AtMol Research Seminar Archive
Index Current Seminars

Easter Term 2008

Date Speaker Institution
Molecular Emission in Regions of Stellar Formation
April 23rd Mr. Antoine Gusdorf Atomic and Molecular Physics

Recent observations show that young stars being formed eject matter at several ten of kilometers per second, in the form of "jets" that impact the matter whose collapse is at the origin of the formation of the star. The supersonic impact between this jet and the parent interstellar cloud of the star generates a shock front, whose structure depends on its velocity as well as on the physical properties of the gas in which it propagates. This shock wave modifies the chemical composition of the gas, partially or totally dissociating the molecular hydrogen, and enables chemical reactions to occur, favoring the formation of characteristics molecules. In this talk, I'll briefly show how to model such regions of shocks, and I will mainly show how we use two of these "shock tracing" molecules (H2 and SiO) to constraint the physical parameters of the pre-shock region.

Modelling Finite Temperature Bose-Einstein Condensates
April 30th Dr. Nikolaos Proukakis Newcastle University

The theoretical study of atomic Bose-Einstein condensates at non-zero temperatures is rather involved, as it requires consideration of the coupled dynamics of the condensate and the thermal cloud. Intense theoretical activity has been undertaken in this area over the past 15 years (building on earlier work) leading to apparently distinct theoretical models. This talk will present the key features of the theoretical approaches currently applied to interpret cold atom experiments, and briefly motivate their origin. Frequent comparison to experiments on excitation frequencies, condensate growth, dynamics of macroscopic structures and fluctuations of the condensate phase will be used as a tool to assess the merits and drawbacks of such theories, thus enabling progress to be made towards a 'complete kinetic theory' for such systems.

The Ogden Centre's 5th Anniversary Celebration
April 30th Ogden Centre Ogden Centre

A little over five years ago, the Prime Minister inaugurated the Ogden Centre for Fundamental Physics at Durham University. The Ogden Centre hosts two world leading research groups, the Institute for Computational Cosmology and the Institute for Particle Physics Phenomenology. The work of these groups lies right at the cutting edge of basic physics research, addressing key questions about the Universe, from the perspectives of very large and very small scales.

The Ogden Centre has been a tremendous success, providing an exciting and stimulating environment in which researchers from all over the world can attack the most fundamental questions about the Universe.

To mark five years of the Ogden Centre, we are planning a series of special events, which will take place on Wednesday 30 April 2008. In the afternoon, speakers from the IPPP and ICC will address 'The Universe: Five Key Questions'. The Ogden Centre's 5th Anniversary Celebration Dinner later that evening will include an address by Lord Rees of Ludlow, the President of the Royal Society.

Click here for the event details.

Gauguin's questions in particle physics: Where are we coming from? Where are we now? Where are we going?
May 1st Professor John Ellis Theory Division, CERN, Geneva, Switzerland

Within particle physics and cosmology Gauguin's questions may be interpreted as: What is the status of the Standard Model? What physics may lie beyond the Standard Model? What is the "Theory of Everything"? What were the early stages of the Big Bang? What is the material content of the Universe today? What is the future of the Universe? In this lecture I highlight how new facilities and ideas in particle physics and cosmology can shed light on the questions raised by Gaugin.

Venue: CLC202 Calman Learning Centre
Date: Thursday 1st May 2008
Time: 4:30pm.

Click here for the event details.

Atomic Physics on a Chip
May 2nd Professor Ed Hinds Imperial College London

Applied Mathematics Seminar Series at 16.00.

The seminar takes place on the 4th floor of the Herschel Building (tall building opposite Haymarket Metro station at Newcastle) in Teaching Room 1.

Why and How to Build a BEC machine to go into a Zero-Gravity Aeroplane
May 7th Dr. Robert Nyman Imperial College, London
Institut d'Optique, Palaiseau, France

In this talk I will explain the I.C.E. (Interférométrie Cohérente pour l'Espace) collaboration, whose mission is to perform ultracold-atom interferometry for inertial sensing in the zero-gravity environment provided by the Zero-G Airbus.

