Entanglement Effect Doubles Laser Beam Data Capacity

Beams from ordinary laser pointers can be made to mimic the phenomenon of quantum entanglement, potentially doubling the amount of data they can carry.

Physicists from The City College of New York, Heriot-Watt University in Scotland and Corning Inc. demonstrated the effect by transforming an ordinary beam into a polarization-dependent vector beam using conventional wave plates.

"At the heart of quantum entanglement is 'nonseparability' — two entangled things are described by an unfactorizable equation," said City College doctoral student Giovanni Milione. "Interestingly, a conventional laser beam's shape and polarization can also be nonseparable."

A conventional laser beam mimics quantum entanglement when it has a polarization-dependent shape. This can be used to encode twice as many bits of information as an ordinary beam. Courtesy of Giovanni Milione.

Exploiting the nonseparability of the vector beam's space and polarization degrees of freedom allowed the researchers to encode two bits of information, where normally they would have been able to encode only one.

Vector beams of this nature can be decoded with low crosstalk using a specialized Mach-Zehnder interferometer.

"In principal, this could be used to double the data speed of laser communication," said City College professor Robert Alfano. "While there's no 'spooky action at a distance,' it's amazing that quantum entanglement aspects can be mimicked by something that simple."

The research was supported in part by the U.S. Army Research Office and published in Optics Letters (doi: 10.1364/OL.40.004887).