233 research outputs found
Nonequilibrium Quantum Phase Transitions in the Dicke Model
We establish a set of nonequilibrium quantum phase transitions in the Dicke
model by considering a monochromatic nonadiabatic modulation of the atom-field
coupling. For weak driving the system exhibits a set of sidebands which allow
the circumvention of the no-go theorem which otherwise forbids the occurence of
superradiant phase transitions. At strong driving we show that the system
exhibits a rich multistable structure and exhibits both first- and second-order
nonequilibrium quantum phase transitions.Comment: 4 pages, 3 Figures, and supplementary material. This new version
contains corrected typos, new references and new versions of the figures.
Published by Physical Review Letter
Floquet stroboscopic divisibility in non-Markovian dynamics
We provide a general discussion of the Liouvillian spectrum for a system
coupled to a non-Markovian bath using Floquet theory. This approach is suitable
when the system is described by a time-convolutionless master equation with
time-periodic rates. Surprisingly, the periodic nature of rates allow us to
have a stroboscopic divisible dynamical map at discrete times, which we refer
to as Floquet stroboscopic divisibility. We illustrate the general theory for a
Schr\"odinger cat which is roaming inside a non-Markovian bath, and demonstrate
the appearance of stroboscopic revival of the cat at later time after its
death. Our theory may have profound implications in entropy production in
non-equilibrium systems.Comment: We changed the title and explained in more detail the definition of
non-Markovian dynamics used in the manuscrip
Photon-resolved Floquet theory in open quantum systems
Photon-resolved Floquet theory keeps track of the photon exchange of a
quantum system with a coherent driving field. It thus complements the standard
full-counting statistics that counts the number of photons exchanged with
incoherent photon modes giving rise to dissipation. In this paper, we introduce
a unifying framework describing both situations. We develop methods suitable
for an analytical evaluation of low-order cumulants of photonic probability
distributions. Within this framework we analyze the two-mode Jaynes-Cummings
model to demonstrate that the Photon-resolved Floquet theory and the standard
full-counting statistics make consistent statistical predictions.
Interestingly, we find that the photon-flux fluctuations diverge for vanishing
dissipation, which can be related to an entanglement effect between the driven
matter system and the driving field. To substantiate our results, we use our
framework to describe efficient photon up-conversion in an ac-driven lambda
system, that is characterized by a high signal-to-noise ratio. As the framework
is non-perturbative and predicts fluctuations, it paves the way towards
non-perturbative spectroscopy, which will assist to improve metrological
methods.Comment: 25 pages, 6 figures, 4 appendices. Comments are welcom
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