In March 2007 and February 2008, we made Magneto-Optical Traps in free fall. Robust laser systems based on telecommunications, fibre technology and frequency doubling provided the laser cooling. Our characterisation of this harsh environment indicate that one day we will be able to test the Universality of Free Fall by comparing atom interferometers of two different species (39K and 87Rb) with long interrogation times (up to 4s), to better than 10^-10.

A second line of research in the lab is dedicated to producing all- optical BECs, sufficiently rapidly for the needs of zero-gravity experiments, using a dynamically-variable-geometry crossed-dipole trap at telecommunication wavelength (1565nm). I will present the latest results on loading such a trap. One important feature is the extraordinarily large light shift (>300MHz) of the excited state of the 87Rb cycling transition. We take "in-situ" absorption images of atoms, resolved by their potential energy to within 5 microKelvin, and follow their evolution with time.

Quantum information in an optical lattice
May 14th Mr. Jonathan Pritchard First Year Report

In this talk I will explain the long term goals of the CO2 lattice experiment to develop a quantum gate, looking at our proposed gate scheme to achieve entanglement of a pair of photons via the dipole blockade for Rydberg atoms.

The talk will focus on recent work on the detection of cold Rydberg atoms using electromagnetically induced transparency which are the first steps in achieving the photonic gate. We have explore the observed depopulation of the Rydberg state as the probe Rabi frequency is increased from the weak probe limit, and found this to be explained by superradiant decay of the Rydberg state.

Spectroscopy on the Rubidium D Lines
May 21st Mr. Paul Siddons First Year Report

This seminar will outline various spectroscopic applications of a thermal rubidium vapour cell, such as controlling the propagation of light pulses by changing the medium's absorptive and dispersive properties. The first step in predicting such properties is modelling the electrical susceptibility of the medium, the parameter which characterises absorption and dispersion.

The focus here will be on the development of a model of a rubidium vapour's susceptibility, taking into account the absolute linestrengths of allowed electric dipole transitions and the motion of atoms parallel to a weak laser beam used to probe the medium. The absorption coefficient and refractive index as a function of frequency are expressed in terms of the complementary error function. Transmission profiles calculated in this way are compared to experimentally measured Doppler-broadened spectra. The role of hyperfine pumping and importance of a weak probe beam is shown.

Rydberg and plasma physics using ultra-cold strontium
May 28th Mr. James Millen First Year Report

We aim to cool and trap strontium to study novel forms of matter such as Rydberg gases and ultra-cold neutral plasmas. Though highly excited these systems display very high spatial correlations. Initially a recently published paper, "Spectroscopy of strontium Rydberg states using electromagnetically induced transparency", will be presented. Electromagnetically induced transparency (EIT) offers a non-destructive method for probing highly excited Rydberg states with high resolution. This method was used to measure the isotope shifts in the 5s18d1D2 and 5s19s1S0 states of strontium.

The apparatus for trapping strontium using a magneto-optical trap is currently under construction. It consists of a Zeeman slower to slow a beam of hot strontium from an oven, and a large "pancake" chamber with optical axes for trapping, exciting and imaging the cooled strontium. An overview of the current progress and an outline of the final experiment will be presented.

Model of EIT on Rubidium atom and Einstein's A coefficient
June 4th Mr. Monsit Tanasittikosol First Year Report

For past decades Rydberg atoms have been one of the areas which physicists and chemists are interested in. The interaction strength between Rydberg atoms can be easily controlled by changing density or changing quantum number n. Furthermore, this interaction is so strong that it creates the dipole blockade effect in an ensemble of Rydberg atoms. This property is useful for building fast logic gates in quantum computing.

