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/ Prof. Hoi Kwong Lo and Prof. Joyce Poon show a quantum key distribution experiment with a silicon chip transmitter for the first time.
Oct 31, 2016

Prof. Hoi Kwong Lo and Prof. Joyce Poon show a quantum key distribution experiment with a silicon chip transmitter for the first time.

The work demonstrates the potential of using silicon photonics to dramatically lower the cost of quantum key distribution and bring it to the mass market in future.

Prof. Hoi Kwong Lo and Prof. Joyce Poon show a quantum key distribution experiment with a silicon chip transmitter for the first time.

The silicon photonic quantum key distribution transmitter (photo credit Jessica MacInnis)

Professors Hoi-Kwong Lo and Joyce Poon in The Edward S. Rogers Sr. Department of Electrical & Computer Engineering (ECE) are working on making quantum key distribution for the masses. Quantum key distribution is a method of sharing a secret key to encrypt and decrypt information with security guaranteed by quantum mechanics. In situations that require impenetrable communication systems for exchange of information, this method of encryption is used — but it comes with a cost, and a footprint.

Despite its effectiveness, use of quantum key distribution is limited because it requires large and complicated equipment. “Right now it is only used in very select industries, like some military and financial institutions,” says Professor Lo. “It’s a niche market because it’s so expensive, and the equipment involved uses discrete components.” Classical methods of producing encryption keys that allow you to shop online with relative security are generated from computational methods. Currently, such classically encrypted keys are secure, but should quantum computers emerge in the near future this type of encryption could be breached. Lo and Poon are working on a way to make quantum key distribution low-cost and accessible for consumer use.

In a paper recently published in Optica, the research groups of Professors Lo and Poon demonstrate an optical transmitter chip for quantum key distribution using a generic silicon photonic process — showing the potential of using wafer-scale fabrication to minimize and reduce the cost of optical components for quantum key distribution encryption methods.

“Classically, we do not send one photon at a time, so someone who wiretaps can just tap off a little bit of those transmitted photons and you would not really have noticed the disruption,” says Professor Poon. “Imagine sending one photon in a random polarization at a time: if someone steals or intercepts a photon in the middle, it would be possible to detect the breach because of the quantum no-cloning theorem.” The challenge is to develop integrated and miniaturized devices for creating these breach-proof encryption keys.

Their solution is to use the existing and well developed infrastructure of semiconductor electronics manufacturing to create silicon photonic integrated circuits for quantum key distribution. Leveraging the existing infrastructure to make the photonic components not only reduces the costs but enables the integration of many devices on the same chip within a millimetre of each other. This is the first time a quantum key distribution transmitter has been integrated on a standard silicon photonic chip.

This new method of achieving quantum key distribution could mean the encryption measures used in sectors with high security requirements could one day be used to protect your personal information like health records and credit card statements. “It’s a practical but elegant approach,” says Poon. “It’s exciting because it really brings together the possibility of integrating quantum communications and classical communications in a very small package.”

More information:
Jessica MacInnis
Senior Communications Officer
The Edward S. Rogers Sr. Department of Electrical & Computer Engineering
416-978-7997; jessica.macinnis@utoronto.ca

The story can be found here on the ECE website:
https://www.ece.utoronto.ca/news/enabling-low-cost-quantum-key-distribution/

The full paper in Optica can be found here:
https://www.osapublishing.org/optica/abstract.cfm?uri=optica-3-11-1274