111 research outputs found
Thermal Baths as Quantum Resources: More Friends than Foes?
In this article we argue that thermal reservoirs (baths) are potentially
useful resources in processes involving atoms interacting with quantized
electromagnetic fields and their applications to quantum technologies. One may
try to suppress the bath effects by means of dynamical control, but such
control does not always yield the desired results. We wish instead to take
advantage of bath effects, that do not obliterate "quantumness" in the
system-bath compound. To this end, three possible approaches have been pursued
by us: (i) Control of a quantum system faster than the correlation time of the
bath to which it couples: Such control allows us to reveal
quasi-reversible/coherent dynamical phenomena of quantum open systems, manifest
by the quantum Zeno or anti-Zeno effects (QZE or AZE, respectively). Dynamical
control methods based on the QZE are aimed not only at protecting the
quantumness of the system, but also diagnosing the bath spectra or transferring
quantum information via noisy media. By contrast, AZE-based control is useful
for fast cooling of thermalized quantum systems. (ii) Engineering the coupling
of quantum systems to selected bath modes: This approach, based on field -atom
coupling control in cavities, waveguides and photonic band structures, allows
to drastically enhance the strength and range of atom-atom coupling through the
mediation of the selected bath modes. More dramatically, it allows us to
achieve bath-induced entanglement that may appear paradoxical if one takes the
conventional view that coupling to baths destroys quantumness. (iii)
Engineering baths with appropriate non-flat spectra: This approach is a
prerequisite for the construction of the simplest and most efficient quantum
heat machines (engines and refrigerators). We may thus conclude that often
thermal baths are "more friends than foes" in quantum technologies.Comment: 27 pages, 17 figure
Trapping state restoration in the randomly-driven Jaynes-Cummings model by conditional measurements
We propose a scheme which can effectively restore fixed points in the quantum
dynamics of repeated Jaynes-Cummings interactions followed by atomic state
measurements, when the interaction times fluctuate randomly. It is based on
selection of superposed atomic states whose phase correlations tend to suppress
the phase fluctuations of each separate state. One suggested realization
involves the convergence of the cavity field distribution to a single Fock
state by conditional measurements performed on two-level atoms with fluctuating
velocities after they cross the cavity. Another realization involves a trapped
ion whose internal-motional state coupling fluctuates randomly. Its motional
state is made to converge to a Fock state by conditional measurements of the
internal state of the ion.Comment: RevTeX, 5 pages, four (EPS) figures automatically included through
epsfig. Physical Review A 1998 (accepted for publication) Two references
added to Ref. [8]. No other change. Final version which will appear in
Physical Review
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