Quantum Information Processing Research Progress

The attempt to build a quantum computer is more ambitious and more revolutionary than any computer advance thus far. It is both a scientific and a philosophical challenge, and one that goes beyond building a better microchip.

The key to this challenge is the dichotomy between the “classical” world and the less intuitive quantum world. Classical information can be read, copied and transcribed. It can be transmitted or broadcast. In contrast, quantum information cannot be read without affecting the information itself. It cannot be faithfully copied or broadcast. What’s more, quantum information can exist in multiple and seemingly mutually contradictory states.

By harnessing such properties, program members hope to perform feats that cannot be achieved via classical computing. Some of these concepts are still theoretical, while others have been implemented in the laboratory.

For example, Quantum Information Processing program members transmitted quantum information via teleportation, the instantaneous transfer of matter from one point to another. In this process of teleportation, the original quantum state is destroyed, but is recreated exactly at its destination location. The paper that describes their theoretical work is one of the most famous in quantum information science. The researchers’ findings are now leading to practical applications in communications and quantum cryptography.

Quantum cryptography harnesses one of the bizarre properties of the subatomic world: A quantum system changes merely by being observed. In quantum cryptography, information is encoded in entangled pairs of particles. CIFAR experimentalists have used entangled photons to create the world’s first “free space quantum cryptography device.” Sender and recipient each have one of an entangled pair. By manipulating and observing these particles, researchers can code and decode messages highly securely. And, if an interloper does try to take a peek at the particles, that mere act of observation will affect the pairs, sending an alert that the message has been compromised.

The work of CIFAR's Quantum Information Processing program also addresses central issues at the heart of our understanding of the physical world, and how we use that world to process information.