15,103 research outputs found
Heralded multiphoton states with coherent spin interactions in waveguide QED
WaveguideQEDoffers the possibility of generating strong coherent atomic
interactions either through appropriate atomic configurations in the
dissipative regime or in the bandgap regime. In this work, we show how to
harness these interactions in order to herald the generation of highly
entangled atomic states, which afterwards can be mapped to generate single mode
multi-photonic states with high fidelities.Weintroduce two protocols for the
preparation of the atomic states, we discuss their performance and compare them
to previous proposals. In particular, we show that one of them reaches high
probability of success for systems with many atoms but low Purcell factors
Non-adiabatic effects in periodically driven-dissipative open quantum systems
We present a general method to calculate the quasi-stationary state of a
driven-dissipative system coupled to a transmission line (and more generally,
to a reservoir) under periodic modulation of its parameters. Using Floquet's
theorem, we formulate the differential equation for the system's density
operator which has to be solved for a single period of modulation. On this
basis we also provide systematic expansions in both the adiabatic and
high-frequency regime. Applying our method to three different systems -- two-
and three-level models as well as the driven nonlinear cavity -- we propose
periodic modulation protocols of parameters leading to a temporary suppression
of effective dissipation rates, and study the arising non-adiabatic features in
the response of these systems.Comment: 12 pages, 8 figure
Hydrodynamics and two-dimensional dark lump solitons for polariton superfluids
We study a two-dimensional incoherently pumped exciton-polariton condensate described by an open-dissipative Gross-Pitaevskii equation for the polariton dynamics coupled to a rate equation for the exciton density. Adopting a hydrodynamic approach, we use multiscale expansion methods to derive several models appearing in the context of shallow water waves with viscosity. In particular, we derive a Boussinesq/Benney-Luke–type equation and its far-field expansion in terms of Kadomtsev-Petviashvili-I (KP-I) equations for right- and left-going waves. From the KP-I model, we predict the existence of vorticity-free, weakly (algebraically) localized two-dimensional dark-lump solitons. We find that, in the presence of dissipation, dark lumps exhibit a lifetime three times larger than that of planar dark solitons. Direct numerical simulations show that dark lumps do exist, and their dissipative dynamics is well captured by our analytical approximation. It is also shown that lumplike and vortexlike structures can spontaneously be formed as a result of the transverse “snaking” instability of dark soliton stripes.Europe Union project AEI/FEDER: MAT2016-79866-
Nonequilibrium Response from the dissipative Liouville Equation
The problem of response of nonequilibrium systems is currently under intense
investigation. We propose a general method of solution of the Liouville
Equation for thermostatted particle systems subjected to external forces which
retains only the slow degrees of freedom, by projecting out the majority of
fast variables. Response formulae, extending the Green-Kubo relations to
dissipative dynamics are provided, and comparison with numerical data is
presented
Quantum trajectories and open many-body quantum systems
The study of open quantum systems has become increasingly important in the
past years, as the ability to control quantum coherence on a single particle
level has been developed in a wide variety of physical systems. In quantum
optics, the study of open systems goes well beyond understanding the breakdown
of quantum coherence. There, the coupling to the environment is sufficiently
well understood that it can be manipulated to drive the system into desired
quantum states, or to project the system onto known states via feedback in
quantum measurements. Many mathematical frameworks have been developed to
describe such systems, which for atomic, molecular, and optical (AMO) systems
generally provide a very accurate description of the open quantum system on a
microscopic level. In recent years, AMO systems including cold atomic and
molecular gases and trapped ions have been applied heavily to the study of
many-body physics, and it has become important to extend previous understanding
of open system dynamics in single- and few-body systems to this many-body
context. A key formalism that has already proven very useful in this context is
the quantum trajectories technique. This was developed as a numerical tool for
studying dynamics in open quantum systems, and falls within a broader framework
of continuous measurement theory as a way to understand the dynamics of large
classes of open quantum systems. We review the progress that has been made in
studying open many-body systems in the AMO context, focussing on the
application of ideas from quantum optics, and on the implementation and
applications of quantum trajectories methods. Control over dissipative
processes promises many further tools to prepare interesting and important
states in strongly interacting systems, including the realisation of parameter
regimes in quantum simulators that are inaccessible via current techniques.Comment: 66 pages, 29 figures, review article submitted to Advances in Physics
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