McMaster University Department of Physics & Astronomy           McMaster University

Group Members & Projects

DeniseKamp Denise Kamp
Denise is a graduate student studying the instabilities of an atomic Bose-Einstein condensate (BEC) in a rotating toroidal trap. An instability can arise because a vortex state in this system decays to a non-rotating state, a process controlled by tuning the interaction strength and the rotation speed. A theoretical description of the process can obtained via the Bogoliubov method that describes elementary excitations of the BEC which have complex or negative energies in the presence of dynamical or energetic instabilities.


Liam Farrell
Liam is a graduate student studying Hawking radiation from acoustic black holes. These fluid analogues of gravitational black holes can be formed in flowing Bose-Einstein condensed gases, where an effective event horizon is formed for sound waves propagating against the fluid flow if the local flow speed exceeds the speed of sound in the gas. Remarkably, Hawking radiation is produced near this acoustic horizon as pairs of sound waves.

sriramsundaram Sriram Sundaram
Sriram is a graduate student currently working on developing a classical field theory formalism for Schwinger pair production (this is the vacuum instability that produces particle-antiparticle pairs in the presence of a static external electric field). We intend to describe pair creation as arising from an added non-unitary boundary condition and thereby uncover hidden symmetries of the problem. I am also interested in studying instabilities and singularities in related optical systems.

WyattKirkby Wyatt Kirkby
Wyatt is a graduate student studying caustics in many-body quantum dynamics. His recent projects include the study of `quantum light-cones' in quenched spin chains, where the spread of correlations exhibit universal behaviour governed by catastrophe theory, and the study of caustics in dynamics of three-mode models, such as a spinor BEC.



Former members:

  Matt Richards

Matthew Richards (-->mathematics tutor)
Matt is a graduate student working on the dynamics of quantum many-body systems near phase transitions. Inspired by the Kibble-Zurek theory, he is using a combination of numerical techniques and analytic calculations to look for scaling propertiesof these systems, especially in the presence of long-rang interactions.

RyanPlestidRyan Plestid (-->Intensity Frontier Fellow at Fermilab)
Ryan is a graduate student studying quantum many-body systems with long-range interactions, especially the quantum version of the Hamiltonian Mean-Field (HMF) model which describes quantum rotors with all-to-all XY coupling. This system, which can be realized using quantum gases in optical cavities, gives us the opportunity to explore phenomena such as ``violent relaxation'' in the quantum regime. Violent relaxation, which is closely related to Landau damping, is a relaxation mechanism known in classical gravitationally bound systems.

Aaron Goldberg (-->graduate student at the University of Toronto)
Aaron is doing his undergraduate thesis on the problem of analogue Hawking radiation in flowing Bose-Einstein condensates and the connection between this problem and quantum catastrophes.

Alan Morningstar (-->PSI Masters programme at the Perimeter Institute-->graduate student at Princeton University)
Alan is doing his undergraduate thesis on the problem of quantum measurement and whether it can be interpreted as a phase transition. This interpretation may allow speed limits to be put on how fast we can perform certain measurements (and still obtain accurate results).

AsmaAlQasimiDr. Asma Al-Qasimi (-->M. Hildred Blewett Fellow at the University of Rochester)
Asma is a postdoctoral fellow working on the problem of quantum caustics and their stability to peculiarly quantum effects such as decoherence (such as occurs during a continuous measurement). According to catastrophe theory, caustics have the property of structural stability which means stability under perturbations. Both ray and wave caustics have this property which explains why caustics are so ubiquitous in nature, but much less is known about the stability of quantum caustics which are singularities than occur in quantum fields.

JesseMumfordJesse Mumford (-->Faculty member in the Department of Science and Engineering Physics, Red Deer College)
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.

website: Dr Jesse Mumford

Faiyaz HasanFaiyaz Hasan (-->Paper [Director of Labs])
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 (-->Preteckt [machine learning and data science])
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 Venkatesh Balasubramanian (-->Faculty member in the Department of Physics, IIT Gandhinagar)
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.

website: Dr Prasanna Venkatesh B

Daniel ThompsonDaniel Thompson (-->Ontario of College of Teachers)
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.

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).

Yohan Yee (-->graduate student at the University of Toronto)
Yohan is doing his undergraduate thesis on the problem of a Bose-Enstein condensate in a triple well potential using the Bose-Hubbard model. He is examing the higher catastrophes that occur during dynamics in this system following a quench.

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.

website: Dr Nicholas Parker