Search results for "classical"
showing 10 items of 2294 documents
Entanglement replication in driven-dissipative many body systems
2012
We study the dissipative dynamics of two independent arrays of many-body systems, locally driven by a common entangled field. We show that in the steady state the entanglement of the driving field is reproduced in an arbitrarily large series of inter-array entangled pairs over all distances. Local nonclassical driving thus realizes a scale-free entanglement replication and long-distance entanglement distribution mechanism that has immediate bearing on the implementation of quantum communication networks.
Dynamical Casimir-Polder force on a partially dressed atom near a conducting wall
2010
We study the time evolution of the Casimir-Polder force acting on a neutral atom in front of a perfectly conducting plate, when the system starts its unitary evolution from a partially dressed state. We solve the Heisenberg equations for both atomic and field quantum operators, exploiting a series expansion with respect to the electric charge and an iterative technique. After discussing the behaviour of the time-dependent force on an initially partially-dressed atom, we analyze a possible experimental scheme to prepare the partially dressed state and the observability of this new dynamical effect.
Classical and quantum vortex leapfrogging in two-dimensional channels
2020
The leapfrogging of coaxial vortex rings is a famous effect which has been noticed since the times of Helmholtz. Recent advances in ultra-cold atomic gases show that the effect can now be studied in quantum fluids. The strong confinement which characterizes these systems motivates the study of leapfrogging of vortices within narrow channels. Using the two-dimensional point vortex model, we show that in the constrained geometry of a two-dimensional channel the dynamics is richer than in an unbounded domain: alongsize the known regimes of standard leapfrogging and the absence of it, we identify new regimes of backward leapfrogging and periodic orbits. Moreover, by solving the Gross-Pitaevskii…
Non-Equilibrium Thermodynamics of Unsteady Superfluid Turbulence in Counterflow and Rotating Situations
2005
The methods of nonequilibrium thermodynamics are used in this paper to relate an evolution equation for the vortex line density $L$, describing superfluid turbulence in the simultaneous presence of counterflow and rotation, to an evolution equation for the superfluid velocity ${\mathbf{v}}_{s}$, in order to be able to describe the full evolution of ${\mathbf{v}}_{s}$ and $L$, instead of only $L$. Two alternative possibilities are analyzed, related to two possible alternative interpretations of a term coupling the effects of the counterflow and rotation on the vortex tangle, and which imply some differences between situations where counterflow and rotation vectors are parallel or orthogonal …
Energy and temperature of superfluid turbulent vortex tangles
2007
We consider three aspects of turbulent vortex tangles in superfluids. First, we outline some contributions to the Vinen’s equation for the time evolution of the vortex line density, related to the presence of pinned vortices incorporating the effects of the walls. Afterwards, we analyze some aspects of the energy balance of the vortex tangle, related to frictional dissipation and to vortex formation and destruction. Finally, we explore the concept of an effective temperature for the vortex tangle, related to the average energy of the vortex loops and to the diffusion coefficient of vortex lines. The combination of these ideas suggests some formal similarities with other kinds of driven none…
Objective features in quantum states
2023
One of the key features of quantum mechanics is that any superposition of quantum states is in itself a legitimate quantum state. This has far reaching consequences, and is behind the stark difference in behaviour between quantum and classical systems. In particular, quantum systems are not -unlike classical ones- intrinsically objective, that is, different observers are not always able to agree on the properties of the system. Understanding the conditions for objectivity in quantum states is therefore key to address the wider issue of the quantum-to-classical transition. Here, we discuss several aspects of quantum objectivity, and in particular subtleties that arise to the definitions of o…
Colloquium: Trapped ions as quantum bits -- essential numerical tools
2009
Trapped, laser-cooled atoms and ions are quantum systems which can be experimentally controlled with an as yet unmatched degree of precision. Due to the control of the motion and the internal degrees of freedom, these quantum systems can be adequately described by a well known Hamiltonian. In this colloquium, we present powerful numerical tools for the optimization of the external control of the motional and internal states of trapped neutral atoms, explicitly applied to the case of trapped laser-cooled ions in a segmented ion-trap. We then delve into solving inverse problems, when optimizing trapping potentials for ions. Our presentation is complemented by a quantum mechanical treatment of…
Motion of the wave-function zeros in spin-boson systems.
1995
In the analytic Bargmann representation associated with the harmonic oscillator and spin coherent states, the wave functions considered as consisting of entire complex functions can be factorized in terms of their zeros in a unique way. The Schr\"odinger equation of motion for the wave function is turned to a system of equations for the zeros of the wave function. The motion of these zeros as a nonlinear flow of points is studied and interpreted for linear and nonlinear bosonic and spin Hamiltonians. Attention is given to the study of the zeros of the Jaynes-Cummings model and to its finite analog. Numerical solutions are derived and dicussed.
Multiphoton Quantum Optics and Quantum State Engineering
2007
We present a review of theoretical and experimental aspects of multiphoton quantum optics. Multiphoton processes occur and are important for many aspects of matter-radiation interactions that include the efficient ionization of atoms and molecules, and, more generally, atomic transition mechanisms; system-environment couplings and dissipative quantum dynamics; laser physics, optical parametric processes, and interferometry. A single review cannot account for all aspects of such an enormously vast subject. Here we choose to concentrate our attention on parametric processes in nonlinear media, with special emphasis on the engineering of nonclassical states of photons and atoms. We present a d…
On-chip frequency combs and telecommunications signal processing meet quantum optics
2018
Entangled optical quantum states are essential towards solving questions in fundamental physics and are at the heart of applications in quantum information science. For advancing the research and development of quantum technologies, practical access to the generation and manipulation of photon states carrying significant quantum resources is required. Recently, integrated photonics has become a leading platform for the compact and cost-efficient generation and processing of optical quantum states. Despite significant advances, most on-chip nonclassical light sources are still limited to basic bi-photon systems formed by two-dimensional states (i.e., qubits). An interesting approach bearing …