18,282 research outputs found
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
Dynamical Stability and Quantum Chaos of Ions in a Linear Trap
The realization of a paradigm chaotic system, namely the harmonically driven
oscillator, in the quantum domain using cold trapped ions driven by lasers is
theoretically investigated. The simplest characteristics of regular and chaotic
dynamics are calculated. The possibilities of experimental realization are
discussed.Comment: 24 pages, 17 figures, submitted to Phys. Rev
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The distribution of Transverse Aeolian Ridges on Mars
Abstract not available
A compact micro-wave synthesizer for transportable cold-atom interferometers
We present the realization of a compact micro-wave frequency synthesizer for
an atom interferometer based on stimulated Raman transitions, applied to
transportable inertial sensing. Our set-up is intended to address the hyperfine
transitions of Rubidium 87 atoms at 6.8 GHz. The prototype is evaluated both in
the time and the frequency domain by comparison with state-of-the-art frequency
references developed at LNE-SYRTE. In free-running mode, it features a residual
phase noise level of -65 dBrad$^2.Hz^{-1} at 10-Hz offset frequency and a white
phase noise level in the order of -120 dBrad^2.Hz^{-1} for Fourier frequencies
above 10 kHz. The phase noise effect on the sensitivity of the atomic
interferometer is evaluated for diverse values of cycling time, interrogation
time and Raman pulse duration. To our knowledge, the resulting contribution is
well below the sensitivity of any demonstrated cold atom inertial sensors based
on stimulated Raman transitions. The drastic improvement in terms of size,
simplicity and power consumption paves the way towards field and mobile
operations.Comment: accepted for publication in Review of Scientific Instruments, 6
pages, 4 figure
Fluctuating Fronts as Correlated Extreme Value Problems: An Example of Gaussian Statistics
In this paper, we view fluctuating fronts made of particles on a
one-dimensional lattice as an extreme value problem. The idea is to denote the
configuration for a single front realization at time by the set of
co-ordinates of the
constituent particles, where is the total number of particles in that
realization at time . When are arranged in the ascending order
of magnitudes, the instantaneous front position can be denoted by the location
of the rightmost particle, i.e., by the extremal value
. Due to interparticle
interactions, at two different times for a single front
realization are naturally not independent of each other, and thus the
probability distribution [based on an ensemble of such front
realizations] describes extreme value statistics for a set of correlated random
variables. In view of the fact that exact results for correlated extreme value
statistics are rather rare, here we show that for a fermionic front model in a
reaction-diffusion system, is Gaussian. In a bosonic front model
however, we observe small deviations from the Gaussian.Comment: 6 pages, 3 figures, miniscule changes on the previous version, to
appear in Phys. Rev.
Controlled splitting of an atomic wave packet
We propose a simple scheme capable of adiabatically splitting an atomic wave
packet using two independent translating traps. Implemented with optical dipole
traps, our scheme allows a high degree of flexibility for atom interferometry
arrangements and highlights its potential as an efficient and high fidelity
atom optical beam splitter.Comment: 4 pages, 4 figures. Accepted by Phys. Rev. Let
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
Accelerator dynamics of a fractional kicked rotor
It is shown that the Weyl fractional derivative can quantize an open system.
A fractional kicked rotor is studied in the framework of the fractional
Schrodinger equation. The system is described by the non-Hermitian Hamiltonian
by virtue of the Weyl fractional derivative. Violation of space symmetry leads
to acceleration of the orbital momentum. Quantum localization saturates this
acceleration, such that the average value of the orbital momentum can be a
direct current and the system behaves like a ratchet. The classical counterpart
is a nonlinear kicked rotor with absorbing boundary conditions.Comment: Submitted for publication in Phys. Rev.
A Bell pair in a generic random matrix environment
Two non-interacting qubits are coupled to an environment. Both coupling and
environment are represented by random matrix ensembles. The initial state of
the pair is a Bell state, though we also consider arbitrary pure states.
Decoherence of the pair is evaluated analytically in terms of purity; Monte
Carlo calculations confirm these results and also yield the concurrence of the
pair. Entanglement within the pair accelerates decoherence. Numerics display
the relation between concurrence and purity known for Werner states, allowing
us to give a formula for concurrence decay.Comment: 4 pages, 3 figure
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