Hau was one of several researchers who succeeded in creating this novel state of matter. She corresponded with a colleague, Stepen Harris at Stanford University, and they came up with the idea that it might be possible to use a small ball of cold atoms to slow down light.
Hau and her group then figured out a way to make it work. Using sodium atoms and two laser beams, they made a new kind of medium that entangles light and slows it down. The laser beams glow yellow-orange like sodium streetlights, and the cigar-shaped cloud of atoms is about eight-thousandths of an inch long and about a third as wide.
Working with Chien Liu, a postdoctoral fellow at Rowland, and Harvard graduate students Zachary Dutton and Cyrus Behroozi, Hau kept tweaking the atoms until they completely stopped laser light. This happens when a second laser beam directed at right angles to the cloud of atoms is cut off. When that laser is switched on again, it abruptly frees the light from the trap and it goes on its way.
Hau explains that light entering the atomic entanglement transfers its energy to the atoms. Light energy raises the atoms to higher energy levels in ways that depend on the frequency and intensity of the light. The laser illuminating the cloud at right angles to the incoming beam acts like a parking brake, stopping the beam inside the cloud when it is shut off. When it is turned on again, the brake is released, the atoms transfer their energy back to the light, and it leaves the end of the cloud at full speed and intensity.
Hau's team stopped light for one-thousandth of a second. Atomically speaking, "this is an amazingly long time," Hau notes. "But we think it can be stopped for much longer."
The CfA researchers used an easier method. They shot laser beams through a dense cloud of rubidium and helium gas. (Rubidium, in its solid or natural form, is a soft, silver-white metal.) The light bounced from atom to atom, gradually slowing down until it stopped. No supervacuum or ultra-cold was needed. In fact, the chamber where the light stopped was at a temperature of 176 degrees F.
This convenience comes at a cost, however. Only half of the incoming light was stored, then recovered, and the storage time was much shorter.
Think of both contraptions as sophisticated light switches that control not just light but information. Incoming light can carry information expressed by changes or modulations of its frequency, amplitude, and phase. When the light stops, that information is stored just like information is stored in the electronic memory of a computer. To access the information, you turn on a control laser, and out it comes.
Hau was one of several researchers who succeeded in creating this novel state of matter. She corresponded with a colleague, Stepen Harris at Stanford University, and they came up with the idea that it might be possible to use a small ball of cold atoms to slow down light.
Hau and her group then figured out a way to make it work. Using sodium atoms and two laser beams, they made a new kind of medium that entangles light and slows it down. The laser beams glow yellow-orange like sodium streetlights, and the cigar-shaped cloud of atoms is about eight-thousandths of an inch long and about a third as wide.
Working with Chien Liu, a postdoctoral fellow at Rowland, and Harvard graduate students Zachary Dutton and Cyrus Behroozi, Hau kept tweaking the atoms until they completely stopped laser light. This happens when a second laser beam directed at right angles to the cloud of atoms is cut off. When that laser is switched on again, it abruptly frees the light from the trap and it goes on its way.
Hau explains that light entering the atomic entanglement transfers its energy to the atoms. Light energy raises the atoms to higher energy levels in ways that depend on the frequency and intensity of the light. The laser illuminating the cloud at right angles to the incoming beam acts like a parking brake, stopping the beam inside the cloud when it is shut off. When it is turned on again, the brake is released, the atoms transfer their energy back to the light, and it leaves the end of the cloud at full speed and intensity.
Hau's team stopped light for one-thousandth of a second. Atomically speaking, "this is an amazingly long time," Hau notes. "But we think it can be stopped for much longer."
The CfA researchers used an easier method. They shot laser beams through a dense cloud of rubidium and helium gas. (Rubidium, in its solid or natural form, is a soft, silver-white metal.) The light bounced from atom to atom, gradually slowing down until it stopped. No supervacuum or ultra-cold was needed. In fact, the chamber where the light stopped was at a temperature of 176 degrees F.
This convenience comes at a cost, however. Only half of the incoming light was stored, then recovered, and the storage time was much shorter.
Think of both contraptions as sophisticated light switches that control not just light but information. Incoming light can carry information expressed by changes or modulations of its frequency, amplitude, and phase. When the light stops, that information is stored just like information is stored in the electronic memory of a computer. To access the information, you turn on a control laser, and out it comes.
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