Proceedings Volume 7023

Quantum Informatics 2007

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Proceedings Volume 7023

Quantum Informatics 2007

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Volume Details

Date Published: 14 May 2008
Contents: 2 Sessions, 22 Papers, 0 Presentations
Conference: Quantum Informatics 2007 2007
Volume Number: 7023

Table of Contents

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Table of Contents

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  • Front Matter: Volume 7023
  • Oral Session
Front Matter: Volume 7023
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Front Matter: Volume 7023
This PDF file contains the front matter associated with SPIE Proceedings Volume 7023, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.
Oral Session
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Quantum computation and hidden variables
Many physicists limit oneself to an instrumentalist description of quantum phenomena and ignore the problems of foundation and interpretation of quantum mechanics. This instrumentalist approach results to "specialization barbarism" and mass delusion concerning the problem, how a quantum computer can be made. The idea of quantum computation can be described within the limits of quantum formalism. But in order to understand how this idea can be put into practice one should realize the question: "What could the quantum formalism describe?", in spite of the absence of an universally recognized answer. Only a realization of this question and the undecided problem of quantum foundations allows to see in which quantum systems the superposition and EPR correlation could be expected. Because of the "specialization barbarism" many authors are sure that Bell proved full impossibility of any hidden-variables interpretation. Therefore it is important to emphasize that in reality Bell has restricted to validity limits of the no-hidden-variables proof and has shown that two-state quantum system can be described by hidden variables. The later means that no experimental result obtained on two-state quantum system can prove the existence of superposition and violation of the realism. One should not assume before unambiguous experimental evidence that any two-state quantum system is quantum bit. No experimental evidence of superposition of macroscopically distinct quantum states and of a quantum bit on base of superconductor structure was obtained for the present. Moreover same experimental results can not be described in the limits of the quantum formalism.
Quantum theory with hidden variables and dynamic chaos
Yu. I. Bogdanov
We consider dynamics of hidden variables for measurements in a generalized bell-type model for a single spin using natural assumptions. The evolution of the system, which can be expressed as dynamic chaos is studied. The equilibrium state that the system evolves to asymptotically is consistent with the predictions of quantum theory.
Quantum computations on ion traps
A. Burkov, Y. Ozhigov
We give the universal scheme of quantum computations on ions of metals in Paul traps and estimate the capacity of this computational model taking into account the uncertainty conditions.
Relative coordinates of coherent electron pair
Constantin V. Usenko, Nataliia O. Cherkashyna
It is shown that relative coordinate and momentum of coherent electron pair have the meaning of observables with the help of quadrupole and magnetic moments. Distributions of quadrupole terms of scalar potential are shown. These distributions have nonclassical properties.
Non-multiple non-equidimensional bases and unsharp measurements
Dmitry V. Dodin, Ilya G. Kovalenko
We consider a procedure of measurement of a quantum system in case when its dimension and the dimension of the basis of a measuring device relate as ratio of integer numbers. This procedure of measurement is introduced here as a "procedure of measurement in different-dimensional bases". We develop a new mathematical formalism describing this kind of measurement. It is demonstrated that when the dimension of the system is divisible by the dimension of basis for the measuring instrument, our results coincide with conventional theoretical developments. We consider measurement in different-dimensional bases as a kind of unsharp measurement.
Probabilistic simulation of quantum states
Yu. P. Rybakov, T. F. Kamalov
To study the properties of the probabilistic bits the geometric approach is preferable. In this approach the projective interpretation of the Hilbert space as the space of rays is used. This model can be employed for simulating Bi-photons, qubits, EPR states and entanglement. The other example concerns the entangled envelope solitons in Kerr dielectric with cubic nonlinearity, where we use two-solitons configurations for modeling the entangled states of photons.
Can the mathematical formalism of quantum mechanics be applied to psychology?
Andrei Khrennikov
We show that (in contrast to rather common opinion) the domain of applications of the mathematical formalism of quantum mechanics is not restricted to physics. This formalism can be applied to the description of various quantum-like (QL) information processing. In particular, the calculus of quantum (and more general QL) probabilities can be used to explain some paradoxical statistical data which was obtained in psychology and cognitive science. We consider the QL description of prisoners dilemma (PD) and so called disjunction effect (violation of Savage's sure thing principle which plays the fundamental role in modern economics).
Quantum averages from Gaussian random fields at the Planck length scale
Andrei Khrennikov
