Quantum rules

There’s an element of predictability when playing chess.

Simple rules define how each piece moves in this thoughtful game of strategy. Now imagine playing a game of chess where suddenly the rules have changed. New moves are allowed and the board has dramatically grown in size. This is, in a nutshell, the challenge of studying quantum computing. It’s a very different game than the classical world.

The rules of classical information are based on our everyday human experiences, where objects have definite states that can be completely determined by observing them (at least in principle).

The rules of quantum information, on the other hand, are defined by the principles of quantum mechanics. They explain the behaviour of small particles like atoms, electrons and photons. Objects can exist in a superposition of several states and sequences of moves can interfere with each other. As a result, the outcomes of processes are often counter-intuitive from a classical perspective.

“This is a strange game that nature plays,” said RICHARD CLEVE, Institute for Quantum Computing (IQC) researcher and IQC Chair in Quantum Computing. “The basic theory of quantum mechanics describes the rules of how our world works, but we’re still trying to fully understand the consequences of these rules.”


Quantum mechanics open up new possibilities for building transformational technologies for computing, healthcare, communications and geological exploration. Cleve’s theoretical research in quantum information theory lays some of the groundwork for programming quantum devices.

“Figuring out what a quantum system is capable of helps guide the exploration of quantum technologies,” said Cleve. “There’s a rich interplay between theory and experiment in the development of architectures for building quantum technologies.”

Cleve has developed some quantum algorithms – sets of instructions that guide quantum mechanical systems – to simulate the evolution of these systems. Designed for quantum computers as small as 50 to 100 qubits, these algorithms move us further along the board towards understanding fundamental quantum behaviour and how we can harness it to build new technologies.

The next move

Cleve joined IQC in 2004. He was an early player to the game when the quantum research community was small. Some even considered quantum information theory to be a risky area of study. But Cleve and his colleagues took the long view and pushed our understanding of quantum and its potential forward. As the field evolves, the fascinating counter-intuitive behaviour of quantum systems keeps Cleve excited as a researcher. He’s ready for the next move.