AtMol Research Seminar Archive
Index Current Seminars

Epiphany 2009

Information: "Journal Club" talks are mandatory presentations by the 2nd year Ph.D. students in the AtMol group on an area of atomic or molecular physics outside of their particular area of expertise. In general the talk will be based around a particular paper. We hope that you will find these talks as informative as any other seminar in the series.

Date Speaker Institution
  Journal Club talk: Cavity cooling of a single atom [ref]
21st January Mr. James Millen

In the first half of this presentation I aim to present a brief and basic introduction to cavity quantum electrodynamics, followed by a short summary of the wide range of experiments that have been carried out on atoms in a cavity. The second half of the talk will concern the specific case of the cooling of a single atom coupled to a high finesse cavity.

  Journal Club talk: An edged view into the blur: Electronmicroscopy [ref (1)] [ref (2)]
28th January Miss Sylvi Haendel

Conventional imaging methods for ultracold quantum gases rely on the interaction of atoms with resonant light. Since the experiments of Franck-Hertz we know that atoms can interact with electrons, thus it is obvious to migrate the idea of electron microscopy to the field of ultracold atoms. Based on a recent publication (Nature 4, 949-953 (2008)) of the group of Herwig Ott at the university of Mainz I'm going to introduce the principle of a scanning electron microscope as an imaging method. An overview of the performed experiments (Appl. Phys. B 89, 447-451 (2007)) is presented as well as the experimental apparatus.

  Journal Club talk: Optomechanics: Back-Action at the mesoscale [ref]
4th February Mr. Jonathan Pritchard

Photons reflecting off a cavity mirror cause a radiation pressure due to the transfer of momentum. This leads to mechanical excitation, which in turn modifies the properties of the radiation field within the cavity, coupling the optical and mechanical degrees of freedom. This places a limit on the displacement sensitivity, important in fields such as gravitational wave detection. By exploiting this interaction however it is possible to cool mechanical resonators to their ground state in a similar way to laser cooling of atoms. This opens the way for experiments exploring the change from classical to quantum behaviour and the creation of non-classical vibrational states.

  Journal Club talk: Zeno's Arrow: from a classical paradox to a quantum effect [ref (1)] [ref (2)]
11th February Mr. Paul Siddons

In the fifth century BC Zeno of Elea devised several paradoxes, include that of his eponymous arrow. The arrow paradox denies the possibility of motion to an arrow in flight. Despite evidence to the contrary, modern philosophers are not satisfied with current resolutions to the paradox. Quantum mechanics provides an adequate solution, whilst at the same time posing another problem: if the quantum arrow's state is measured frequently enough, motion ceases. This is the quantum Zeno effect, and in this seminar I will present a solution to the paradox and problem, and briefly describe some uses of this quantum effect.

  Bose Einstein condensates in arbitrary time-dependent potentials and ultra cold Rydberg atoms in optical dipole traps.
18th February Dr Calum MacCormick Open University

In this talk I will discuss two loosely related experimental topics. Firstly I will describe an approach to optical trapping which allows the realisation of dynamic, fully arbitrary and sufficiently stable potentials for the manipulation of Bose-Einstein condensates. BECs are created in a variety of geometries, cinluding toroids, ring lattices and square lattices. Matter wave interference patterns confirm that the trapped gas is a condensate. In the second part of the talk i present a new experimental project at the Open Univesity which is designed to study ultra-cold Rydberg atoms in micron-sized optical dipole traps.

  Journal Club talk: From quantum to classical: watching a single photon become a wave [ref]
25th February Mr. Richard Abel

In this presentation I will give a brief introduction to how light can be described as a classical or particle like state. I will introduce an experiment (science 306, 660 2004) where a single photon added coherent state is produced and the transition from wavelike to particle like behaviour of light observed. I will then discuss how this experiment has been extended to alternating sequences of photon creation and annihilation. This allows the noncommutativity of the creation and annihilation operator to directly observed.

