McMaster University Department of Physics & Astronomy           McMaster University

Group Members & Projects

JesseMumfordJesse Mumford
Jesse is a graduate student studying the problem of impurity atoms in Bose-Einstein condensates (BECs). For example, a single impurity atom in a BEC in a double well potential can be considered as a paradigm for the measurement problem in quantum mechanics: the impurity acts as a microscopic quantum system (in fact, a spin) that we want to measure and the BEC acts as a macroscopic measuring device.

Faiyaz HasanFaiyaz Hasan
Faiyaz is a graduate student working on modelling on-demand transfer of light between optical cavities or waveguides. This has applications in quantum information processing. The basic idea is to take advantage of avoided crossings between optical modes in order to transfer light between two waveguides, either moving a mirror or changing the refractive index of one of the guides. One of the key questions is whether this can be done adiabatically.

Nick MiladinovicNick Miladinovic
Nick is a graduate student and is working on cavity-QED. His project concerns the Abraham-Minkowski paradox which refers to two conflicting results for the momentum of a photon inside a dielectric medium. Normally, a single atom has an absolutely negligible affect on a beam of light, but inside a high-Q optical cavity the atom and the light can become strongly coupled. We are investigating whether a single atom in cavity can significantly change the momentum of cavity photons, and if so, under what circumstances one would expect the Abraham or the Minkowski results. This work has implications for using intra-cavity Bloch oscillations of cold atoms for measuring forces such as gravity.

Prasanna BalasubramanianPrasanna Balasubramanian
Prasanna is a graduate student and is working on ultra-cold atoms inside optical cavities. This is a project that mixes cavity quantum optics with ultra-cold atoms. In the presence of an external force such as gravity atoms in an optical lattice will undergo Bloch oscillations whose period will tell us the strength of the force. We hope this system might allow precision measurements of gravity at small distances (<1mm) where it is least well known.


Daniel ThompsonDaniel Thompson
Dan is an undergraduate student enrolled in the coop physics program at McMaster. He is spending one of his coop terms doing research on ultracold atoms in double well potentials, with a special focus on calculating the density of quantum states near a classical separatrix of the motion. This is part of a bigger project trying to understand the quantum-to-classical transition in many body systems.



Former members:

Ben CrigerBen Criger (->graduate student at the IQC in Waterloo)
Ben is doing his undergraduate thesis project on exchange interactions between dipolar atoms in ultra-cold Bose and Fermi gases. Dipole-dipole interactions are partly repulsive and partly attractive. It has been suggested (Huang 1987, Nozieres 1995) that attractive interactions can lead to fragmentation in Bose-Einstein condensates (i.e. not just one state is occupied macroscopically) and we are investigating these effects for the case of the dipolar interaction.


Matthew Farrar (->graduate student at Cornell)
Matt's project involves simulating beam splitters for Bose-Einstein condensates. The idea is to raise a central barrier in the BEC in an adiabatic way, i.e. without generating excitations, if possible. The BEC is described by the Gross-Pitaevskii equation (a type of non-linear Schrodinger equation) and the nonlinearity plays a crucial role. This is relevant to experiments that will use BECs for interferometry, i.e. matter-wave interferometry that makes use of the wave nature of quantum particles.

Graham KrahnGraham Krahn (->graduate student at UC Riverside)
Graham is an undergraduate student at UBC and spent summer 2008 working at McMaster on the theory of atomic Josephson junctions (JJs). The first JJs were made in the 1960s from two metallic superconductors separated by a thin layer of insulator through which electrons can quantum mechanically tunnel. They are a paradigm of quantum coherence phenomena in many-electron systems and Brian Josphson won the Nobel prize for proposing them. JJ's can also be made from two Bose-Einstein condensates trapped in a double-well potential. In atomic systems one has the advantage of much greater control over the system parameters and also the types of measurement one performs (recall that measurements play a very important role in quantum theory which is not yet competely understood).

Frank MulanskyFrank Mulansky (->graduate student at the Technical University of Dresden)
Frank is visiting our group for six months from the Dresden University of Technology in Germany. He is studying the problem of an impurity atom in a BEC in a double well potential. Our view of this system is that the BEC acts like a measuring device which measures the position of the impurity (i.e. left or right well). The BEC can be tuned between being a classical or a quantum system depending upon the number of atoms it contains.

Dr. Nicholas ParkerDr Nicholas Parker (->Faculty member in the Department of Mathematics, University of Newcastle)
Nick is a Commonwealth fellow who is researching Bose-Einstein condensates with dipole-dipole interactions. The long-range and anisotropic nature of the dipolar interactions leads to a number of novel effects in these systems including collapse instabilities which Nick is tackling.