The talk begins with a discussion on Rydberg atoms and the EIT effect e.g. dark states. The dark state will be graphically explained, which can be analogous to the Bloch sphere. A review of [1] will be illustrated. Then the theoretical model of EIT in rubidium atoms will be discussed. Also the way to find the radial integral between the Rydberg state and the P3/2 state will be given during the talk.

[1] Kasapi A, J. Opt. Soc B, 13, p. 1347.

A Two-Species Mixture of Quantum Degenerate Bose Gases: Past, Present and Future.
June 11th Mr. Danny McCarron First Year Report

The long term goal of the Mixture experiment is to produce deeply bound ground state heteronuclear molecules by exploiting inter-species Feshbach resonances and through using the technique of stimulated Raman adiabatic passage (STIRAP). This seminar will give details on the path to achieving this goal.

The current experimental setup will be introduced and problems located within the setup will be identified. Solutions to these problems will be presented including optical trapping and the introduction of a new method to generate an error signal for laser locking - modulation transfer spectroscopy. The theory behind modulation transfer will be given and experimental lineshapes will be compared to those predicted by the theory. Details on future experiments using both the current and improved experimental setups will be presented.

Annual Department Research Event
June 12th Condensed Matter Durham University

Thursday 12th June, Ph8.

Condensed Matter Physics deals with interactions between astronomically large numbers of atoms/particles and the complex physics that results. It is an area that requires complex quantum mechanics and statistical physics to understand from first principles the behaviour of materials and to design new materials with tailored properties. The talks will demonstrate the diversity of research within the Condensed Matter Physics research group at Durham

14.15 Professor Peter Hatton: Welcome and opening address

14.20 Dr. Stewart Clark: Predicting the properties of materials from quantum mechanics

14.45 Professor Andy Monkman: Understanding femtosecond processes in polymers, organic electroactive materials and devices

15.10 Break for Tea

15.35 Professor Peter Hatton: Beyond the Standard Model

16.00 Professor Damian Hampshire: Superconductors in high magnetic fields

16.25 Dr. Andy Brinkman: Crystal Growth, X-ray detectors and a University Spin out

16.50 Close

A technical report detailing the implementation of a moving coil transport system for ultra cold Rubidium atoms, based on the JILA-Durham design
June 13th Mr. Benjamin Sherlock University of Oxford

Magnetic transport of laser cooled atoms away from the MOT region is becoming an increasingly popular method of improving optical access for manipulating and imaging ultra cold and Bose condensed atoms. This report will present some changes made to the JILA-Durham system including static coil magnetic transport and a pyramidal MOT, along with the motivations for these changes.

Friday 13th June
10:00 a.m.
Ph 30

Multiparticle entanglement of neutral atoms by Rydberg excitation in an optical lattice
June 18th Mr. Richard Abel First Year Report

The study of Rydberg atoms is motivated by the possibility of achieving scaleable Quantum information processing using arrays of neutral atoms. The optical lattice Rydberg experiment aims to load Rb atoms into a lattice, excite them to Rydberg states and detect energy signatures of isolated pairs and triplets of atoms. The interactions of Rydberg atoms will be introduced and the goals of the experiment outlined. The vacuum system design will be presented and details of the assembly considered. The lasers required for the experiment will be detailed along with techniques used for stabilization. Laser locking using EIT signals in vapour cells will be discussed and examples of error signals given. The performance of the laser locking system will be briefly demonstrated with examples of EIT data in a Rb vapour cell. Finally futures plans for the experiment will be given.

Solitons in trapped atomic Bose-Einstein condensates
June 25th Dr. Andrew Martin University of Southampton

Solitons, vortices and other excitations in Bose-Einstein condensates of trapped cold atoms are topics of intense current interest. I will present the results of my thesis, which concern the effects of trapping potentials on the soliton (particle-like) character of bright solitary waves in attractively interacting atomic Bose-Einstein condensates. If time permits I will also discuss the Bose-Einstein condensate theoretical research efforts in the Southampton applied maths group, which model the quantum and thermal noise in condensates trapped in optical lattices.