97 research outputs found
Hydrodynamic nucleation of vortices and solitons in a resonantly excited polariton superfluid
We present a theoretical study of the hydrodynamic properties of a quantum
gas of exciton-polaritons in a semiconductor microcavity under a resonant laser
excitation. The effect of a spatially extended defect on the superfluid flow is
investigated as a function of the flow speed. The processes that are
responsible for the nucleation of vortices and solitons in the wake of the
defect are characterized, as well as the regimes where the superfluid flow
remains unperturbed. Specific features due to the non-equilibrium nature of the
polariton fluid are put in evidence
A self-contained quantum harmonic engine
We propose a system made of three quantum harmonic oscillators as a compact
quantum engine for producing mechanical work. The three oscillators play
respectively the role of the hot bath, the working medium and the cold bath.
The working medium performs an Otto cycle during which its frequency is changed
and it is sequentially coupled to each of the two other oscillators. As the two
environments are finite, the lifetime of the machine is finite and after a
number of cycles it stops working and needs to be reset. We analyse the
entanglement and quantum discord generated during the strokes and show that
high work generation is always accompanied by large quantum correlations.Comment: Updated, published version. See also related but independent work
from Pozas-Kerstjens et al. arXiv:1708.0636
Critical velocity in resonantly driven polariton superfluids
We study the necessary condition under which a resonantly driven exciton
polariton superfluid flowing against an obstacle can generate turbulence. The
value of the critical velocity is well estimated by the transition from
elliptic to hyperbolic of an operator following ideas developed by Frisch,
Pomeau, Rica for a superfluid flow around an obstacle, though the nature of
equations governing the polariton superfluid is quite different. We find
analytical estimates depending on the pump amplitude and on the pump energy
detuning, quite consistent with our numerical computations
Tracer particle diffusion in a system with hardcore interacting particles
In this study, inspired by the work of K. Nakazato and K. Kitahara [Prog.
Theor. Phys. 64, 2261 (1980)], we consider the theoretical problem of tracer
particle diffusion in an environment of diffusing hardcore interacting crowder
particles. The tracer particle has a different diffusion constant from the
crowder particles. Based on a transformation of the generating function, we
provide an exact formal expansion for the tracer particle probability density,
valid for any lattice in the thermodynamic limit. By applying this formal
solution to dynamics on regular Bravais lattices we provide a closed form
approximation for the tracer particle diffusion constant which extends the
Nakazato and Kitahara results to include also b.c.c. and f.c.c. lattices.
Finally, we compare our analytical results to simulations in two and three
dimensions.Comment: 28 pages with appendix, 5 figure. To appear in JSTA
Quantum squeezing generation versus photon localization in a disordered microcavity
We investigate theoretically the nonlinear dynamics induced by an intense
pump field in a disordered planar microcavity. Through a self-consistent
theory, we show how the generation of quantum optical noise squeezing is
affected by the breaking of the in-plane translational invariance and the
occurrence of photon localization. We find that the generation of single-mode
Kerr squeezing for the ideal planar case can be prevented by disorder as a
result of multimode nonlinear coupling, even when the other modes are in the
vacuum state. However, the excess noise is a non-monotonous function of the
disorder amplitude. In the strong localization limit, we show that the system
becomes protected with respect to this fundamental coupling mechanism and that
the ideal quadrature squeezing generation can be obtained
Metamorphoses of the flow past an obstacle of a resonantly-driven bistable polariton fluid
Motivated by recent experiments, we theoretically analyze the flow past an
obstacle of a one-dimensional "quantum fluid of light" which is resonantly
driven, and exhibits bistability. The flow is found to abruptly change several
times when the fluid velocity or the obstacle potential strength are increased.
In contrast to the cases of usual fluids and superfluids, the transitions take
place between stationary states. They involve the fluid bistability in an
essential way. Remarkably, at the transitions points, the fluid in the obstacle
wake lies in the unstable intermediate density state
Dynamical symmetries and crossovers in a three-spin system with collective dissipation
We consider the non-equilibrium dynamics of a simple system consisting of
interacting spin- particles subjected to a collective damping. The model
is close to situations that can be engineered in hybrid electro/opto-mechanical
settings. Making use of large-deviation theory, we find a Gallavotti-Cohen
symmetry in the dynamics of the system as well as evidence for the coexistence
of two dynamical phases with different activity levels. We show that additional
damping processes smoothen out this behavior. Our analytical results are backed
up by Monte Carlo simulations that reveal the nature of the trajectories
contributing to the different dynamical phases.Comment: 6 pages, 5 figure
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