5 research outputs found
The Super-Strong Coupling Regime of Cavity Quantum Electrodynamics
We describe a qualitatively new regime of cavity quantum electrodynamics, the
super strong coupling regime. This regime is characterized by atom-field
coupling strengths of the order of the free spectral range of the cavity,
resulting in a significant change in the spatial mode functions of the light
field. It can be reached in practice for cold atoms trapped in an optical
dipole potential inside the resonator. We present a nonperturbative scheme that
allows us to calculate the frequencies and linewidths of the modified field
modes, thereby providing a good starting point for a quantization of the
theory.Comment: Figures rearranged and introduction rewritte
Quasi-spin wave quantum memories with dynamic symmetry
For the two-mode exciton system formed by the quasi-spin wave collective
excitation of many atoms fixed at the lattice sites of a crystal, we
discover a dynamic symmetry depicted by the semi-direct product algebra
in the large limit with low excitations. With the
help of the spectral generating algebra method, we obtain a larger class of
exact zero-eigenvalue states adiabatically interpolating between the initial
state of photon-type and the final state of quasi-spin wave exciton-type. The
conditions for the adiabatic passage of dark states are shown to be valid, even
with the presence of the level degeneracy. These theoretical results can lead
to propose new protocol of implementing quantum memory robust against quantum
decoherence.Comment: 6 pages, 2 figures,with some reservations. Accepted for publication
in Phys. Rev .Let
Darboux transformations of coherent states of the time-dependent singular oscillator
Darboux transformation of both Barut-Girardello and Perelomov coherent states
for the time-dependent singular oscillator is studied. In both cases the
measure that realizes the resolution of the identity operator in terms of
coherent states is found and corresponding holomorphic representation is
constructed. For the particular case of a free particle moving with a fixed
value of the angular momentum equal to two it is shown that Barut-Giriardello
coherent states are more localized at the initial time moment while the
Perelomov coherent states are more stable with respect to time evolution. It is
also illustrated that Darboux transformation may keep unchanged this different
time behavior.Comment: 13 page