Albert Einstein’s cool theory carried out at York

In 1924, Albert Einstein, working with Satyendra Nath Bose, predicted that near absolute zero, bosons (particles named after Bose) would all occupy the same state. Eighty years later, York physics Professor William van Wijngaarden is the first in Canada to achieve what is now known as Bose-Einstein condensation (BEC).

Right: William van Wijngaarden

“The process is analogous to stopping a semi on the 401 highway by throwing ping-pong balls at it,” van Wijngaarden muses. “It requires a lot of ping-pong balls, but eventually, the truck will stop.” Replace the semi with rubidium atoms and the ping-pong balls with photons, and this is the image of the cooling process.

In order to achieve BEC, atoms must be cooled to near absolute 0 (-273° C). To accomplish this, van Wijngaarden and Baolong Lu – a post-doctoral fellow who left York in June to accept a position in China – spent three years developing a refrigeration system incorporating infrared lasers. This “atom fridge” also had to incorporate an excellent vacuum to prevent the cold atoms from colliding. Further, the atoms had to be trapped in magnetic fields to prevent them hitting the walls of the vacuum.

The motivation for this process is that matter behaves differently at very low temperatures than it does at room temperature. Certain fluids when cooled can pass through small capillaries without any resistance, also known as superfluidity. Other materials have no electrical resistance at low temperatures which is called superconductivity.

Van Wijngaarden and Lu’s current design involves using magnets whose size is in the neighborhood of 10 centimetres. Van Wijngaarden would like to create an alternate trap using micron-thin gold wires on silicon wafers. This would allow for an array of locations, in one or two dimensions, for trapping the atoms. “The long-term applications, which may be decades in the making,” says van Wijngaarden, “could use trapped atoms for information storage and perhaps even quantum computation.”

Quantum computation, allowing for much faster computers, could solve problems that are inherently unsolvable with current computers. “Essentially, a conventional computer operates on one bit at a time, while a quantum computer operates on a large number of bits at a time. But all of this is still in the theoretical stages,” says van Wijngaarden, who is continuing to refine the cooling process with He Ming, his new post-doctoral fellow.

The project’s success is at least partially attributable to van Wijngaarden’s two Bachelor degrees, one in physics and one in computer science. “The cold atom project requires extensive use of computers to execute the millisecond timing necessary to achieve condensation,” he says. This interdisciplinary background has enabled him to oversee all aspects of the project.

Van Wijngaarden also holds masters and PhD degrees in physics from Princeton and he completed a one-year post-doc at Yale. He led the creation of the National Photonics Network Centre of Excellence in 1999, chaired NSERC’s Steering Committee for General Physics in 2001 and is currently an appraiser for the Ontario Council of Graduate Universities, as well as Chair of the Commission on Atomic, Molecular and Optical Physics for the International Union of Pure and Applied Physics.

All projects, including work on precision spectroscopy which tests atomic theory, as well as work on climate change, are funded by NSERC.

Shoshana Green, a York graduate student in English who writes about research at York University, sent this article to YFile.