AtMol Research Seminar Archive
Index Current Seminars

Michaelmas Term 2006

Date Speaker Home
Special Seminar: A Synchrotron for Ultracold Neutral Molecules
August 29th Dr David Carty University of Oxford
Dynamical coherence of impenetrable (Girardeau-Tonks) bosons
October 18th Dr Dimitri Gangardt University of Birmingham

Cold atoms are a tool to explore non-equilibrium quantum phenomena. In my talk I will present an example of such phenomenon: the reversible dynamical fermionisation of one-dimensional bosons in the strongly interacting (Girardeau-Tonks) regime. I will review known results on the momentum distribution of bosons in this impenetrable limit in the continuum and on optical lattices and show how coherence is drastically reduced during one-dimensional oscillations of large amplitude.

Half-cycle cut-offs in harmonic spectra and robust carrier-envelope phase retrieval
October 25th Mr Luke Chipperfield Imperial College

The use of high harmonic radiation to create and control events on attosecond timescales has grown at a phenomenal rate. This has been led by our ability to generate shorter and shorter pulses of light from lasers, approaching a single oscillation of the light wave. One of the forefront challenges of optical science is the development of new techniques for measuring the carrier-envelope phase (CEP) of these few-cycle light pulses.

In this talk I will show the first experimental observation of high-harmonic emission at individual half-cycles of the laser field. These half-cycle cut-offs (HCOs) present a new method for measuring the CEP. Additionally, HCOs can be used in a simple experimental arrangement to generate isolated attosecond pulses whose wavelength can be tuned through adjusting the CEP.

Optical Feshbach resonances and atom-molecule dark states in 87Rb
November 1st Mr Patrick Tierney Durham University
Cats, Gates & Qubits in an Ion Trap Quantum Computer
November 8th Dr Dave Lucas University of Oxford

Ion traps are presently the physical systems closest to being able to implement the theoretical ideas of quantum computing. I will describe recent progress in Oxford in demonstrating the basic building blocks of the system, long-lived quantum memory qubits and high-fidelity quantum logic gates. We have used two ground hyperfine states of the calcium-43 ion as qubit states, and measured a coherence time of 1.2(2) seconds, which can be extended up to ~1 minute with a simple spin-echo technique. Using qubits based in calcium-40, we have entangled two ions with 83(3)% fidelity - an elementary quantum logic gate. The same gate operation applied to a single ion gives "Schroedinger Cat" states where the spin and motion of the ion are entangled, and squeezing of the motional state is inferred.

Formation and Interactions of Ultracold Molecules
November 15th Dr Roland Wester Universität Freiburg

Photoassociation has been established as a powerful tool to create ultracold molecules from pairs of ultracold atoms. We have used cw photoassociation to prepare ensembles of cesium dimers in an optical dipole trap. With such ensembles we have carried out studies of ultracold atom-molecule collisions. Recently the formation of ultracold molecules with femtosecond laser pulses using coherent control techniques has been proposed by several groups. I will present results for coherent control of the photodissociation of ultracold molecules and discuss the status of our activities towards femtosecond photoassociation.

Rotational quenching in ultra-cold atom-molecule and molecule-molecule collisions.
November 22nd Mr Steven Wrathmall Durham University

I will be providing a review of previous, and recent work, carried out on the quantum-mechanical scattering calculations of rotational quenching cross sections in cold and ultra-cold molecules. There will also be a general discussion on molecular inelastic, and elastic, collision processes and their importance in developing efficient cooling and trapping techniques for neutral polar molecules.

Grover's Search Algorithm - Implementation with trapped ions.
November 29th Mr Andrew Martin Durham University

Quantum computing has been described as an exciting new paradigm for computing, offering possible speed up over classical computing by direct use of quantum logic. Currently, there are two useful quantum algorithms that have been found to give speedup over their classical counterpart. One of these is Grover's algorithm, which performs a search of an unordered database. I will describe the working of this algorithm and then discuss a recent implementation with trapped ions reported in Physical Review A 72 050306(R) (2005).

  Excitons in semiconductors for room temperature BEC
December 6th Prof Jeremy J Baumberg University of Southampton