| Title | 60-Year-Old Limit to Lasers Overturned by Quantum Researchers | |
| Date | Wednesday October 28 2020, @03:09PM | |
| Author | martyb | |
| Topic | ||
| from the a-few-drinks-shy-of-incoherence dept. | ||
60-year-old limit to lasers overturned by quantum researchers:
A team of Australian quantum theorists has shown how to break a bound that had been believed, for 60 years, to fundamentally limit the coherence of lasers.
The coherence of a laser beam can be thought of as the number of photons (particles of light) emitted consecutively into the beam with the same phase (all waving together). It determines how well it can perform a wide variety of precision tasks, such as controlling all the components of a quantum computer.
Now, in a paper published in Nature Physics, the researchers from Griffith University and Macquarie University have shown that new quantum technologies open the possibility of making this coherence vastly larger than was thought possible.
"The conventional wisdom dates back to a famous 1958 paper by American physicists Arthur Schawlow and Charles Townes," said Professor Howard Wiseman, project leader and Director of Griffith's Centre for Quantum Dynamics.
[...] "They showed theoretically that the coherence of the beam cannot be greater than the square of the number of photons stored in the laser," he said.
"In our paper, we have shown that the true limit imposed by quantum mechanics is that the coherence cannot be greater than the fourth power of the number of photons stored in the laser," said Associate Professor Dominic Berry, from Macquarie University.
"When the stored number of photons is large, as is typically the case, our new upper bound is much bigger than the old one."
Journal Reference:
Travis J. Baker, Seyed N. Saadatmand, Dominic W. Berry, et al. The Heisenberg limit for laser coherence, Nature Physics (DOI: 10.1038/s41567-020-01049-3)
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