55,963 research outputs found
Manipulation of the dynamics of many-body systems via quantum control methods
We investigate how dynamical decoupling methods may be used to manipulate the
time evolution of quantum many-body systems. These methods consist of sequences
of external control operations designed to induce a desired dynamics. The
systems considered for the analysis are one-dimensional spin-1/2 models, which,
according to the parameters of the Hamiltonian, may be in the integrable or
non-integrable limits, and in the gapped or gapless phases. We show that an
appropriate control sequence may lead a chaotic chain to evolve as an
integrable chain and a system in the gapless phase to behave as a system in the
gapped phase. A key ingredient for the control schemes developed here is the
possibility to use, in the same sequence, different time intervals between
control operations.Comment: 10 pages, 3 figure
Quantum interference-induced stability of repulsively bound pairs of excitations
We study the dynamics of two types of pairs of excitations which are bound
despite their strong repulsive interaction. One corresponds to doubly occupied
sites in one-dimensional Bose-Hubbard systems, the so-called doublons. The
other is pairs of neighboring excited spins in anisotropic Heisenberg spin-1/2
chains. We investigate the possibility of decay of the bound pairs due to
resonant scattering by a defect or due to collisions of the pairs. We find that
the amplitudes of the corresponding transitions are very small. This is a
result of destructive quantum interference and explains the stability of the
bound pairs.Comment: 12 pages, 3 figure
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