AtMol Research Seminar Archive
Index Current Seminars

Easter 2009

Date Speaker Institution
 Quantum Optics of Quantum Dot Spins
29th April Dr Mete Atatüre University of Cambridge

Self-assembled semiconductor quantum dots have atom-like properties such as discrete energy levels coupled by optical transitions, and their coherence properties can be revealed in quantum-optics experiments. Further, these transitions are governed by spin-dependent optical selection rules. This opens a channel to control and detect a single spin in a quantum dot via lasers. However, quantum dots can also interact strongly with a spin (nuclei) and/or a charge (electrons) reservoir of the solid-state environment leading to a rich source of interaction mechanisms. Consequently, identifying the regimes of these mechanisms is crucial for achieving a level of control in solid-state-based systems similar to that of atoms. I will provide a highlight of recent progress on all-optical control and measurement of quantum dot spins.

  Exploring attosecond phenomena in ionization of multi-electron atoms and molecules by single photon absorption and strong laser fields
6th May Dr. Agapi Emmanouilidou University of Massachusetts

We investigate multi-ionization processes using novel classical and semiclassical methods and find very good agreement with experiments on the triple photoionization of lithium by a single photon. Our method reveals surprising mechanisms for multi-electron escape: The four-body Coulomb ionization proceeds through a sequence of electron-electron collisions involving three-body Coulomb subsystems. These attosecond time-scale collisions can explain the surprising configurations of three- and four-electron escape for small excess energies. The break-up geometries are found to depend on the initial state of the atom, contrary to conventional wisdom based on two-electron atoms. Thus our studies point the way for future experiments which will test our findings. These novel classical and semiclassical techniques have been recently generalized to describe strongly driven atomic and molecular systems. We demonstrate the predictive power of these techniques by exploring the frequency dependence of double ionization of the strongly driven Helium. Unexpected effects emerge for strongly driven diatomic molecules for intensities in an intermediate regime.

 
13th May Prof. Gerard Meijer Fritz-Haber-Institut der Max-Planck-Gesellschaft
  First Year Seminar: Nanowires - Atom bouncing, atom trapping
20th May Mr. Adam West

Ultracold atoms are a relatively well understood aspect of physics. The nanowire project aims to take this well known phenomenon and combine it with nanomagnetic structures to reveal some new physics, and some interesting applications. The domain walls that form in our "wiggly wires" are what make them so interesting when they interact with our atoms. The talk will look at two aspects in particular - a magnetic atom mirror, using thousands of domain walls, and a mobile atom trap, which uses just one.

  Quantum state engineering of light fields
27th May Prof. Myungshik Kim Queens University, Belfast

A light field may be a very useful resource in the applications of quantum mechanics for information processing. A refined light field may also be used for the control and manipulations of a system at the quantum level. In this presentation, we show that a light field can be used and modified to manifest exotic nonclassicality with the help of unitary or non-unitary operations.

  First Year Seminar: Strontium project
3rd June Mr. Graham Lochead

Strontium is a useful element to study cold plasma and Rydberg physics due to its two electron outer shell structure. This talk will focus on the laser locking techniques for the main cooling transition laser and the linewidth narrowing system that is being implemented for the intercombination transition that will be used for second stage cooling. A novel design for a pyramid MOT for strontium will also be talked about.

  First Year Seminar: Towards a Two-Species Quantum Degenerate Bose Gas
10th June Mr. Daniel Jenkin

Quantum degenerate atomic gases are currently a hot topic in the field of atomic and molecular physics. Many groups are now striving to produce ultracold molecules where standard laser cooling techniques are not adequate. One method is to produce ultracold molecules from pre-cooled atoms via a combination of magneto-association and Feshbach resonance prior to laser manipulation being utilised to transfer the molecules to the ground state via a process known as Stimulated Raman Adiabatic Passage (STIRAP).

This talk will focus on our efforts towards producing a ground state dipolar quantum gas, the ongoing improvements to the experimental setup including the construction of an optical dipole trap and recent results involving the optimisation of the pyramid MOT.

  First Year Seminar: Number-conserving dynamics of Bose-Einstein condensates
17th June Mr. Tom Billam

Mean field theory has become the standard description of an atomic Bose- Einstein condensate (BEC) at zero temperature. However, at finite temperatures there is no standard description: many, very different, descriptions are still being developed.

The goal of a new project within the AtMol group is to apply one of these descriptions --- a `number-conserving' theory, in which the total number of atoms is explicitly conserved --- to the problem of bright soliton formation and dynamics in atomic BECs. This talk will firstly introduce the problem of bright soliton formation, and secondly introduce the number-conserving description we will use to study it. In particular, we will compare this number-conserving description, and others, to the more conventional symmetry- breaking descriptions, making clear the advantages number-conserving theories have when studying bright solitons. Thirdly, we will discuss how to apply the theory numerically and present the results we have so far, before concluding with an outline of our future work.

  First Year Seminar: Bright Matter Wave Solitons: Formation, Dynamics and Quantum Reflection
24th June Miss Anna Marchant

Solitons are self-focusing wave packets that can propagate over long distances without change in shape and emerge from collisions unaltered. In the context of Bose-Einstein condensation, one can create both dark and bright solitons. Bright solitons form when the atomic interactions are attractive and correspond to self-trapped atomic waves packets that do not disperse. Such solitons are ideal candidates for atom interferometry and for probing short range atom-surface interactions and measurements of quantum reflection.

Our project will use Rb-85 condensates where a broad Feshbach resonance allows the precise control of the s-wave scattering length. This system has already been used to probe the collapse of a condensate and to demonstrate the formation of solitons. The new apparatus currently under construction is designed to probe soliton collisions and dynamics in more depth and in the longer term to study quantum reflection from a solid surface.

This talk will present the progress of our work towards this exciting goal.