We show that the mathematical formalism of quantum mechanics can be interpreted as a method for approximation of classical (measure-theoretic) averages of functions f : L2(R3) → R. These are classical physical variables in our model with hidden variables - Prequantum Classical Statistical Field Theory (PCSFT). In this paper we provide a simple stochastic picture of such a quantum approximation procedure. In the probabilistic terms this is nothing else than the approximative method for computation of averages for functions of random variables. Since in PCSFT the space of hidden variables is L2(R3), the role of a classical random variable is played by a random field. In PCSFT we consider Gaussian random fields representing random fluctuations at the prequantum length scale. Quantum mechanical expression for the average (given by the von Neumann trace formula) is obtained through moving from the prequantum length scale to the quantum one (the scale at that we are able to perform measurements).
An investigation of the antiferromagnet-based NMR quantum register in inhomogeneous magnetic field
Alexander A. Kokin, Vladimir A. Kokin
It is given the refinements and further development of NMR model of quantum register based on easy-axis nuclear spin-free antiferromagnet, which was presented previously in paper. The model suggests that external magnetic field is directed along the easy axis, normally to the plate surface and has a weak constant gradient along the nuclear spin chain of quantum register. In present paper it is evaluated the general expression for indirect coupling between nuclear spins due to hyperfine nuclear-electron coupling in substituted atoms and spin-wave propagation in antiferromagnet close to critical point of quantum phase transition in antiferromagnet of spin-flop type. It is given also an estimation of quantum states decoherence rate, which is caused by the interaction of nuclear spins with spin waves in antiferromagnet.
Non locality: mystery or myth?
A survey of a study leading to the conclusion that there is no support for non locality in Quantum Mechanics is presented. Models based on Malus' Law for generic EPR and GHZ experiments are cited. It is observed that 'entangled' polarization, as governed by the SU(2) group structure, cannot be a quantum phenomenon. The implications of these results for researches on quantum computing are considered.
Hidden time interpretation of quantum mechanics and no-protocol argument
P. V. Kurakin
Previously suggested hidden time interpretation of quantum mechanics allows to reproduce the same predictions as standard quantum mechanics provides, since it is based on Feynman many - paths formulation of QM. While new experimental consequences of this interpretation are under investigation, some advantages can be enumerated. (1) The interpretation is much field theoretic - like in classical sense, so it is local in mathematical sense, though quantum (physical) non-locality is preserved. (2) The interpretation is based on one type of mathematical objects, rather than two different (Hilbert space vectors and operators). (3) The interpretation, as it was argued, overcomes the problem of hidden variables in a radically new way, with no conflict to Bell's theorem. Recently an important argument against hidden variables - like formulations of quantum theory was risen - "no protocol" argument. It is argued in the paper, that hidden time interpretation successfully overcomes this argument.
Thermal entanglement in a case of two spin temperatures
In this paper we study the influence of pulse NMR on the usefulness of the entanglement in a two-qubit XXZ chain at different temperatures of the Zeeman and dipole-dipole reservoirs as resource for quantum teleportation via the standard teleportation protocol. We show that the nonzero entanglement produced at a high temperature and the initial polarization exceeding some threshold value after a (π/2)y pulse of RF field is an useful resource. We also report on the exact calculation of the necessary and sufficient conditions of entanglement for an ensemble of spin pairs under non-equilibrium states.
On degenerate bispinor states of the Dirac wave equation system for an electron in an electrostatic field
B. K. Novosadov
An additional degeneracy has been found for Dirac equations system describing an electron in electrostatic field which corresponds to spin direction degeneracy in the nonrelativistic model. This property may be used to construct relativistic electronic configurations entangling bispinor electronic states.
Macroscopic wavefunction for ensemble of ultracold atoms trapped in optical labyrinth
We discuss a possibility of a pinning of quantized matter wave vortices by optical vortices in specially arranged optical dipole traps. The vortex-antivortex optical arrays of rectangular symmetry are shown to transfer angular orbital momentum to support "antiferromagnet-like" matter waves. The separable Hamiltonian for matter waves is proposed which allows to factorize of the 3D - wavefunction exactly in a product of 1D - harmonic oscillator's ground state and 2D - vortex-antivortex wavefunction. The wavefunction's phase gradient field associated with the field of classical velocities via Madelung transformation forms labyrinth-like structure. The macroscopic wavefunction of periodically spaced BEC superfluid vortices appears to be less influenced by decoherence.
Numerical method of entangled state selection in association of molecules
K. S. Arakelov, Yu. I. Ozhigov
