1,353 research outputs found
Fast SWAP gate by adiabatic passage
We present a process for the construction of a SWAP gate which does not
require a composition of elementary gates from a universal set. We propose to
employ direct techniques adapted to the preparation of this specific gate. The
mechanism, based on adiabatic passage, constitutes a decoherence-free method in
the sense that spontaneous emission and cavity damping are avoided.Comment: 5 pages, 4 figures, submitted to Phys. Re
Adiabatic tracking for photo- and magneto-association of Bose-Einstein condensates with Kerr nonlinearities
We develop the method of adiabatic tracking for photo- and
magneto-association of Bose-Einstein atomic condensates with models that
include Kerr type nonlinearities. We show that the inclusion of these terms can
produce qualitatively important modifications in the adiabatic dynamics, like
the appearance of bifurcations, in which the trajectory that is being tracked
loses its stability. As a consequence the adiabatic theorem does not apply and
the adiabatic transfer can be strongly degraded. This degradation can be
compensated by using fields that are strong enough compared with the values of
the Kerr terms. The main result is that, despite these potentially detrimental
features, there is always a choice of the detuning that leads to an efficient
adiabatic tracking, even for relatively weak fields
On the topology of adiabatic passage
We examine the topology of eigenenergy surfaces characterizing the population
transfer processes based on adiabatic passage. We show that this topology is
the essential feature for the analysis of the population transfers and the
prediction of its final result. We reinterpret diverse known processes, such as
stimulated Raman adiabatic passage (STIRAP), frequency-chirped adiabatic
passage and Stark-chirped rapid adiabatic passage (SCRAP). Moreover, using this
picture, we display new related possibilities of transfer. In particular, we
show that we can selectively control the level which will be populated in
STIRAP process in Lambda or V systems by the choice of the peak amplitudes or
the pulse sequence
Adiabatic Evolution for Systems with Infinitely many Eigenvalue Crossings
We formulate an adiabatic theorem adapted to models that present an
instantaneous eigenvalue experiencing an infinite number of crossings with the
rest of the spectrum. We give an upper bound on the leading correction terms
with respect to the adiabatic limit. The result requires only differentiability
of the considered spectral projector, and some geometric hypothesis on the
local behaviour of the eigenvalues at the crossings
Optimized time-dependent perturbation theory for pulse-driven quantum dynamics in atomic or molecular systems
We present a time-dependent perturbative approach adapted to the treatment of
intense pulsed interactions. We show there is a freedom in choosing secular
terms and use it to optimize the accuracy of the approximation. We apply this
formulation to a unitary superconvergent technique and improve the accuracy by
several orders of magnitude with respect to the Magnus expansion.Comment: 4 pages, 2 figure
Field-free two-direction alignment alternation of linear molecules by elliptic laser pulses
We show that a linear molecule subjected to a short specific elliptically
polarized laser field yields postpulse revivals exhibiting alignment
alternatively located along the orthogonal axis and the major axis of the
ellipse. The effect is experimentally demonstrated by measuring the optical
Kerr effect along two different axes. The conditions ensuring an optimal
field-free alternation of high alignments along both directions are derived.Comment: 5 pages, 4 color figure
Adiabatic creation of entangled states by a bichromatic field designed from the topology of the dressed eigenenergies
Preparation of entangled pairs of coupled two-state systems driven by a
bichromatic external field is studied. We use a system of two coupled spin-1/2
that can be translated into a three-state ladder model whose intermediate state
represents the entangled state. We show that this entangled state can be
prepared in a robust way with appropriate fields. Their frequencies and
envelopes are derived from the topological properties of the model.Comment: 10 pages, 9 figure
Stimulated Raman Adiabatic Passage via bright state in Lambda medium of unequal oscillator strengths
We consider the population transfer process in a Lambda-type atomic medium of
unequal oscillator strengths by stimulated Raman adiabatic passage via
bright-state (b-STIRAP) taking into account propagation effects. Using both
analytic and numerical methods we show that the population transfer efficiency
is sensitive to the ratio q_p/q_s of the transition oscillator strengths. We
find that the case q_p>q_s is more detrimental for population transfer process
as compared to the case where . For this case it is possible to
increase medium dimensions while permitting efficient population transfer. A
criterion determining the interaction adiabaticity in the course of propagation
process is found. We also show that the mixing parameter characterizing the
population transfer propagates superluminally
Atom-photon, atom-atom and photon-photon entanglement preparation via fractional adiabatic passage
We propose a relatively robust scheme to generate maximally entangled states
of (i) an atom and a cavity photon, (ii) two atoms in their ground states, and
(iii) two photons in two spatially separate high-Q cavities. It is based on the
interaction via fractional adiabatic passage of a three-level atom traveling
through a cavity mode and a laser beam. The presence of optical phases is
emphasized.Comment: 6 pages, 7 figures. We have changed the title, the abstract and the
text. The references have been updated. (Accepted by Phys. Rev. A
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