2,527 research outputs found
Quantum Fuel with Multilevel Atomic Coherence for Ultrahigh Specific Work in a Photonic Carnot Engine
We investigate scaling of work and efficiency of a photonic Carnot engine
with the number of quantum coherent resources. Specifically, we consider a
generalization of the "phaseonium fuel" for the photonic Carnot engine, which
was first introduced as a three-level atom with two lower states in a quantum
coherent superposition by [M. O. Scully, M. Suhail Zubairy, G. S. Agarwal, and
H. Walther, Science {\bf 299}, 862 (2003)], to the case of level atoms
with coherent lower levels. We take into account atomic relaxation and
dephasing as well as the cavity loss and derive a coarse grained master
equation to evaluate the work and efficiency, analytically. Analytical results
are verified by microscopic numerical examination of the thermalization
dynamics. We find that efficiency and work scale quadratically with the number
of quantum coherent levels. Quantum coherence boost to the specific energy
(work output per unit mass of the resource) is a profound fundamental
difference of quantum fuel from classical resources. We consider typical modern
resonator set ups and conclude that multilevel phaseonium fuel can be utilized
to overcome the decoherence in available systems. Preparation of the atomic
coherences and the associated cost of coherence are analyzed and the engine
operation within the bounds of the second law is verified. Our results bring
the photonic Carnot engines much closer to the capabilities of current
resonator technologies.Comment: 15 pages, 8 figure
Optical bistability in one dimensional doped photonic crystals with spontaneously generated coherence
We investigate optical bistability in a multilayer one-dimensional photonic
crystal where the central layer is doped with -type three level atoms.
We take into account the influence of spontaneously generated coherence when
the lower atomic levels are sufficiently close to each other, in which case
Kerr-type nonlinear response of the atoms is enhanced. We calculate the
propagation of a probe beam in the defect mode window using numerical nonlinear
transfer matrix method. We find that Rabi frequency of a control field acting
on the defect layer and the detuning of the probe field from the atomic
resonance can be used to control the size and contrast of the hysteresis loop
and the threshold of the optical bistability. In particular we find that, at
the optimal spontaneously generated coherence, three orders of magnitude lower
threshold can be achieved relative to the case without the coherence.Comment: 9 pages, 7 figure
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