Long Distance Communication, Quantum Encryption from Slow Light

Tuning optical resonators gives researchers control over transparency

Excerpts and salient points ~

+  This feature of light is more than a mathematical trick; optical quantum memory, optical storage and other systems that depend on interactions of just a few photons at a time rely on the process, called electromagnetically induced transparency, also known as EIT.

+  Because of its usefulness in existing and emerging quantum and optical technologies, researchers are interested in the ability to manipulate EIT without the introduction of an outside influence, such as additional photons that could perturb the already delicate system. Now, researchers at the McKelvey School of Engineering at Washington University in St. Louis have devised a fully contained optical resonator system that can be used to turn transparency on and off, allowing for a measure of control that has implications across a wide variety of applications.

Using a nanoparticle as a ‘tuning device,’ researchers have devised a way to control electromagnetically induced transparency — a feature of light which allows it to pass through opaque media.

+  One of the more important — and interesting — functions of EIT is its ability to create “slow light.” The speed of light is always constant, but the actual value of that speed can change based on the properties of the medium through which it moves. In a vacuum, light always travels at 300,000,000 meters per second.

+  With EIT, people have slowed light down to leight meters per second, Wang said. “That can have significant influence on the storage of light information. If light is slowed down, we have enough time to use the encoded information for optical quantum computing or optical communication.” If engineers can better control EIT, they can more reliably depend on slow light for these applications.

+  Manipulating EIT could also be used in the development of long distance communication. A tuning resonator can be indirectly coupled to another resonator kilometers away along the same fiber optic cable. “You could change the transmitted light down the line,” Yang said.

+  This could be critical for, among other things, quantum encryption.

Source:  Washington University.  Washington University,  Tuning optical resonators gives researchers control over transparency…

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