95 research outputs found
Effect of dissipative forces on the theory of a single-atom microlaser
We describe a one-atom microlaser involving Poissonian input of atoms with a
fixed flight time through an optical resonator. The influence of the cavity
reservoir during the interactions of successive individual atoms with the
cavity field is included in the analysis. The atomic decay is also considered
as it is nonnegligible in the optical regime. During the random intervals of
absence of any atom in the cavity, the field evolves under its own dynamics. We
discuss the steady-state characteristics of the cavity field. Away from laser
threshold, the field can be nonclassical in nature.Comment: 9 pages in LaTex; 3 PS figure
Quantum integrability and Bethe ansatz solution for interacting matter-radiation systems
A unified integrable system, generating a new series of interacting
matter-radiation models with interatomic coupling and different atomic
frequencies, is constructed and exactly solved through algebraic Bethe ansatz.
Novel features in Rabi oscillation and vacuum Rabi splitting are shown on the
example of an integrable two-atom Buck-Sukumar model with resolution of some
important controversies in the Bethe ansatz solution including its possible
degeneracy for such models.Comment: Latex, 7 pages, 1 figure. Final version to be published in J Phys A
(as Letter
Quantum integrable multi atom matter-radiation models with and without rotating wave approximation
New integrable multi-atom matter-radiation models with and without rotating
wave approximation (RWA) are constructed and exactly solved through algebraic
Bethe ansatz. The models with RWA are generated through ancestor model approach
in an unified way. The rational case yields the standard type of
matter-radiaton models, while the trigonometric case corresponds to their
q-deformations. The models without RWA are obtained from the elliptic case at
the Gaudin and high spin limit.Comment: 9 pages, no figure, talk presented in int. conf. NEEDS04 (Gallipoli,
Italy, July 2004
On Collective Effects in Cavity Quantum Electrodynamics
We investigate the role of collective effects in the micromaser system as
used in various studies of the physics of cavity electrodynamics. We focus our
attention on the effect on large-time correlations due to multi-atom
interactions. The influence of detection efficiencies and collective effects on
the appearance of trapping states at low temperatures is also found to be of
particular importance.Comment: 10 pages, 7 figures, 36 reference
Macroscopic Interference Effects in Resonant Cavities
We investigate the possibility of interference effects induced by macroscopic
quantum-mechanical superpositions of almost othogonal coherent states - a
Schroedinger cats state - in a resonant microcavity. Despite the fact that a
single atom, used as a probe of the cat state, on the average only change the
mean number of photons by one unit, we show that this single atom can change
the system drastically. Interference between the initial and almost orthogonal
macroscopic quantum states of the radiation field can now take place.
Dissipation under current experimental conditions is taken into account and it
is found that this does not necessarily change the intereference effects
dramatically.Comment: 20 pages, 3 figure
Solvable model of a strongly-driven micromaser
We study the dynamics of a micromaser where the pumping atoms are strongly
driven by a resonant classical field during their transit through the cavity
mode. We derive a master equation for this strongly-driven micromaser,
involving the contributions of the unitary atom-field interactions and the
dissipative effects of a thermal bath. We find analytical solutions for the
temporal evolution and the steady-state of this system by means of phase-space
techniques, providing an unusual solvable model of an open quantum system,
including pumping and decoherence. We derive closed expressions for all
relevant expectation values, describing the statistics of the cavity field and
the detected atomic levels. The transient regime shows the build-up of mixtures
of mesoscopic fields evolving towards a superpoissonian steady-state field
that, nevertheless, yields atomic correlations that exhibit stronger
nonclassical features than the conventional micromaser.Comment: 9 pages, 16 figures. Submitted for publicatio
Dynamics, correlations and phases of the micromaser
The micromaser possesses a variety of dynamical phase transitions
parametrized by the flux of atoms and the time-of-flight of the atom within the
cavity. We discuss how these phases may be revealed to an observer outside the
cavity using the long-time correlation length in the atomic beam. Some of the
phase transitions are not reflected in the average excitation level of the
outgoing atom, which is the commonly used observable. The correlation length is
directly related to the leading eigenvalue of the time evolution operator,
which we study in order to elucidate the phase structure. We find that as a
function of the time-of-flight the transition from the thermal to the maser
phase is characterized by a sharp peak in the correlation length. For longer
times-of-flight there is a transition to a phase where the correlation length
grows exponentially with the flux. We present a detailed numerical and
analytical treatment of the different phases and discuss the physics behind
them.Comment: 60 pages, 18 figure files, Latex + \special{} for the figures, (some
redundant figures are eliminated and others are changed
Recognizing Speech in a Novel Accent: The Motor Theory of Speech Perception Reframed
The motor theory of speech perception holds that we perceive the speech of
another in terms of a motor representation of that speech. However, when we
have learned to recognize a foreign accent, it seems plausible that recognition
of a word rarely involves reconstruction of the speech gestures of the speaker
rather than the listener. To better assess the motor theory and this
observation, we proceed in three stages. Part 1 places the motor theory of
speech perception in a larger framework based on our earlier models of the
adaptive formation of mirror neurons for grasping, and for viewing extensions
of that mirror system as part of a larger system for neuro-linguistic
processing, augmented by the present consideration of recognizing speech in a
novel accent. Part 2 then offers a novel computational model of how a listener
comes to understand the speech of someone speaking the listener's native
language with a foreign accent. The core tenet of the model is that the
listener uses hypotheses about the word the speaker is currently uttering to
update probabilities linking the sound produced by the speaker to phonemes in
the native language repertoire of the listener. This, on average, improves the
recognition of later words. This model is neutral regarding the nature of the
representations it uses (motor vs. auditory). It serve as a reference point for
the discussion in Part 3, which proposes a dual-stream neuro-linguistic
architecture to revisits claims for and against the motor theory of speech
perception and the relevance of mirror neurons, and extracts some implications
for the reframing of the motor theory
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