What’s Quantum Computing?

by Alan Auerbach

I can hardly remember life before computers. And that’s what some future generation might be saying about quantum computers. To explain them, John Donohue, an experimental physicist with the Institute for Quantum Computing at the University of Waterloo, gave our retirees a Zoom presentation on Feb 26.

He introduced some of the broader context around quantum technologies—which exploit the rules of the “quantum world.” These rules often differ from those we’re used to, but they can be used to make incredibly accurate predictions at the sub-microscopic scale. Researchers are still far from understanding the potential or the limits of quantum technology, and some constructs are inferential rather than directly observable. Still, there have been some highly practical outcomes, so let’s start by mentioning the main ones.

In medicine, there’s the mri machine, and new photon detectors built at UW that resulted in more accurate monitoring of drug dosage in cancer treatment. In seeing what’s where at a distance, there’s gps monitoring, as well as radar detectors and the more accurate lidar, one of which may help keep your present or future car safe in its proper lane. Without semiconductor transistors, our world would be different. As a final example, when a microsatellite is launched next year, photons can be relayed from Waterloo to anywhere in the world as a communication channel for quantum cryptographics. This Quantum EncrYption and Science Satellite (qeyssat) is a collaboration between UW and the Canadian Space Agency.

Like the micro-scale on which it operates, quantum issues may not be well known but they have a major presence in their own realm. Not only is UW’s Institute quite massive (over 150 grad students) but its founding in 2002 makes it the oldest such in the world. Kitchener-Waterloo subsequently invested a lot to build the “Quantum Valley” that contains research facilities like the Institute for Quantum Computing and the Perimeter Institute, as well as start-up companies, fabrication facilities, and business-related resources.

Beyond Waterloo, researchers around the world have joined forces to explore how the power of the strange rules that prevail in the submicroscopic realm of the atom can be harnessed in a computer and contribute to cybersecurity. Many government and corporate research labs like Microsoft Research, Google, ibm and AT&T Labs have a quantum computing group, or, like nasa’s Ames Research Center and the Hewlett-Packard Corporation, are looking to start one. The National Quantum Initiative is a billion-dollar investment in the U.S., and a group in New York (MagiQ Technologies) has a quantum computing start-up with the goal of building a “quantum Internet.” One of John’s slides showed a total of some 14 billion dollars provided world-wide for advancing quantum physics.

After his introduction, John described how quantum mechanics was discovered in the early 1900s through researchers like Max Planck studying the properties of light. They discovered many phenomena that seemed strange. For example, they found that it was possible to “count” light like a bucket of marbles, that every particle could behave like a wave with the right handling, and that two objects could act as a single unit through a process called entanglement.

Let’s back up. An ordinary computer stores information in units called bits (0’s or 1’s), typically represented by electrical currents or voltages that are either high or low. A quantum computer also stores information, but by using the states of sub-microscopic (atom level) particles. Classically, the electron in, say, a hydrogen atom, can be in a high or low energy state. But in the weird world of quantum physics, the state of the electron is not just high or low but a weighted combination of both simultaneously, called by physicists a “superposition” of states so that a bit can be both a 0 and a 1. Hence, a quantum bit is more complex than its classical counterpart.

When researchers discover methods of exploiting this vast pool of stored information to extract an answer in far fewer steps—methods impossible on a classical computer—it will be possible to speed up the computation. Many researchers are trying to find quantum algorithms for problems that are beyond the reach of classical devices, and others are working on quantum cryptographic schemes to replace existing schemes in case a practical device is built.

Dr. Donohue ended with mentioning the Quantum Cryptography School for Young Students, a program on the present and future of quantum computing, imaging, and cryptography. It’s online, August 3 to 13, and free, but past applications have been competitive. High school students 15 or older, preferably who took (or are taking) Gr 11 math and physics, can apply by April 30 to https://uwaterloo.ca/iqc/qcsys. Their goal should not be to have a quantum computer on their desk, but a better understanding of the bizarre world of quantum physics. Which they can then kindly explain to me.