"Quantum Entangled" Laser Pointers Could Double Data Speed

High-power green laser pen. Robin Lund/Shutterstock

A team of physicists has developed a way for ordinary laser beams to mimic quantum entanglement, allowing telecommunication to carry information more quickly.

Quantum entanglement might sound like a term straight out of science fiction, but it is a very real, albeit curious, phenomenon. A pair or a group of particles might have a property that is shared among them, in a way that they cannot be described independently from one another. In quantum mechanics, when you measure a certain property of a particle, such as its energy, you force the system to “collapse”: The value of the property will remain the same.

If the property is entangled, the collapse will affect all the particles in your quantum state, no matter the distance. Originally, this seemed a violation of special relativity, as the collapse could affect instantaneously two particles at either end of the universe. This has been described as "spooky action at a distance." In reality, no information is passed between the particles, so relativity is not broken. The state is simply being observed, and thus will collapse. The physical size of the state (e.g. distance between particles) is irrelevant.

“At the heart of quantum entanglement is ‘nonseparability’ – two entangled things are described by an unfactorizable equation,” said City College Ph.D. student Giovanni Milione and lead author of the study in a statement. “Interestingly, a conventional laser beam (a laser pointer)’s shape and polarization can also be nonseparable.”

Light is polarized if the electromagnetic waves that make up light oscillate only on a specific plane. Light with different polarization is used in 3D cinema: Each eyepiece on the goggles has filters that let only a certain type of polarization through, thus creating the illusion of a three-dimensional image.

The researchers were able to make the shape and polarization of the laser beam nonseparable by making the polarization shape-dependent: They called this configuration a vector beam. By analyzing the vector beam's polarization, one can get information about the shape. With a single measurement, it is possible to extract twice the information from the laser beam.

“In principal, this could be used to double the data speed of laser communication,” added CCNY Distinguished Professor of Physics and co-author 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 is published in the latest issue of Optics Letters

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