Scientists Demonstrate Long Distance Quantum Communication

 
 
By Wayne Rash  |  Posted 2016-09-24 Print this article Print
 
 
 
 
 
 
 
Quantum Encryption

NEWS ANALYSIS: Scientists have shown that some subatomic particles exhibit quantum entanglement, which potentially enables unhackable communications that may be able to travel faster than the speed of light.

 

The theory of quantum entanglement has been around for over half a century, but until recently this very strange property of some subatomic particles has been difficult to prove. Now experiments are showing it's a very real phenomenon.

Quantum entanglement is a property that allows those particles to share characteristics, so that when they're put into close proximity, they become indistinguishable. Two or more particles can become entangled, so that when scientists measure the state of one particle, other particles appear to exhibit the same state.

When talking about the state of some particle, that means determining some characteristic such as the spin of the particle. Because of Heisenberg's Uncertainty principle, you can never know all of the characteristics of a particle, such as its speed and location.

If you measure its speed, you can't measure its location and vice versa. But once you measure one characteristic of one particle, the uncertainty of the others collapses and they display the same characteristic.

What's important is that change from uncertainty to knowing a specific state of the particle happens instantaneously, without regard to distance. This means that if you were to separate the particles by sending one to Pluto while keeping the other on Earth, the change in state would be detected instantly instead of taking the average 4.5 hours it takes a signal to reach the planet at the speed of light.

The idea that information could be transmitted faster than the speed of light deeply troubled physicist Albert Einstein, who famously labeled it as "spooky action at a distance." But in reality, the communication between the entangled particles apparently takes place outside of the bounds of normal time and space as we experience them.

So does this mean that we're suddenly able to carry on faster-than-light communications, like the ones you see in movies such as Star Trek? Not exactly. This is because you first must physically take one of the entangled particles to the remote location before the communication can take place.

Then while the state change of the particle may be instantaneous, you can't transmit much data. Effectively, you can think of each particle as holding one bit of information, and you must entangle each of them.

Experiments confirming the ability to transmit information using quantum entanglement were carried out in August in Calgary, Alberta, and Heifi, China. The results were published on Sept. 20, in Nature Photonics here and here. These experiments were successful, but limited. The Chinese team was more successful and was able to transmit 17 entangled photons over a distance of several miles.

An earlier experiment in the Canary Islands was able to transmit entangled photons over a longer distance of about 80 miles using lasers.



 
 
 
 
 
 
 
 
 
 
 
 
 

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