1,636 research outputs found
The triangle map: a model of quantum chaos
We study an area preserving parabolic map which emerges from the Poincar\' e
map of a billiard particle inside an elongated triangle. We provide numerical
evidence that the motion is ergodic and mixing. Moreover, when considered on
the cylinder, the motion appear to follow a gaussian diffusive process.Comment: 4 pages in RevTeX with 4 figures (in 6 eps-files
Regular and Anomalous Quantum Diffusion in the Fibonacci Kicked Rotator
We study the dynamics of a quantum rotator kicked according to the
almost-periodic Fibonacci sequence. A special numerical technique allows us to
carry on this investigation for as many as kicks. It is shown that
above a critical kick strength the excitation of the system is well described
by regular diffusion, while below this border it becomes anomalous, and
sub-diffusive. A law for the dependence of the exponent of anomalous
sub-diffusion on the system parameters is established numerically. The analogy
between these results and quantum diffusion in models of quasi-crystal and in
the kicked Harper system is discussed.Comment: 7 pages, 4 figures, submitted to Phys. Rev.
Chaotic enhancement in microwave ionization of Rydberg atoms
The microwave ionization of internally chaotic Rydberg atoms is studied
analytically and numerically. The internal chaos is induced by magnetic or
static electric fields. This leads to a chaotic enhancement of microwave
excitation. The dynamical localization theory gives a detailed description of
the excitation process even in a regime where up to few thousands photons are
required to ionize one atom. Possible laboratory experiments are also
discussed.Comment: revtex, 19 pages, 23 figure
Emergence of Fermi-Dirac Thermalization in the Quantum Computer Core
We model an isolated quantum computer as a two-dimensional lattice of qubits
(spin halves) with fluctuations in individual qubit energies and residual
short-range inter-qubit couplings. In the limit when fluctuations and couplings
are small compared to the one-qubit energy spacing, the spectrum has a band
structure and we study the quantum computer core (central band) with the
highest density of states. Above a critical inter-qubit coupling strength,
quantum chaos sets in, leading to quantum ergodicity of eigenstates in an
isolated quantum computer. The onset of chaos results in the interaction
induced dynamical thermalization and the occupation numbers well described by
the Fermi-Dirac distribution. This thermalization destroys the noninteracting
qubit structure and sets serious requirements for the quantum computer
operability.Comment: revtex, 8 pages, 9 figure
Anomalous diffusion and dynamical localization in a parabolic map
We study numerically classical and quantum dynamics of a piecewise parabolic
area preserving map on a cylinder which emerges from the bounce map of
elongated triangular billiards. The classical map exhibits anomalous diffusion.
Quantization of the same map results in a system with dynamical localization
and pure point spectrum.Comment: 4 pages in RevTeX (4 ps-figures included
Negative differential thermal resistance and thermal transistor
We report on the first model of a thermal transistor to control heat flow.
Like its electronic counterpart, our thermal transistor is a three-terminal
device with the important feature that the current through the two terminals
can be controlled by small changes in the temperature or in the current through
the third terminal. This control feature allows us to switch the device between
"off" (insulating) and "on" (conducting) states or to amplify a small current.
The thermal transistor model is possible because of the negative differential
thermal resistance.Comment: 4 pages, 4 figures. SHortened. To appear in Applied Physics Letter
Dynamical Localization: Hydrogen Atoms in Magnetic and Microwave fields
We show that dynamical localization for excited hydrogen atoms in magnetic
and microwave fields takes place at quite low microwave frequency much lower
than the Kepler frequency. The estimates of localization length are given for
different parameter regimes, showing that the quantum delocalization border
drops significantly as compared to the case of zero magnetic field. This opens
up broad possibilities for laboratory investigations.Comment: revtex, 11 pages, 3 figures, to appear in Phys. Rev. A, Feb (1997
Eigenstates of Operating Quantum Computer: Hypersensitivity to Static Imperfections
We study the properties of eigenstates of an operating quantum computer which
simulates the dynamical evolution in the regime of quantum chaos. Even if the
quantum algorithm is polynomial in number of qubits , it is shown that the
ideal eigenstates become mixed and strongly modified by static imperfections
above a certain threshold which drops exponentially with . Above this
threshold the quantum eigenstate entropy grows linearly with but the
computation remains reliable during a time scale which is polynomial in the
imperfection strength and in .Comment: revtex, 4 pages, 4 figure
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