Physicists have found a way to freeze light in its tracks
In short: Although light typically moves at a massive 300,000 km per second, researchers have managed to halt a laser beam entirely. By routing light through prepared gaseous atoms, experts can halt a light pulse and resume it instantly.
In these landmark experiments, researchers used lasers and ultracold atoms to manipulate light. One group, led by Ron Walsworth from the Harvard-Smithsonian Center for Astrophysics, demonstrated how a light beam could be stopped and then sent speeding off again. Another group, led by Lene Hau at Harvard University and the Rowland Institute, achieved similar results by using a control laser beam tuned to a specific frequency. This process puts the atoms into a 'dark state,' a condition where the atoms cannot absorb light as they normally would.
The mechanism relies on transferring information from the electromagnetic fields of the light beam into the state of the gas atoms. For example, David Phillips noted that using over 10^12 atoms makes the resulting state very robust. To stop the beam, researchers fade out the control beam smoothly to avoid destroying the dark state. While some methods involve photons being 'swallowed' by an atomic cloud, other techniques, such as those from a team at TU Darmstadt, involve preserving the photons so the light literally stands still.
This ability to control light is not merely a physical gimmick; it addresses a fundamental obstacle in quantum computing. Standard quantum computing attempts to preserve quantum states within single atoms, yet such states are extremely fragile and prone to disruption by ambient noise. By stopping light, scientists can potentially use photons as information carriers that transfer data between nodes, providing a more stable way to transport and store information in a quantum system.
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Sources
- Summary by Intellect · source: How to Stop Light in Its Tracks
- Also: Stop light | New Scientist
- Also: www.nature.com — Stopping light in its tracks | Nature
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