Tin Cans and String Theory

Some kids have sent words through two tin cans and a piece of string; quantum communication can send them encoded in particles of light.

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Do you remember tin can telephones? You and a friend would each be holding an empty can, connected by a string stretched out tightly. You could speak to one another, with the string carrying the sound waves from one end to the other. Well, telecommunications have come a long way since childhood. Replacing the strings are glass cables (fibre optics) that transmit light along their length as the information carriers. In this digital age, scientists are now looking at ways to use quantum communication to make information more compact and secure than ever before by sending fibre optic signals as single particles (photons) of light.

Aephraim Steinberg, professor of physics at the Centre for Quantum Information and Quantum Control at the University of Toronto, explains that by manipulating individual photons, we are unlocking ways to communicate and store information in new ways. In the quantum world, “all of the different answers you think are conceivable can in some sense be a part of the bigger reality out there at the same time. It makes the world a much more complicated but also a much more exciting place, if you learn how to describe the simultaneous possibilities,” says Steinberg.

By expanding beyond the classical binary method of storing computing information as 0s and 1s, quantum computing can store more information in less space, opening up new methods for compressing and encrypting information. Scientists are now going beyond basic information storage and transmission to make information interact, such as in calculations.

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Prof. Aephraim Steinberg is a Professor of Physics at the University of Toronto, where he is a founding member of the Centre for Quantum Information and Quantum Control.  His group carries out research using the experimental tools of quantum optics and laser-cooled atoms to address fundamental problems in quantum mechanics such as “what is the best way to measure a quantum system?”, “can quantum information be compressed?”, and “when a particle ‘tunnels’ across a ‘classically forbidden’ region of space, how much time does it spend there?”  Steinberg obtained his B.Sc. at Yale, and spent a year working with future Nobel laureate Serge Haroche in Paris before moving to Berkeley to do his Ph.D. with Ray Chiao, where he carried out a measurement of the seemingly faster-than-light “single-photon tunneling time.”  He then learned the ropes of laser cooling in Elisabeth Giacobino’s group at the University of Paris and in the lab of another future Nobelist, Bill Phillips, at the National Institute of Standards and Technology in Maryland, before taking up his position at Toronto in 1996. He is a Fellow of the American Physical Society and the Canadian Institute for Advanced Research, and an Affiliate Member of the Perimeter Institute.  His 2011 experiment measuring “average trajectories” for photons in a two-slit interferometer was selected by Physics World magazine as the “breakthrough of the year.”