We represent the economy method of separation of the entangled states of GHZ and W types which arise in the process of association of a single molecule. It makes possible to separate these types of quantum states in the simulation of real processes like the association of molecular ion of hydrogen by means of existing computers with the strictly limited memory. Numerical realization of this method is in process; we represent the semiclassical part of it, that is based on Landau-Ziner description of the association of molecules. Results of statistical processing of the row of numerical experiments are shown.
Influence of surrounding spin environment on two-spin system ESR spectra
S. N. Dobryakov, V. V. Privezentsev
Computer simulation ESR spectra two-spin systems for a typical case dipole spectrum of two-spin system without super fine interaction (SFI) and anisotropies of the g-factor (g1=g2) in view of relaxation parameters (collision frequencies is lead vmn and lapping functions pmn). The theoretical form dipole ESR spectra of two-spin systems depending on concentration of active spin particles and own line width is calculated. Simulation has shown, that ESR spectra contain great volume of information about two-spin systems structure and elementary (equilibrium and non-equilibrium) spin reactions with its participation.
Geometric information in eight dimensions vs. quantum information
Victor I. Tarkhanov, Michael M. Nesterov
Complementary idempotent paravectors and their ordered compositions, are used to represent multivector basis elements of geometric Clifford algebra G3,0 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.
Problem of detection of Rydberg atoms and quantum information processing
D. B. Tretyakov, I. I. Ryabtsev, I. I. Beterov, et al.
We have developed a simple theoretical model describing multi-atom signals that could be measured in experiments on resonant energy transfers in an ensemble of a few Rydberg atoms. We have shown that an efficiency of the selective field-ionization detector, which is less than 1, leads to the mixing up of the spectra of the resonant energy transfer registered for various numbers of detected Rydberg atoms. This may impede the possible observations of dipole blockade or coherent two-atom interaction required to perform basic quantum gates. The formulae are presented, which help to estimate an actual mean Rydberg atom number in an excitation volume per one exciting laser pulse at a given detection efficiency. We have also found that a measurement of relationship of the amplitudes of resonances observed in the one- and two-atom signals provides a straightforward determination of the absolute detection efficiency and actual mean Rydberg atom number. This novel method is advantageous as it is independent of the specific experimental conditions. We also performed a testing experiment on the resonant energy transfers in a small excitation volume of the velocity selected Na atomic beam. The observed one- and two-atom resonances were analyzed and compared with the theoretical predictions. A good agreement between experiment and theory in the width and amplitudes of the resonances has confirmed the validity of simple approximations used in the developed theoretical model.
Application of superconducting quantum interferometer in quantum computer development
A. I. Golovashkin, A. L. Karuzskiy, A. A. Orlikovskiy, et al.
Various variants of use high-sensitivity superconducting quantum interferometers (SQUID) in problems closely connected with development of a quantum computer are considered. 1.Hardware realization of a method of definition of midget concentration of the paramagnetic centers, based on measurement of their magnetization SQUID in a mode of modulation microwave saturation of magnetic sublevels is offered. The method will allow make testing of semi-conductor materials necessary for creation of a spin solid-state quantum computer. 2.The opportunity of application SQUID for reading a condition of the quantum register, based on the quantum-statistical mechanism, allowing registered a state of single spin, is considered. 3.The circuit super low noise the quantum electrometer, based on use SQUID is offered as a measuring instrument of magnetization of spin system in which exchange interaction is adjusted by potential on in parallel connected managing electrodes (on type a spin ensemble computer).
Optically driven nanostructures as the basis for large-scale quantum computing
Alexander V. Tsukanov
We propose a large-scale quantum computer architecture based upon the regular arrays of dopant atoms implanted into the semiconductor host matrix. The singly-ionized pairs of donors represent charge qubits on which arbitrary quantum operations can be achieved by application of two strongly detuned laser pulses. The implementation of two-qubit operations as well as the qubit read-out utilize the intermediate circuit containing a probe electron that is able to shuttle along the array of ionized ancilla donors providing the indirect conditional coupling between the qubits. The quantum bus strategy enables us to handle the qubits connected in parallel and enhances the efficiency of the quantum information processing. We demonstrate that non-trivial multi-qubit operations in the quantum register (e.g., an entanglement generation) can be accomplished by the sequence of the optical pulses combined with an appropriate voltage gate pattern.
Selective control of states of a three-level quadrupolar nucleus using non-selective radio-frequency pulses
V. E. Zobov, V. P. Shauro
The scheme for obtaining the composite operator of the selective rotation from nonselective RF pulses separated by intervals of free evolution has been proposed for quadrupole nuclei. On an example of three levels, it has been shown that the rotation by this operator is performed with accuracy comparable with the accuracy of a simple selective RF pulse, but in shorter time.