One of the best ways to understand a complex system is to study its fundamental components. To better understand the behaviour of atoms, they can be chilled to a millionth of a degree above absolute zero. "Ultra-cold atoms are the coldest things in the universe that we know about, probably the coldest things that we will ever make," said Duncan O'Dell, assistant professor of atomic, molecular and optical physics in the Department of Physics and Astronomy at McMaster University.
The study of ultra-cold atoms began in 1995 with the development of the first Bose-Einstein condensate, in which gaseous bosons are cooled down to almost absolute zero. The discovery received the 2001 Nobel Prize in Physics. "They were able to cool a bunch of atoms so that they all wound up in their quantum mechanical ground state, which is the lowest energy you can get anything," O'Dell explained. This relatively new field of research also encompasses more traditional areas, such as condensed matter physics, nuclear physics and quantum optics.
At temperatures approaching absolute zero, ultra-cold atoms are almost motionless, except for some residual movement called zero point energy. In addition to their reduced movement, ultra-cold atoms behave more like waves than billiard balls. Quantum fluids like Bose-Einstein condensates are unlike typical fluids like water because they remain in a liquid state even at extremely low temperatures. Their constant movement due to their zero point energy prevents the liquid from freezing into a solid. "What they represent is our greatest control over nature," said O'Dell. "When you can control nature at the single atom level, but also do it with an arbitrary number of atoms, you're really king."
Ultra-cold atoms enable atomic clocks to make very precise measurements of time. They are also used in interferometers, which measure interference between two beams of light or matter. As the light beams travel along different paths, they experience slightly different environments, which affects the phase of the light. When the beams recombine, the interferometer measures the phase difference as a product of interference.
Matter wave interferometers use waves of atoms directed along paths using electromagnetic fields. They can be used to measure gravity across very short distances. Since the atoms' wavelength is much smaller than that of light, atom interferometers are much more sensitive than light interferometers. "You could have atoms go on two different trajectories: one close to a heavy block of material and one a bit further away and you look at the differences in their behaviour," O'Dell explained.
For professors like O'Dell, the learning process never stops. The department's positive learning environment fosters knowledge sharing between faculty members, even though their research interests are incredibly diverse. "Physics is a unified whole," said O'Dell. "Although we're all working on different subsystems, there is a lot of overlap between the general ideas. My colleagues are certainly experts, so I know there's a huge reservoir of information I can draw upon."
In 2008 I am teaching the graduate course Physics 740: advanced quantum mechanics II.
In 2009/2010 I am teaching in the Integrated Science degree program and also PHYS 1BA3 (Introduction to Modern Physics).
In 2011/2012 I am teaching in the Integrated Science degree program and also PHYS 3C03 (Analytical Mechanics).
Dear Prospective Graduate Student,
I am currently looking for one student who would like to do their MSc/PhD at McMaster in the theory of ultra-cold atoms, beginning September 2010 or thereabouts. My research focuses on the quantum dynamics of simple systems, and ultra-cold atoms provide an excellent setting for this. I currently have two graduate students: Prasanna Balasubramanian, and Nick Miladinovic. Prasanna is studying ultra-cold atoms inside optical cavities which is a project that combines quantum optics with cold atom physics and has applications in the precision measurement of gravity (the least well understood fundamental force). Nick is studying methods for transferring light between two or more optical cavities, which is a project that combines quantum optics with adiabatic quantum mechanics and has applications in quantum information science. Both these projects are in collaboration with the experimental group run by Professor Ed Hinds at the Centre for Cold Matter. I also have research projects in collaboration with other theory groups in the general area of Bose-Einstein condensates.
Here are some reasons why I am currently working on ultra-cold atoms:
- They are simple and controllable systems that strike at the heart of quantum mechanics. For example, the creation of Bose-Einstein condensates in atomic gases (2001 Nobel prize in Physics for Cornell, Ketterle, and Wieman) created a macroscopic quantum system that can be easily probed and manipulated.
- Theory and experiment work hand in hand in this field. Beware: your theory might well be tested in the laboratory before you’ve finished your PhD!
- They combine physics from two major disciplines: Atomic, Molecular and Optical physics (which includes quantum optics), and Condensed Matter Physics. The field is therefore rich in opportunity and benefits greatly from cross- fertilization. As a student in this area you can gain experience in a broad range of subjects.
- Ultra-cold atoms are being used to address both fundamental questions, e.g. quantum phase transitions, or superfluidity, as well as technologically relevant questions such as the possibility of using ultra-cold atoms to realize the quantum logic gates necessary to build a quantum computer.
If you would like to know more about ultra-cold atoms take a look at the popular article by James Anglin and Wolfgang Ketterle:
If you think you might like to do research in this area I encourage you to email me at firstname.lastname@example.org .