Dissipation control in cavity QED with oscillating mode structures

We demonstrate how a time-dependent dissipative environment may be used as a tool for controlling the quantum state of a two-level atom. In our model system the frequency and coupling strength associated with microscopic reservoir modes are modulated, while the principal features of the reservoir structure remain fixed in time. Physically, this may be achieved by containing a static atom-cavity system inside an oscillating external bath. We show that it is possible to dynamically decouple the atom from its environment, despite the fact that the two remain resonant at all times. This can lead to Markovian dynamics, even for a strong atom-bath coupling, as the atomic decay becomes inhibited into all but a few channels; the reservoir occupation spectrum consequently acquires a sideband structure, with peaks separated by the frequency of the environmental modulation. The reduction in the rate of spontaneous emission using this approach can be significantly greater than could be achieved with an oscillatory atom-bath detuning using the same parameters

Radio-frequency dressed lattices for ultracold alkali atoms

Ultracold atomic gases in periodic potentials are powerful platforms for exploring quantum physics in regimes dominated by many-body effects as well as for developing applications that benefit from quantum mechanical effects. Further advances face a range of challenges including the realization of potentials with lattice constants smaller than optical wavelengths as well as creating schemes for effective addressing and manipulation of single sites. In this paper we propose a dressed-based scheme for creating periodic potential landscapes for ultracold alkali atoms with the capability of overcoming such difficulties. The dressed approach has the advantage of operating in a low-frequency regime where decoherence and heating effects due to spontaneous emission do not take place. These results highlight the possibilities of atom-chip technology in the future development of quantum simulations and quantum technologies, and provide a realistic scheme for starting such an exploration

Control of atomic decay rates via manipulation of reservoir mode frequencies

We analyse the problem of a two-level atom interacting with a time-dependent dissipative environment modelled by a bath of reservoir modes. In the model of this paper the principal features of the reservoir structure remain constant in time, but the microscopic structure does not. In the context of an atom in a leaky cavity this corresponds to a fixed cavity and a time-dependent external bath. In this situation we show that by chirping the reservoir modes sufficiently fast it is possible to inhibit, or dramatically enhance the decay of the atomic system, even though the gross reservoir structure is fixed. Thus it is possible to extract energy from a cavity-atom system faster than the empty cavity rate. Similar, but less dramatic effects are possible for moderate chirps where partial trapping of atomic population is also possible.Comment: 12 pages, 9 figure

Exact quantum jump approach to open systems in Bosonic and spin baths

A general method is developed which enables the exact treatment of the non-Markovian quantum dynamics of open systems through a Monte Carlo simulation technique. The method is based on a stochastic formulation of the von Neumann equation of the composite system and employs a pair of product states following a Markovian random jump process. The performance of the method is illustrated by means of stochastic simulations of the dynamics of open systems interacting with a Bosonic reservoir at zero temperature and with a spin bath in the strong coupling regime.Comment: 4 pages, 2 figure

Extended Gaussian wave packet dynamics

We examine an extension to the theory of Gaussian wave packet dynamics in a one-dimensional potential by means of a sequence of time dependent displacement and squeezing transformations. Exact expressions for the quantum dynamics are found, and relationships are explored between the squeezed system, Gaussian wave packet dynamics, the time dependent harmonic oscillator, and wave packet dynamics in a Gauss-Hermite basis. Expressions are given for the matrix elements of the potential in some simple cases. Several examples are given, including the propagation of a non-Gaussian initial state in a Morse potential

Two-dimensional atom trapping in field-induced adiabatic potentials

We show how to create a novel two-dimensional trap for ultracold atoms from a conventional magnetic trap. We achieve this by utilizing rf-induced adiabatic potentials to enhance the trapping potential in one direction. We demonstrate the loading process and discuss the experimental conditions under which it might be possible to prepare a 2D Bose condensate. A scheme for the preparation of coherent matterwave bubbles is also discussed

High harmonic generation and periodic level crossings

Published versio

Atom trapping and two-dimensional Bose-Einstein condensates in field-induced adiabatic potentials

We discuss a method to create two-dimensional traps as well as atomic shell, or bubble, states for a Bose-Einstein condensate initially prepared in a conventional magnetic trap. The scheme relies on the use of time-dependent, radio frequency-induced adiabatic potentials. These are shown to form a versatile and robust tool to generate novel trapping potentials. Our shell states take the form of thin, highly stable matter-wave bubbles and can serve as stepping-stones to prepare atoms in highly-excited trap eigenstates or to study `collapse and revival phenomena'. Their creation requires gravitational effects to be compensated by applying additional optical dipole potentials. However, in our scheme gravitation can also be exploited to provide a route to two-dimensional atom trapping. We demonstrate the loading process for such a trap and examine experimental conditions under which a 2D condensate may be prepared.Comment: 16 pages, 10 figure

Time dependent partial waves and vortex rings in the dynamics of wave packets

We have found a new class of time dependent partial waves which are solutions of time dependent Schr\"odinger equation for three dimensional harmonic oscillator. We also showed the decomposition of coherent states of harmonic oscillator into these partial waves. This decomposition appears perticularly convenient for a description of the dynamics of a wave packet representing a particle with spin when the spin--orbit interaction is present in the hamiltonian. An example of an evolution of a localized wave packet into a torus and backwards, for a particular initial conditions is analysed in analytical terms and shown with a computer graphics.Comment: 10 pages, LaTeX, 6 postscript figures, submitted to J. Phys. A: Math. Ge

Phase properties of a new nonlinear coherent state

We study phase properties of a displacement operator type nonlinear coherent state. In particular we evaluate the Pegg-Barnett phase distribution and compare it with phase distributions associated with the Husimi Q function and the Wigner function. We also study number- phase squeezing of this state.Comment: 8 eps figures. to appear in J.Opt