47 research outputs found
Thermal entanglement and efficiency of the quantum Otto cycle for the su(1,1) Tavis-Cummings system
The influence of the dynamical Stark shift on the thermal entanglement and
the efficiency of the quantum Otto cycle is studied for the su(1,1)
Tavis-Cummings system. It is shown that the degree of the thermal entanglement
becomes larger as the dynamical Stark shift increases. In contrast, the
efficiency of the Otto cycle is degraded with an increase of the values of
dynamical Stark shift. Expressions for the efficiency coefficient are derived.
Using those expressions we identify the maximal efficiency of the quantum Otto
cycle from the experimentally measured values of the dynamical Stark shiftComment: to appear in J.Phys.
Spin-orbital phase synchronization in the magnetic field-driven electron dynamics in a double quantum dot
We study the dynamics of an electron confined in a one-dimensional double
quantum dot in the presence of driving external magnetic fields. The orbital
motion of the electron is coupled to the spin dynamics by spin orbit
interaction of the Dresselhaus type. We derive an effective time-dependent
Hamiltonian model for the orbital motion of the electron and obtain a
synchronization condition between the orbital and the spin dynamics. From this
model we deduce an analytical expression for the Arnold tongue and propose an
experimental scheme for realizing the synchronization of the orbital and spin
dynamics.Comment: 6 figures, 14 page
Pulse and quench induced dynamical phase transition in a chiral multiferroic spin chain
Quantum dynamics of magnetic order in a chiral multiferroic chain is studied.
We consider two different scenarios: Ultrashort terahertz (THz) excitations or
a sudden electric field quench. Performing analytical and numerical exact
diagonalization calculations we trace the pulse induced spin dynamics and
extract quantities that are relevant to quantum information processing. In
particular, we analyze the dynamics of the system chirality, the von Neumann
entropy, the pairwise and the many body entanglement. If the characteristic
frequencies of the generated states are non-commensurate then a partial loss of
pair concurrence occurs. Increasing the system size this effect becomes even
more pronounced. Many particle entanglement and chirality are robust and
persist in the incommensurate phase. To analyze the dynamical quantum
transitions for the quenched and pulsed dynamics we combined the Weierstrass
factorization technique for entire functions and Lanczos exact diagonalization
method. For a small system we obtained analytical results including the rate
function of Loschmidt echo. Exact numerical calculations for a system up to 40
spins confirm phase transition. Quench- induced dynamical transitions have been
extensively studied recently. Here we show that related dynamical transitions
can be achieved and controlled by appropriate electric field pulses.Comment: 13 pages, 10 figures, submitted in PR