limited measurements on optical signals. We consider different classes of boson deformations and found that intensity measurement on coherent or thermal states would be suitable for their detection making, at least in principle, tests of boson deformation feasible with current quantum optical technology. On the other hand, we found that the quantum signal-to-noise ratio (QSNR) is vanishing with the deformation itself for all the considered classes of deformations and probe signals, thus making any estimation procedure of photon deformation inherently inefficient. A partial way out is provided by the polynomial dependence of the QSNR on the average number of photons, which suggests that, in principle, it would be possible to detect deformation by intensity measurements on high-energy thermal states.
      PubDate: Thu, 24 Apr 2014 06:27:26 GMT
       
  • Effect of temperature on non-Markovian dynamics in Coulomb crystals
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. In this paper, we generalize the results reported in Phys. Rev. A88 (2013) 010101 and investigate the flow of information induced in a Coulomb crystal in presence of thermal noise. For several temperatures we calculate the non-Markovian character of Ramsey interferometry of a single 1/2 spin with the motional degrees of freedom of the whole chain. These results give a more realistic picture of the interplay between temperature, non-Markvoanity and criticality.
      PubDate: Thu, 24 Apr 2014 06:27:25 GMT
       
  • General structure of quantum collisional models
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. We point to the connection between a recently introduced class of non-Markovian master equations and the general structure of quantum collisional models. The basic construction relies on three basic ingredients: a collection of time dependent completely positive maps, a completely positive trace preserving transformation and a waiting time distribution characterizing a renewal process. The relationship between this construction and a Lindblad dynamics is clarified by expressing the solution of a Lindblad master equation in terms of demixtures over different stochastic trajectories for the statistical operator weighted by suitable probabilities on the trajectory space.
      PubDate: Thu, 24 Apr 2014 06:27:25 GMT
       
  • Spatial separation and entanglement of identical particles
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. We reconsider the effect of indistinguishability on the reduced density operator of the internal degrees of freedom (tracing out the spatial degrees of freedom) for a quantum system composed of identical particles located in different spatial regions. We explicitly show that if the spin measurements are performed in disjoint spatial regions then there are no constraints on the structure of the reduced state of the system. This implies that the statistics of identical particles has no role from the point of view of separability and entanglement when the measurements are spatially separated. We extend the treatment to the case of n particles and show the connection with some recent criteria for separability based on subalgebras of observables.
      PubDate: Thu, 24 Apr 2014 06:27:24 GMT
       
  • Multipartite entanglement and few-body Hamiltonians
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print. We investigate the possibility to obtain higly multipartite-entangled states as non-degenerate eigenstates of Hamiltonians that involve only short-range and few-body interactions. We study small-size systems (with a number of qubits ranging from three to five) and search for Hamiltonians with a maximally multipartite entangled state (MMES) as a non-degenerate eigenstate. We then find conditions, including bounds on the number of coupled qubits, to build a Hamiltonian with a Greenberger–Horne–Zeilinger (GHZ) state as a non-degenerate eigenstate. We finally comment on possible applications.
      PubDate: Thu, 24 Apr 2014 06:27:24 GMT
       
  • On non-binary quantum repeated-root cyclic codes
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print.
      PubDate: Mon, 14 Apr 2014 07:13:02 GMT
       
  • EXPLICIT RELATION BETWEEN ALL LOWER BOUND TECHNIQUES FOR QUANTUM QUERY
           COMPLEXITY
    • Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print.
      PubDate: Mon, 25 Nov 2013 06:28:10 GMT
       
 
 
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