9 research outputs found
Engineering fidelity echoes in Bose-Hubbard Hamiltonians
We analyze the fidelity decay for a system of interacting bosons described by
a Bose-Hubbard Hamiltonian. We find echoes associated with "non-universal"
structures that dominate the energy landscape of the perturbation operator.
Despite their classical origin, these echoes persist deep into the quantum
(perturbative) regime and can be described by an improved random matrix
modeling. In the opposite limit of strong perturbations (and high enough
energies), classical considerations reveal the importance of self-trapping
phenomena in the echo efficiency.Comment: 6 pages, use epl2.cls class, 5 figures Cross reference with nlin,
quant-phy
Chaos and Complexity of quantum motion
The problem of characterizing complexity of quantum dynamics - in particular
of locally interacting chains of quantum particles - will be reviewed and
discussed from several different perspectives: (i) stability of motion against
external perturbations and decoherence, (ii) efficiency of quantum simulation
in terms of classical computation and entanglement production in operator
spaces, (iii) quantum transport, relaxation to equilibrium and quantum mixing,
and (iv) computation of quantum dynamical entropies. Discussions of all these
criteria will be confronted with the established criteria of integrability or
quantum chaos, and sometimes quite surprising conclusions are found. Some
conjectures and interesting open problems in ergodic theory of the quantum many
problem are suggested.Comment: 45 pages, 22 figures, final version, at press in J. Phys. A, special
issue on Quantum Informatio
Quantum chaotic system as a model of decohering environment
As a model of decohering environment, we show that quantum chaotic system
behave equivalently as many-body system. An approximate formula for the time
evolution of the reduced density matrix of a system interacting with a quantum
chaotic environment is derived. This theoretical formulation is substantiated
by the numerical study of decoherence of two qubits interacting with a quantum
chaotic environment modeled by a chaotic kicked top. Like the many-body model
of environment, the quantum chaotic system is efficient decoherer, and it can
generate entanglement between the two qubits which have no direct interaction.Comment: 5 pages, 3 figures. Published version