The speed of light is often regarded as the ultimate cosmic speed limit, but researchers have now managed to slow it down dramatically—to just 61 kilometers per hour. This was achieved by using a Bose-Einstein condensate (BEC), a peculiar quantum state of matter that allows light to be slowed or even stopped entirely. This discovery, which builds on decades of research, has implications for quantum physics, computing, and information storage.
The Quantum Jelly Effect
In everyday conditions, light moves at 299,792,458 meters per second in a vacuum, and its speed decreases slightly when passing through materials like glass or water. However, these reductions are relatively small. In contrast, when light travels through a Bose-Einstein condensate, it can be slowed to a near standstill.
A Bose-Einstein condensate is an exotic state of matter, first predicted by Albert Einstein and Satyendra Nath Bose, that occurs when a gas is cooled to temperatures just above absolute zero. Under these conditions, the atoms behave as a single quantum entity, exhibiting superfluidity and interacting with light in ways not seen in ordinary materials.
A Breakthrough in Light Manipulation
Decades of research have led to a major breakthrough in controlling light. The ability to slow and manipulate it using BECs was first demonstrated in the late 1990s by Lene Hau and her team at Harvard University (Harvard SEAS). In their groundbreaking experiment, they cooled sodium atoms to an ultra-low temperature and directed laser pulses into the condensate. As the photons interacted with the ultracold atoms, the speed of light dropped dramatically to just 17 meters per second—comparable to a person jogging.
Subsequent developments have shown that not only can light be slowed, but it can also be completely halted and stored within the condensate. An experiment published in Nature (Nature) demonstrated how researchers could stop light entirely for a brief period and then release it without losing information. This remarkable ability to trap and later retrieve light raises the possibility of storing optical information in atomic systems, a potential game-changer for quantum computing.
The Mechanics Behind Slow Light
The reason BECs can slow light lies in a phenomenon known as electromagnetically induced transparency (EIT). This process manipulates how atoms in the condensate interact with light, creating a medium that dramatically alters the speed of photons passing through it. When a control laser is used, it effectively opens a transparent window in the normally opaque condensate, allowing the light pulse to travel through it at an extremely slow speed.
Experimental observations confirm the significance of this effect. Researchers have demonstrated that slow light pulses can be compressed, reducing their spatial size within the condensate while still maintaining their original information content (Optica). This compression could play a crucial role in future applications involving data storage and information processing.
From Quantum Memory to Computing
This discovery paves the way for groundbreaking applications.
・Quantum computing – The ability to store and retrieve light-based information could be used in quantum memory, allowing for the development of advanced photon-based processors. This could enable powerful quantum computers that operate on principles vastly different from today’s electronics.
・Optical data storage – Since light can be trapped and later released, BECs could function as optical memory units, leading to the next generation of ultra-fast, energy-efficient data storage systems.
・Precision sensors – The sensitivity of light to changes in the environment when slowed could make BEC-based devices excellent quantum sensors, capable of detecting even the smallest changes in external conditions.
These advancements challenge the traditional understanding of the nature of light and quantum mechanics. Research in this field continues, as scientists seek new ways to manipulate photonic information and develop technologies that were once thought impossible. https://www.msn.com/en-us/news/technology/physicists-slow-down-light-to-just-61-kilometers-per-hour-using-ultracold-quantum-matter/ar-AA1z9Btc
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