13,325 research outputs found
Magnetic Field Satellite (Magsat) data processing system specifications
The software specifications for the MAGSAT data processing system (MDPS) are presented. The MDPS is divided functionally into preprocessing of primary input data, data management, chronicle processing, and postprocessing. Data organization and validity, and checks of spacecraft and instrumentation are dicussed. Output products of the MDPS, including various plots and data tapes, are described. Formats for important tapes are presented. Dicussions and mathematical formulations for coordinate transformations and field model coefficients are included
Influence of qubit displacements on quantum logic operations in a silicon-based quantum computer with constant interaction
The errors caused by qubit displacements from their prescribed locations in
an ensemble of spin chains are estimated analytically and calculated
numerically for a quantum computer based on phosphorus donors in silicon. We
show that it is possible to polarize (initialize) the nuclear spins even with
displaced qubits by using Controlled NOT gates between the electron and nuclear
spins of the same phosphorus atom. However, a Controlled NOT gate between the
displaced electron spins is implemented with large error because of the
exponential dependence of exchange interaction constant on the distance between
the qubits. If quantum computation is implemented on an ensemble of many spin
chains, the errors can be small if the number of chains with displaced qubits
is small
Survival of quantum effects for observables after decoherence
When a quantum nonlinear system is linearly coupled to an infinite bath of
harmonic oscillators, quantum coherence of the system is lost on a decoherence
time-scale . Nevertheless, quantum effects for observables may still
survive environment-induced decoherence, and be observed for times much larger
than the decoherence time-scale. In particular, we show that the Ehrenfest
time, which characterizes a departure of quantum dynamics for observables from
the corresponding classical dynamics, can be observed for a quasi-classical
nonlinear oscillator for times . We discuss this observation in
relation to recent experiments on quantum nonlinear systems in the
quasi-classical region of parameters.Comment: submitted to PR
Creation of entanglement in a scalable spin quantum computer with long-range dipole-dipole interaction between qubits
Creation of entanglement is considered theoretically and numerically in an
ensemble of spin chains with dipole-dipole interaction between the spins. The
unwanted effect of the long-range dipole interaction is compensated by the
optimal choice of the parameters of radio-frequency pulses implementing the
protocol. The errors caused by (i) the influence of the environment,(ii)
non-selective excitations, (iii) influence of different spin chains on each
other, (iv) displacements of qubits from their perfect locations, and (v)
fluctuations of the external magnetic field are estimated analytically and
calculated numerically. For the perfectly entangled state the z component, M,
of the magnetization of the whole system is equal to zero. The errors lead to a
finite value of M. If the number of qubits in the system is large, M can be
detected experimentally. Using the fact that M depends differently on the
parameters of the system for each kind of error, varying these parameters would
allow one to experimentally determine the most significant source of errors and
to optimize correspondingly the quantum computer design in order to decrease
the errors and M. Using our approach one can benchmark the quantum computer,
decrease the errors, and prepare the quantum computer for implementation of
more complex quantum algorithms.Comment: 31 page
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The distribution of Transverse Aeolian Ridges on Mars
Abstract not available
Perturbation Theory for Quantum Computation with Large Number of Qubits
We describe a new and consistent perturbation theory for solid-state quantum
computation with many qubits. The errors in the implementation of simple
quantum logic operations caused by non-resonant transitions are estimated. We
verify our perturbation approach using exact numerical solution for relatively
small (L=10) number of qubits. A preferred range of parameters is found in
which the errors in processing quantum information are small. Our results are
needed for experimental testing of scalable solid-state quantum computers.Comment: 8 pages RevTex including 2 figure
Dynamical Stability of an Ion in a Linear Trap as a Solid-State Problem of Electron Localization
When an ion confined in a linear ion trap interacts with a coherent laser
field, the internal degrees of freedom, related to the electron transitions,
couple to the vibrational degree of freedom of the ion. As a result of this
interaction, quantum dynamics of the vibrational degree of freedom becomes
complicated, and in some ranges of parameters even chaotic. We analyze the
vibrational ion dynamics using a formal analogy with the solid-state problem of
electron localization. In particular, we show how the resonant approximation
used in analysis of the ion dynamics, leads to a transition from a
two-dimensional (2D) to a one-dimensional problem (1D) of electron
localization. The localization length in the solid-state problem is estimated
in cases of weak and strong interaction between the cites of the 2D cell by
using the methods of resonance perturbation theory, common in analysis of 1D
time-dependent dynamical systems.Comment: 18 pages RevTe
Quantum computing with magnetic atoms in optical lattices of reduced periodicity
We investigate the feasibility of combining Raman optical lattices with a
quantum computing architecture based on lattice-confined magnetically
interacting neutral atoms. A particular advantage of the standing Raman field
lattices comes from reduced interatomic separations leading to increased
interatomic interactions and improved multi-qubit gate performance.
Specifically, we analyze a Zeeman system placed in Raman fields which exhibit periodicity. We find
that the resulting CNOT gate operations times are in the order of millisecond.
We also investigate motional and magnetic-field induced decoherences specific
to the proposed architecture
The Super-Strong Coupling Regime of Cavity Quantum Electrodynamics
We describe a qualitatively new regime of cavity quantum electrodynamics, the
super strong coupling regime. This regime is characterized by atom-field
coupling strengths of the order of the free spectral range of the cavity,
resulting in a significant change in the spatial mode functions of the light
field. It can be reached in practice for cold atoms trapped in an optical
dipole potential inside the resonator. We present a nonperturbative scheme that
allows us to calculate the frequencies and linewidths of the modified field
modes, thereby providing a good starting point for a quantization of the
theory.Comment: Figures rearranged and introduction rewritte
Quantum logic operations and creation of entanglement in a scalable superconducting quantum computer with long-range constant interaction between qubits
We consider a one-dimensional chain of many superconducting quantum
interference devices (SQUIDs), serving as charge qubits. Each SQUID is coupled
to its nearest neighbors through constant capacitances. We study the quantum
logic operations and implementation of entanglement in this system.
Arrays with two and three qubits are considered in detail. We show that the
creation of entanglement with an arbitrary number of qubits can be implemented,
without systematic errors, even when the coupling between qubits is not small.
A relatively large coupling constant allows one to increase the clock speed of
the quantum computer. We analytically and numerically demonstrate the creation
of the entanglement for this case, which can be a good test for the
experimental implementation of a relatively simple quantum protocol with many
qubits. We discuss a possible application of our approach for implementing
universal quantum logic for more complex algorithms by decreasing the coupling
constant and, correspondingly, decreasing the clock speed. The errors
introduced by the long-range interaction for the universal logic gates are
estimated analytically and calculated numerically. Our results can be useful
for experimental implementation of quantum algorithms using controlled magnetic
fluxes and gate voltages applied to the SQUIDs. The algorithms discussed in
this paper can be implemented using already existing technologies in
superconducting systems with constant inter-qubit coupling.Comment: 24 page
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