A very cool twist on optical communications

University of Ottawa breakthrough could have implications for quantum computing and communications

A very cool twist on optical communications
Credit: Optica

University of Ottawa researchers say their discovery that a twisted optical beam in a vacuum travels more slowly than the speed of light could be a boon for quantum computing and communications, and could benefit enterprise IT shops down the line.

Their research, which began in late 2013, is outlined in the paper "Observation of subluminal twisted light in vacuum," published in The Optical Society's Optica journal.

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In a nutshell, twisted light holds potential for more efficient and secure communications. Research lead Ebrahim Karimi, an assistant professor at the University of Ottawa,  responded to a handful of questions via email to elaborate on what this breakthrough means.

Any insights into the likelihood of twisted light being applied commercially, and if so, how far into the future?

The currently available data transmission system is based on wavelength multiplexing, in which information is encoded onto different "colours." This technique has already reached its fundamental limits, and thus seeking for additional degrees of freedom is clearly indicated. Twisted nature of light can potentially be used to enhance the communication capacity, and therefore, may provide a revolution to communication since its "information space" is unbounded.

What about this discovery would be of interest to enterprise IT professionals?

There are numerous interests in the application of twisted beams for communication and information purposes -- twisted photons would enhance both communication capacity and security, and would provide a novel platform for developing quantum computers. Most of the photonics quantum computation techniques, such as algorithms and gates, are based on the quantum interaction of two (or multi) photons. Such types of interaction depend on the arrival time of these photons, thus, one needs to take this new finding on the speed of twisted photons into account.

Can you describe in layman’s terms what you mean by quantum communications? While on the topic, what’s your thinking about how close we are to quantum computing exiting the lab for commercial applications?

Quantum communications consist of a set of methods using fundamental principles of quantum mechanics in order to communicate information either enhancing the security or the efficiency of the communication scheme. In many of these protocols, light is used as the carrier of information. It is thus interesting to make use of the quantum nature of single photons of light, in order to communicate information effectively. Specifically, in our research, we encode information on single photons using the twisting degree of freedom of light. This unique property can be used in many quantum cryptography schemes for communication.

Can you elaborate on how twisted light one day could be used to enable more secure communications?

Quantum mechanics allows for the existence of the state to be in a superposition, being simultaneously a "0" and "1" bits. This superposition nature will prevent anyone to reveal the encoded information since the sender can randomly switch from the logical ("0" or "1" bits) to the superposition basis. Thus, 50% of the time the decoded information is wrong. This process is completely random for any individual attempting to reveal the information. At the final step, 'sender' shares the random process with the 'receiver', and during this process, the wrong basis is discarded. Both 'sender' and 'receiver' have a set of shared bits now, which is named secure keys. Twisted light provides more security since the number of these superposition bases is unb

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