Natural Sciences and Engineering Research Council of Canada
Symbol of the Government of Canada

Common menu bar links

Past Winner
2007 E.W.R. Steacie Memorial Fellowship

Aephraim Steinberg


University of Toronto

Aephraim Steinberg
Aephraim Steinberg

Scientists have probed the intricacies of quantum mechanics for a century without apparently discovering its limits. Only recently, however, has technology become sophisticated enough to attempt direct observations, manipulations of subatomic particles and measurements of quantum phenomena. University of Toronto physicist Aephraim Steinberg is at the cutting edge of those efforts.

“We're not actually on the fringe, but you can see it from where we're standing,” he says, quoting a catch phrase used by researchers who study the sometimes bizarre and seemingly paradoxical phenomena of the quantum world.

Dr. Steinberg's work to date includes a number of seminal developments that have earned him numerous accolades from his peers, as well as a 2007 NSERC E.W.R. Steacie Memorial Fellowship. Whether he's studying the phenomena of “entanglement” or “tunneling,” or the behaviour of ultracold matter, the ultimate goal is to understand how to make use of particles that don't play by the rules, or at least not by rules that physicists understand as well as they would like.

Entanglement is a good example. It refers to the process by which two particles become so deeply connected that it is impossible to describe what is happening to one without taking into account what the other is doing. Albert Einstein found this one of the most disturbing aspects of quantum mechanics, calling it “spooky actions at a distance.”

“That's one of the elements of quantum mechanics that's currently seen as the most shocking, the most mysterious, the one that is so distinct from classical mechanics that it has the greatest possibility for new applications,” says Dr. Steinberg.

His contribution to studying entanglement includes developing a scalable technique to entangle three or more photons in a way that could allow the production of smaller, faster computer chips and increase precision in measurement.

And then there's the quest to build a quantum computer, predicted to be vastly more powerful than any machine in existence today. While he and his group are not tackling all of the engineering challenges of building a quantum computer, Dr. Steinberg has helped advance the state-of-the-art for one of the leading candidate systems – an optical lattice that uses light to trap atoms.

He also sees a definite advantage in taking advantage of entanglement. “A large quantum system actually stores exponentially more information than the same system would without entanglement,” he points out.

However it ends up being built, the catch remains figuring out how to control the information. “The challenge is how to get it in, how to get it out, how to manipulate it, how to even know what you've done,” observes Dr. Steinberg. “There's a non-negligible chance that we'll never produce a full-scale general quantum computer, but I'd say there's a better chance that we will.”

Another area of Dr. Steinberg's research involves cooling a group of atoms down to a minute fraction above absolute zero, a fascinating process in itself that uses the physical force exerted by a finely tuned laser to slow the motion of individual atoms to a virtual standstill. In one form of ultracold matter, known as a Bose-Einstein condensate, atoms are so closely packed that they start behaving collectively rather than being distinguishable as individual particles.

Among other things, working with ultracold matter may help clarify the quantum phenomenon of “tunneling,” which involves a particle traveling through an area that classical physics says should be off limits (such as a photon going through a mirror instead of reflecting). Not only can particles do this but ,if they do, Dr. Steinberg has proved that they move faster than the speed of light in the process. That result appears contradictory, but since everything in quantum mechanics has some uncertainty attached to it, he says tunneling does not in fact violate any cherished physical principles.

He's more interested in finding out where a particle spends its time in crossing such a forbidden barrier, and if there are any useful applications. “It turns out that even just understanding the history of a particle is a very thorny question in quantum mechanics because particles don't follow definite trajectories as they do classically,” he adds.

This brings up a major challenge for researching quantum physics: if a tree falls in a quantum forest, it does matter whether anyone is there to hear it – the very act of measuring and observing them changes how particles behave at the subatomic level. That may not be all bad, though, explains Dr. Steinberg. “Some of the proposals for quantum computing try to show how if you take the concept that every measurement intrinsically disturbs a system and turn it around, it doesn't have to be a weakness of quantum mechanics. It can instead be something we could use to manipulate a system in ways that weren't possible before that realization was made.”

This is a fast-moving, competitive field, but Dr. Steinberg doesn't plan to let that deter him from taking his time and studying things in depth. “Very often fields like this degenerate into a race where one tries to count how many of something one can put together,” he says. “We don't want to leave behind the other issue of exactly what sorts of states one can create, what the applications of each state would be, what the best way to characterize them is. We're trying to do those things in parallel.”