77 research outputs found
Correlated photon dynamics in dissipative Rydberg media
Rydberg blockade physics in optically dense atomic media under the conditions
of electromagnetically induced transparency (EIT) leads to strong dissipative
interactions between single photons. We introduce a new approach to analyzing
this challenging many-body problem in the limit of large optical depth per
blockade radius. In our approach, we separate the single-polariton EIT physics
from Rydberg-Rydberg interactions in a serialized manner while using a
hard-sphere model for the latter, thus capturing the dualistic particle-wave
nature of light as it manifests itself in dissipative Rydberg-EIT media. Using
this approach, we analyze the saturation behavior of the transmission through
one-dimensional Rydberg-EIT media in the regime of non-perturbative dissipative
interactions relevant to current experiments. Our model is able to capture the
many-body dynamics of bright, coherent pulses through these strongly
interacting media. We compare our model with available experimental data in
this regime and find good agreement. We also analyze a scheme for generating
regular trains of single photons from continuous-wave input and derive its
scaling behavior in the presence of imperfect single-photon EIT.Comment: Final version. 6 pages, 4 figures (+ Supplemental Material; 7 pages,
3 figures
Persistence of locality in systems with power-law interactions
Motivated by recent experiments with ultra-cold matter, we derive a new bound
on the propagation of information in -dimensional lattice models exhibiting
interactions with . The bound contains two terms: One
accounts for the short-ranged part of the interactions, giving rise to a
bounded velocity and reflecting the persistence of locality out to intermediate
distances, while the other contributes a power-law decay at longer distances.
We demonstrate that these two contributions not only bound but, except at long
times, \emph{qualitatively reproduce} the short- and long-distance dynamical
behavior following a local quench in an chain and a transverse-field Ising
chain. In addition to describing dynamics in numerous intractable long-range
interacting lattice models, our results can be experimentally verified in a
variety of ultracold-atomic and solid-state systems.Comment: 5 pages, 4 figures, version accepted by PR
Photon-Photon Interactions via Rydberg Blockade
We develop the theory of light propagation under the conditions of electromagnetically induced transparency in systems involving strongly interacting Rydberg states. Taking into account the quantum nature and the spatial propagation of light, we analyze interactions involving few-photon pulses. We show that this system can be used for the generation of nonclassical states of light including trains of single photons with an avoided volume between them, for implementing photon-photon gates, as well as for studying many-body phenomena with strongly correlated photons
Non-equilibrium fixed points of coupled Ising models
Driven-dissipative systems are expected to give rise to non-equilibrium
phenomena that are absent in their equilibrium counterparts. However, phase
transitions in these systems generically exhibit an effectively classical
equilibrium behavior in spite of their non-equilibrium origin. In this paper,
we show that multicritical points in such systems lead to a rich and genuinely
non-equilibrium behavior. Specifically, we investigate a driven-dissipative
model of interacting bosons that possesses two distinct phase transitions: one
from a high- to a low-density phase---reminiscent of a liquid-gas
transition---and another to an antiferromagnetic phase. Each phase transition
is described by the Ising universality class characterized by an (emergent or
microscopic) symmetry. They, however, coalesce at a
multicritical point, giving rise to a non-equilibrium model of coupled
Ising-like order parameters described by a
symmetry. Using a dynamical renormalization-group approach, we show that a pair
of non-equilibrium fixed points (NEFPs) emerge that govern the long-distance
critical behavior of the system. We elucidate various exotic features of these
NEFPs. In particular, we show that a generic continuous scale invariance at
criticality is reduced to a discrete scale invariance. This further results in
complex-valued critical exponents and spiraling phase boundaries, and it is
also accompanied by a complex Liouvillian gap even close to the phase
transition. As direct evidence of the non-equilibrium nature of the NEFPs, we
show that the fluctuation-dissipation relation is violated at all scales,
leading to an effective temperature that becomes "hotter" and "hotter" at
longer and longer wavelengths. Finally, we argue that this non-equilibrium
behavior can be observed in cavity arrays with cross-Kerr nonlinearities.Comment: 19+11 pages, 7+9 figure
Realizing Exactly Solvable SU(N) Magnets with Thermal Atoms
We show that thermal fermionic alkaline-earth atoms in a flat-bottom trap
allow one to robustly implement a spin model displaying two symmetries: the
symmetry that permutes atoms occupying different vibrational levels of
the trap and the SU() symmetry associated with nuclear spin states. The
high symmetry makes the model exactly solvable, which, in turn, enables the
analytic study of dynamical processes such as spin diffusion in this SU()
system. We also show how to use this system to generate entangled states that
allow for Heisenberg-limited metrology. This highly symmetric spin model should
be experimentally realizable even when the vibrational levels are occupied
according to a high-temperature thermal or an arbitrary non-thermal
distribution.Comment: 12 pages, 5 figures (including supplemental materials
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