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Colloquia

ics Colloquium
Friday, February 13, 2004
4:00 PM
Physics Building, Room 204
Note special time.
Daniel J. Gauthier [Host: Olivier Pfister]
Duke University - Fitzpatrick Center for Photonics and Communication Systems
"Measuring the Information Velocity in Fast- and Slow-Light Media"
ABSTRACT:
By all accounts, modern science and engineering has a very good understanding of how to use pulses of light to communicate information. It is, after all, the basis for one of the world's biggest and fastest-growing industries. And yet, the fundamental question of how fast information travels remains unanswered. The engineering community, starting with the seminal work by Shannon, has studied information rates, but has essentially ignored the question of the velocity of information. The physics community, initially prompted by an apparent challenge to Einstein's special theory of relativity, has been debating the issue off and on for almost 100 years. Surprisingly, the issue remains unresolved. There is no clear definition of the information velocity because there is only a vague understanding of where information is contained on a waveform. I will review the information velocity debate and present a technique for experimentally measuring the velocity of information for the case were the group velocity of a pulse of light vastly exceeds the speed of light in vacuum (a so-called "fast-light medium") or is much slower than the speed of light in vacuum (a "slow-light medium"). Our research suggests that the information velocity is equal to the speed of light in vacuum, independent of the characteristics of the medium. A tutorial on this topic, including links to recent publications, can be found at: By all accounts, modern science and engineering has a very good understanding of how to use pulses of light to communicate information. It is, after all, the basis for one of the world's biggest and fastest-growing industries. And yet, the fundamental question of how fast information travels remains unanswered. The engineering community, starting with the seminal work by Shannon, has studied information rates, but has essentially ignored the question of the velocity of information. The physics community, initially prompted by an apparent challenge to Einstein's special theory of relativity, has been debating the issue off and on for almost 100 years. Surprisingly, the issue remains unresolved. There is no clear definition of the information velocity because there is only a vague understanding of where information is contained on a waveform. I will review the information velocity debate and present a technique for experimentally measuring the velocity of information for the case were the group velocity of a pulse of light vastly exceeds the speed of light in vacuum (a so-called "fast-light medium") or is much slower than the speed of light in vacuum (a "slow-light medium"). Our research suggests that the information velocity is equal to the speed of light in vacuum, independent of the characteristics of the medium. A tutorial on this topic, including links to recent publications, can be found at: http://www.phy.duke.edu/research/photon/qelectron/proj/infv/

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