Scientists trap light inside crystal for 1 minute

Light, the fastest thing in the known universe, has been trapped in a crystal for one minute by scientists at the University of Darmstadt in Germany.

 

The feat could eventually lead to the creation of long-range quantum networks, tech site Extremetech.com reported.

 

"Beyond being utterly cool, this breakthrough could lead to the creation of long-range quantum networks — and perhaps, tantalizingly, this research might also give us some clues on accelerating light beyond the universal speed limit," it said.

 

It added this was a step forward from earlier this year, when the Georgia Institute of Technology stopped light for 16 seconds.

 

The same University of Darmstadt team in 2001 had stopped light entirely but only for a fraction of a second. In 1999, scientists slowed light down to just 17 meters per second.

 

"One minute is extremely, extremely long. This is indeed a major milestone," NewScientist quoted Thomas Krauss at the University of St Andrews, UK, as saying.

 

 

Stopping light

 

In stopping light, the German team use a technique called electromagnetically induced transparency (EIT), involving a cryogenically cooled opaque crystal of yttrium silicate doped with praseodymium.

 

"A control laser is fired at the crystal, triggering a complex quantum-level reaction that turns it transparent. A second light source (the data/image source) is then beamed into the now-transparent crystal. The control laser is then turned off, turning the crystal opaque," Extremetech said.

 

"Not only does this leave the light trapped inside, but the opacity means that the light inside can no longer bounce around — the light, in a word, has been stopped," it added.

 

Energy from the photons is picked up by atoms within the crystal, and the “data” carried by the photons is converted into atomic spin excitations.

 

To get the light back out of the crystal, the control laser is turned on, and the spin excitations are emitted at photons.

 

"These atomic spins can maintain coherence (data integrity) for around a minute, after which the light pulse/image fizzles. In essence, this entire setup allows the storage and retrieval of data from light memory (or should that be optical memory?)," Extremetech said.

 

Quantum network and barriers

 

Light-based memory that preserves quantum coherence, such as polarization and entanglement, may lead to the creation of a long-range quantum network.

 

NewScientist added tens of seconds of light storage are needed for a device called a quantum repeater, which would stop and then re-emit photons used in secure communications.

 

This would preserve their quantum state over long distances.

 

However, Extremetech said there are still some barriers in the way of a quantum Internet.

 

"We must find a method of coherently storing light that introduces so little noise that single photons can still be reliably stored/retrieved, and we need to do it at room temperature, too. Cryogenics might be acceptable at the data center level, but I can’t imagine having a cryogenically cooled router in my house," it said.  — ELR, GMA News