  Journal Club talk: A pumped atom laser [ref (1)] [ref (2)]
4th March Mr. Danny McCarron

In this talk I will present an introduction to the atom laser, originally demonstrated by the MIT group in 1997, before briefly reviewing the history and development of this device. I will then report on recent exciting progress made in this field by the Atom Laser Group at the ARC Centre for Quantum-Atom Optics, Australia. Here while continuously output-coupling an atom laser beam new atoms are simultaneously and irreversibly pumped into the lasing mode from a physically separate source. This represents an important step along the path to a continuous atom laser.

  Mesoscopic ensembles on a magnetic lattice atom chip for quantum information science
11th March Dr. Shannon Whitlock Universiteit van Amsterdam

We have recently produced the first two-dimensional lattice of magnetic microtraps for ultracold atoms based on patterned magnetic films [1]. This novel system bridges the gap between individual atomic clouds realised with chip-scale microtraps and optical lattices which contain a single atom per site. We load hundreds of tightly confining and optically resolved array sites with mesoscopic atom clouds and subsequently cool them to the temperature required for quantum degeneracy. An atomic shift register, the cold-atom analog of an electronic CCD, can transport the clouds; while local manipulation is possible using focused lasers. High atomic densities have allowed a small and well defined number of atoms to be prepared in each trap, forming an ideal starting point for quantum information processing with neutral atoms. We use absorption imaging and advanced image processing techniques to reliably detect as few as 1 to 10 atoms per lattice site and apply spatial correlation analysis to the measured density distributions to reveal the quantum fluctuations typical of mesoscopic atomic systems. In the near future we plan to incorporate laser excited Rydberg states of the atoms to mediate long-range interactions between neighbouring microtraps. Furthermore, Rydberg excitations could be used to entangle mesoscopic ensembles of atoms for use in quantum information processing. We expect this system to be the ideal platform for studying many particle entanglement and quantum information processing with neutral atoms on an atom chip.

[1] S. Whitlock, R. Gerritsma, T. Fernholz and R. J. C. Spreeuw, New J. Phys. 11 023021 (2009)

  Journal Club talk: Quantum Internet [ref]
18th March Mr. Monsit Tanasittikosol

Quantum networks provide opportunities and challenges across a range of intellectual and technical frontiers, including quantum computation, communication and metrology. The realization of quantum networks composed of many nodes and channels requires new scientific capabilities for generating and characterizing quantum coherence and entanglement. Fundamental to this endeavour are quantum interconnects, which convert quantum states from one physical system to those of another in a reversible manner. Such quantum connectivity in networks can be achieved by the optical interactions of single photons and atoms, allowing the distribution of entanglement across the network and the teleportation of quantum states between nodes [1].

This network can be achieved by exploiting the strong interaction between atom and cavity and the information is sent using the idea of entanglement between ensembles of atoms. In this presentation I will discuss how people use these two ideas to build a quantum network.

  Exotic Bound States in Cold Rydberg Gases
25th March Prof. James Shaffer Universität Stuttgart

The study of cold Rydberg atom molecules has been one of the research directions driving the field of cold Rydberg gases. Cold Rydberg atom molecules are exciting because of the interesting properties that these extraordinary objects possess. Molecules formed by two cold Rydberg atoms are called macrodimers since the atoms are bound at distances > 1 micron. It has been suggested that due to their delicate nature, macrodimers can be used to study vacuum fluctuations if they are placed in cavities or next to surfaces, quenching in ultracold collisions, correlations in quantum gases and Rydberg atom interactions including their controllability with applied electric fields. Molecules can also be formed by a ground state atom and a Rydberg atom. These types of molecules exhibit a particulary unique binding mechanism where it is the Rydberg electron scattering off of the ground state atom that binds the Rydberg atom and ground state atom together. We will describe experiments where these exotic states of matter have been observed in laser cooled and trapped gases.

Faraday Discussion 142: Cold and Ultracold Molecules

  15th-17th April

Durham University will host the Royal Society of Chemistry Faraday Discussion 142 on "Cold and Ultracold Molecules". The meeting will focus on the enormous recent advances in our ability to produce and trap samples of translationally cold and ultracold molecules, highlighting the current experimental and theoretical challenges. Click here for further details.

EuroQUAM satellite meeting

  18th April

Following the Faraday Discussion there will be a one-day EuroQUAM satellite meeting on Saturday 18 April 2009. Contact Simon Cornish for details.